A sensor system for a zinc-air battery

Abstract

A system including a plurality of electrochemical cells and a sensor system for the same. The sensor system may utilize a multiplexer with isolation circuitry.

Description

A SENSOR SYSTEM FOR A ZINC-AIR BATTERYCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of USSN 63 / 740,480 filed December 31, 2024, the entire contents of which are herein incorporated by reference.FIELD OF INVENTION

[0002] The present disclosure relates to the field of zinc-air batteries, and more particularly to a sensor system for a zinc-air battery.BACKGROUND

[0003] The zinc-air battery technology has been known for over 100 years but has yet to be successfully commercialized. In a conventional charge cycle, an electrolyte comprising zinc hydroxide releases zinc metal in a charge section, which precipitates as a solid and accumulates in a discharge section. During discharge, the solid zinc metal is converted back to zinc hydroxide, liberating electrons in the process. The charging and discharge modes of operation for zinc-air batteries are operable via separate terminals, for which charging and discharging platforms commercially available for other battery technologies are not configured. Further, charge and discharge control over zinc-air batteries rely on sensor systems not present in conventional commercially available chargers for other types of battery chargers.SUMMARY

[0004] In general, one innovative aspect of the subject matter described herein can be embodied in an electrochemical cell system that includes a plurality of cells with first and second cells. The plurality of cells may each include a negative charge terminal and a positive charge terminal and a negative discharge terminal and a positive discharge terminal. The electrochemical cell system may be adapted to discharge power to a current sink and to charge based on powerfrom a current source. The electrochemical cell system may include charge switching circuitry operably coupled to at least one of the positive charge terminal and the negative charge terminal of the first and second cells to control supply of power from the current source to the first and second cells.

[0005] The electrochemical cell system may include a sensor system operably coupled to a first cell of the plurality of cells, and may include a multiplexer operable to selectively couple the a first negative node and a second negative node to a first input of a sensor circuit and to selectively couple a first positive node and a second positive node of the first cell to a second input of the sensor circuit. The multiplexer may include first and second positive-side optical isolators operably coupled to the first input of the sensor circuit and respectively coupled to the first positive node of the first cell and the second positive node of the first cell. The first positive-side optical isolator may be configured to selectively couple the first positive node of the first cell to the first input of the sensor circuit, and the second positive-side optical isolator may be configured to selectively couple the second positive node of the first cell to the first input of the sensor circuit.

[0006] The multiplexer may include first and second negative-side optical isolators operably coupled to the second input of the sensor circuit and respectively coupled to the first negative node of the first cell and the second negative node of the first cell. The first negative-side optical isolator may be configured to selectively couple the first negative node of the first cell to the second input of the sensor circuit, and the second negative-side optical isolator may be configured to selectively couple the second negative node of the first cell to the second input of the sensor circuit.

[0007] The electrochemical cell system may include a controller configured to direct operation of the multiplexer to selectively obtain sensor output from the sensor circuit indicativeof a voltage differential between the first positive node and first negative node and to selectively obtain sensor output from the sensor circuit indicative of a voltage differential between the second positive node and the second negative node.

[0008] The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. In particular, one embodiment includes all the following features in combination.

[0009] In some embodiments, the first positive node is a positive charge terminal, the second positive node is a positive discharge terminal, the first negative node is a negative charge terminal, and the second negative node is a negative discharge terminal.

[0010] In some embodiments, the first positive node is a positive charge terminal, the first negative node is a node of the charge switching circuitry, the second positive node is a positive discharge terminal, and the second negative node is a node of discharge switching circuitry.

[0011] In some embodiments, the sensor system is operably coupled to a second cell of the plurality of cells, where the multiplexer is operable to selectively couple a third negative node of the second cell and a fourth negative node of the second cell to the first input of the sensor circuit and to selectively couple a third positive node of the second cell and a fourth positive node of the second cell to the second input of the sensor circuit.

[0012] In some embodiments, the sensor circuit may include a differential amplifier with a first differential input and a second differential input that correspond respectively to the first and second inputs, where the differential amplifier may include an output operably coupled to an analog-to-digital converter configured generate the sensor output.

[0013] In some embodiments, the controller may direct activation of the first positive-side optical isolator and the first negative-side optical isolator to couple the positive charge terminal of the first cell to the first input and the negative charge terminal of the first cell to the second input.

[0014] In some embodiments, the first positive-side optical isolator may include a first light element and a first phototransistor operable to selectively couple the positive charge terminal of the first cell to the first input in response to supply of power to the first light element.

[0015] In some embodiments, the first negative-side optical isolator may include a second light element and a second phototransistor operable to selectively couple the negative charge terminal of the first cell to the second input in response to supply of power to the second light element.

[0016] In some embodiments, the electrochemical cell system may include first discharge switching circuitry operably coupled to the positive discharge terminal of the first cell. The first discharge switching circuitry may be operable to selectively provide current to the current sink from the first cell. The electrochemical cell system may include second discharge switching circuitry operably coupled to the positive discharge terminal of the second cell and the negative discharge terminal of the first cell. The second discharge switching circuitry may be operable to selectively provide current to the current sink from the second cell.

[0017] In some embodiments, the first and second discharge switching circuitry may be configured to substantially isolate charging and discharging of the first and second cells.

[0018] In some embodiments, the electrochemical cell system may include first charge switching circuitry operably coupled to the positive charge terminal of the first cell. The first charge switching circuitry may be operable to selectively provide current output from the current source to the positive charge terminal of the first cell. The electrochemical cell system may includesecond charge switching circuitry operably coupled to the positive charge terminal of the second cell. The second charge switching circuitry operable to selectively provide the current output from the current source to the positive charge terminal of the second cell, where the second charge switching circuitry may receive the current output from the current source via at least one of the first cell and the first charge switching circuitry.

[0019] In some embodiments, receipt of current output from the first cell in the second charge switching circuitry may include receiving the current output from the current source via the negative charge terminal of the first cell, and where receipt of current output from the first charge switching circuitry may include receiving the current output from the current source via at least one of a direct connection to the first charge switching circuitry and an indirect connection to the first charge switching circuitry at the positive charge terminal of the first cell.

[0020] In some embodiments, at least one of the first charge switching circuitry and the second charge switching circuitry may be operable to selectively bypass current flow into the positive charge terminal of the first cell to provide current from the current source to the second charge switching circuitry.

[0021] In some embodiments, the first charge switching circuitry may selectively bypass current flow into the positive charge terminal of the first cell by directing current to a node of the first cell that is connected to the negative charge terminal of the first cell and the second charge switching circuitry.

[0022] In some embodiments, the second charge switching circuitry may selectively bypass current flow into the positive charge terminal of the first cell by disconnecting from the negative charge terminal of the first cell and connecting to the positive charge terminal of the first cell.

[0023] In some embodiments, the controller may be operable to selectively discharge power from one or both of the first and second cells, and where the controller may be operable to selectively charge one or both of the first and second cells.

[0024] In some embodiments, the controller may be operable to control whether one or both of the first and second cells may be discharged by selectively bypassing the first and second cells via operation of the first and second discharge switching circuitry.

[0025] In some embodiments, the controller may be operable to control whether one or both of the first and second cells may be charged by selectively bypassing the first and second cells via operation of the first and second charge switching circuitry.

[0026] In some embodiments, the first discharge switching circuitry may be operable to selectively provide current to the current sink from the first cell via the positive discharge terminal of the first cell, and where the second discharge switching circuitry may be operable to selectively provide current to the current sink from the second cell via the positive discharge terminal of the second cell.

[0027] In some embodiments, the current sink may be a boost converter operable to convert power from the electrochemical cell system to power an external load.

[0028] In some embodiments, the current source may be a buck converter operable to convert external power for charging the electrochemical system.

[0029] Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited to the details of operation or to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention may be implemented in various other embodiments and of being practiced or being carried out in alternative ways not expressly disclosed herein. Also, itis to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the invention to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the invention any additional steps or components that might be combined with or into the enumerated steps or components. Any reference to claim elements as “at least one of X, Y and Z” is meant to include any one of X, Y or Z individually, and any combination of X, Y and Z, for example, X, Y, Z; X, Y; X, Z; and Y, Z.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Fig. 1 shows an electrochemical cell system according to one embodiment.

[0031] Fig. 2 shows an electrochemical cell system according to another embodiment.

[0032] Fig. 3 shows an electrochemical cell system according to yet another embodiment.

[0033] Fig. 4 shows a sensor system according to one embodiment.

[0034] Fig. 5 shows a multiplexer according to one embodiment.

[0035] Fig. 6 shows a demultiplexer according to one embodiment.

[0036] Fig. 7 shows signal output from an amplifier according to one embodiment.

[0037] Fig. 8 shows a plot of common mode voltage vs. error according to one embodiment.

[0038] Fig. 9 shows a cell of the electrochemical cell system according to one embodiment.DETAILED DESCRIPTION

[0039] An electrochemical cell system according to one embodiment is shown in Fig. 1 and generally designated 100. The electrochemical cell system 100 in the illustrated embodiment includes a plurality of cells 10-1, 10-2, 10-3 . . . 10-N, charge switching circuitry 101, and discharge switching circuitry 102. The charge switching circuitry 101 and the discharge switching circuitry 102 may be operably coupled to a controller 160, which may direct operation of the charge switching circuitry 101 and the discharge switching circuitry 102 according to one or more aspects described herein. For instance, the controller 160 may direct operation of the charge switching circuitry 101 and the discharge switching circuitry 102 such that simultaneous charging and discharging of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N is prevented. In a charging mode with the charge switching circuitry 101 active to charge the plurality of cells 10-1, 10-2, 10-3 . . .10-N, the plurality of cells 10-1, 10-2, 10-3 . . . 10-N may form a charge string. In a discharging mode with the discharge switching circuitry 102 active to discharge the plurality of cells 10-1, 10-2, 10-3 . . . 10-N, the plurality of cells 10-1, 10-2, 10-3 . . . 10-N may form a discharge string.

[0040] As described herein, the electrochemical cell system 100 may include zinc-air cells, or possibly other types of metal-air cells, four terminals that can either be connected to form a charge string or a discharge string, but not both a charge string and a discharge string at the same time. Battery systems may have imperfect reliability and without cell fault tolerance, and a single cell failure can take the entire system offline. Additionally, cells within a string are not perfectly equal in performance and capacity and fall out of state-of-charge balance over time. The cells 10-1, 10-2, 10-3 . . . 10-N of the electrochemical cell system 100 may have a greater impedance / voltage asymmetry than other conventional cell types, such as Li-ion or lead-acid, limiting the suitability of off-the-shelf charger / inverters in voltage and current ranges. Due to limitations withzinc wiping during charging, a zinc-air based cell may need to be charged above a lower charge current limit. The charge switching circuitry 101 and the controller 160 according to one embodiment may be operable to comply with these limitations of metal-air based cells, such as zinc-air based cells.

[0041] In the illustrated embodiment, the plurality of cells 10-1, 10-2, 10-3 . . . 10-N each includes 1) a positive charge terminal and a positive discharge terminal that are separate from each other and 2) a negative charge terminal and a negative discharge terminal that are separate from each other. In one aspect, the charge switching circuitry 101 may be operably coupled to the positive charge terminal and the negative charge terminal of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N to selectively control charging of one or more of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N, while the discharge switching circuitry 102 may be operatively coupled to the negative charge terminal and the negative discharge terminal of the plurality of cells 10-1, 10-2, 10-3 . . .10-N to selectively control discharging of one or more of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. In other words, the charge and discharge sections of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N may be physically separated with each section having a positive and negative terminal; thus, the zinc-air battery may use cells with four terminals. It is noted that an unwanted side reaction of one or more cells may be possible if the discharge and charge sections are connected at the same time, potentially damaging one or more cells.

[0042] In one embodiment, a string of four terminal cells 10-1, 10-2, 10-3 . . . 10-N with the aforementioned terminal connection constraints may be presented as a two terminal battery to an external inverter, charger, or solar charger. In one embodiment, the controller 160 of the electrochemical cell system 100 (e.g., a string controller) may coordinate the charge switching circuitry 101 and the discharge switching circuitry 102 (e.g., a plurality of solid-state switches(SSS) on each set of charge and discharge terminals of each cell) relative to a current sink 150 and a current source 140 (either of which may be DC / DC converters) on each charge and discharge string of cells. Solid-state switches may enable faster switching times over mechanical counterparts, allowing use cases such as uninterruptable power source (UPS) applications. It is to be understood, as described herein, that the switches provided in the charge switching circuitry 101 and the discharge switching circuitry 102 are not limited to solid-state switches — any type of switch may be used. Further, there are a variety of types of solid-state switches that may be used in solid-state switch configurations so that the present disclosure is not limited to any one type of solid-state switch. Yet further, any combination of different types of switches may be utilized (e.g., so that multiple types of switches may be provided in the charge switching circuitry 101 and / or the discharge switching circuitry 102.) Optionally, in configurations where the output of the current source 140 and the input of the current sink 150 are not isolated, the controller 160 may direct operation of another switch (e.g., an SSS) at the end of the charge and discharge strings to isolate charge and discharge ground returns, as shown in Fig. 2 and referenced as selector switch 230. The electrochemical cell system 100 may allow each of the charge and discharge string of cells 10-1, 10-2, 10-3 . . . 10-N to operate at a voltage range and terminal configuration compatible with off-the-shelf power conversion equipment.

[0043] The plurality of cells 10-1, 10-2, 10-3 . . . 10-N in the illustrated embodiment may each correspond to an electrochemical cell that together provide an electrochemical system in the form of a zinc-air battery. Discharge of a cell 10-1, 10-2, 10-3 . . . 10-N may involve a reaction with oxygen in air to form ions that migrate into a zinc past and form zincate, releasing electrons that provide current for supply to a load. Charging of a cell 10-1, 10-2, 10-3 . . . 10-N may involve precipitation of zinc to liberate oxygen from the discharge reaction products. It is to be understoodthat the plurality of cells 10-1, 10-2, 10-3 . . . 10-N, as well as the charge and / or discharge modes for the cells 10-1, 10-2, 10-3 . . . 10-N, may vary from application to application and that the present disclosure is not limited to any particular construction or mode of charging and discharging of a cell 10-1, 10-2, 10-3 . . . 10-N.

[0044] In the illustrated embodiment of Fig. 1, the plurality of cells 10-1, 10-2, 10-3 . . .10-N may be coupled to a current source 140, such as a charger (e.g., a buck converter), operable to supply current to the plurality of cells 10-1, 10-2, 10-3 . . . 10-N, or a subset thereof, for charging according to the state of the charge switching circuitry 101. The plurality of cells 10-1, 10-2, 10-3 . . . 10-N may also be coupled to a current sink 150, such as a booster (e.g., a boost converter), operable to receive current from the plurality of cells 10-1, 10-2, 10-3 . . . 10-N, or a subset thereof, for discharging according to the state of the discharge switching circuitry 102.

[0045] The current source 140 may be a charge buck converter configured to allow up to a target current, configured by the controller 160, to flow into the charge string without dropping a main bus (e.g., a DC bus) below a set threshold (e.g., 52.5V) by reducing the charge current to 0A as the main bus approaches the threshold.

[0046] The current sink 150 may be a discharge boost converter configured to amplify the voltage of the discharge string of cells 10-1, 10-2, 10-3 . . . 10-N to a target voltage at the main bus (e.g., 47V, 48VDC, 60VDC, 72VDC, 96VDC, and 120VDC) and may be enabled by the controller 160 as long as sufficient discharge string voltage is present.

[0047] The charge switching circuitry 101 according to one embodiment may include a plurality of switching circuits 110-1, 110-2, 110-3 . . . 110-N. The switching circuits 110-1, 110-2, 110-3 . . . 110-N may be selectively controlled by the controller 160 to selectively charge one or more of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. In one embodiment, charging of thecells 10-1, 10-2, 10-3 . . . 10-N can be conducted according to a characteristic of each of the cells 10-1, 10-2, 10-3 . . . 10-N, such as a state of charge of a cell 10-1, 10-2, 10-3 . . . 10-N. For instance, one or more of the cells 10-1, 10-2, 10-3 . . . 10-N may be selectively bypassed relative to charging current provided from the current source 140 based on the characteristic.

[0048] The switching circuits 110-1, 110-2, 110-3 . . . 110-N may each include one or more switches in the form of solid state switches (e.g., MOSFETs). The switches of the switching circuits 110-1, 110-2, 110-3 . . . 110-N may be operated according to directives from the controller 160. Additionally, or alternatively, the switching circuits 110-1, 110-2, 110-3 . . . 110-N may include internal circuitry capable of selectively activating a bypass mode based on a characteristic of the cells 10-1, 10-2, 10-3 . . . 10N that can be sensed by the internal circuitry. Additionally, or alternatively, the switching circuits 110-1, 110-2, 110-3 . . . 110-N may receive a directive from circuitry other than the controller 160, such as a cell management board (CMB) described herein and associated with a cell 10-1, 10-2, 10-3 . . . 10N, to selectively activate a bypass mode based on a characteristic of the cells 10-1, 10-2, 10-3 . . . 10N. For instance, the cell, itself, may include sensor circuitry operable to direct the switching circuit to activate a bypass mode.

[0049] Bypass of a cell 10-1, 10-2, 10-3 . . . 10-N for charging may be achieved in a variety of ways. In the illustrated embodiment of Fig. 1, the cell 10-1 may be selectively bypassed by the switch 110-1, which may be operably coupled to the positive charge terminal of the cell 10-1 and the negative charge terminal of the cell 10-1. The switching circuit 110-1 may be selectively controlled to direct current from the current source 140 through the cell 10-1 or so that such current bypasses the cell 10-1. To direct current from the current source 140 through the cell 10-1, the switching circuit 110-1 may be controlled to provide a current path for the current from the current source 140 to flow from the positive charge terminal to the negative charge terminal. To bypassthe cell 10-1, the switching circuit 110-1 may be controlled so that another current path is provided for current to flow with a substantially lower potential for current. For instance, a selectable bypass switch of the switching circuit 110-1 may be activated to provide a current path between the positive charge terminal of the cell 10-1 and a downstream connection, such as the positive terminal of the second cell 10-2 or the current source 140. To provide current between the positive charge terminal and the negative charge terminal of the cell 10-1, a selective charge switch of the switching circuit 110-1 may be activated, while the selectable bypass switch is deactivated, to provide a current path from the positive charge terminal to the negative charge terminal and then to the downstream connection, such as the positive charge terminal of the cell 10-2 or the current source 140. Charge and charge bypass modes for each of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N may be selectively controlled by the charge switching circuitry 101 in a similar manner, with a respective switching circuit 110-1, 110-2, 110-3 . . . 110-N being controllable to selectively charge or bypass an associated cell 10-1, 10-2, 10-3 . . . 10-N.

[0050] The discharge switching circuitry 102 in one embodiment may include a plurality of switching circuits 120-1, 120-2, 120-3 . . . 120-N. The switching circuits 120-1, 120-2, 120-3 . . . 120-N may be selectively controlled by the controller 160 to selectively discharge one or more of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. In one embodiment, discharging of the cells 10- 1, 10-2, 10-3 . . . 10-N can be conducted according to a characteristic of each of the cells 10-1, 10- 2, 10-3 . . . 10-N, such as a state of charge of a cell 10-1, 10-2, 10-3 . . . 10-N. For instance, one or more of the cells 10-1, 10-2, 10-3 . . . 10-N may be selectively bypassed relative to discharging current provided toward the current sink 150 based on the characteristic (e.g., state of charge or voltage). Similar to control over the plurality of switching circuits 110-1, 110-2, 110-3 . . . 110-N of the charge switching circuitry 101, the controller may direct operation of the plurality ofswitching circuits 120-1, 120-2, 120-3 . . . 120-N of the discharge switching circuitry 102 based on sensor output from the sensor system 162, such as a state of charge.

[0051] Bypass of a cell 10-1, 10-2, 10-3 . . . 10-N for discharging may be achieved in a variety of ways. In the illustrated embodiment of Fig. 1, the cell 10-1 may be selectively bypassed by the switching circuit 120-1, which may be operably coupled to the positive discharge terminal of the cell 10-1 and the negative discharge terminal of the cell 10-1. The switching circuit 120-1 may be selectively controlled to direct current from the cell 10-1 to the current sink 150 or so that a current path between the positive and negative discharge terminals is effectively bypassed for the cell 10-1. To direct current to the current sink 150 from the cell 10-1, the switching circuit 120-1 may be controlled to provide a current path for current generated from the cell 10-1 relative to the positive and negative discharge terminals for supply to the current sink 150. To bypass the cell 10-1, the switching circuit 120-1 may be controlled so that another current path is provided for current to flow with a substantially lower potential for current. For instance, a selectable bypass switch of the switching circuit 120-1 may be activated to provide a current path between the positive discharge terminal of the cell 10-1 and an upstream connection, such as the positive terminal of the second cell 10-2 or the current sink 150. To provide current between the positive charge terminal and the negative charge terminal of the cell 10-1, a selective discharge switch of the switching circuit 120-1 may be activated, while the selectable bypass switch is deactivated, to provide a current discharge path between the positive discharge terminal to the negative discharge terminal and then to a downstream connection, such as another switching circuit 120 or the current sink 150. Discharge and discharge bypass modes for each of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N may be selectively controlled by the discharge switching circuitry 102 in a similarmanner, with a respective switching circuit 120-1, 120-2, 120-3 . . . 120-N being controllable to selectively discharge or bypass an associated cell 10-1, 10-2, 10-3 . . . 10-N.

[0052] A sensor system 162 may be provided in the electrochemical cell system 100 that is coupled to the one or more components thereof, such as the charge switching circuitry 101, and operable to provide sensor output indicative of a characteristic (or characteristics) pertaining to each of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. For instance, the characteristic may correspond to a voltage and / or a state of charge of a particular cell among the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. The sensor system 162 may obtain such sensor output for each of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N, and provide this sensor output to the controller 160 which may in turn, based on the senor output, selectively determine which of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N to charge with current from the current source 140. The sensor system 162 may include a plurality of sensors separately associated with each of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N — e.g., the sensor system 162 may include sensor aspects of the CMBs described herein.

[0053] Additionally, or alternative to being coupled to one or more components of the charge switching circuitry 101, the sensor system 162 may optionally be coupled to the discharge switching circuitry 102 and operable to provide sensor output indicative of a characteristic (or characteristics) pertaining to each of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. For example, the characteristic may correspond to a state of charge of a cell among the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. The controller 160 may obtain such sensor output from the sensor system 162, and selectively determine which of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N to discharge for supply of current to the current sink 150.

[0054] The controller 160 may include electrical circuitry and components to carry out the functions and algorithms described herein. Generally speaking, the controller 160 may include one or more microcontrollers, microprocessors, digital signal processors (DSP), and / or other programmable electronics that are programmed to carry out the functions described herein. The controller 160 may additionally or alternatively include other electronic components that are programmed to carry out the functions described herein, or that support the microcontrollers, microprocessors, and / or other electronics. The other electronic components include, but are not limited to, one or more field programmable gate arrays (FPGAs), systems on a chip, volatile or nonvolatile memory, discrete circuitry, integrated circuits, application specific integrated circuits (ASICs) and / or other hardware, software, or firmware. Such components can be physically configured in any suitable manner, such as by mounting them to one or more circuit boards, or arranging them in other manners, whether combined into a single unit or distributed across multiple units. Such components may be physically distributed in different positions in the system or aspects thereof, or they may reside in a common location within the system or an aspect thereof. When physically distributed, the components may communicate using any suitable serial or parallel communication protocol, such as, but not limited to, CAN, LIN, Vehicle Area Network (VAN), FireWire, I2C, RS-232, RS-485, Ethernet, LAN, WiFi, and Universal Serial Bus (USB).

[0055] The controller 160 may direct the charge switching circuitry 101 and the discharge switching circuitry 102, and optionally a switch similar to the selector switch 230 in Fig. 2, to provide at least three additional functions in the electrochemical cell system 100: 1) they may enable cells 10-1, 10-2, 10-3 . . . 10-N to be selectively bypassed in charge or discharge or both to provide cell fault tolerance to the string; 2) they may allow string current to be adjusted for a given current output from the current source 140 (e.g., charger output power); and 3) they may enabletrim balancing of the cells 10-1, 10-2, 10-3 . . . 10-N by selectively removing cells from the string to bring the maximum and minimum cell states of charge closer to the string average state of charge.

[0056] In one embodiment, the controller 160 may be operable to detect a drop in the main bus to which the electrochemical cell system 100 is coupled (e.g., if the sun sets or the grid fails and it falls below a threshold voltage, such as 48V). The controller 160 may be coupled to the current source 140 and / or the current sink 150 (e.g., via an analog and / or digital electronic circuit) in order to enable or disable operation thereof. For instance, the controller 160 may enable or disable a DC / DC buck / charger (e.g., the current source 140) and / or a DC / DC boost converter (e.g., a current sink 150). If the main bus drops below a threshold voltage, the controller 160, as described herein, may open the charge string via the charge switching circuitry 101 and close the discharge string via the discharge switching circuitry 102, allowing power to flow from the plurality of cells 10-1, 10-2, 10-3 . . . 10-N through the current sink 150 in the form of a DC / DC boost converter that amplifies the discharge string voltage to support the main bus.

[0057] When the bus voltage is supported by solar or an AC charger to a voltage level high enough to charge, the controller 160 may detect this voltage level threshold. In response, the controller 160 may wait until the voltage level is stable above the voltage level threshold, and then open the discharge string via the discharge switching circuitry 102, close the charge string via the charge switching circuitry 101, and enable the current source 140 in the form of DC / DC buck / charger to supply current to the charge string.

[0058] In one embodiment, the controller 160 may measure discharge string voltage, and if this string voltage is below a voltage threshold, the controller 160 may send a message to anexternal device (such as a power conversion system) to connect the main bus to grid power or another power source, if available, to avoid a system shutdown.

[0059] In one embodiment, the controller 160 may interface via a communication network, such as a CAN bus, with an air pump (not shown) associated with the electrochemical cell system 100. The air pump may deliver air to the cells 10-1, 10-2, 10-3 . . . 10-N in the respective cell string according to a directive from the controller 160. For instance, the controller 160 may direct the air pump to adjust its speed based on whether the string is charging, discharging, or idle. The controller 160 may determine a speed of the air pump based on cell string air demand, which is related to discharge current. The higher the current, the higher the air demand. The amount needed may be determined by the stoichiometric ratio of the zinc oxidation reaction.

[0060] In one embodiment, the controller 160 may communicate with the sensor system 162 via a communication network, such as a CAN bus. The sensor system 162 in one aspect may include a plurality of cell management boards (CMBs) capable of measuring charge and discharge voltages of each cell 10-1, 10-2, 10-3 . . . 10-N on which the CMB is provided. Optionally, the CMB may be configured to also manage wiper and pump operation associated with the respective cell 10-1, 10-2, 10-3 . . . 10-N.

[0061] The controller 160, as described herein, may also be coupled to an external power source switch (e.g., a grid connect trigger) via a communication network, such as a CAN bus, to control supply of external power to the DC bus.

[0062] In one embodiment, as described herein, the controller 160 may be directly wired to the switching circuits 110, 120 of the respective charge and discharge switching circuits 101, 102 to control operation thereof. The switching circuits 110, 120 may be provided in the form of a daisy-chain connection between cells 10-1, 10-2, 10-3 . . . 10-N.

[0063] In one embodiment, the controller 160 may be configured to estimate the average state of charge of the string using one or both of two methods: 1) count Amp-hours of charge entering and leaving a string of cells 10-1, 10-2, 10-3 . . . 10-N, with efficiency coefficients, in combination with a time-based self-discharge parameter and 2) count Amp-hours of charge entering and leaving the string of cells 10-1, 10-2, 10-3 . . . 10-N. This state of charge may be communicated via a communication network, such as a CAN bus.

[0064] Optionally, the controller 160 may direct operation of the charge switching circuitry 101 and / or the discharge switching circuitry 102 via a communication network, such as a CAN bus. For instance, the controller 160 may direct the charge switching circuitry 101 and / or the discharge switching circuitry 102 to selectively bypass and / or un-bypass one or more cells 10-1, 10-2, 10-3 . . . 10-N.

[0065] The controller 160 may operate according to one or more modes of operation including a minimum charge current for wiping mode, a string resistance estimation / high resistance connection detection mode, and a cell control - low voltage bypass mode.

[0066] For the minimum charge current for wiping mode, the controller 160 may temporarily disable the charge if available power does not allow for the cell string to be charged above a set current threshold. If the charge current is below the threshold for a set time, the controller 160 may disable the charger for a set time before trying again.

[0067] The sensor system 162 according to one embodiment is shown in Fig. 4 and is operably coupled to the positive and negative charge terminals of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. Alternatively, or additionally, the sensor system 162 may be operably coupled to the positive and negative discharge terminals of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. The sensor system 162 may be configured to measure a characteristic of power, such as a voltage,relative to positive and negative terminals of a cell 10, including relative to positive and negative charge terminals and / or positive and negative discharge terminals of a cell 10. The sensor system 162 may include a multiplexer 400 operable to selectively connect positive and negative terminals of a cell 10 from among the plurality of cells 10 to a sensor circuit 490. The multiplexer 400 may obtain a channel selection signal from the controller 160, which may direct the multiplexer 400 to select positive and negative terminals from one of the plurality of cells 10 via supply of the channel selection signal. The sensor system 162 according to one embodiment may reside on the CMB of a cell 10 and may be used to measure several voltages of the cell 10. The sensor system 162 may allow several voltages of each cell 10 to be accurately measured by its own CMB, avoiding long runs of wires, avoiding electromagnetic noise, and keeping wiring within a cell string neat and tidy.

[0068] In the illustrated embodiment, the sensor system is distributed, where on each cell, four measurements may be conducted by an onboard sensor as depicted in Fig. 9. For instance, on each cell, the multiplexer 400 and sensor circuit 490 may be provided, as well and ADC and a processor for communicating sensor information to a component external to the cell 10. Each cell 10 may include its own multiplexor 400 and sensor circuit 490 as well as related components described herein. The optocoupler outputs may be provided to one differential amp, whose output goes into an ADC of a processor on the CMB.

[0069] Additionally, or alternatively, the sensor system may manage larger groups of cells e.g. 4 cells with one board. The max V_CE on the optocouplers may limit the number of connections, e.g. if max V_CE on the optocoupler is 7V, then if the charge voltage is about 2.2V, then the maximum difference between each voltage on a common bank of optocouplers may beabout 6.6V if selections are made between 4 cells at a time. This configuration may provide increased centralization, while also using a level of distributed sensor circuit components.

[0070] In one embodiment, to avoid costly and inefficient isolated power converters on each CMB, a cluster of CMBs for cells 10 may be powered from a single isolated power supply, such that all of the CMBs comprising the cluster have a common ground. However, in this configuration, the voltages of the cells 10 may have a common mode depending on the position of each cell 10 in the string. When the common mode of the voltage being measured exceeds the power rail of the voltage measurement hardware on the CMB, a sensor of the sensor system 162 may not be configured to measure the voltage.

[0071] The sensor system 162 in one embodiment may achieve multiple high common mode differential voltage measurements using one amplifier 430 (e.g., an op-amp). The multiplexer control signals from the controller 160 or another component of the system may be isolated from the measurement input signals, avoiding issues with conventional analog multiplexers where input signals must also fall within a small range from the multiplexer power rails.

[0072] The sensor system 162, or portions thereof, may be powered by a source that is not the cell string, avoiding potential issues arising when the cells are isolated from each other when trying to use a battery management chip. This power source configuration may also avoid using many high common mode differential op-amps, which are very expensive. It is noted that the primary enabler of avoiding many high common mode differential op-amps is the multiplexer arrangement. The isolated external power source is an aspect that may aid in limiting the common mode within each cluster.

[0073] Positive and negative nodes of a cell 10 may be supplied as first and second inputs to the sensor circuit 490, which may determine the characteristic of power with respect to the first and second inputs. For instance, the sensor circuit 490 may determine a voltage difference between the first and second inputs supplied from the multiplexer 400 for the cell 10. The sensor circuit 490, in one embodiment, may include an amplifier 430 (e.g., a differential amplifier) and an analog to digital converter 440 coupled to an output of the amplifier 430. Optionally, the analog to digital converter 440 may be integrated into the controller 160 so that the output of the differential amplifier 430 may be supplied directly to the controller 160. The analog to digital converter 440 may supply an encoded value indicative of the characteristic of power (e.g., a voltage difference) sensed by the sensor circuit 490 relative to the first and second inputs.

[0074] In one embodiment, by providing the multiplexer 400, a single sensor circuit 490 may optionally be utilized to provide sensor output indicative of the characteristic of power relative to positive and negative nodes of a cell 10. The positive and negative nodes of the cell 10 may correspond to any two nodes of the cell 10, including positive and negative charge terminals, positive and negative discharge terminals, a positive charge terminal and a node of the charge switching circuitry, or a positive discharge terminal and a node of the discharge switching circuitry, or any combination thereof.

[0075] The multiplexer 400 in one embodiment may include positive side selection circuitry 410 and negative side selection circuitry 420 respectively operable to select positive and negative nodes (of a cell 10 based on a channel selection signal) for supply respectively to the first and second inputs of the sensor circuit 490.

[0076] The positive side selection circuitry 410 and the negative side selection circuitry 420 may each include a plurality of optical isolators 480. The plurality of optical isolators 480 ofthe positive side selection circuitry 410 may each be coupled to the first input of the sensor circuit 490, and the plurality of optical isolators 480 of the negative side selection circuitry 420 may each be coupled to the second input of the sensor circuit 490. In this configuration, the plurality of optical isolators 480 of the positive side selection circuitry 410 may be controlled to selectively couple a positive node of a cell 10 to the first input, and the plurality of optical isolators 480 of the negative side selection circuitry 420 may be controlled to selectively couple a negative node of a cell 10 to the second input.

[0077] In one embodiment, on each CMB, a multiplexer 400 may be provided that feeds an amplifier 430 (e.g., a high common mode differential op-amp), which in turn may provide a single ended voltage that is measured by the analog to digital converter 440. The multiplexer 400 takes in parallel digital signals to select one output from multiple inputs. The optical isolators 480 may also enable a more compact and reliable configuration, in conjunction with isolation, over conventional electromechanical relays. Further, such optical isolators 480 utilize much less energy for activation relative to conventional electromechanical relays.

[0078] The multiplexer 400 according to one embodiment enables isolation among the cells 10 and isolation among nodes of each cell 10, enabling avoiding powering the multiplexer 400 with power from the string of cells 10 or powering the sensor system 162 based on power from charge terminals whose function is not to discharge power in contrast to the discharge terminals separate from the charge terminals. Further, the multiplexer 400 enables avoidance of isolated power converters for each CMB or analog to digital converter. The isolated power converters and associated power supplies may take up board space and draw additional idle power over the multiplex 400 configuration according to one embodiment described herein.

[0079] Each of the optical isolators 480 may be coupled to a positive node or negative node of a cell 10 of the plurality of cells 10, depending on whether the optical isolator 480 is provided in the positive or negative side selection circuitry 410, 420. For instance, in the illustrated embodiment of Fig. 5, each of the optical isolators 480 includes a phototransistor arranged to selectively couple a node to an input of this sensor circuit 490 in response to supply of power to an LED of the optical isolator 480. An optical isolator 480 provided in the positive side selection circuitry 410 may include a light element (e.g., an LED) and a phototransistor operable to selectively couple the positive node of a cell 10 to the first input of the sensor circuit 490 in response to supply of power to the light element. And, an optical isolator 480 provided in the negative side selection circuitry 420 may include a light element and a phototransistor operable to selectively couple the negative node of a cell 10 to the second input of the sensor circuit 490 in response to supply of power to the light element.

[0080] Isolation may be provided by the optical isolators 480 as depicted in Fig. 5. The current transfer ratio of the optical isolators 480 may be a consideration in implementations. For instance, while a small activation current may be enough for a digital signal in the context of applications for a conventional optical isolator 480, in the depicted embodiment, analog signals are being passed through the optical isolators 480. The high resistance of the photo transistor in the optical isolator 480 at low activation currents may affect measurements.

[0081] In the illustrated embodiment, the input differential voltages of the positive and negative nodes (e.g., positive and negative charge terminals or positive and negative discharge terminals) to be measured may be connected to a pair of optical isolators 480. In the multiplexer 400, all outputs for the optical isolators 480 with the positive input are connected, and all outputs for optical isolators 480 with the negative input are connected. The positive and negative opticalisolator outputs may be connected to the corresponding input of the amplifier 430 (e.g., high common mode op-amp). Each pair of optical isolators 480 is driven by a common signal from a selection circuit 450 as described herein.

[0082] It is worth noting that, in the illustrated embodiment of Fig. 5, the inputs to the optical isolators 480 may need to be within a specific range of each other, such as within 7V of each other depending on the operating parameters of the optical isolators 480 and the circuit configuration. For purposes of an electrochemical cell system according to one embodiment, within the cell 10, the voltage ranges are not that high or greater than the specific range for the optical isolators 480. The voltage ranges being considered low is a consideration when using the multiplexer over multiple cells within a string due to the common mode differences.

[0083] The optical isolators 480 in conjunction with the sensor circuit 490 may enable avoidance of voltage divider constructions, which in cases of high common mode applications, are often expensive and rely on a divide ratio being large to fit the voltages under the supply rails. This can result in high signal to noise ratios, where the noise is amplified in the main signal.

[0084] A selection circuit 450 may be provided in conjunction with the multiplexer 400 to facilitate selection of nodes for supply to the first and second inputs of the sensor circuit 490. The selection circuit 450 and the illustrated embodiment includes a plurality of transistors 452 (e.g., MOSFETs) operable to selectively activate one or more optical isolators 480 via supply of power to a light element thereof. The output of each transistor 452 may be supplied to both the positive side selector circuit 410 and the negative side selection circuitry 420 so that by activating one transistor of 452, the optical isolators 480 in each of the positive and negative side selection circuitry 410, 420 may be activated for coupling the positive and negative nodes of the cell to the first and second inputs of the sensor circuit 490.

[0085] Although the selection circuit 450 may be directly controlled by the controller 160 — in the illustrated embodiment of Fig. 6, the selection circuit 450 is operated by a demultiplexer circuit 460 operable to translate first and second channel select inputs SI, S2 and translate these inputs to a channel selection output provided to one or more of the transistors 452 of the selection circuit 450. In other words, the demultiplexer circuit 460 may decode the input channel select lines, so that for n channel select lines, 2An channels of measurement may be provided. In the illustrated embodiment of Fig. 6, the inputs SI and S2 can be generated from the controller 160 and / or a controller for the cell 10 (e.g., the CMB). One of Y1 to Y4 may be output according to the input, where each of Y1 to Y4 may be connected to the gate of one of the transistors 452 (SEL1 to SEL4) in Fig. 5. As an example, if the channel select inputs correspond to a 01 binary value (SI is low, S2 is high), the demultiplexer circuit 460 may activate Y1 and leave the other outputs low. This Y1 output may be supplied to one of the transistors 452, which may in turn activate an optical isolator 480 in both the positive and negative side selection circuitry 410, 420 in order to select positive and negative nodes of the cell 10 to the first and second inputs of the sensor circuit 490.

[0086] Using the multiplexer 400 in conjunction with the selection circuit 450 and the demultiplexer circuit 460, the system may achieve response times of less than one millisecond. This can be seen in Fig. 7, which shows an example switching behavior of the analog multiplexer 400 with the trace showing output voltage of the amplifier 430. The measure error in the depicted configuration may be less than 2 mV up to common mode voltages of 150 V as depicted in the plot of Fig. 8, which shows measurement error as a function of common mode.

[0087] In practice, controller 160 (e.g., as part of the CMB) may cycle through, selecting each output of the multiplexer 400 for measurement by the analog to digital converter 440. Inembodiments with a cell 10 as depicted in Fig. 1, there may be four voltages of interest to measure, and these voltages may be measured periodically, such as once every second. The illustrated embodiment of Fig. 9 depicts the cell 10-1 along with the charge switching circuit 110-1 and the discharge switching circuit 120-1. In this configuration, the positive charge terminal of the cell 10-1 corresponds to a first positive node Pl, and the negative charge terminal of the cell 10-1 corresponds to a first negative node Nl. The positive discharge terminal of the cell 10-1 corresponds to a second positive node P2, and the negative discharge terminal of the cell 10-1 corresponds to a second negative node Nl. Further, a negative node of the charge switching circuitry 110-1 may correspond to a third negative node N3, and a negative node of the discharge switching circuitry 120-1 may correspond to a fourth negative node N4. The differences between positive and negative nodes among these nodes may be informative about the cell 10-1. For instance, the voltage VI between the first positive node Pl and the first negative node Nl may be indicative of a charge voltage of the cell 10-1. The voltage V2 between the first positive node Pl and the third negative node N3 may be indicative of a charge voltage of the cell 10-1 including relay loss. If V2 is greater than VI plus a threshold value (e.g., 20 mV), then the charge switching circuitry 110-1 (e.g., a relay) or a connection for the sensor system may be defective. The voltage V3 between the second positive node P2 and the second negative node N2 may be indicative of a discharge voltage of the cell 10-1. The voltage V4 between the second positive node P2 and fourth negative node N4 may be indicative of a discharge voltage of the cell 10-1 including relay loss. If V4 is greater than V3 plus a threshold value (e.g., 20m V), the discharge switching circuit 120-1 or a connection for the sensor system may be defective. Each of the identified nodes can be provided as an input to the multiplexer 400, which can be connected to an input of the differential amplifier 430.

[0088] Each measurement or combination of measurements (VI, V2, V3, V4) in one embodiment can provide an indication about the cell operation beyond just the power. For example, low electrode voltage (VI, V3) may be indicative of a short circuit. A difference between the “around relay” measurement (V2 or V4) compared to the “electrodes” measurement (VI or V3) may be indicative of a loose connection or a faulty relay.

[0089] Due to the low settling time of the output of the multiplexer 400, it may be possible to sample all four voltages frequently.

[0090] A real-time operating system task may be provided by the controller 160 that controls digital output pins to switch between the inputs and measure the output of the multiplexer 400 using the ADC 440. The task could operate as a state machine for various stages of the measurement, such as switching inputs, waiting for the output signal to settle, and performing the ADC conversion.

[0091] Turning to Fig. 2, an electrochemical cell system according to one embodiment is shown and generally designated 200. The electrochemical cell system 200 is similar to the electrochemical cell system 100 in several ways but different in others. For instance, the electrochemical cell system 200 includes a plurality of cells 10-1, 10-2, 10-3 constructed in the same manner as those discussed herein in conjunction with the electrochemical cell system 100. Likewise, the electrochemical cell system 200 includes a current source 140 and a current sink 150 that are constructed in the same manner as the electrochemical cell system 100.

[0092] In the illustrated embodiment, the electrochemical cell system 200 includes charge switching circuitry 201 and discharge switching circuitry 202 that may be operably coupled to a controller 260, which may be similar to the controller 160 and able to direct operation of the charge switching circuitry 201 and the discharge switching circuitry 202 according to one or more aspectsdescribed herein. For instance, similar to the controller 160, the controller 260 may direct operation of the charge switching circuitry 201 and the discharge switching circuitry 202 such that simultaneous charging of the plurality of cells 10-1, 10-2 . . . 10-N is prevented.

[0093] In one aspect, the charge switching circuitry 201 may be operably coupled to the positive charge terminal and the negative charge terminal of the plurality of cells 10-1, 10-2 . . .10-N to selectively control charging of one or more of the plurality of cells 10-1, 10-2 . . . 10-N, while the discharge switching circuitry 202 may be operatively coupled to the negative charge terminal and the negative discharge terminal of the plurality of cells 10-1, 10-2 . . . 10-N to selectively control discharging of one or more of the plurality of cells 10-1, 10-2 . . . 10-N.

[0094] The charge switching circuitry 201 according to one embodiment may include a plurality of switching circuits 210-1, 210-2 . . . 210-N. The switching circuits 210-1, 210-2 . . .210-N may be selectively controlled by the controller 260 to selectively charge one or more of the plurality of cells 10-1, 10-2 . . . 10-N. In one embodiment, charging of the cells 10-1, 10-2 . . . 10-N can be conducted according to a characteristic of each of the cells 10-1, 10-2 . . . 10-N, such as a state of charge of a cell 10-1, 10-2 . . . 10-N. For instance, one or more of the cells 10-1, 10-2 . . . 10-N may be selectively bypassed relative to the charging current provided from the current source 140 based on the characteristic.

[0095] Bypass of a cell 10-1, 10-2, 10-3 . . . 10-N in the electrochemical cell system 200 may be achieved in a different manner from the electrochemical cell system 100. For instance, in the illustrated embodiment of Fig. 2, the cell 10-1 may be selectively bypassed by the switching circuit 210-1, which may be operably coupled to the positive charge terminal of the cell 10-1 and the negative charge terminal of the cell 10-1. Similar to the switch 110-1, the switching circuit 210-1 may be selectively controlled to direct current from the current source 140 through the cell10-1 or so that such current bypasses the cell 10-1. To direct current from the current source 140 through the cell 10-1, the switching circuit 210-1 may be controlled to provide a current path for the current from the current source 140 to flow from the positive charge terminal to the negative charge terminal. To bypass the cell 10-1, the switching circuit 210-1 may be controlled so that another current path is provided for current to flow with a substantially lower potential for current. For instance, a selectable bypass switch of the switching circuit 210-1 may be activated to bypass the positive charge terminal of the cell 10-1 and direct current from the current source 140 to a downstream connection, such as another switching circuit 210 of the charge switching circuitry 201. Bypass of the positive charge terminal of the cell 10-1 may be provided by directing current from the current source 140 to the negative charge terminal of the cell 10-1 so that such current does not flow between the positive and negative charge terminals of the cell 10-1.

[0096] To provide current between the positive charge terminal and the negative charge terminal of the cell 10-1, a selective charge switch of the switching circuit 210-1 may be activated, while the selectable bypass switch is deactivated, to provide a current path from the positive charge terminal to the negative charge terminal and then to the downstream connection, such as another switching circuit 210 of the charge switching circuitry 201. Charge and charge bypass modes for each of the plurality of cells 10-1, 10-2 . . . 10-N may be selectively controlled by the charge switching circuitry 101 in a similar manner, with a respective switching circuit 210-1, 210-2 . . .210-N being controllable to selectively charge or bypass an associated cell 10-1, 10-2, 10-3 . . .10-N.

[0097] The discharge switching circuitry 202 in one embodiment may include a plurality of switching circuits 220-1, 220-2 . . . 120-N. The switching circuits 220-1, 220-2 . . . 120-N may be selectively controlled by the controller 260 to selectively discharge one or more of the pluralityof cells 10-1, 10-2 . . . 10-N. In one embodiment, discharging of the cells 10-1, 10-2 . . . 10-N can be conducted according to a characteristic of each of the cells 10-1, 10-2, 10-3 . . . 10-N, such as a state of charge of a cell 10-1, 10-2, 10-3 . . . 10-N.

[0098] For instance, one or more of the cells 10-1, 10-2 . . . 10-N may be selectively bypassed relative to discharging current provided toward the current sink 150 based on the characteristic. Similar to control over the plurality of switching circuits 210-1, 210-2 . . . 210-N of the charge switching circuitry 201, the controller 260 may direct operation of the plurality of switching circuits 220-1, 220-2 . . . 120-N of the discharge switching circuitry 202 based on sensor output from the sensor system 162, such as a state of charge.

[0099] Bypass of a cell 10-1, 10-2 . . . 10-N for discharging may be achieved in a variety of ways as described herein. In the illustrated embodiment of Fig. 2, the cell 10-1 may be selectively bypassed by the switching circuit 220-1, which may be operably coupled to the positive discharge terminal of the cell 10-1 and the negative discharge terminal of the cell 10-1. The switching circuit 220-1 may be selectively controlled to direct current from the cell 10-1 to the current sink 150 or so that a current path between the positive and negative discharge terminals is effectively bypassed for the cell 10-1. To direct current to the current sink 150 from the cell 10-1, the switching circuit 220-1 may be controlled to provide a current path for current generated from the cell 10-1 relative to the positive and negative discharge terminals for supply to the current sink 150. To bypass the cell 10-1, the switching circuit 220-1 may be controlled so that another current path is provided for current to flow with a substantially lower potential for current. For instance, a selectable bypass switch of the switching circuit 220-1 may be activated to provide a current path between the negative discharge terminal of the cell 10-1 and an upstream connection, such as the negative discharge terminal of a downstream cell or the current sink 150. To obtain currentbetween the positive charge terminal and the negative charge terminal of the cell 10-1, a selective discharge switch of the switching circuit 120-1 may be activated, while the selectable bypass switch is deactivated, to provide a current discharge path between the positive discharge terminal to the negative discharge terminal and then to a downstream connection, such as another cell 10-1, 10-2 . . . 10-N or the current sink 150. Discharge and discharge bypass modes for each of the plurality of cells 10-1, 10-2 . . . 10-N may be selectively controlled by the discharge switching circuitry 102 in a similar manner, with a respective switching circuit 220-1, 220-2 . . . 220-N being controllable to selectively discharge or bypass an associated cell 10-1, 10-2 . . . 10-N.

[0100] A sensor system 262 may be provided in the electrochemical cell system 200, similar to the sensor system 162 and the electrochemical cell system 100, that is coupled to the one or more components thereof, such as the charge switching circuitry 201, and operable to provide sensor output indicative of a characteristic (or characteristics) pertaining to each of the plurality of cells 10-1, 10-2 . . . 10-N. For instance, the characteristic may correspond to a state of charge of a particular cell among the plurality of cells 10-1, 10-2 . . . 10-N. The sensor system 262 may obtain such sensor output for each of the plurality of cells 10-1, 10-2 . . . 10-N, and provide this sensor output to the controller 160 which may in turn, based on the senor output, selectively determine which of the plurality of cells 10-1, 10-2 . . . 10-N to charge with current from the current source 140. The controller 160, additionally, or alternatively, may selectively determine based on the sensor output which of the plurality of cells 10-1, 10-2 . . . 10-N to discharge into the current sink 150.

[0101] In the illustrated embodiment, the electrochemical cell system 200 includes a selector switch 230 operable to selectively couple the charge switching circuitry 201 or the discharge switching circuitry 202 to ground and a respective one of the current source 140 and thecurrent sink 150, depending on the mode of operation (i.e., charge mode or discharge mode). The selector switch 230 may correspond to a ground interrupt switch used in a “positive switching” configuration, depicted in Fig. 2, because the two negative terminals are at different potentials. If the two negative terminals of the cell 10-N are not isolated from the main bus, then there will be current flowing between the two.

[0102] An alternative embodiment of an electrochemical cell system is shown in Fig. 3 and generally designated 300. The electrochemical cell system 300 is similar to the electrochemical cell system 100 in several ways but different in others. For instance, the electrochemical cell system 300 includes a plurality of cells 10-1, 10-2, 10-3 . . . 10-N constructed in the same manner as those discussed herein in conjunction with the electrochemical cell system 100. Likewise, the electrochemical cell system 200 includes a current source 140 and a current sink 150 that are constructed in the same manner as the electrochemical cell system 100. The electrochemical cell system 300 may include a sensor system (not shown) that is similar to the sensor system 162 described herein.

[0103] Unlike the electrochemical cell system 100, the electrochemical cell system 300 controls charge and discharge modes of the system via discharge switching circuitry 302 (e.g., without charge switching circuitry). A controller 360 of the electrochemical cell system 300, similar to the controller 160, may be provided to control charging and discharging of the electrochemical cell system 300. The positive and negative charge terminals of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N may be connected to enable charging of all of the cells via current from the current source 140. During a charge mode in which the current source 140 is suppling current to the plurality of cells 10-1, 10-2, 10-3 . . . 10-N, the discharge switching circuitry 302 may be directed to deactivate a plurality of switching circuits 302-1, 320-2, 320-3 . . . 320-N by acontroller 360 to disconnect the discharge path for each of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N to prevent simultaneous charging and discharging of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N. In a discharge mode, the plurality of switching circuits 320-1, 320-2, 320-3 . . . 320-N of the discharge switching circuitry 302 may be activated by the controller 360 to provide a circuit path through the positive and negative discharge terminals of the plurality of cells 10-1, 10-2, 10-3 . . . 10-N and the current sink 150.

[0104] Operation of the electrochemical cell system 300 may be similar to the electrochemical cell system 100 except operation of charge switching circuitry. Instead, as discussed, the discharge switching circuitry 302 may be configured and controlled so that discharge and charge sections or strings are not connected at the same time and so that an unwanted side reaction of one or more cells can be avoided.

[0105] A sensor system 362 may be provided in the electrochemical cell system 300, similar to the sensor system 162 and the electrochemical cell system 100, that is coupled to the one or more components thereof, such as the discharge switching circuitry 302, and operable to provide sensor output indicative of a characteristic (or characteristics) pertaining to each of the plurality of cells 10-1, 10-2 . . . 10-N. For instance, the characteristic may correspond to a state of charge of a particular cell among the plurality of cells 10-1, 10-2 . . . 10-N.

[0106] Directional terms, such as “vertical,” “horizontal,” “top,” “bottom,” “upper,” “lower,” “inner,” “inwardly,” “outer” and “outwardly,” are used to assist in describing the invention based on the orientation of the embodiments shown in the illustrations. The use of directional terms should not be interpreted to limit the invention to any specific orientation(s).

[0107] The above description is that of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of theinvention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described invention may be replaced by alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. Further, the disclosed embodiments include a plurality of features that are described in concert and that might cooperatively provide a collection of benefits. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits, except to the extent otherwise expressly set forth in the issued claims. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.

Claims

CLAIMSThe embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electrochemical cell system, said system comprising:a plurality of cells including first and second cells, the plurality of cells each including a negative charge terminal and a positive charge terminal and a negative discharge terminal and a positive discharge terminal, the electrochemical cell system adapted to discharge power to a current sink and to charge based on power from a current source;charge switching circuitry operably coupled to at least one of the positive charge terminal and the negative charge terminal of the first and second cells to control supply of power from the current source to the first and second cells;a sensor system operably coupled to a first cell of the plurality of cells, the sensor system including a multiplexer operable to selectively couple a first negative node and a second negative node to a first input of a sensor circuit and to selectively couple a first positive node and a second positive node of the first cell to a second input of the sensor circuit;the multiplexer including first and second positive-side optical isolators operably coupled to the first input of the sensor circuit and respectively coupled to the first positive node of the first cell and the second positive node of the first cell, the first positive-side optical isolator configured to selectively couple the first positive node of the first cell to the first input of the sensor circuit, the second positive-side optical isolator configured to selectively couple the second positive node of the first cell to the first input of the sensor circuit;the multiplexer including first and second negative-side optical isolators operably coupled to the second input of the sensor circuit and respectively coupled to the first negative node of the first cell and the second negative node of the first cell, the first negative-side optical isolator configured to selectively couple the first negative node of the first cell to the second input of the sensor circuit, the second negative-side optical isolator configured to selectively couple the second negative node of the first cell to the second input of the sensor circuit; anda controller configured to direct operation of the multiplexer to selectively obtain sensor output from the sensor circuit indicative of a voltage differential between the first positive node and the first negative node and to selectively obtain sensor output from the sensor circuit indicative of a voltage differential between the second positive node and the second negative node .

2. The electrochemical cell system of claim 1 wherein:the first positive node is a positive charge terminal;the second positive node is a positive discharge terminal;the first negative node is a negative charge terminal; andthe second negative node is a negative discharge terminal.

3. The electrochemical cell system of claim 1 wherein:the first positive node is a positive charge terminal;the first negative node is a node of the charge switching circuitry;the second positive node is a positive discharge terminal; andthe second negative node is a node of discharge switching circuitry.

4. The electrochemical cell system of any preceding claim wherein the sensor system is operably coupled to a second cell of the plurality of cells, wherein the multiplexer is operable to selectively couple a third negative node of the second cell and a fourth negative node of the second cell to the first input of the sensor circuit and to selectively couple a third positive node of the second cell and a fourth positive node of the second cell to the second input of the sensor circuit.

5. The electrochemical cell system of claim 1 wherein the sensor circuit includes a differential amplifier with a first differential input and a second differential input that correspond respectively to the first and second inputs, wherein the differential amplifier includes an output operably coupled to an analog-to-digital converter configured generate the sensor output.

6. The electrochemical cell system of claims 1 or 5 wherein the controller directs activation of the first positive-side optical isolator and the first negative-side optical isolator to couple the positive charge terminal of the first cell to the first input and the negative charge terminal of the first cell to the second input.

7. The electrochemical cell system of claim 6 wherein the first positive-side optical isolator includes a first light element and a first phototransistor operable to selectively couple the positive charge terminal of the first cell to the first input in response to supply of power to the first light element.

8. The electrochemical cell system of claim 7 wherein the first negative-side optical isolator includes a second light element and a second phototransistor operable to selectively couple thenegative charge terminal of the first cell to the second input in response to supply of power to the second light element.

9. The electrochemical cell system of any preceding claim, comprising:first discharge switching circuitry operably coupled to the positive discharge terminal of the first cell, the first discharge switching circuitry operable to selectively provide current to the current sink from the first cell; andsecond discharge switching circuitry operably coupled to the positive discharge terminal of the second cell and the negative discharge terminal of the first cell, the second discharge switching circuitry operable to selectively provide current to the current sink from the second cell.

10. The electrochemical cell system of claim 9, wherein the first and second discharge switching circuitry to substantially isolate charging and discharging of the first and second cells.

11. The electrochemical cell system of any preceding claim, comprising:first charge switching circuitry operably coupled to the positive charge terminal of the first cell, the first charge switching circuitry operable to selectively provide current output from the current source to the positive charge terminal of the first cell; andsecond charge switching circuitry operably coupled to the positive charge terminal of the second cell, the second charge switching circuitry operable to selectively provide the current output from the current source to the positive charge terminal of the second cell, wherein the second charge switching circuitry receives the current output from the current source via at least one of the first cell and the first charge switching circuitry.

12. The electrochemical cell system of claim 11, wherein receipt of current output from the first cell in the second charge switching circuitry includes receiving the current output from the current source via the negative charge terminal of the first cell, and wherein receipt of current output from the first charge switching circuitry includes receiving the current output from the current source via at least one of a direct connection to the first charge switching circuitry and an indirect connection to the first charge switching circuitry at the positive charge terminal of the first cell.

13. The electrochemical cell system of claims 11 or 12, wherein at least one of the first charge switching circuitry and the second charge switching circuitry is operable to selectively bypass current flow into the positive charge terminal of the first cell to provide current from the current source to the second charge switching circuitry.

14. The electrochemical cell system of claim 13, wherein the first charge switching circuitry selectively bypasses current flow into the positive charge terminal of the first cell by directing current to a node of the first cell that is connected to the negative charge terminal of the first cell and the second charge switching circuitry.

15. The electrochemical cell system of claims 13 or 14, wherein the second charge switching circuitry selectively bypasses current flow into the positive charge terminal of the first cell by disconnecting from the negative charge terminal of the first cell and connecting to the positive charge terminal of the first cell.

16. The electrochemical cell system of claims 11, 12, 13, 14, or 15, wherein the controller is operable to selectively discharge power from one or both of the first and second cells, and wherein the controller is operable to selectively charge one or both of the first and second cells.

17. The electrochemical cell system of claim 14, wherein the controller is operable to control whether one or both of the first and second cells is being discharged by selectively bypassing the first and second cells via operation of first and second discharge switching circuitry.

18. The electrochemical cell system of claims 14 or 17, wherein the controller is operable to control whether one or both of the first and second cells is being charged by selectively bypassing the first and second cells via operation of the first and second charge switching circuitry.

19. The electrochemical cell system of claim 9, wherein the first discharge switching circuitry is operable to selectively provide current to the current sink from the first cell via the positive discharge terminal of the first cell, and wherein the second discharge switching circuitry operable to selectively provide current to the current sink from the second cell via the positive discharge terminal of the second cell.

20. The electrochemical cell system of any preceding claim, wherein the current sink is a boost converter operable to convert power from the electrochemical cell system to power an external load.

21. The electrochemical cell system of any preceding claim, wherein the current source is a buck converter operable to convert external power for charging the electrochemical system.

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