A reconfigurable battery system with fault management

Abstract

A reconfigurable battery system which has a plurality of cells, each cell is selectively connectable in a series relationship with one or more other cells, by a switching circuit, to control a combined series output voltage. The switching circuit has a plurality of switches arranged to, individually or in selective combinations, control the series connection, or bypass, of each cell in the plurality of cells, where the switching circuit has at least a first switch group and a second switch group, each group comprising a selection of switches. A plurality handshake circuits are each configured to control one or more handshake signals. A plurality of cell controllers is each configured to operate in one of an operational mode and one or more fault modes based on one or more received handshake signals, in the operational mode, operate the switches of the first switch group, and in a fault mode, selectively operate at least one switch in the second switch group based on a received handshake signal.

Description

[0001] A RECONFIGURABLE BATTERY SYSTEM WITH FAULT MANAGEMENT Technical Field

[0002] The invention generally relates to electronics assemblies associated with energy storage systems, and in particular to a system to manage faults in storage devices or control devices.

[0003] Background

[0004] Energy storage systems for applications such as full electric vehicles, hybrid electric vehicles, and stationary energy storage in grid connected or off grid applications, frequently include an arrangement of multiple energy storage cell units.

[0005] In energy storage systems that include multiple energy storage cell units, the multiple cell units are usually connected in a series arrangement by a switching circuit. The switching circuit has switches which are arranged to control the series connection of a cell to another cell, or to bypass a cell from a series arrangement of cells. The switches are controlled by a controller, typically based on a desired output voltage from the series connection of cells.

[0006] In such systems, there is a problem where failure of a cell, switch or controller typically renders the energy storage system inoperable.

[0007] It is therefore an object of the invention to alleviate or improve upon the aforementioned disadvantages of the prior art, or at least provide the public with a useful choice. Other objects will be apparent to those skilled in the art.

[0008] Summary of the invention

[0009] In a first aspect the invention relates to a reconfigurable battery cell system comprising: a plurality of cells connectable in series to provide an output voltage; a switching circuit comprising a plurality of switches arranged to control the series connection of each cell in the plurality of cells and thereby the output voltage; wherein the switching circuit comprises switch groups, each switch group defined by a combination of switches comprising:

[0010] • 0 closed switches breaks the series connection,

[0011] • one or more closed switches is configured to either connect or bypass the cell in / from the series connection,

[0012] • one or more closed switches is configured to cause a short circuit of at least one cell; a “n” plurality of cell controllers, each cell controller configured to connect with switches from at least one switch group; a handshake circuit configured to control one or more handshake signals based on detection of an operational fault in one or more of:

[0013] • a component of the handshake circuit,

[0014] • a switch of a switch group,

[0015] • a cell controller,

[0016] • a cell,

[0017] • a power supply to the handshake circuit and / or a cell controller; wherein the plurality of cell controllers comprise: a first cell controller configured to control switches in a first switch group; a second cell controller configured to control switches in a second switch group, wherein the second (n+1) cell controller is further configured to selectively control at least one switch of the first switch group based on the one or more handshake signals.

[0018] In another aspect the invention relates to a reconfigurable battery cell system comprising: a plurality of cells connectable in series to provide an output voltage; a switching circuit comprising a plurality of switches arranged to control the series connection of each cell in the plurality of cells and thereby the output voltage; wherein the switching circuit comprises switch groups, each switch group defined by a combination of switches comprising:

[0019] • 0 closed switches breaks the series connection,

[0020] • one or more closed switches is configured to either connect or bypass the cell in / from the series connection,

[0021] • one or more closed switches is configured to cause a short circuit of at least one cell; a “n” plurality of cell controllers, each cell controller configured to connect with switches from at least one switch group; a handshake circuit configured to control one or more handshake signals based on detection of an operational fault in one or more of:

[0022] • a component of the handshake circuit,

[0023] • a switch of a switch group,

[0024] • a cell controller,

[0025] • a cell,

[0026] • a power supply to the handshake circuit and / or a cell controller; wherein the plurality of cell controllers comprise: a first cell controller configured to control switches in a first switch group; the first controller further configured to operate close? a switch in the first switch group based on the one or more handshake signals (from n-1).

[0027] In another aspect the invention relates to a reconfigurable battery system, comprising: a plurality of cells selectively connectable in series to control an output voltage; a switching circuit comprising a plurality of switches arranged to, individually or in combination, selectively control the connection of each cell in the plurality of cells, the switching circuit comprising at least a first switch group and a second switch group, each group comprising a selection of switches; a plurality handshake circuits, each configured to control one or more handshake signals; a plurality of cell controllers, each cell controller configured to: operate in at least an operational mode or one or more fault modes based on the one or more received handshake signals, in the operational mode, operate the switches of the first switch group, and in a fault mode, selectively operate at least one switch in a second switch group based on a received handshake signal.

[0028] In another aspect the invention relates to a reconfigurable battery system, comprising: a plurality of cells, each cell selectively connectable in a series relationship with one or more other cells, by a switching circuit, to control an a combined series output voltage; a the switching circuit comprising a plurality of switches arranged to, individually or in selective combinations, control the series connection, or bypass, of each cell in the plurality of cells, the switching circuit comprising at least a first switch group and a second switch group, each group comprising a selection of switches; a plurality handshake circuits, each configured to control one or more handshake signals; a plurality of cell controllers configured to receive, each cell controller configured to: operate in at least one of an operational mode or and one or more fault modes based on one or more received handshake signals, in the operational mode, operate the switches of the first switch group, and in a fault mode, selectively operate at least one switch in a the second switch group based on a received handshake signal. In some embodiments, the reconfigurable battery system comprises: a plurality of cell modules, each module comprising a first cell and second cell, each cell having two terminals and wherein one of the terminals of each of the first cell and the second cell are connected, thereby defining modules nodes comprising a first node being the first cell terminal of the first cell, a second node being second terminals of the first cell and second cell, and third node being the third terminal of the second cell; and wherein the first, second and third nodes of each of a pair of more modules in the system are linked by a set of three switches of the switching circuit; wherein the first switch group comprises three switches linking first, second and third nodes of a first and a second cell module, and the second switch group comprises three switches linking first, second and third nodes of the second and a third cell module.

[0029] In some embodiments, the system as claimed in any one of claims 1 to 19, wherein the reconfigurable battery system comprises: a plurality of cell modules, each module comprising: a first and a second module terminal, a battery cell, a series switch configured to connect or disconnect the battery cell in series with the first and second module terminal, and a parallel switch configured to bypass the battery cell by the connection of the first terminal to the second module terminal; wherein the first switch group comprises the series switch and the parallel switch of a first cell module, and the second switch group comprises the series switch and the parallel switch of a second cell module.

[0030] In some embodiments, the plurality of cell modules comprises a plurality of cell module pairs, wherein each pair comprises the direct connection with a common node: the first module terminal of a first cell module, the second module terminal of a second cell module, a negative terminal of a first battery cell of the first cell module, and a positive terminal of a second battery cell of the second cell module.

[0031] In another aspect the invention relates to a reconfigurable battery system, comprising: a plurality of cells, each cell selectively connectable in a series relationship with one or more other cells, by a switching circuit, to control a combined series output voltage; the switching circuit comprising a plurality of switches arranged to, individually or in selective combinations, control the series connection, or bypass, of each cell in the plurality of cells, the switching circuit comprising at least a first switch group and a second switch group, each group comprising a selection of switches; a plurality handshake circuits, each configured to control one or more handshake signals; a plurality of cell controllers each configured to: operate in one of: an operational mode, and, one or more fault modes based on one or more received handshake signals, in the operational mode, operate the switches of the first switch group, and in a fault mode, selectively operate at least one switch in the second switch group based on a received handshake signal.

[0032] In some embodiments, the reconfigurable battery system comprises a plurality of battery cells connectable at least in series to control the output voltage.

[0033] In some embodiments, the switching circuit is configured to connect or bypass one or more cells in the system to control the output voltage.

[0034] In some embodiments, the cell controllers are each configured to, in the operational mode, control the connection or bypass of one or more cells to thereby control the output voltage.

[0035] In some embodiments, each switch group is defined by a combination of switches comprising: 0 closed switches breaks the series connection, one or more closed switches is configured to either connect or bypass the cell in / from the series connection, one or more closed switches is configured to cause a short circuit of at least one cell; In some embodiments, each handshake circuit is configured to control one or more handshake signals based on detection of a fault in one or more of: a component of a handshake circuit, a switch of a switch group, a cell controller, a cell, a power supply supplying a handshake circuit and / or a cell controller.

[0036] In some embodiments, the switching circuit comprises switch groups and control domain groups, each switch group defined by a combination of switches comprising: 0 closed switches breaks the series connection, 1 closed switch either connects or bypasses the cell in / from the series connection, and more than one closed switch causes a short circuit of at least one cell.

[0037] In some embodiments, the switching circuit comprises switch groups and control domain groups, each switch group defined by a combination of switches comprising: 0 closed switches breaks the series connection, a predetermined number of closed switch(s) is configured to either connect or bypass the cell in / from the series connection, more than the predetermined number of closed switches causes a short circuit of at least one cell

[0038] In some embodiments, in a further fault mode, the first cell controller is configured to selectively close one switch of the first switch group based on one or more handshake signals from another handshake circuit.

[0039] In some embodiments, the first cell controller configured to control switches in a first switch group; the first controller further configured to operate close? a switch in the first switch group based on the one or more handshake signals (from n-1). (OmA + HS_FB)

[0040] In some embodiments, each cell controller (n) is further configured to, in the operation mode: operate at least one switch (switch Am) of the first switch group (m) based on a handshake signal.

[0041] In some embodiments, the handshake circuit further comprises a level shifting circuit operable to interface a cell controller to at least one switch in the switch group selectively controlled by another controller.

[0042] In some embodiments, the one or more handshake signals comprise one or more of: an operational or fault mode of a first cell controller transmitted to a second controller; an operational or fault mode of a second cell controller transmitted to the first controller; and / or a command transmitted from the first cell controller to control at least one switch in the first switch group for the operational mode of the first cell controller; and wherein the second cell controller is configured to replace control of the at least one switch in the first switch group based on the fault mode of the first cell controller; and / or wherein the first cell controller is configured to close a switch of the first switch group other than the at least one switch selectively controlled by the second controller based on the fault mode of the second controller.

[0043] In some embodiments, the fault status of the first cell controller is based on a failure of one or more of: a switch in the first switch group configured to either connect or bypass a cell, and / or a cell connected to a switch in the first switch group; and / or wherein the fault status of the second cell controller is based on a failure of one or more of: a switch in the second switch group configured to either connect or bypass a cell, and / or a cell connected to a switch in the second switch group. In some embodiments, the one or more handshake signals further comprise a fault status based on a fault in a component of the handshake circuit; and in response: the second cell controller is configured to replace control of the at least one switch in the first switch group based on the fault in a component of the handshake circuit; and the first cell controller is configured to close a switch of the first switch group other than the at least one switch selectively controlled by the second controller based on the fault in a component of the handshake circuit; wherein the circuit further comprises a plurality of short circuit protection circuits (SCPC) connected with each switch of the first switch group, the SCPC configured to override the operation of the at least one switch or the switch of the first switch group other than the at least one switch.

[0044] In some embodiments, one or more handshake signals comprise one or more of: a communication line for each of the operational or fault status of the first cell controller transmitted to the second controller, the operational or fault status of the second cell controller transmitted to the first controller, and / or the command transmitted from the first cell controller to control the at least one switch in the first switch group for the operational state of the first cell controller; a communication line comprising modulated, encoded data comprising the operational or fault status of the first cell controller transmitted to the second controller, the operational or fault status of the second cell controller transmitted to the first controller, and / or the command transmitted from the first cell controller to control the at least one switch in the first switch group for the operational state of the first cell controller.

[0045] In some embodiments, the handshake circuit comprises a finite state machine having an output controlled by inputs based on a fault in any one or more of the following: a component of the handshake circuit, a switch of a switch group, a cell controller, a cell, and / or a power supply to the handshake circuit and / or a cell controller.

[0046] In some embodiments, the handshake circuit comprises a finite state machine having an output having states, at least one state controlled by inputs based on a fault in any one or more of the following: a component of the handshake circuit; a power supply to the handshake circuit and / or a cell controller.

[0047] In some embodiments, the at least one state is controlled by inputs based on any one or more of the following: an operational or fault status of a first cell controller transmitted to the second controller, an operational or fault status of a second cell controller transmitted to the first controller, and / or a fault in a component of the handshake circuit.

[0048] In some embodiments, the output further comprises states controlled by inputs from the first cell controller to control the status of the at least one switch.

[0049] In some embodiments, the handshake circuit comprises a first circuit portion and a second circuit portion, the first circuit portion configured for control by a first cell controller, the second circuit portion configured for control by a second controller, the first and second circuits connected by a single link; the handshake circuit configured to control the single analogue link in one of three or more states, each state represented by a different current magnitude; the states comprising: an operational or fault status of the first cell controller transmitted to the second cell controller, a control signal determining the on state of the at least one switch, a control signal determining the off state of the at least one switch. In some embodiments, the three or more states comprises three states..

[0050] In some embodiments, the handshake circuit comprises a first circuit portion and a second circuit portion, the first circuit portion configured for control by a first cell controller, the second circuit portion configured for control by a second controller, the first and second circuits connected by a communication link comprising: a single link, or a plurality of data lines.

[0051] In some embodiments, the reconfigurable battery system further comprises an interconnected sequence of switching circuits each with a cell controller, and the handshake circuit comprises portions of: a transmitter portion configured to transmit the one or more handshake signals to the next adjacent cell controller in the chain, and a receiver portion controller configured to receive the one or more handshake signals from the previous adjacent cell controller in the chain, such that handshake circuits form a sequence of the cell controllers.

[0052] In some embodiments, the sequence includes a first cell controller, the next adjacent cell controller in the sequence, and the previous adjacent cell controller in the sequence, and upon detection of a cell failure: the transmitter portion connected with the first cell controller transmits a handshake signal representing a fault status to the next adjacent cell controller; the receiver portion connected with the first cell controller transmits a handshake signal representing a fault status to the previous cell controller; to control the switching circuit to bypass the cell from the series connection.

[0053] In some embodiments, the reconfigurable battery system further comprises an interconnected sequence of switching circuits each with a cell controller, and the handshake circuit comprises portions of: a transmitter portion connected with a first cell controller and configured to transmit the one or more handshake signals to a second cell controller, and a receiver portion at the second cell controller configured to receive the one or more handshake signals from the first cell controller, such that handshake circuits and first and second cell controllers form at least part of the interconnected sequence.

[0054] In some embodiments, the reconfigurable battery system further comprises an interconnected sequence of switching circuits each with a cell controller, wherein one or more cell controllers in the sequence comprises a receiver configured to receive one or more handshake signals from a previous cell controller in the sequence, and a transmitter configured to transmit one or more handshake signals to a next controller in the sequence.

[0055] In some embodiments, the handshake circuit comprises a component of a cell controller.

[0056] In some embodiments, the handshake circuit comprises a controller.

[0057] In some embodiments, the cell controller comprises the handshake circuit.

[0058] In some embodiments, the handshake circuit comprises components connected to the cell controller.

[0059] In some embodiments, the system comprises a handshake circuit for each cell controller.

[0060] In some embodiments, the system comprises a handshake circuit. In some embodiments, the handshake circuit comprises a circuit connected to adjacent cell controllers in the interconnected sequence of cell controllers.

[0061] In some embodiments, the handshake circuit comprises a transmitter portion and a receiver portion, each portion connected to a separate cell controller.

[0062] In some embodiments, the handshake circuit comprises a transmitter portion and a receiver portion, each portion facilitated by a separate cell controller.

[0063] In another broad aspect the invention relates to a method controlling a reconfigurable battery cell system, the system comprising: a plurality of cells connectable in series to provide an output voltage; a switching circuit comprising a plurality of switches arranged to control the series connection of each cell in the plurality of cells and thereby the output voltage; wherein the switching circuit comprises switch groups and control domain groups, each switch group defined by a combination of switches comprising: 0 closed switches breaks the series connection, one or more closed switches is configured to either connect or bypass the cell in / from the series connection, one or more closed switches is configured to cause a short circuit of at least one cell; a plurality of cell controllers, each cell controller configured to connect with switches from a switch group; a handshake circuit configured to control one or more handshake signals based on detection of an operational fault in one or more of: a component of the handshake circuit, a switch of a switch group, a cell controller, a cell, a power supply to the handshake circuit and / or a cell controller; wherein the plurality of cell controllers comprise a first cell controller and a second cell controller, the method comprising the steps of: operating a first cell controller to control switches in a first switch group; operating a second cell controller to control switches in a second switch group; receiving with the second controller, one or more handshake signals; and operating the second cell controller to selectively control at least one switch of the first switch group based on the received one or more handshake signals.

[0064] In some embodiments, there is a plurality of cell modules, each module comprising a first cell and second cell, each cell having two terminals and wherein one of the terminals of each of the first cell and the second cell are connected, thereby defining modules nodes comprising a first node being the first cell terminal of the first cell, a second node being second terminals of the first cell and second cell, and third node being the third terminal of the second cell; and wherein the first, second and third nodes of each of a pair of more modules in the system are linked by a set of three switches of the switching circuit; wherein the first switch group comprises three switches linking first, second and third nodes of a first and a second cell module, and the second switch group comprises three switches linking first, second and third nodes of the second and a third cell module.

[0065] In some embodiments, there is a plurality of cell modules, each module comprising: a first and second terminal, a battery cell, a series switch configured to connect or disconnect the battery cell in series with the first and second terminal, and a parallel switch configured to bypass the battery cell by the connection of the first terminal to the second terminal; wherein the first switch group comprises the series switch and the parallel switch of a first cell module, and the second switch group comprises the series switch and the parallel switch of a second cell module.

[0066] In another broad aspect the invention relates to a method controlling a reconfigurable battery cell system, the method comprising operating one or more controllers to perform the steps of: operating a switching circuit comprising a plurality of switches arranged to control the series connection of each cell in a plurality of cells and thereby an output voltage from the series connection of cells; wherein the switching circuit comprises switch groups, each switch group defined by a combination of switches comprising: 0 closed switches breaks the series connection, one or more closed switches is configured to either connect or bypass the cell in / from the series connection, one or more closed switches is configured to cause a short circuit of at least one cell; operating a first cell controller to control switches in at least a first switch group; operating a second cell controller to control switches in at least a second switch group; receiving with a handshake circuit a number of status signals indicative of an operational fault in one or more of a component of the handshake circuit, a switch of a switch group, a cell controller, a cell, a power supply to the handshake circuit and / or a cell controller; and determining, with the handshake circuit an operational fault from one or more of the status signals; transmitting from the handshake circuit one or more handshake signals based on a determined operational fault; receiving with the second controller, the one or more handshake signals from the handshake circuit; operating the second cell controller to selectively control at least one switch of the first switch group based on the received one or more handshake signals.

[0067] In some embodiments, the invention relates to any one or more of the above statements in combination with any one or more of any of the other statements. Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

[0068] The entire disclosures of all applications, patents and publications, cited above and below, if any, are hereby incorporated by reference. This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0069] To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

[0070] The term “and / or” referred to in the specification and claim means “and” or “or”, or both. The term “comprising” as used in this specification and claims means “consisting at least in part of”. When interpreting statements in this specification and claims which include that term, the features, prefaced by that term in each statement all need to be present but other features can also be present. Related terms such as “comprise” and “comprised” are to be interpreted in the same manner.

[0071] As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including,” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. Brief description of the drawings

[0072] The invention can be better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other, emphasis instead being placed upon clearly illustrating the principles of the invention. Furthermore, like reference numerals designate corresponding parts throughout the several views.

[0073] Figure 1 shows an exemplary reconfigurable battery system, including switch groups and control domain groups.

[0074] Figure 2A shows an exemplary embodiment of a reconfigurable battery system where there is a plurality of cells selectively connectable in a series connection to control an output voltage based on the combined voltages of the series connected cells.

[0075] Figure 2B shows a simplified view of the circuit of Figure 2A.

[0076] Figure 3A shows the circuit of Figure 1 with the inclusion of a plurality of handshake circuits which are operable to generate a plurality of handshake signals.

[0077] Figure 3B shows a diagram of the chain cell controllers, and handshake circuit portions configured to transmit and receive handshake signals.

[0078] Figure 3C shows how each cell controller contains or is associated with a handshake circuit Tx portion and Rx portion. Adjacent cell controllers in the sequence may be connected only via a single wire of the handshake circuit.

[0079] Figure 4A shows an input and output state table according to some embodiments. Figure 4B is a truth table for the exemplary circuits of Figure 2A and 2B.

[0080] Figure 5A illustrates an example of a handshake signal transmission circuit between cell controllers where a single analogue link connects two handshake circuits from switch group CCn to switch group CCn+1.

[0081] Figure 5B illustrates an example of a handshake signal transmission circuit where three parallel transmission lines connect two handshake circuits from switch group CCn to switch group CCn+1.

[0082] Figure 5C for the impedance control method, each of the impedance control elements Z1 , Z2 and Z3 can be implemented by a pull-up level shifter circuit.

[0083] Figure 6 which is a pull up source, a pullup resistor, and a mosfet.

[0084] Figure 7 illustrates another example of a handshake signal transmission circuit where a transmitted signal tout is modulated, and a received signal is demodulated with a demodulator.

[0085] Figure 8 shows a shift register may be used to serialise the data bits and send them to an adjacent cell controller.

[0086] Figure 9 shows a daisy chain arrangement of shift registers which support both parallel inputs and parallel outputs.

[0087] Figures 10(A) -10(E) illustrate other examples of reconfigurable battery systems, each having a switching circuit configured to allow the series connection or bypass of each cell in the circuit.

[0088] Figure 11 is an exemplary impedance control element.

[0089] Figure 12A illustrates a state machine where outputs are based on particular inputs, and particularly a finite state machine representation of the truth table of Figure 4A Figure 12B shows a finite state machine for the exemplary circuits of Figure 2A and 2B.

[0090] Figure 13 shows a diagram of system components which contribute to failsafe functionality across a variety of the above-described failure possibilities.

[0091] Figure 14 shows the voltage output of the system after a fault mode has occurred.

[0092] Figure 15 shows a schematic of logic elements operable with a single analogue link where HS_FB signal, HS_OK and HS_CMD signals are transmitted through a single analogue link within a handshake circuit. Detailed description

[0093] Embodiments of the present disclosure are now described. Exemplary methods, devices, assemblies and systems are described herein. It should be understood that the word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other embodiments or features. More generally, the embodiments described herein are not meant to be limiting. It will be readily understood that certain aspects of the disclosed systems and methods can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein.

[0094] In this specification, the terms “energy storage module”, "battery cell unit", "cell unit", “cell” or “cell module” are generally intended to refer to a module or device which can store an electrical charge and can refer to an individual battery cell or a block of cells connected in parallel, or a multitude of individual battery cells or blocks of parallel cells or a mix of cells connected in series and / or parallel. Where the terms battery cell, cell or cell unit is used, equally applicable are battery module, module, cell module or module unit, where a module may contain one or more cells in series and / or in parallel.

[0095] In this specification, the term “energy storage module” may also refer to a block of cells connected in parallel and / or series and which further includes circuit components such as fuses, resistors, passively controlled diodes, capacitors or inductors are connected in series and / or parallel with individual cells. The term “energy storage unit”, “storage unit”, “battery cell unit” or “cell unit” may also refer to non-battery energy storage elements such as fuel cells and supercapacitors.

[0096] In some embodiments, the energy storage modules may be designed to include one or more energy storage units enabling a charge capacity of at least 10Ah, 20Ah 40Ah, 60Ah, 100Ah, 200Ah, or 400Ah ampere hours. In some embodiments, the plurality of energy storage units may comprise a first and a second energy storage unit, with the first energy storage unit having a charge capacity that is substantially larger than the charge capacity of the second energy storage unit.

[0097] Embodiments of the invention discussed in this specification relate to a battery control system comprising a circuit module comprising a pair of output terminals configured to provide a target output voltage. The module comprises a string of series connected or connectable cell modules which may be referred to as a reconfigurable battery system. Such cell modules typically comprise a first terminal and a second terminal, at least one cell, and a switching circuit configured to connect the first terminal to the second terminal thereby bypassing the at least one cell, or connect the at least one cell between the first terminal and the second terminal thereby including the cell in a series connection.

[0098] The cell module may contain any number of cells in series, or parallel, or a combination of series and parallel, and the switching circuit controls the at least the series connection of any one of those cells to the cell terminals. For example, in a reconfigurable battery system it is common for the switching circuit to control the connection of those cells to the terminals or for the terminals to be connected such that the cells are bypassed. Other cell configurations are possible and may be facilitated by a switching circuit configuration which is designed to reverse the polarity of cells within the cell module. Polarity control may be provided by, for example, Fl- Bridge or 2n+2 inverted H-Bridge circuit topologies.

[0099] Circuits for supporting cells and the arrangement of switches for controlling connected or bypassed states of cells can have many configurations. In some embodiments, the cells and associated switching circuit have a fixed number of switches, such as two, for each cell. However, in other embodiments, the switching circuit may have combinations of two or more switches which are configured to operate to connect or bypass a cell. A controller is configured to control the switching of one or more cell modules to target the circuit module output voltage. The term controller as used in this specification will most commonly be used to describe the functions of one or more processing devices such as microprocessors. A controller may be a single processor, or a combination of multiple processing devices as may be practical. A controller will typically feature output pins which are operably connected to switching devices to control the state of that switching device. For example, the pin of a microprocessor may be connected to operate the gate of a MOSFET switching device.

[0100] In some embodiments, there is a controller configured to control functionality of the system such as the determination of a target voltage, and the output signals required to operate the switching circuit of one or multiple cell modules to generate the target output voltage.

[0101] In some embodiments, the output voltage of the reconfigurable battery system is determined by a plurality of controllers operating to control specific switches which need to be connected in order to connect a number of cells in series to achieve a target voltage. The target voltage will typically be predetermined on the basis of the output voltage requirement for the system. For example, in some embodiments, the system is configured to generate a mains output voltage which may be a sinusoidal 110 to 240V signal at 50 to 60Hz. Other examples include DC voltage applications such as would be found in an electric vehicle (EV), EV charging device, or other more general DC application. As such, the target output voltage may be time varying or time static. A reconfigurable battery system is most often found with lithium-based cells and as such the cell voltage is typically operated between 2.5 and 4.2V per cell.

[0102] In some embodiments, there are multiple controllers configured to control groups of switching devices which are arranged to control the connection or bypass of one or more cells. These controllers are referred to as cell controllers. In such embodiments, cell controllers are each connected to one or more switches and figured to control the switches in order to bypass or include any specific one or more cells in order to meet the target output voltage. In some embodiments, each cell controller operates under the control of a master controller which, for example, is configured to send a target output voltage requirement to the cell controllers which in turn interpret that requirement and determine whether to include or bypass cells under its control. The master cell controller is often referred to as a central stack controller. In other embodiments, the cell controllers operate together based on an algorithm which controls or determines the connection of cells. Various other control techniques are possible which operate cell controllers, connect or bypass cells and achieve a target output voltage.

[0103] In these reconfigurable battery systems, it is possible for a cell, a switch, or a cell controller to fail. A failure may be an open circuit of a cell or switch which breaks the series connection of cells, therefore failing to produce an output voltage from the system.

[0104] A failure may also be a closed circuit of a cell or switch. A closed circuit of a cell may cause a catastrophic event such as the overheating or destruction of a cell under its control. Similarly, the closed-circuit failure of a switch may mean a cell is shorted, and / or that a cell is always connected to the system output.

[0105] A failure may also be where a cell controller is rendered inoperable. Possible causes include a brown out, where there is a power supply fluctuation; a black out, where there is a power supply failure; or a fault in the controller device itself. Implications of a failed cell controller may be that one or more switches operated by the controller are left in an uncontrolled state which may be open, closed, or some intermediary state. In any case, such instances may lead to a cell short, the voltage output sent to zero, or non-zero, or other similarly hazardous occurrence.

[0106] Embodiments of the invention discussed herein relate to solutions to the abovementioned problems associated with a failure within the reconfigurable battery system. In such embodiments, the reconfigurable battery system has a plurality of cells selectively connectable in series to control an output voltage. A switching circuit is configured to selectively connect the cells in series with a plurality of switches. The switches are arranged to, individually or in combination, selectively control the connection of each cell in the plurality of cells. The switching circuit has at least a first switch group and a second switch group, each group comprising a selection of switches. Operation of the switch groups will be discussed in further detail below. The reconfigurable battery system also has a plurality of handshake circuits, each configured to control one or more handshake signals.

[0107] The system employs the plurality of handshake circuits to oversee and control one or more handshake signals. These signals serve as a means of communication within the system, ensuring that each cell controller is aware of another cell controller status and control intentions.

[0108] Details and operation of the handshake circuits is also discussed in detail below. Operation of the handshake circuits and switching circuit is performed by a plurality of cell controllers and detailed operation and functions are described further below. In some embodiments, each cell controller is configured to operate in at least an operational mode, or one or more fault modes based on the one or more received handshake signals, in the operational mode, operate the switches of the first switch group, and in a fault mode, selectively operate at least one switch in a second switch group based on a received handshake signal from a handshake circuit.

[0109] Exemplary implementations of the invention are described in relation to exemplary arrangements of cells which may be within a reconfigurable battery system. One exemplary cell configuration for a reconfigurable battery system is shown in Figure 1 which is particularly useful because an output voltage generated by connecting any of the cells in series may have either polarity without the need of an H-Bridge or an inverter. In some embodiments, and within the circuit of Figure 1 , there is an arrangement of cells that are selectively connectable to provide an output voltage. A switching circuit is configured around the arrangement of cells and has a plurality of switches arranged to selectively control the connection of each cell in a series connection with one or more other cells. The connection is at least in series with the output and includes the selectable series connection with any one or more other cells in the arrangement. The switching circuit therefore comprises a plurality of switches arranged to control the series connection of each cell in the plurality of cells and thereby the output voltage.

[0110] The circuit of Figure 1 represents one operational example of a reconfigurable battery system to which the invention is applicable. However, many other configurations of cells and switches is possible while retaining the advantages of the invention. Figure 1 Can be described in terms of nodes, but that represents only one possible way to describe the many connections and configurations cells and switches may take. In the Figure 1 example, there are a plurality of cell modules, each module comprising a first cell and second cell, each cell having two terminals and wherein one of the terminals of each of the first cell and the second cell are connected, thereby defining modules nodes comprising a first node being the first cell terminal of the first cell, a second node being second terminals of the first cell and second cell, and third node being the third terminal of the second cell. The first, second and third nodes of each of a pair of more modules in the system are linked by a set of three switches of the switching circuit. The first switch group comprises three switches linking first, second and third nodes of a first and a second cell module, and the second switch group comprises three switches linking first, second and third nodes of the second and a third cell module. In some embodiments, the circuit comprises only the first cell and first and second nodes.

[0111] It follows that the cell terminals may be arranged in many other ways, and as such, the configuration of applicable circuits is best described according to a set of rules which define the possible configurations of applicable circuits. Therefore, according to embodiments of the invention, the switching circuit comprises switch groups and control domain groups defined within a set of rules which are discussed below.

[0112] Switch Groups

[0113] Figure 1 depicts switch groups in a reconfigurable battery system, each grouped as indicated by a dashed line. Control domain groups are indicated by the dotted line. The switches of the switching circuit are grouped on the basis of being under the control of a cell controller which controls the normal (fault-free) operation of the system. Each switch group is therefore operably connected to and associated with a cell controller during normal circuit operation.

[0114] In some embodiments, each switch group is defined by a combination of switches comprising:

[0115] • 0 closed switches breaks a series connection of cells,

[0116] • one or more closed switches is configured to either connect or bypass a cell in / from the series connection, and

[0117] • one or more closed switches is configured to cause a short circuit of at least one cell.

[0118] For example, a switch arranged in series with a cell such controls the cell from being connected or disconnected from the series connection. A switch arranged in parallel with a cell and another switch in series with the cell controls a bypass path around the cell when closed. In this example, when the switch in parallel is closed, the switch in series must be open to avoid short circuiting the cell, and similarly, when the parallel switch is open, the series switch is closed such that the circuit is not an open circuit thereby disconnecting the output voltage. Based on these series and parallel switch arrangements as a building block, a reconfigurable battery system is provided where any cell can be connected in series with another cell or cells to provide a combined output voltage. In the same circuit, any cell can be bypassed by the parallel arranged switch to remove it from the series connection. Other configurations of the reconfigurable battery system are possible, such as where one or more cells share a series or parallel configured switch, and for one or more switches to be configured to connect in series, or bypass, groups of other cells or switches.

[0119] Figure 1 is one such example of a circuit conforming to the above rules. In addition, it is clear from the circuit of Figure 1 that only one switch from each switch group is to be closed at any one time to ensure short circuiting of a cell does not occur.

[0120] In some embodiments, each switch group is defined by a combination of switches comprising:

[0121] • 0 closed switches breaks the series connection,

[0122] • a predetermined number of closed switch(s) is configured to either connect or bypass the cell in / from the series connection, and

[0123] • more than the predetermined number of closed switches causes a short circuit of at least one cell.

[0124] In each case, a switch group contains at least one switch which is configured to bypass a part of the switching circuit which might have failed for any reason, due to the failure of, for example, a switch, a cell, or a cell controller, or other reason. In some embodiments, the at least one switch is therefore configured in parallel with at least one other switch. In this way, controlling the at least one switch to be an open or short circuit can compensate for a cell or switch which has failed in the opposite state. In the exemplary circuit of Figure 1 , each switch group comprises switches A, B and C which are grouped together and under the operational control of a cell controller. The four switch groups shown are therefore under the control of an associated four cell controllers. The four cell controllers operating the four switch groups are denoted (from left to right) as m-1, m, m+1 , and m+2. Each of the switches A, B, C in this example can be operated to account for the failure of at least one of the other switches in this switch group. Any number of switch groups may be present in a given circuit and other cell and switch configurations are possible.

[0125] Control domain switch groups

[0126] The switches of the switching circuit are also grouped on the basis of a cell controller which controls a faulted operation of the system. At least one switch from each switch group is therefore connected to and associated with two cell controllers, a first cell controller which operates a first switch group during normal operation, and a second cell controller which operates a second switch group during normal operation. Therefore, a control domain switch group includes at least one switch from a first switch group, and at least one switch of a second switch group. In this way, where there is a failure of a cell controller, for example, if one or more switches in a switch group are unable to be operated by the failed cell controller, then another cell controller is able to operate the switch within its control domain to bypass the failed circuit section.

[0127] The following annotations are also referred to with reference to Figure 1 and other exemplary systems:

[0128] • Cell controller cell controllers (mCCn),

[0129] • Control domain switch groups (CDn) of cell controllers (CCn), and

[0130] • Switch Groups (SGm).

[0131] In the circuit of Figure 1 , there is a one to one relationship between CDn, CCn, and mCCn - Control domain group, Cell Controller; and an overlapped relationship between these and switch groups SGm. For example, CDn governs 106 Am-1 , (Bm), 108 Cm; and CDn+1 governs 106 Am, (Bm+1), 108 Cm+1.

[0132] Control of a switch in a switch group by a cell controller is based on a signal received from the handshake circuit which will be explained in further detail below.

[0133] Figures 10(A) -10(E) illustrate other examples of reconfigurable battery systems, each having a switching circuit configured to allow the series connection or bypass of each cell in the circuit. Each of these Figures also indicates switches included in switch groups and included in control domain groups.

[0134] In the circuit of Figure 10(A) and 10(B), 21 , there is a system which each have a plurality of cell modules. The cell modules may be defined in terms of a first and second terminal, meaning connection points for current to enter or exit the module. Within each cell module is one or more battery cells. A switching circuit is configured as part of the module and provides a current path through the battery cells, or to bypass the battery cells. In the circuits show, there is a series switch configured to connect or disconnect the battery cell in series with the first and second terminal, and a parallel switch configured to bypass the battery cell by the connection of the first terminal to the second terminal. A first switch group comprises the series switch and the parallel switch of a first cell module, and a second switch group comprises the series switch and the parallel switch of a second cell module. A controller is thereby configured to operate the series and parallel switch of each module as its primary switch group, and when in a fault mode, operate the parallel bypass switch of another switch group.

[0135] The circuit of Figure 10(B) differs from that of Figure 10(A) in that two battery cells are directly connected. However, the series and bypass switches remain functionally equivalent. Here, the plurality of cell modules each comprise a plurality of cell module pairs, wherein each pair comprises the direct connection with a common node. The common node directly connects the first module terminal of a first cell module, the second module terminal of a second cell module, a negative terminal of a first battery cell of the first cell module, and a positive terminal of a second battery cell of the second cell module. Such a circuit may be preferable for use with battery modules which physically incorporate two cells within one package, and where those cells are physically connected within the package.

[0136] The depicted reconfigurable battery system circuits are commonplace in the art. For example, the circuit of Figure 10A is published in IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL 58, NO. 9, SEPTEMBER 2011, entitled A New BMS Architecture Based on Cell Redundancy, by authors: Antonio Manenti, Andrea Abba, Alessandro Merati, Sergio M. Savaresi, Member, IEEE, and Angelo Geraci, Senior Member, IEEE. The circuits of Figures 10B-E are published in US patent application 20210265710A1. Each of these publications is incorporated by reference. Cell controllers

[0137] The cell controllers are configured to operate switches of the switching circuit. In some embodiments, there is a cell controller configured to operate each switch group. In some embodiments, each cell controller is configured to operate at least one switch group and at least one control group. Accordingly, in some embodiments, the reconfigurable battery system contains many cell controllers, where each cell controller is configured to operate one switch group and one control group.

[0138] Each cell controller is typically tasked with operating switches in its switch group based on a target output voltage of the reconfigurable battery system. In some embodiments, the target output voltage is determined by a master controller which transmits information to each cell controller which is able to be interpreted in order to operate the switches of the switch group at a particular time such that the combined cells switched in the series configuration generates the target output voltage.

[0139] In some embodiments, a cell controller is typically implemented by a microprocessor device and may optionally include supporting hardware to facilitate the desired functionality of the device. In some embodiments, the cell controller includes the handshake circuit or comprises a part of the handshake circuit.

[0140] Handshake circuit

[0141] Figure 3A shows the circuit of Figure 1 with the inclusion of a plurality of handshake circuits which are operable to generate a plurality of handshake signals.

[0142] In some embodiments each handshake circuit comprises two functional sections which are a signal transmitter, a signal receiver. In some embodiments, the signal transmitter also provides the function of a feedback signal generator. In some embodiments, the feedback signal is received by a feedback signal receiver region of the handshake circuit. In some embodiments, one or more handshake circuits comprise a subset of these sections. In some embodiments, a cell controller is configured to implement at least a section of a handshake circuit, such as the transmitter, receiver or feedback signal generation sections.

[0143] The reconfigurable battery system is an interconnected sequence of cells and switch groups, where each switch group is controlled by a cell controller. Accordingly, the sequence is a chain of cells and cell controllers. Figure 3A denotes the chain and in particular notes that there is a handshake circuit associated with each cell controller in the chain. However, in some embodiments, the handshake circuit comprises circuit portions where:

[0144] • a transmitter portion configured to transmit the one or more handshake signals to the next adjacent cell controller in the chain,

[0145] • and a receiver portion controller configured to receive the one or more handshake signals from the previous adjacent cell controller in the chain,

[0146] • such that handshake circuits form a sequence of the cell controllers.

[0147] Here, the next adjacent cell controller in the sequence, and the previous adjacent cell controller in the sequence, and upon detection of a cell failure:

[0148] • the transmitter portion connected with the first cell controller transmits a handshake signal representing a fault status to the next adjacent cell controller;

[0149] • the receiver portion connected with the first cell controller transmits a handshake signal representing a fault status to the previous cell controller; to thereby control the switching circuit to bypass the cell from the series connection. In some embodiments, the reconfigurable battery system further comprises an interconnected sequence of switching circuits each with a cell controller, and the handshake circuit comprises portions of: • a transmitter portion connected with the first cell controller and configured to transmit the one or more handshake signals to the second cell controller, and

[0150] • a receiver portion at the second cell controller configured to receive the one or more handshake signals from the first cell controller,

[0151] • such that handshake circuits and first and second cell controllers form at least part of the interconnected sequence.

[0152] For example, the exemplary reconfigurable battery system of Figure 3A shows a controller n having a handshake circuit tx 304a (Tx n)configured to transmit a handshake signal to controller n+1 , where that signal is received by handshake circuit receiver 304b. Controller n+1 is configured to transmit a handshake circuit feedback signal back to controller n. Further, controller n-1 has a handshake circuit tx configured to transmit a handshake signal to controller n, where that signal is received by handshake circuit receiver 302b (Rx n-1).

[0153] Figure 3B shows a diagram of the chain cell controllers, and handshake circuit portions configured to transmit and receive handshake signals.

[0154] Each cell controller has three digital outputs (dOP) and 3 digital inputs (dIP). Each handshake (HSn) circuit has a transmitter portion Txn and a receiver portion Rx n. The Txn is part of CCn in terms of physical proximity and electrical connections, digital signals from and to Txn are connected with the cell controller mCCn. Rx n is part of CCn+1 in terms of physical proximity and electrical connections, digital signals from and to Rx n are tied to mCCn+1.

[0155] Each cell controller mCCn is connected with the transmitter portion (Txn) of CCn and the receiver portion (Rxn-1) of the previous CCn-1. This means that cell controller CCn+1 has a receiver portion Rxn for receiving handshake signals from the previous cell controller CCn. CCn+1 also has a Transmitter portion Txn+1 , noting that the Transmitter portion Txn+1 is for transmitting the handshake signal to from Txn+1 to Rxn+1, Rxn+1 being part of the next adjacent controller CCn+2.

[0156] Accordingly, each cell controller in the sequence is configured to send an ‘OK’ signal, indicating it is undertaking normal operation to the next controller, and is configured to send a feedback (FB) handshake signal to the previous controller. The FB handshake signal is effectively an OK handshake signal in the reverse direction.

[0157] Figure 3C shows how each cell controller contains or is associated with a handshake circuit Tx portion and Rx portion. Adjacent cell controllers in the sequence may be connected only via a single wire of the handshake circuit.

[0158] In Figure 3C, items are labelled as follows: 350-Controlier n1 , 351 =FB, 352=Tx, 353=Rx, 354=FB, 355=Tx, 356=Rx, 357=Sw C, 358=Sw A, 359=Sw C, 360=Sw A, 361 “Sw B, 362=Sw B, 363=Sw B, 364=Sw B, 365=Sw A, 366= Sw C, 367=Sw A 368=Sw C, 369=Controlier n-2, 370=FB, 371 =Rx, 372=Tx, 373=Controller n, 374=FB, 375=Rx, 376=Tx, 377=Controller n+2, 378= FB, 379=Rx, 380=Tx, 381=Switch Group m-1 , 382=Switch Group m, 383=Switch Group m+1 , 384=+12V(n), 385=+12V(n+1), 386=dQP ,HS...TxFB. 387=dlP_ . HS__RxOK 388=dlP HS RxCMD, 389=GND(n+1), 390=304b Rx n Receiver. 391=+3.3V(n), 392=dOP„HS_TxOK, 393=dOPJHS..Jx.CMD, 394=GND(n), 395=306a Tx n+i Transmitter, 396=dlP__HS_RxFB, 397=+12V(n). 398=+12V(n+1).

[0159] 399=dOP__HS__TxFB, 400=dlP . HSJFxOK. 401=dlP__HS__RxCMD, 402=GND(n+1), 403=302b Rx n-1 Receiver, 404=210 Handshake Link, 405=+3.3V(n), 406=dOP_HS_ TxOK, 407=dlP__HS__TxCMD, 408=dOP_HS_TxCMD, 409=GND(n), 410=304a TX n Transmitter.

[0160] The six signals 202a1 , 202a3, 202a2, 202b2, 202b3, 202b1 shown in Figure 3B are connected with the cell controller mCCn. The left three signals 202a1 , 202a3, 202a2 in the table are connected with the 304a transmitter (Txn) side of CCn. The right three signals in the table are tied to the 203b receiver (Rxn-1) side of CCn-1 , located to the left of the CCn transmitter 304a, and meant to receive signals from transmitter 302a (Txn-1) of the previous cell controller CCn-1. The handshake signal 202a2 dlP_HS_RxFB (n) is essentially the same signal as 202b1 dOP_HS_TxFB(n+1), where CCn+1 communicates to CCn that CCn+1 is not OK (i.e. has determined a fault or has faulted) via a feedback signal 202b1 dlP_HS_TxFB travelling from right to left (from 304b Receiver Rxn+1 to 304a Transmitter Txn).

[0161] In some embodiments, the handshake circuit is configured to control one or more handshake signals based on detection of an operational fault in one or more of:

[0162] • a component of the handshake circuit,

[0163] • a switch of a switch group,

[0164] • a cell controller,

[0165] • a cell,

[0166] • a power supply to the handshake circuit and / or a cell controller.

[0167] In some embodiments, the handshake circuit comprises a set of finite states, where states include switch control signal or cell controller status. The handshake circuit can be viewed as a finite state machine having an output having states, at least one state controlled by inputs based on a fault in any one or more of a component of the handshake circuit or a power supply to the handshake circuit and / or a cell controller. In some embodiments, the at least one state of the finite state machine is controlled by inputs based on any one or more of the following: an operational or fault status of the first cell controller transmitted to the second controller, an operational or fault status of the second cell controller transmitted to the first controller, and / or a fault in a component of the handshake circuit.

[0168] In some embodiments, the output of the finite state machine further comprises states controlled by inputs from the first cell controller to control the status of the at least one switch.

[0169] Figure 4A shows an input and output state table according to some embodiments. Figure 12A illustrates a state machine where outputs are based on particular inputs, and particularly a finite state machine representation of the truth table of Figure 4A. The states include an operational or fault status of the first cell controller transmitted to the second controller and is represented as the OK signal. In the reverse direction, an operational or fault status of the second cell controller transmitted to the first controller is represented by the FB signal.

[0170] The OK and FB signals result in a first output state of the finite state machine as shown also in Figure 12A, which represents states which control the fault mode operation of a cell controller. There are at least two more states controlled by inputs from the first cell controller to control the status of at least one switch from a second switch group which is in the control domain group of the first cell controller, and these are shown as states two and three in the truth table shown by Figure 4A.

[0171] Exemplary inputs from the first controller as shown in Figure 4A are the CMD signal is OFF, which results in state 2 that drives the switch ON; and CMD signal is ON, which drives the switch OFF.

[0172] During the operational mode of the cell controller, the CMD signal drives the switch ON or OFF via the level shifting function of the handshake circuit. During a fault mode, the second cell controller takes over the control of the switch from a switch group in the control domain of the adjacent cell controller. The CMD signal is either ignored or overridden by the second cell controller in this scenario.

[0173] Cell controller operation

[0174] According to preferred embodiments, each cell controller is configured to operate in at least two modes. In a first mode, a cell controller is configured to operate the switches of a first switch group and that is intended to be a ‘normal’ operational mode of the reconfigurable battery system. In a second mode, a cell controller is configured to operate at least the switches of a control domain, being at least one switch from a first switch group, and at least one switch of a second switch group, and that is intended to be a ‘fault’ operational mode of the of the reconfigurable battery system.

[0175] Operation of a cell controller in an operational mode or a fault mode is based on receiving a change in one or more handshake signals indicative of one or more of the above operational faults. In some embodiments, a cell controller is configured to change from the operational mode to the fault when a change in one or more handshake signals occurs.

[0176] In exemplary embodiments, the mode of each cell controller is selectively controlled by one or more handshake circuits. Each handshake circuit is configured to generate one or more handshake signals operable to be received by a cell controller and thereby selectively control the operation mode of the cell controller. The handshake signals comprise fault data and will be discussed in further detail below.

[0177] Accordingly, each cell controller is configured to:

[0178] • operate in at least an operational mode or one or more fault modes based on the one or more received handshake signals,

[0179] • in the operational mode, operate switches of a first switch group comprising a selection of the plurality of switches of the switching circuit,

[0180] • in a fault mode, selectively operate at least one switch in a second switch group based on a handshake signal.

[0181] Cell controller operation - Operation mode

[0182] In the operation mode, a cell controller is configured to operate the switches of its associated switch group. In some embodiments, the operation modes comprise a mode where each cell controller is further configured to, in the operation mode, operate at least one switch (switch Am) of the first switch group (m) based on a handshake signal. In some embodiments, at least one switch of the cell controller switch group is operation based on a handshake signal received from another cell controller. For example, a first handshake controller is configured to transmit, via the handshake circuit, a control signal to a second controller, and the second controller is configured to operate the switch of its switch group based on the received handshake control signal. Further details of the operation mode are discussed with reference to an exemplary circuit of Figure 2A.

[0183] Cell controller operation - Fault mode

[0184] Embodiments of the invention are directed to ensuring a controller has operational control over a switch group, and to ensure the operation rules of the switch group (to avoid short-circuiting a battery cell or open circuiting the series string of cells) remain true. For example, when a first cell controller determines, from the handshake signals, that an adjacent second cell controller is non-functional, it will take over the operation of a switch from the switch group of that adjacent second cell controller. That is, the first cell controller will take over operation of the switch in its control domain switch group shared by the second controller as the operational switch group.

[0185] The handshake signals are configured in such a way that failure of the handshake circuit itself, such as due to a component failure or power failure, will cause the first controller to take over operation of the switch in the control domain group shared by the second cell controller switch group.

[0186] Particular fault conditions are monitored by cell controllers. When a cell controller determines there is a fault with any feature it is configured to monitor, it is configured to operate to cause the handshake circuit to transmit that fault to one or more other cell controllers. Direct signalling between cell controllers, via the handshake circuit, in this manner facilitates a fast reaction speed (microseconds) which can overcome latency associated with regular communication channels (milliseconds) that might exist between cell controllers and a central controller. In this way, catastrophic events such as open or short circuit failures can be addressed before significant heat build-up or significant loss of output occurs.

[0187] In some embodiments, a cell controller is configured to determine there is a fault in a switch it monitors, and via the handshake circuit can transmit a signal to other cell controllers.

[0188] In some embodiments, a cell controller is configured to determine there is a fault in a cell it monitors, and via the handshake circuit can transmit a signal to other cell controllers. In some embodiments, a cell controller is configured to transmit, via the handshake circuit, a signal indicative of the fault to the next and the previous cell controllers in a series string of cell controllers. In this way, each of the next and previous controllers are able to change to a fault mode where a defective switch, cell or component is located.

[0189] In some embodiments, the handshake circuit comprises states which represent regular operational functions or faults. The states are discussed in further details below. However, one state includes a natural or unpowered state of the handshake circuit. In this way, a cell controller is able to receive a handshake signal, determine the state, and act accordingly. For example, if a handshake circuit or cell controller were to lose power, the handshake circuit would undertake the unpowered signal state and a receiving cell controller would determine a fault mode operation on that basis. The unpowered state of the handshake circuit is referred to as the relaxed state and discussed in further detail below.

[0190] In the fault mode, a cell controller is configured to override and therefore take over operation of at least one switch which is in the control domain group and not in the switch group, from another cell controller based on the one or more signals received from the handshake circuit. For example, a first cell controller is configured to operate switches in a first switch group in an operation mode and override the control of at least one switch in a second switch group from a second cell controller.

[0191] More specifically, CCn+1 detects a fault or is caused to enter into a fault mode on the basis of the received handshake signal indicative of the same, then “take over” a switch in the control domain which is not in the switch group of the cell controller. When such a fault is determined, there being always one switch operable by a working cell controller (closable) is enabled by partitioning controller domains to overlap partially with switch groups. So that the next cell controller in the sequence can “take over”, upon detection of the fault handshake signal. Related is the software preprogramed default action to close which switch and open which switch upon detection of a failure.

[0192] Specifically, when CCn+1 determines that CCn has a fault, or any one or more of a number of faults has caused CCn+1 to enter into a fault mode, via receiving and determining a handshake signal (HS_OK) from CCn to CCn+1 , CCn+1 takes over a switch that’s not in its switch group SGm, such as Am. A fault could be in one or more of:

[0193] • a component of the handshake circuit,

[0194] • a switch of a switch group,

[0195] • a cell controller,

[0196] • a cell,

[0197] • a power supply to the handshake circuit and / or a cell controller.

[0198] In some embodiments, in a further fault mode, the first cell controller is configured to selectively close one switch of the first switch group based on one or more handshake signals from another handshake circuit. More specifically, when CCn detects that CCn+1 has a fault, or any one or more of a number of faults has caused CCn to enter into a fault mode via detecting a feedback handshake signal (HS_FB) from CCn+1 to CCn, CCn closes a switch in its own switch group SGm other than the switch (e.g. Am) that’s also in the control domain of CCn+1, for example, CCn closes switch Cm. In some embodiments, the operation modes comprise a mode where first cell controller configured to control switches in a first switch group, where the one or more handshake signals comprise one or more of:

[0199] • an operational or fault mode of a first cell controller transmitted to a second controller;

[0200] • an operational or fault mode of a second cell controller transmitted to the controller; and / or • a command transmitted from the first cell controller to control at least one switch in the first switch group for the operational mode of the first cell controller; and

[0201] • wherein the second cell controller is configured to replace control of the at least one switch in the first switch group based on the fault mode of the first cell controller; and / or

[0202] • wherein the first cell controller is configured to close a switch of the first switch group other than the at least one switch selectively controlled by the second controller based on the fault mode of the second controller.

[0203] In some embodiments, the operation modes comprise a mode where wherein the fault status of the first cell controller is based on a failure of one or more of:

[0204] • a switch in the first switch group configured to either connect or bypass a cell, and / or

[0205] • a cell connected to a switch in the first switch group; and / or

[0206] • wherein the fault status of the second cell controller is based on a failure of one or more of:

[0207] • a switch in the second switch group configured to either connect or bypass a cell, and / or

[0208] • a cell connected to a switch in the second switch group.

[0209] Fault determination - Cell failure

[0210] In some embodiments, a controller is configured to measure cell parameters including voltage, and cell temperature. In some embodiments, the controller is configured to determine a cell failure the basis of:

[0211] • A cell voltage being above or below a safe range of operating voltages, for example, by comparing to one or more thresholds;

[0212] • A cell temperature being above or below a safe range of operating voltages, for example, by comparing to one or more thresholds;

[0213] • A difference between the voltages of any two or more cells exceeding a threshold, typically indicating the reconfigurable battery system is in need of cell balancing;

[0214] • Any other measurement that indicates a critical failure of cells.

[0215] Accordingly, a cell controller is configured to switch to a fault mode based on a change in one or more handshake signals indicating a cell failure.

[0216] Fault determination - Cell controller failure

[0217] Typically there is cell monitoring circuitry and / or software which, upon detection of cell failures such as those listed above, sends a fault signal to a central controller, which in turn instructs cell controllers to bypass the problematic cells. However, this communication occurs via the stack communication bus and the decision to bypass the problematic cells are made via algorithms in the central controller. In case of a fault in the communication bus, the central controller, a bug in the software, or a higher-level fault such that a prompt assertion of switches to bypass the cells cannot be relied upon, the handshake circuit can be operated to force determined faulted cells to be bypassed by a cell controller. In this way there is redundancy in responding to cell failures.

[0218] In some embodiments, a cell controller is configured to determine the failure of another cell controller based on one of a change in the feedback signal received. For example, if a cell controller configured to transmit a feedback handshake signal were to fail, such as from a power failure, then the feedback signal would change.

[0219] In another example, one handshake signal is a command signal. A cell controller is therefore configured to determine whether another cell controller has failed based on a change in the command signal.

[0220] Accordingly, a cell controller is configured to switch to a fault mode based on a change in one or more handshake signals indicating a cell controller failure. Fault determination - Switch failure

[0221] In some embodiments, a cell controller is configured to determine a failure of a switch in its associated switch group.

[0222] In some embodiments, a cell controller is configured to monitor the voltage at a connection point, and in particular, determine a change in voltage at that connection point has occurred when a switch under control of the cell controller changes state. For example, one or more switches operated to connect a cell will produce a voltage transitioning from one voltage to a higher voltage, or vice versa. Accordingly, the operational function of a switch in the switch group can be determined based on the change in voltage at the appropriate monitoring location. In instances where the voltage change fails to occur, the controller is configured to signal the handshake circuit of the fault condition and the handshake circuit is configured to transmit a handshake signal to another cell controller based on this occurrence.

[0223] Accordingly, a cell controller is configured to switch to a fault mode based on a change in one or more handshake signals indicating a switch failure.

[0224] In some embodiments, switches of the system are implemented by MOSFETs, and the system further includes a MOSFET failure detection (MFD) circuit which is configured to measure the voltage across a given MOSFET and compares this to a reference voltage. If the MOSFET drain-source voltage exceeds the reference then The MOSFET gate drive is disabled, thereby forcibly opening the MOSFET. In some embodiments, the reference voltage is 60 mV.

[0225] A 60 mV reference voltage allows determination of multiple situations:

[0226] • A closed MOSFET has more than about 400A flowing from drain to source, and due to ohms law the developed voltage has exceeded 60mV.

[0227] • A MOSFET that should be closed with typically 100A flowing from drain-source is not closed due to a gate drive failure or similar situation. In this case the battery voltage will be seen across the MOSFET which is substantially higher than 60mV. Sometimes more than the battery voltage, let me know if you need to know more.

[0228] • A closed MOSFET has higher than expected resistance and although the typical current of 100A is flowing, the problem is diagnosed via ohms law due to high resistance (similar to the above)

[0229] • A MOSFET that should be open (revealing >60mV) is closed due to a fault, whereby <60mV is observed when it should be substantially >60mV. In this case we are using to confirm that the MOSFET was initially opened successfully.

[0230] Accordingly, in some embodiments, the one or more handshake signals further comprise a fault status based on a fault in a component of the handshake circuit; and in response: the second cell controller is configured to replace control of at least one switch in the first switch group based on the fault in a component of the handshake circuit; and the first cell controller is configured to close a switch of the first switch group other than the at least one switch selectively controlled by the second controller based on the fault in a component of the handshake circuit. In some embodiments, the circuit further has a plurality of short circuit protection circuits connected with each switch of the first switch group, the short circuit protection circuits configured to override the operation of the at least one switch or the switch of the first switch group other than the at least one switch.

[0231] MFD circuit

[0232] The MFD circuit is more commonly known as Short Circuit Protection Circuit (SCPC), MOSFET overcurrent protection circuit or IGBT Desaturation Protection circuit. It is an analogue circuit and mechanism in nature and the MFDs of all the switches within a switch group are electrically connected. When a failure has been detected (and / or a sudden increase in current), the MFD circuit will force open all the connected switches. In some embodiments, the MFD is configured to send a fault signal to the cell controller that the switch has failed, and then the cell controller. In some embodiments, the cell controller is configured to poll the switch by sending a signal to open / close it to determine if the switch has failed OPEN or failed CLOSED. The MFD connects switches A B C in the same circuit path, and triggers when a sudden surge in current to OPEN all switches that can still be opened.

[0233] MFDs acts as a form of failsafe for instances when a switch fails in a shorted state and operates to signal the cell controller that an appropriate control can be applied to avoid cell shorting. When a failure mode is not addressed correctly by the handshake circuit, MFDs arbitrate the final states of the switches to ensure that the system continues to operate.

[0234] Fault determination - Failure of the handshake circuit

[0235] In some embodiments, a controller, such as the cell controller is configured to provide the handshake circuit. In such embodiments, handshake signals generated by the handshake circuit will be affected by the same or similar issues as discussed above in relation to cell controller failures.

[0236] In some embodiments, the handshake circuit is a separate circuit which interfaces with one or more cell controllers. In some embodiments, the handshake circuit comprises a circuit with one or more discrete components, and a failure of the handshake circuit comprises a failure in any one or more of the discrete components. Accordingly, embodiments of the handshake circuit comprising discrete components are configured in such a way that the component failure causes a change in one or more handshake signals. One exemplary circuit with discrete components is discussed below in relation to Figure 2A. As discussed above, a cell controller is configured to switch to a fault mode based on a change in one or more handshake signals.

[0237] Fault determination - Relaxed state of the handshake circuit

[0238] In some embodiments, the handshake circuit is configured to embody a state where signal transmissions are halted. In this state, a handshake circuit receiver circuit (such as a cell controller) is configured to interpret the halted signal transmission as a failure indication and in turn is configured to change from the operational state to the fault state.

[0239] In some embodiments, the handshake circuit is implemented by a circuit where a power outage or control input failure causes the signal transmission to take a particular form referred to herein as a “relaxed state”. In some embodiments, the relaxed state is a natural state of the handshake circuit in response to a failure occurring such as a power outage or malfunctioning cell controller. In some embodiments, the relaxed state of the handshake circuit is controlled by a feature of the handshake circuit, such as a cell controller configured to generate an output to control handshake circuit transmitter function into the relaxed state.

[0240] In some embodiments, the relaxed state is defined as the state of the handshake circuit when there is a power outage.

[0241] Handshake signal transmission

[0242] In some embodiments, a single handshake link is used to carry the handshake signals. In other embodiments, multiple links are used. In some embodiments, the signals that represent the various states are analog. In other embodiments, they are digital.

[0243] In some embodiments, the handshake circuit comprises a finite state machine having an output having states, at least one state controlled by inputs based on a fault in any one or more of a component of the handshake circuit or a power supply to the handshake circuit and / or a cell controller.

[0244] In some embodiments, the at least one state of the finite state machine is controlled by inputs based on any one or more of the following: an operational or fault status of the first cell controller transmitted to the second controller, an operational or fault status of the second cell controller transmitted to the first controller, and / or a fault in a component of the handshake circuit.

[0245] In some embodiments, the output of the finite state machine further comprises states controlled by inputs from the first cell controller to control the status of the at least one switch.

[0246] In some embodiments, the handshake circuit comprises a first circuit portion and a second circuit portion, the first circuit portion configured for control by the first cell controller, the second circuit portion configured for control by the first second controller, the first and second circuits connected by a single link. Single link examples are discussed further below, and may be an analogue based circuit, serial analogue, or serial digital based communication channel. In some embodiments, the handshake circuit is configured to control a single analogue link in one of three or more states, each state represented by a different current magnitude.

[0247] In some embodiments each cell controller is configured to operate in at least an operational mode, or one or more fault modes based on the one or more handshake signals received via a handshake link, which may include single or multiple handshake signal transmission paths. In the operational mode, the cell controller is configured to operate the switches of the first switch group, and in a fault mode, selectively the cell controller is configured to operate at least one switch in a second switch group based on a received handshake signal. States of the handshake link include an operational or fault status of a first cell controller transmitted to a second cell controller, a control signal determining the on state of at least one switch in a second switch group, a control signal determining the off state of at least one switch in the second switch group.

[0248] Some examples of handshake signal transmission include serial transmission. All serial transmission is time domain transmission. In order to let failure modes, result in the relaxed state of the handshake circuit, the handshake circuit transmitter would normally be sending pulses over a serial link which gets received and the receiver would normally be expecting it to come within a certain schedule within a certain time window. If it doesn't arrive within that time window, the receiving cell controller would assume that the transmitting cell controller was not able to send the transmission either because the transmitting cell controller was malfunctioning or the power supply had failed, or other failure modes, such as when the transmitting cell controller has deliberately not to send a signal in order to signal that there was a fault that it knew about, for example, upon detection of a switch or cell failure. Conversely, if the receiving cell controller wanted to send a NOT OK signal back via a feedback signal, then in some embodiments the receiving cell controller is configured not to transmit its serial data back, and therefore the transmitter side cell controller would realise the message has not arrived within a scheduled time window; or in other embodiments, the receiving cell controller passively if the power supply was to go down on the receiver side the feedback signal would be zeros. Therefore, the relaxed state of the handshake circuit may be implemented in a number of ways based on time-based signal control.

[0249] Handshake signal transmission - Single analogue link

[0250] Figure 5A illustrates an example of handshake signal transmission circuit between cell controllers where a single analogue link 508 connects two handshake circuits from switch group CCn to switch group CCn+1.

[0251] In some embodiments, the handshake circuit signals are analogue signals transmitted via a single link. In some embodiments, the signals comprise a combination of voltages indicative of particular data. In some embodiments, the signals comprise current magnitudes where the magnitude and / or direction are indicative of particular data.

[0252] Figure 15 shows a schematic of logic elements operable with a single analogue link where HS_FB signal, HS_OK and HS_CMD signals are transmitted through a single analog link 508 within a handshake circuit. A current source is used to modulate and demodulate handshake signals to provide handshake functions and level-shifting. The CMD signal, the HS_OK signal, and the HS_FB signal are represented by analogue current levels (0, 1 , 10 mA) on the single handshake link 210. Both HS_OK and HS_FB can cause a 0mA state of the handshake circuit which is the relaxed state of the handshake circuit. This state is caused by a variety of fault modes including: a loss of a power supply to the handshake circuit and / or a cell controller, a fault in a component of the handshake circuit, an operational or fault status of the first cell controller transmitted to the second controller, and an operational fault status of the second cell controller transmitted to the first controller.

[0253] In the depicted circuit, the CMD signal causes either a 1 mA or a 10 mA state of the handshake circuit and is used to lead or command the switch which is selectively controlled by the adjacent cell controller based on the HS_OK and HS_FB signals. During normal operation, the CMD signal being an ON signal is encoded into a 10 mA current state by the transmitter portion, and decoded from the 10mA state by the receiver portion, to turn ON the switch; the CMD signal being an OFF signal is encoded into a 1 mA current state by the transmitter portion, and decoded from the OAm state by the receiver portion, to turn OFF the switch.

[0254] Upon fault modes, either or both of HS_OK or HS_FB signals cause a 0 mA state in the handshake link 210, which is interpreted by whichever cell controller that is still healthily functional to attempt to address the fault by closing a predetermined switch that it is preconfigured to and able to close, and in the process also ignore and / or override the CMD signal.

[0255] If the fault is from cell controller n, then the HS_OK is transmitted by controller n and received by controller n+1 , and cell controller n+1 responds by closing the switch that’s selective controlled by it. If the fault is from cell controller n+1, then the HS_FB is sent by controller n+1 and received by controller n, and cell controller n responds by closing a switch within controller n’s switch group (m) other than the one that is selectively controlled by controller n+1.

[0256] Handshake signal transmission - parallel digital

[0257] Figure 5B illustrates an example of a handshake signal transmission circuit where three parallel transmission lines connect two handshake circuits from switch group CCn to switch group CCn+1. In this example, a digital isolator, such as an optocoupler, connects each circuit. Isolators may be required where switch groups do not share a common ground and voltage offsets between groups require offsetting or mitigating. Figure 5B shows a similar example where an impedance control device provides an interface between handshake circuits.

[0258] In the depicted example, the three parallel transmission lines correspond with three transmitters and three receivers. The signals are: the handshake command signal from CCn to CCn+1, a handshake OK signal from CCn to CCn+1 , and the handshake feedback signal from CCn+1 to CCn.

[0259] A digital isolator (such as an SO-8 or SO-16 digital isolator chip) is one example of a suitable interface component, has inherent isolation and can have its both sides at different voltage potentials. Such a device lends itself well to being used as a handshake circuit which also functions as a level shifter.

[0260] The advantage is digital isolator embodiments are easy to realise and design. Another advantage is that given these are IC chips and not discrete circuit components which potentially provides more reliability.

[0261] The impedance control device as seen in Figure 5C for the impedance control method, each of the impedance control elements Z1 , Z2 and Z3 can be implemented by a pull-up level shifter circuit 602 such as shown in Figure 6 which is a pull up source, a pullup resistor, and a mosfet. Alternatively, each of Z1 , Z2 and Z3 may be implemented using capacitor or transformer-based coupling methods or any other implementations that provide either isolation and / or level shifting as may be desired. The circuit of Figure 5B uses three separate lines, each can be designed to relax into a “failure state” of each handshake link. For example, if the OK line transmits an OK signal but a component has failed in the CMD line, the failure in the CMD line may not automatically or directly result in a NOT OK signal on the OK line, and thus the adjacent controller may not be signalled to “take over” to assert its switch. A work around may be that either CMD or OK line being relaxed into the relaxed state (e.g., 0 mA) to signal a handshake NOT OK status, resulting in a take-over action from the adjacent cell controller.

[0262] Handshake signal transmission - Frequency modulation

[0263] Figure 7 illustrates another example of a handshake signal transmission circuit where a transmitted signal fout is modulated, and a received signal is demodulated with a demodulator. The depicted example is based on frequency modulation and the handshake signal may contain one signal or multiple serial signals. Other forms of modulation can be implemented as desired.

[0264] In FM modulation, the handshake data is encoded in a variation of a carrier signal frequency, and the demodulator is configured to extract this information. In order to send signals back - receiver de-tunes the circuit by altering its impedance. In other words, the frequency demodulator would need to change its loading characteristics to detune the frequency. The frequencies are derived from partly tuning on the transmitter and partly tuning on the receiver, so that they are each able to detect that both sides are ok.

[0265] In some embodiments, a further state is encoded by frequency = 0 (DC). The advantage to this is that this can also possibly be realised using a single wire to connect to adjacent cell controllers.

[0266] In some embodiments, an interface component Z is required, such as the transmitter side (at a first controller) and the receiving side (at the adjacent controller) have ill- defined ground voltages, level shifting is still required and may be achieved with the impedance control element of Figure 6.

[0267] In some embodiments, 0 Hz can represent the “relaxed state” to signify a fault and would occur, for example, in a fault caused by a power supply failure.

[0268] Each cell controller can also be programmed to transmit a 0 Hz signal upon detection that a switch it monitors has failed. Some component failures may also result in 0 Hz. Other frequencies can be used to signal a fault, such as when a frequency is too much higher or lower than the predefined frequencies for the OK, CMD and FB signals. For example, a component failure in a part of the handshake circuit may result in the inability to achieve the pre-defined frequencies or the frequencies that the other cell controller is configured to expect.

[0269] Handshake signal transmission - Serial bi-directional

[0270] Figure 8 shows a shift register may be used to serialise the data bits and send them to an adjacent cell controller. An advantage of this form of transmission technique is that the shift register could be possibly implemented by a cell controller. Here, the data is clocked in and demodulated as part of time domain multiplexing. Impedance control elements may be required and, in some embodiments, the isolating elements also provide a level shifting function.

[0271] Handshake signal transmission - Serial daisy chain

[0272] Figure 9 shows a daisy chain arrangement of shift registers which support both parallel inputs and parallel outputs. Compared with the serial bidirectional embodiment, here the clock is shared, the data does move around in circles.

[0273] Failsafe operation

[0274] Figure 13 shows a diagram of system components which contribute to failsafe functionality across a variety of the above-described failure possibilities. In particular, a first failsafe is addressed by functions of the handshake circuit according to the associated failure monitoring inputs such as a cell failure or switch failure. A second failsafe is addressed by functions of the handshake circuit according to the associated failure monitoring inputs such as a failure of a component of the handshake circuit. A third failsafe is based on the operation of the MFD circuit: when failure is not addressed directly by the handshake circuit, MFDs arbitrate the final states of the switches to ensure that the RBS continues to operate.

[0275] Accordingly, in some embodiments, the system comprises any combination of the above-described failsafe functions.

[0276] Self-healing

[0277] In some embodiments, the system is configured to implement a self-healing function whereby a target output voltage is met for a combination of series connected cells which do not include cells in a switch group associated with an identified fault. Figure 14 shows the voltage output of the 114 system. After a fault mode has occurred, the system recovers after just a few cycles (each cycle being 20 milliseconds in a 50Hz AC example). Following the failure, at stage 1 , the immediate action by the adjacent nodes to maintain the current and that is using the handshake line to immediately reroute power. But it's not an optimal routing and actually hasn't fully restored the waveform. However, the central controller has not received any update that those cells are not available, and so will include them a determination of cells to connect to generate the target output voltage up until a point at stage two, where the central controller now receives data from a cell controller that that node has failed and recalculates all of the nodes.

[0278] The above example assumes an open loop control scheme, in a closed loop control the complete self-recovery can occur within just one cycle. In a closed loop control scheme, no one device calculates how many cells are needed to provide a certain voltage, what you do is you keep adding more cells until you reach the demand. So upon detection that voltage has dropped below the demand, another cell will be substituted in place of the failed or inactive cell.

[0279] The following description is made with specific reference to the exemplary handshake circuit shown in Figure 2A and 2B unless noted otherwise.

[0280] Handshake circuit with signal transmission from a single analogue link

[0281] Figure 2A shows an exemplary embodiment of a reconfigurable battery system where there are a plurality of cells 102a, 102b, 104a, 104b selectively connectable in series to control an output voltage. The arrangement of cells in this example is based on the circuit structure shown in Figure 3A. The system includes a switching circuit comprising a plurality of switches arranged to, individually or in combination, selectively control the connection of each cell in the plurality of cells with the circuit output terminals. The switching circuit has at least a first switch group and a second switch group, each group comprising switches arranged to control a selection of cells. Here, a first switch group includes switches operable to control the connection of cells 102a, 102b under the control of a cell controller n and a second switch group includes switches operable to control the connection of cells 104a, 104b under the control of a cell controller n+1. The system includes a plurality of handshake circuits, each configured to control one or more handshake signals. The handshake circuits comprise circuit parts including a transmitter under the control of cell controller n 222, and a receiver under control of the cell controller n+1 202. Each cell controller is configured to operate in at least an operational mode or one or more fault modes based on the one or more received handshake signals. In the operational mode, a cell controller will operate the switches of the first switch group. In a fault mode, a cell controller will selectively operate at least one switch in another switch group based on a received handshake signal.

[0282] The exemplary circuit has a Tx subcircuit and Rx subcircuit connected by a handshake control link. The receiver subcircuit has:

[0283] • Rx power input configured to provide power to the Rx subcircuit;

[0284] • A controller status input configured to receive a signal indicative of cell controller operation AND spoil handshake control link via the assertion cell controller NO OK assertion switch; • A cell controller NOT OK assertion switch circuit “an input configured to receive a signal indicative of the cell controller operational status and / or cell failure(etc)”

[0285] • Decoder / resistor ladder configured to decode and output OK and CMD states on the handshake control link;

[0286] • A current mirror circuit configured to mirror the current (information) from the handshake control link to the decoder I resistor ladder.

[0287] The Tx subcircuit has:

[0288] • A Tx power input configured to provide power to the receiver circuit;

[0289] • A controller status input configured to receive a signal indicative of cell controller operation AND spoil handshake control link via the assertion cell controller NO OK assertion switch;

[0290] • Current mirror;

[0291] • A NOT OK switch input;

[0292] • An encoder I current source.

[0293] The Rx and Tx circuit operate to control current across the control link in one of a plurality of states, the states as set out in relation to the state machine of Figures 4 and 12.

[0294] In particular, the power source 114 is configured to supply power to the handshake circuit 200 which is also the power supply for the cell controller CCn+1. The cell controller 222 on the left CCn is the “leader” during normal operation in the depicted diagram due to the inclusion of the handshake transmitter circuit while the cell controller 224 on the right CCn+1 is the follower due to the inclusion of the handshake circuit receiver.

[0295] The logical control of the whole switch group of SGm including switch 106 Am and switch 108 Cm (and Bm). Controller CCn in normal operation asserts control of switch Am via level shifting, which is required because of the ill-defined, unspecified or varying voltages between the ground 110 of Controller CCn (and mCCn) and the ground 112 of Controller CCn+1 (and mCCn+1) (command signal needs to be of a different voltage). The grounds are of variable voltages due to the difference in current paths and voltage when switch A is closed (and switch C open) as opposed to when switch C is closed (and switch A open).

[0296] The circuits of Figure 3A, and others shown in Figure 10 have an operational rule where each switch group must only have 1 switch closed per group at any time to avoid shorting cell terminals. If the two cell controllers mCCn and mCCn+1 were to make independent decisions, then synchronisation would become complex. Thus, in near to real time (<1 ps) mCCn is able to affect the state of switch 108 Cm via a gate drive circuit, switch Bm, and switch 106 Am through level shifting.

[0297] Fault mode of switch C failing open

[0298] The cell controller 220a on the left mCCn also monitors Switch 108 Cm via an MFD (Mosfet Failure Detection) signal from the gate drive circuitry of switch 108 Cm. In some embodiments, an MFD is a short circuit protection circuit (SCPC) connected with each switch of a switch group. There will be more description of how it works later. The MFD signal is directly connected to the 220a mCCn cell controller. In case a failure of Switch 108 Cm is detected, 220a mCCn is notified of this failure and asserts a NOT OK signal via 202a1 dOP_HS_Tx_OK on the left (Transmitter 212a Txn), which spoils the handshake link by causing 0 mA in the 210 handshake link, which in turn results in a NOT OK signal via 202b2 dlP_HS_Rx_OK on the right (Receiver 202b Rxn+1), which is inputted to 202b1 mCCn+1 to let it know to “take over” because a failure has occurred. The take-over action can, for example, entail the immediate closing of switch 106 Am assuming 108 Cm has failed open. Due to the mechanism of the MFD, the MFD of switch 108 Cm will trigger if switch 108 Cm fails OPEN or if Switch 106 Am fails SHORT.

[0299] A similar sequence follows when Switch 106 Am has failed short. If the MFD of switch 108 Cm is triggered, this could imply that Switch 106 Am has failed SHORT. Since Switch 106 Am has failed short, a high short circuit current will be developed when mCCn attempts to turn ON switch 108 Cm, resulting in the MFD of switch 108 Cm to trigger. Once the MFD of switch 108 Cm triggers, Micro mCCn “spoils” the handshake link by causing 0 mA in the 210 handshake link, which in turn results in a NOT OK signal via 202b2 dlP_HS_Rx_OK on the right. Micro mCCn sees 202b2 dlP_HS_Rx_OK = 0V (NOT OK) and leaves Switch 106 Am ON (CLOSED) (i.e. doesn't try to turn it OFF(OPEN)). The result for either a OPEN circuit failure of switch 108 Cm or a SHORT circuit failure of Switch 106 Am is the same Accordingly, the cell controller on the right CCn+1 is configured as follows:

[0300] • Cell controller on the right CCn+1 is the “follower” during normal operation and operates switches in its switch group.

[0301] • To monitor a switch in its control group (observing Switch 106 Am), ready to “take over” as a backup controller for switch Am.

[0302] • To monitor Switch 106 Am via the MFD signal from the gate drive circuitry of Switch 106 Am.

[0303] • To provide backup control of Switch 106 Am of SGm (202b cell controller asserts switch 106 Am) in case the “leader” controller (CCn) fails.

[0304] Fault mode of switch A failing open

[0305] When MFD detects that Switch 106 Am has failed OPEN, this failure is detected by 202b mCCn+1 , which sends a NOT OK signal via 202b1 dOP_HS_Tx_FB to spoil the handshake link by causing 0 mA in the handshake link 210, which in turn results in a NOT OK signal via 202a2 dlP_HS_Rx_FB on the left (Txn), which is inputted into 220a mCCn to let it know that CCn+1 is not ok so that 202a mCCn should assert its switch 108 Cm, for example by immediately closing switch 108 Cm assuming that 106 Am has failed OPEN.

[0306] Due to the mechanism of the MFD, the MFD of switch 106 Am will trigger if switch 106 Am fails OPEN or if Switch 108 Cm fails SHORT. A similar sequence follows when Switch 108 Cm has failed short. If the MFD of switch 106 Am is triggered, this could imply that Switch 108 Cm has failed SHORT. Since Switch 108 Cm has failed SHORT, a high short circuit current will be developed when mCCn+1 attempts to turn ON switch 106 Am, resulting in the MFD of switch 106 Am to trigger. Once the MFD of switch 106 Am triggers, Micro mCCn+1 “spoils” the handshake link by causing 0 mA in the 210 handshake link(via sending a NOT OK in 202b1 DOP_HS_TxFB, which in turn is reflected in a NOT OK signal 202b1 dOP_HS_TxFB on the left. Micro mCCn+1 sees 202b1 DOP_HS_TxFB = 0V (NOT OK) and assumes Switch 108 Cm ON (CLOSED) (i.e. doesn't try to turn 106 switch Am ON (CLOSED), keeping its 106 switch Am OPEN). The result for either an OPEN circuit failure of switch 106 Am or a SHORT circuit failure of Switch 108 Cm is the same.

[0307] In the circuit there is an input configured to receive a signal indicative of a cell controller operational status, 204a Assertion switch (for cell controller 220a mCCn NOT OK). The input is activated by 202a1 dOP_HS_Tx_OK from 220a mCCn. This digital output signal is output from cell controller 220a mCCn upon awareness of an error, or upon MFD (Mosfet Failure Detection) signal from switch 108 Cm gate drive circuitry, in the case that switch 108 Cm has failed. Note MFD signal from 108 Cm could also mean that switch 106 Am has failed SHORT.

[0308] Switch 204a (which is controlled by 202a1 dOP_HS_TxOK) is responsible for providing a voltage to the base of Q4a 230. When switch 204a is OFF, the voltage (around 2.6V) is not present on the base of Q4a 230 and hence the handshake link is spoiled. (In order for the current source Q4a 230 to work, the base of Q4a 230 should be -2.7V, -> emitter of Q4a = 2.7V - 0.7V = 2V and the current is determined by resistors R16 and R17. Therefore, if the base of Q4a (230) = 0V, handshake link current = 0mA).

[0309] Figure 2B shows a simplified view of the circuit of Figure 2A. Each Handshake circuit 200 is made up of the Transmitter (Txn) in the current controller CCn and the Receiver (Rxn) in the next adjacent controller CCn+1. The handshake circuit depicted in Figures 2A and 2B are powered by the 12V power supply 114 of the cell controller CCn+1 or the 12V power supply of n (CCn) (not shown). Note the 226 diode OR gate to select either of the 12V power sources based on external conditions such as whether switch A or C is ON or if one of the switches is experiencing a transient. Handshake circuit functions to provide level shifting during normal operation. In this specification, the handshake circuit 200 may also be referred to as a level shifting circuit.

[0310] Handshake signals during normal operation include transmission of the command signal: CMD = ON , OFF. Where CMD - Originates from mCCn at the transmitter side 202a3 dOP_HS_TxCMD, propagates into a digital output signal at the receiver side 202b3 dlP_HS_RxCMD to drive switch Am. During normal operation, CCn leads the entire Switch Group m (Am, Bm,Cm). CCn+1 only monitors. The command signal and monitoring is conducted via the single wire link between the transmitter portion 212a and receiver portion 212b of the handshake circuit 200. In this specification, this wire is referred to as the handshake link 210 in this specification.

[0311] Command Signal level shifted Level shifter signals include a command signal CMD, which drives switch A ON or OFF based on the current magnitude in the handshake link 210. In this embodiment, a 10 mA state of the handshake link 210 represents the ON command to switch A, and a 1 mA state of the handshake link 210 represents the OFF command to switch A. Note that in alternative embodiments there could be more I evels: 20 mA, 30 mA, etc. For exa m p I e :

[0312] Referring to Figure 2A, the level shifter 200 between the transmitter 212a TXn and the receiver 212b Rxn+1 is shown. The level shifting circuit 200 Is this completed circuit via the use of a current source 208a. The 12V power supply 114 of the right controller CCn+1 provides power for this level shifting circuit.

[0313] Current source / encoder

[0314] The current source / encoder 208a is the right branch for 1 mA from the current source, and the left branch (switch 228) creates a parallel resistance when the 228 switch is closed leading to 10mA.

[0315] A third state - a relaxed state of the handshake circuit

[0316] There is a third state which is a 0 mA state of the handshake link 210 representing a Not OK state. This can also be understood as a “relaxed” state of the handshake circuit as a loss or power results in this state, amongst many types of fault modes. In a fault operation (as opposed to normal operation), CCn+1 detects fault then “take over” switch A. When such a fault is detected, there being always one switch operable by a working controller (closable) is enabled by partitioning controller domains to overlap partially with switch groups. So that the next controller can “take over”, upon detection of the fault handshake signal. Related is the software preprogramed default action to close which switch and open which switch upon detection of a failure.

[0317] Other failure modes are also anticipated by the circuit, including:

[0318] • A failure of a component in the handshake circuit;

[0319] • A gate drive circuit failure;

[0320] • Digital controller failure (e.g. cell controller , ASIC);

[0321] • 12 V power supply (114 of Figure 2A) - if this fails the level shifter will not work;

[0322] • 3.3V power supply (232 of Figure 2B) - 3.3V fails, unable to create 3.3V unable to create 2.7V thus no current can be generated in the current source.

[0323] A feedback signal for OK in the reverse direction (receiver in CCn+1 -> transmitter in CCn) where 202b1 dOP_HS_TxFB is a digital output signal of 202b mCCn+1 to let 202a CCn know that it (202b mCCn+1) is NOT OK. So it is a way for the receiver side 212b Rxn+1 to let the transmitter side Txn 212a know that there’s a problem at the receiver side cell controller 202b mCCn+1.

[0324] Note that 202b1 dOP_HS_Tx_FB being toggled “NOT OK” means a 0 mA state is created in the handshake link and via 206a current mirror this “NOT OK” signal is mirrored in the digital input signal 202a2 dlP_HS_RxFB, inputted into cell controller 220a mCCn to notify mCCn that the receiver side 220b mCCn+1 is NOT OK. Transmitter 212a

[0325] Figures 2A and 2B also show a handshake circuit transmitter including various components of the transmitter portion 212a of the embodiment shown in Figure 2B. Level shifting of command signals

[0326] Via the current source / encoder 208a, a digital output signal from mCCn denoted dOP_HS_TxCMD (labelled 202a3) passes through switch 228 and this digital command signal is encoded into a 10 mA state of the handshake link 210 representing the ON command to switch A, and a 1 mA state of the handshake link 210 representing the OFF command to switch A. Note: In alternative embodiments there could be more levels: 20mA, 30mA, etc.

[0327] Choice of current values

[0328] The values of the current magnitudes represent various states. In particular, 1 mA in the handshake link denotes an "all OK" state, which is the state a system will be in without any detected faults. It is prudent for this current to be as low as possible to minimise operating power of the system since this will be the most common minimum current in the link (maximum current = ~10 mA when the CMD signal is activated). Further, it is advantageous to provide a readily distinguishable difference between the two most common states. In this example, there is an order of ten difference between the two current states of 1 mA and 10 mA. Other representations are equally possible, such as 0.5 mA and 5 mA) in order to account for component tolerances in the receiver circuit as well as high transient dV / dt situations that the system faces. The current representing the state should also be readily distinguishable from the noise floor.

[0329] Third state (Relaxed state) - 0mA (Handshake OK signal - dlP_HS_RxOK) Most failure modes of these circuits result in a relaxation - 0 mA - in the handshake link 210. The receiver is configured to interpret the signals as follows:

[0330] Relaxation of the handshake link 210 (0 mA) results in 202b2 dlP_HS_RxOK (202b2) being NOT OK (0 in the table). And this digital input signal is inputted into cell controller 220b mCCn+1 to let it know to “take over” because a failure has occurred.

[0331] Encoder / Current source 208a

[0332] An OFF command is encoded into a 1mA current in the handshake link 210. The OFF command is sent via the digital output signal 202a3 dOP_HS_TxCMD) 1 mA of current flow will flow through my pull up resistor, regardless of the voltage and it's pulled up and also regardless of the resistance is the most important one. And this lends itself well to having an ill-defined voltage between the 110 grounds of the two circuits and gives me a very good level shifting ability which is able to deal with unspecified or varying voltages between them by using the current source as current as an intermediate variable.

[0333] An ON command is encoded into a 10 mA current in the handshake link 210. The ON command is sent via the digital output signal 202a3 dOP_HS_TxCMD) 10 mA created by a second resistor in parallel with a 228 switch (shown in the encoder 208a).

[0334] Current mirror 206a

[0335] The current mirror 206a mirrors the base current of Q4A 230. If the base current is high, it indicates at mCC(n+1) has set dOP_HS_TxFB low (indicating a fault).

[0336] Assertion switch 204a (for cell controller 220a mCCn NOT OK) The 204a Assertion switch is activated by 202a1 dOP_HS_Tx_OK from 220a mCCn. This digital output signal is output from cell controller 220a mCCn upon awareness of an error in itself, or upon MFD (Mosfet Failure Detection) signal from switch 108 Cm’s gate drive circuitry, in the case that switch 108 Cm has failed. Note that an MFD signal from 108 Cm could also indicate that switch 106 Am has failed SHORT. Switch 204a (which is controlled by 202a1 dOP_HS_TxOK) is responsible for providing a voltage to the base of Q4a 230. When switch 204a is OFF, the voltage (around 2.6 V) is not present on the base of Q4a 230 and hence the handshake link is spoiled. (In order for the current source Q4a 230 to work, the base of Q4a 230 should be ~2.7 V, -> emitter of Q4a = 2.7V - 0.7V = 2V and the current is determined by resistors R16 and R17. Therefore, if the base of Q4a (230) = 0V, handshake link current = 0mA) Receiver 212b:

[0337] Level shifting - Handshake CMD signal 202b3 dlP_HS_RxCMD to be input into the gate driver of switch 106 Am to directly drive it. Receiver 212b side needs to take the current 10 mA 1 1mA sent from the Transmitter 212a and turn it into something that the gate driver can use to activate switch 106 Am. dlP_HS_RxOK (202b2) represents a Handshake OK signal. The receiver is configured to interpret the signal as follows:

[0338] Current mirror 206b

[0339] A current that flows in the collector of the left transistor (Q2A) will be copied and mirrored to flow in the collector of the right transistor (Q2B).

[0340] Decoder / Resistor ladder 208b

[0341] There is a decoder / resistor ladder 208b. It consists of two stacked resistors able to decode trinary levels of current - 10mA, 1mA, and 0mA into two separate binary voltages - one drives 202b2 dlP_HS_RxOK, one drives 202b3 dlP_HS_RxCMD.

[0342] This takes the copied current and decodes it into voltages via the two resistors (R10, R13) in the current ladder 208b.

[0343] Lower resistor R13, decodes into 202b3 dlP_HS_Rx_CMD which in turn drives switch Am after buffering (202b4) - See figure 2A. This is the CMD ON / OFF signal during the normal operation of CCn to “lead” the opening / closing of switch 106 Am via the level shifting of the handshake link, in real-time (a few ps). Meaning the cell controller 220a mCCn has direct control of the gate driver of switch 106 Am during normal operation, (via signals 202b3 and 202b4 connected to switch Am’s gate driver shown in Figure 2A).

[0344] Upper resistor R10, decodes into 202b2 dlP_HS_Rx_OK which in turn is received by cell controller mCCn+1 to be notified that a failure has occurred in the handshake circuit (including the level shifting circuit) or in the left controller CCn, so that mCCn+1 needs to “take over” the assertion of switch Am - for example, by closing switch Am assuming that mCCn and / or the level shifting is not ok and thus no longer able to “lead” the operation of switch Am.

[0345] This is designed such that when V2=l x (R1 +R2), R1 and R2 are designed such that V2 is high enough to trigger the CMOS input of 202b2 dlP_HS_RxOK only if and when I is >= 1 mA.

[0346] Note that when 202b2 dlP_HS_Rx_OK is a NOT OK signal, mCC(n+1) will take over and try to force switch 106 Am ON (CLOSED) and keep it closed.

[0347] Assertion switch 204b (for cell controller 220b mCCn+1 NOT OK)

[0348] An assertion switch 204b is activated by digital output signal 202b1 dOP_HS_Tx_FB from 220b mCCn+1.

[0349] This is the Feedback signal (FB) from CCn+1 to CCn to let CCn know if CCn+1 is NOT OK. (In the reverse direction of the 202b2 dlP_HS_RxOK mechanism - reverse direction meaning from CCn+1 to CCn).

[0350] Note that 202b1 dOP_HS_Tx_FB being toggled “NOT OK” means a 0 mA state is created in the 210 handshake link and via 206a current mirror this “NOT OK” signal is mirrored in the digital input signal 202a2 dlP_HS_RxFB, inputted into cell controller 220a mCCn to notify 220a mCCn that the receiver side mCCn+1 is NOT OK. Specifically, once power to the 210 handshake link is cut off (0 mA state), the transistor Q4A cannot work. Its base effectively looks just like a diode. This means that a much higher current than the normal base current of transistor Q4A (230 in Figure 2B) will flow through the 206a current mirror. Therefore dOP_HS_RxFB will transition from LOW (in this case signalling all “OK”) to HIGH (in this signalling “NOT OKTFault”).

[0351] A sequence of cell controllers

[0352] Referring to Figure 3B, each cell controller has 3 digital outputs (dOP) and 3 digital inputs (dIP). These signals are also shown in Figure 2A and 2B. Referring to Figure 3A, each handshake (HSn) circuit has a transmitter portion Txn and a receiver portion Rxn. Txn is part of CCn in terms of physical proximity and electrical connections, digital signals from and to Txn are tied to cell controller mCCn. Rxn is part of CCn+1 in terms of physical proximity and electrical connections, digital signals from and to Rxn are tied to mCCn+1.

[0353] Each cell controller mCCn is tied to the transmitter portion (Txn) of CCn and the receiver portion (Rxn-1) of the previous CCn-1 , which is another way of saying controller CCn+1 has a receiver portion Rxn for receiving handshake signals from the previous cell controller CCn. CCn+1 also has a Transmitter portion Txn+1, noting that the Transmitter portion Txn+1 is for transmitting the handshake signal to from Txn+1 to Rxn+1, Rxn+1 being part of the next adjacent controller CCn+2.

[0354] Ability to send OK to the next controller, ability to send FB to the previous controller. FB is effectively an OK in the reverse direction.

[0355] With reference to the components of the system outlined in Figure 3C, each controller contains the handshake circuit Tx portion and Rx portion. Adjacent controllers are connected only via a single signal wire of the handshake circuit.

[0356] All six signals 202a1 , 202a3, 202a2, 202b2,202b3,202b1 are tied to the cell controller mCCn. Left three signals 202a1 , 202a3, 202a2 are tied to the 304a transmitter (Txn) side of CCn. Right three signals are tied to the 203b receiver (Rxn-1) side of CCn-1 , located to the left of CCn’s transmitter 304a, and meant to receive signals from transmitter 302a (Txn-1) of the previous cell controller CCn-1.

[0357] 202a2 dlP_HS_RxFB (n) is essentially the same signal as 202b1 dOP_HS_TxFB(n+1), it’s CCn+1 telling CCn that CCn+1 is not ok via a feedback signal 202b1 dlP_HS_TxFB travelling from right to left (from 304b Receiver Rxn+1 to 304a Transmitter Txn).

[0358] Power Failure (12V or 3.3V)

[0359] In the circuit of Figure 2A, if 12V or 3.3V or the processor fails on CCn, switch 106Am will be closed and the following sequence will take place:

[0360] • - 12V or 3.3V or micro failure on CCn.

[0361] • - Transistor Q4 will turn OFF -> 0mA current in 210 Handshake link.

[0362] • - dlP_HS_RxOK is LOW on CCn+1

[0363] • - micro mCCn+1 takes over and switches 106 Am ON / CLOSED.

[0364] If 12V or 3.3V fails on CCn+1 , switch 108 Cm will be closed and the following sequence will take place:

[0365] • - 12V or 3.3V or micro failure on CCn+1.

[0366] • - dOP_HS_TxFB will go to 0V -> 0mA current in 210 Handshake link and no power to 210 Handshake link.

[0367] • - dlP_HS_RxFB will transition from LOW (all OK) to HIGH (Fault).

[0368] • - micro mCCn closes switch 108 Cm.

[0369] Cell failure

[0370] Cell failures include the below:

[0371] • Too high / low module voltage and / or cell voltage of individual battery cells of the battery unit.

[0372] • Modules and / or cell temperature too high / low during charging / discharging.

[0373] • Excessive difference in cell voltages between individual battery cells (debalancing) of the battery unit.

[0374] • Other measurements that indicate a critical failure of battery cells of the battery module / battery unit.

[0375] In some embodiments there is cell monitoring circuitry and / or software which, upon detection of cell failures such as those listed above, sends a fault signal to the central controller, which in turn instructs cell controllers to bypass the problematic cells. However, this communication occurs via the stack communication bus and the decision to bypass the problematic cells are made via algorithms in the central controller. In case that there is a fault in the communication bus, the central controller, a bug in the software, or a higher-level fault such that a prompt assertion of switches to bypass the cells cannot be relied upon, the handshake circuit can be used to force the bypass locally. In this way there’s also redundancy in responding to cell failures. An added benefit is that the handshake circuit is able to react much faster than the stack central controller.

[0376] Referring to Figure 11, specifically, if a cell failure (1112, 1114) is detected by the cell controller mCCn 1106, then mCCn is configured to send a NOT OK feedback signal 202b1 via the handshake link to mCCn-1 1108 to cause it to assert its switch C 1102 closed, and to also send a NOT OK handshake_OK signal to mCCn+1 1110 to assert its switch A 1104 closed, leading to both cells 1112 1114 being bypassed in a manner faster and more reliably than via the a communication bus and a central controller could manage this task. This avoids catastrophic events occurring.

[0377] Cell controller failure including the switch that it monitors directly

[0378] Cell controller failures cause the same response as power failures. Failure of a switch that the cell controller monitors is also responded to in the same way by the embodiment, as described below.

[0379] Note that although a failure in either adjacent cell controllers causes the same state in the handshake link (0 mA), the embodiment is able to discern which cell controller is not ok by seeing that if it’s 202b1 dOP_HS_Tx_FB on the right (and thus also dlP_HS_Rx_FB on the left) that’s the NOT OK signal or if it’s 202a1 dOP_HS_Tx_OK on the left that’s the NOT OK signal. The former indicates that 220b mCCn+1 (right) has failed so that 220a mCCn (left) should assert its switch 108 Cm closed and keep it closed and assert switch 106 Am open and keep it open because switch 106 Am is no longer reliably monitored by 220b mCCn+1 (right) anymore, and the latter indicates 220a mCCn (left) has failed and thus 220b mCCn+1 (right) should “take over” to assert switch Am closed and keep it closed assuming that switch 108 Cm can no longer be reliably closed anymore. In the case that assumption about which of switches 106 Am / 108 Cm can’t be closed anymore is wrong, any attempts that causes more than one switch per group be closed will trigger MFD’s (Figure 2A) default response to immediately open any switch that’s still able to be opened. This outcome is polled shortly after by the respective cell controllers which in turn informs the central (stack) controller of the fixed states of these switches. In other words, each cell controller (mCCn or mCCn+1) will know whether it has caused the handshake link to fail unless the handshake link has failed due to a component failure in the handshake link itself (which is a separate case).

[0380] For example, if mCCn reports a fault, it will do so via its dOP_HS_TxOK signal. mCCn+1 will read this via its dlP_HS_RxOK signal. mCCn+1 will know that mCCn has indeed caused the handshake link to fail because mCCn+1 itself will be reporting that it is OK via its dOP_HS_TxFB signal. So it is clear to mCCn+1 that mCCn has "spoiled" the handshake link. Now, mCCn+1 will react appropriately, by closing switch 106 Am. The reverse happens if mCCn+1 reports a fault to mCCn via dOP_HS_TxFB. Whichever cell controller (220a mCCn or 220b mCCn+1) observes the relaxed 0 mA in the handshake link 210, and knows that it itself is OK, assumes the other side has lost control (either the other cell controller is not functional, lost power, or a switch that it monitors has failed), assumes that the other side’s switch is open and cannot be closed, and proceeds to assert its own switch closed. In other words, when cell controller mCCn+1 observes a relaxed handshake link (0 mA), it “takes over” and asserts switch 106 Am closed and keeps it closed, assuming also that CCn can no longer close its switch 108 Cm. On the other hand, when cell controller mCCn observes a relaxed handshake link (0 mA), it assumes that either mCCn+1 has stopped functioning or that switch Am has failed OPEN, and it asserts its switch 108 Cm CLOSED and keeps in closed, knowing mCCn+1 and the handshake circuit combined mechanism to provide backup control of switch 106 Am can no longer be relied on. The above two scenarios result in either switch 106 Am being kept closed and switch108 Cm being kept open, or switch 106 Am being kept open and switch 108 Cm being kept closed (MFD will ensure that only one switch either 108 Cm or 106 Am is CLOSED). These fixed states are polled by their cell controllers and notified to the central controller some cycles later in soft-time so that the software in the stack controller takes their fixed states into account in continuing to operate the stack by bypassing / including unaffected cells.

[0381] If any of the assumptions are wrong leading to both switch 106 Am and 108 Cm being closed by their cell controllers, the Mosfet Failure Detection (MFD) mechanism kicks in in real time to force one of the switches open (See figure 2A). This mechanism is in real time because MFD is analogue in nature. In other words, if a handshake circuit component fails, both mCCn and mCC(n+1) will receive a fault and the first to act on it will be able to close their respective switch (either 108 Cm or 106 Am first) and the other will receive a MFD fault signal telling it to keep it's switch OPEN.

[0382] Switch failure

[0383] If cell controller mCCn at the transmitter side fails, it’s able to assert a NOT OK signal via the digital output signal 202a1 dOP_HS_TxOK, which, via 206a current mirror, toggles the handshake link into the relaxed state (0 mA). Additionally, if switch Cm, which mCCn monitors via MFD, fails, mCCn can also assert a NOT OK signal via the same digital output signal 202a1.

[0384] If cell controller mCCn+1 at the receiver side failed, it’s able to assert a NOT OK signal via the digital output signal 202b1 dOP_HS_TxFB, which, via 206b current mirror, toggles the handshake link into the relaxed state (0 mA). Additionally, If switch Am, which mCCn+1 monitors via MFD, fails, , mCCn+1 can also assert a NOT OK signal via the same digital output signal 202b1.

[0385] Handshake component failure

[0386] For most of the component failures in the handshake circuit, If it’s a component in the handshake circuit in either of the portions (left - Txn, right Rxn+1), a 0 mA results in the handshake link (relaxed state of the handshake link) and it is assumed that the level shifting is NOT OK (not working) and thus cell controller mCCn+1 “takes over” operation of switch Am. Any relaxation of the handshake link results in 202b2 dlP_HS_Rx_OK being toggled “NOT OK”, and inputted into the cell controller mCCn+1 to “take over” assertion of switch Am by closing it and keeping it closed. Upon such a failure, the default action for switch Cm is to be asserted open by its cell controller mCCn. In most cases mCCn is configured to do this via 202a2 dlP_HX_RxFB, which mirrors 202b2 dlP_HS_RxOK via current mirrors 206b or 206a. If there is a component failure in the link where both cell controllers are otherwise both active and healthy and they both simultaneously observe 0 mA, then they will both attempt to close switch106 Am and switch 108 Cm at the same time. In this particular circumstance, where neither the cell controllers are non-functional, but unable to communicate, due to a very rare component failure. In that case, then the MFD will take over and one of the MOSFETs will be forced to open by the MFD circuit to protect the MOSFETs.

[0387] Therefore, there is no disambiguation if a handshake circuit component has failed for most of the components. If a component fails, default actions (preconfigured cell controllers) are performed. If there’s a collision, then the MFD handles that occurrence.

[0388] Switch B failure

[0389] Operation of the system in relation to switch B is because it is not important for the understanding or the implementation of the invention. For all other failures than switch failures (such as a cell controller, power, handshake link components), the state of switch B (whether ON or OFF) doesn't matter because for these failures, the system will always default to only one of the 3 switches in the channel being turned ON (either A or C).

[0390] For example, For MOSFET failures, If Switch B fails open circuit: This fault will be caught when mCCn tries to turn ON switch B and switch B's MFD fails (because mCCn also monitors the MFD of switch B). The result will be that only one switch in the channel will be turned ON (most likely switch A in this case even though switch C is perfectly capable because the system may not want to discharge this cell module anymore.

[0391] If Switch B fails short circuit, and if switch A turns ON first, its MFD will trigger and mCCn+1 will spoil the handshake link. mCCn will then turn ON switch C and its MFD will fail. Now since the handshake link is already spoiled, mCCn should know that it is in fact switch B that has failed short and will leave switch C open. The result is that B is the only switch in the channel that is closed.

[0392] If Switch C turns ON first, its MFD will trigger and mCCn will spoil the handshake link. mCCn+1 will then turn ON switch A and its MFD will fail! Now since the handshake link is already spoiled, mCCn+1 should know that it is in fact switch B that has failed short and will leave switch C open. The result is that B is the only switch in the channel that is closed.

[0393] State machine and truth table

[0394] Figure 4B and Figure 12B show a truth table and depict a finite state machine for the exemplary circuits of Figure 2A and 2B. It is desired that mCCn is to (lead) operate mCCn+Ts switch (Am) when there is no fault signalled in the handshake link. This means the handshake signal CMD from mCCn directly drives mCCn+Ts switch. But as soon as there’s a fault signalled in the handshake link, we want mCCn+1 to (take over) drive mCCn+Ts switch (Am) as part of that cell controllers change from the operation mode to the fault mode. In the circuit of Figure 2A, when the OK signal is 0 (NO OK), the CMD is ignored by the handshake circuit and thus in turn ignored by switch (Am) under the next controller domain. This is because a NOT OK in the handshake link results in a 0 mA state which cannot drive switch Am ON, regardless of the value of CMD. However, in some other embodiments, the CMD signal from mCCn may be overridden by a command signal from mCCn+1 as controller mCCn+1 has taken over.

[0395] In the circuit of Figure 2A, a current source and current mirror (Figure 4B and Figure 12B), and we encode two signals into three states, such as shown in the state machine of Figure 12B and the truth table of Figure 4B. In other embodiments, multiple analogue levels can be encoded into the current magnitude increasing the number of states that can be represented on a single wire (Table 1 and Table 2) to reduce the hardware required. Having additional states can be useful in disambiguating different fault modes, for example, by having additional current levels representing additional states corresponding to different types of failures. Another exemplary application could be if the cell controller has determined that one of its mosfets has failed and wants to signal that specific failure. However, an advantage of the circuit of Figure 2A is that most failures at transmitter and receiver result in a handshake link which has relaxed to a zero current state (including even when there’s no power), which is convenient for detecting failures with analogue circuits and taking action without requiring a processor determination or other software-based function. It also has low latency due to analogue signalling, avoiding the need for a data packet to be clocked as would be the case in a serial digital link. This is very convenient as the current source is inherently a level shifter which is ideally suited to sending signals between cell controllers with dis-similar ground reference potentials.

[0396] Table 1 - Logical Embodiments - further states encoded Table 2 - Logical Embodiments - further states encoded

[0397] MFD (Mosfet Failure Detection) Circuits

[0398] In the circuit of Figure 2A, there is an MFD Circuit built into the gate drive for each switch (A, B and C). The MFD is an analogue circuit and mechanism in nature and the MFDs of all the switches within a switch group are electrically connected.

[0399] When a failure has been detected (and / or a sudden increase in current), the MFD circuit will force open all the connected switches. I.e. If either 106 Am or 108 Cm fails short the MFDs in both Am and Cm will attempt to open both switches in order to preserve whichever switch(es) that can still be saved. Specifically, If 106Am fails SHORT, the MFD on 108 Cm will trigger when mCCn tries to switch 108 Cm ON. If 108 Cm fails SHORT, the MFD on 106 Am will trigger when mCC(n+1) tries to turn 106 Am ON.

[0400] The MFD is able to only send a fault signal to the cell controller that the switch has failed, and then the cell controller would have to poll the switch (test the switch by sending a signal to open / close it) to determine if it’s failed OPEN or failed CLOSED. The MFD connects switches A B C in the same switch group, and triggers when a sudden surge in current is detected to OPEN all switches that can still be opened. Accordingly, the exemplary embodiment of Figure 2A further comprises an MFD circuit combined with the gate drive for each switch in the switch circuit.

[0401] Where in the foregoing description reference has been made to elements or integers having known equivalents, then such equivalents are included as if they were individually set forth.

[0402] Although the invention has been described by way of example and with reference to particular examples, it is to be understood that modifications and / or improvements may be made without departing from the scope or spirit of the invention.

Claims

Claims1. A reconfigurable battery system, comprising: a plurality of cells, each cell selectively connectable in a series relationship with one or more other cells, by a switching circuit, to control a combined series output voltage; the switching circuit comprising a plurality of switches arranged to, individually or in selective combinations, control the series connection, or bypass, of each cell in the plurality of cells, the switching circuit comprising at least a first switch group and a second switch group, each group comprising a selection of switches; a plurality handshake circuits, each configured to control one or more handshake signals; a plurality of cell controllers each configured to:• operate in one of an operational mode and one or more fault modes based on one or more received handshake signals,• in the operational mode, operate the switches of the first switch group, and• in a fault mode, selectively operate at least one switch in the second switch group based on a received handshake signal.

2. The system of claim 1, wherein each handshake circuit is configured to control one or more handshake signals based on detection of a fault in any one or more of:• a component of a handshake circuit,• a switch of a switch group,• a cell controller,• a cell,• a power supply supplying a handshake circuit and / or a cell controller.

3. The system of claim 1 or claim 2, wherein the switching circuit comprises switch groups and control domain groups, each switch group defined by a combination of switches comprising:• 0 closed switches breaks the series connection,• 1 closed switch either connects or bypasses the cell in / from the series connection, and• more than one closed switch causes a short circuit of at least one cell.

4. The system of any one of claims 1 to 3, wherein in a further fault mode, a first cell controller is configured to selectively close one switch of the first switch group based on one or more handshake signals from another handshake circuit.

5. The system of any one of claims 1 to 4, wherein each cell controller is further configured to, in the operational mode: operate at least one switch of the first switch group based on a handshake signal.

6. The system of any one of claims 1 to 5, wherein the handshake circuit further comprises a level shifting circuit operable to interface a cell controller to at least one switch in the switch group selectively controlled by another controller.

7. The system of any one of claims 1 to 7, wherein the one or more handshake signals comprise one or more of:• an operational or fault mode status of a first cell controller transmitted to a second controller;• an operational or fault mode status of a second cell controller transmitted to the first controller; and / or• a command transmitted from the first cell controller to control at least one switch in the first switch group for the operational mode of the first cell controller; and wherein the second cell controller is configured to replace control of the at least one switch in the first switch group based on the fault mode of the first cell controller; and / or wherein the first cell controller is configured to close a switch of the first switch group other than the at least one switch selectively controlled by the second controller based on the fault mode of the second controller.

8. The system as claimed in claim 7, wherein the fault status of the first cell controller is based on a failure of one or more of:• a switch in the first switch group configured to either connect or bypass a cell, and / or• a cell connected to a switch in the first switch group; and / or wherein the fault status of the second cell controller is based on a failure of one or more of:• a switch in the second switch group configured to either connect or bypass a cell, and / or• a cell connected to a switch in the second switch group.

9. The system as claimed in claim 7, wherein the one or more handshake signals further comprise a fault status based on a fault in a component of the handshake circuit; and in response: the second cell controller is configured to replace control of the at least one switch in the first switch group based on the fault in a component of the handshake circuit; and the first cell controller is configured to close a switch of the first switch group other than the at least one switch selectively controlled by the second controller based on the fault in a component of the handshake circuit; wherein the circuit further comprises a plurality of short circuit protection circuits (SCPC) connected with each switch of the first switch group, the SCPC configured to override the operation of the at least one switch or the switch of the first switch group other than the at least one switch.

10. The system as claimed in claim 7, wherein one or more handshake signals comprise one or more of:• a communication line for each of the operational or fault status of the first cell controller transmitted to the second controller, the operational or fault status of the second cell controller transmitted to the first controller, and / or the command transmitted from the first cell controller to control the at least one switch in the first switch group for the operational state of the first cell controller;• a communication line comprising modulated, encoded data comprising the operational or fault status of the first cell controller transmitted to the second controller, the operational or fault status of the second cell controller transmitted to the first controller, and / or the command transmitted from the first cell controller to control the at least one switch in the first switch group for the operational state of the first cell controller.

11. The system as claimed in any one or more of claims 1 to 10, wherein the handshake circuit comprises a finite state machine having an output controlled by inputs based on a fault in any one or more of the following: a component of the handshake circuit,a switch of a switch group, a cell controller, a cell, and / or a power supply to the handshake circuit and / or a cell controller.

12. The system as claimed in claim 11 , wherein the handshake circuit comprises a finite state machine having an output having states, at least one state controlled by inputs based on a fault in any one or more of the following: a component of the handshake circuit; a power supply to the handshake circuit and / or a cell controller.

13. The system as claimed in claim 12, wherein the at least one state is controlled by inputs based on any one or more of the following:• an operational or fault status of a first cell controller transmitted to the second controller,• an operational or fault status of a second cell controller transmitted to the first controller, and / or• a fault in a component of the handshake circuit.

14. The system as claimed in claim 13, wherein the output further comprises states controlled by inputs from the first cell controller to control the status of the at least one switch.

15. The system as claimed in any one or more of claims 1 to 14, wherein the handshake circuit comprises a first circuit portion and a second circuit portion, the first circuit portion configured for control by a first cell controller, the second circuit portion configured for control by a second controller, the first and second circuits connected by a single link; the handshake circuit configured to control the single analogue link in one of three or more states, each state represented by a different current magnitude; the states comprising:• an operational or fault status of the first cell controller transmitted to the second cell controller,• a control signal determining the on state of the at least one switch,• a control signal determining the off state of the at least one switch.

16. The system as claimed in any one or more of claims 1 to 15, wherein the handshake circuit comprises a first circuit portion and a second circuit portion, the first circuit portion configured for control by a first cell controller, the second circuit portion configured for control by a second controller, the first and second circuits connected by a communication link comprising: a single link, or a plurality of data lines.

17. The system as claimed in any one or more of claims 1 to 16, wherein the reconfigurable battery system further comprises an interconnected sequence of switching circuits each with a cell controller, and the handshake circuit comprises portions of: a transmitter portion configured to transmit the one or more handshake signals to the next adjacent cell controller in the chain, and a receiver portion controller configured to receive the one or more handshake signals from the previous adjacent cell controller in the chain, such that handshake circuits form a sequence of the cell controllers.

18. The system as claimed in claim 17, wherein the sequence includes a first cell controller, the next adjacent cell controller in the sequence, and the previous adjacent cell controller in the sequence, and upon detection of a cell failure: the transmitter portion connected with the first cell controller transmits a handshake signal representing a fault status to the next adjacent cell controller; the receiver portion connected with the first cell controller transmits a handshake signal representing a fault status to the previous cell controller; to control the switching circuit to bypass the cell from the series connection.

19. The system as claimed in any one or more of claims 1 to 18, wherein the reconfigurable battery system further comprises an interconnected sequence of switching circuits each with a cell controller, and the handshake circuit comprises portions of: a transmitter portion connected with a first cell controller and configured to transmit the one or more handshake signals to a second cell controller, and a receiver portion at the second cell controller configured to receive the one or more handshake signals from the first cell controller, such that handshake circuits and first and second cell controllers form at least part of the interconnected sequence.

20. The system as claimed in any one of claims 1 to 19, wherein the reconfigurable battery system comprises: a plurality of cell modules, each module comprising a first cell and second cell, each cell having two terminals and wherein one of the terminals of each of the first cell and the second cell are connected, thereby defining modules nodes comprising a first node being the first cell terminal of the first cell, a second node being second terminals of the first cell and second cell, and third node being the third terminal of the second cell; and wherein the first, second and third nodes of each of a pair of more modules in the system are linked by a set of three switches of the switching circuit; wherein the first switch group comprises three switches linking first, second and third nodes of a first and a second cell module, and the second switch group comprises three switches linking first, second and third nodes of the second and a third cell module.

21. The system as claimed in any one of claims 1 to 19, wherein the reconfigurable battery system comprises: a plurality of cell modules, each module comprising: a first and a second module terminal, a battery cell, a series switch configured to connect or disconnect the battery cell in series with the first and second module terminal, and a parallel switch configured to bypass the battery cell by the connection of the first terminal to the second module terminal; wherein the first switch group comprises the series switch and the parallel switch of a first cell module, and the second switch group comprises the series switch and the parallel switch of a second cell module.

2. The system as claimed in claim 21 , wherein the plurality of cell modules comprises a plurality of cell module pairs, wherein each pair comprises the direct connection with a common node: the first module terminal of a first cell module, the second module terminal of a second cell module, a negative terminal of a first battery cell of the first cell module, and a positive terminal of a second battery cell of the second cell module.

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