Energy Delivery System

Abstract

An energy delivery system that combines multiple energy storage sources / systems of different chemical compositions or physical structures with a common control system that is configured to output energy from the systems according to the different performance characteristics of each system, thereby optimizing various operating characteristics of the combined system. The control system is configured to utilize separate variable impedance circuitry for each energy storage system to adjust the relative output current or discharge rate of each energy storage system to optimize, for example, the cycle life, depth of discharge, temperature, delivered power, and / or perceived safety of each energy storage system.

Description

[Technical Field]

[0001] This application is a continuation-in-part of U.S. Patent Application No. 16 / 760,762, filed April 30, 2020, which is a national stage application of International Application No. PCT / US2017 / 068301, filed December 22, 2017, both of which are hereby incorporated by reference. This application also claims priority to U.S. Provisional Patent Application No. 62 / 882,817, filed August 5, 2019, which is hereby incorporated by reference.

[0002] The present invention relates generally to energy sources for electronic devices, and more particularly to an energy storage system or system for delivering energy from an energy storage source. [Background technology]

[0003] This section is intended to introduce various aspects of the art that may be related to example embodiments of the present disclosure. This discussion is believed to be helpful in providing a framework to facilitate a better understanding of certain aspects of the present disclosure. Accordingly, it should be understood that this section is to be read in this light, and not necessarily as admissions of prior art.

[0004] There is an ever-increasing reliance on energy devices capable of providing electrical power to enable technological conveniences. Primarily, electrical power is generated from a continuously operating network grid. However, due to remote locations or obstacles where the power grid is unavailable, power must be supplied from off-grid sources. Energy can be drawn from off-grid devices and systems using these sources, including chemical, potential, or kinetic energy storage, and delivered or converted to be compatible with existing electrical grid frameworks to complete electrical work. Examples of chemical energy storage systems include, but are not limited to, lithium batteries, nickel batteries, flow cell batteries, and lead-acid batteries. Examples of potential energy storage systems include, but are not limited to, parametric devices such as lithium capacitors, supercapacitors, and electric double-layer capacitors (ELDCs). Examples of kinetic energy storage systems include, but are not limited to, rotating mass systems such as flywheels and other mechanical devices coupled by a mechanical-to-electrical conversion process. Throughout this disclosure, these terms may be used interchangeably in reference to energy delivery devices, each capable of applying voltage, supplying current, and / or delivering electrical energy to perform work.

[0005] The performance characteristics of batteries, capacitors, or other energy storage systems are generally determined by the device's structure and, in the case of electrochemical storage devices, their chemical composition. Such characteristics include, but are not limited to, volumetric energy density (watt-hours per unit volume), gravimetric energy density (watt-hours per unit mass), power density (i.e., the rate at which energy can be extracted from the device), charge / discharge cycle life, operating temperature range, electrode voltage, and overall stability over time. Moreover, in the case of batteries, some chemical compositions are more stable during fault conditions, thereby producing batteries that are more resistant to thermal runaway and are therefore considered "safer" than other chemical compositions. For example, lithium-ion batteries are one of the most commonly used electrochemical energy storage devices. Additionally, due to fluctuations in market prices for certain raw materials, significant price differences can exist between battery cells of different compositions when considering the cost per watt-hour of stored energy. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Patent Application No. PCT / US2017 / 068301 [Patent Document 2] U.S. Patent Application Serial No. 16 / 760,762 [Non-patent literature]

[0007] [Non-Patent Document 1] R. Rao et al., "Battery Modeling for Energy-Aware System Design," Computer, Vol. 36, No. 12, pp. 77-87 Summary of the Invention [Problem to be solved by the invention]

[0008] Battery cells (also referred to herein as “energy cells”) are typically combined in series and / or parallel combinations to form battery cell stacks (also referred to herein as “cell stacks” or “battery stacks”), which, when combined with appropriate control systems, form the basis of modern battery-based energy storage / delivery systems. However, there is a lack of, and therefore a need for, energy delivery systems that can safely combine multiple different energy storage sources or systems (e.g., including battery cells based on multiple chemical compositions). Such energy storage / delivery systems may have not only electrical performance advantages, but also cost, safety, and / or lifetime advantages. For example, by carefully combining cells of different chemical compositions, one energy storage system may be composed of cells that are chemically optimized for price, safety, and / or extended calendar and cycle life, while another energy storage system may be composed of cells that are optimized for several different but otherwise important parameters. [Means for solving the problem]

[0009] One aspect of the present invention provides an energy delivery system comprising: a first energy storage system, a second energy storage system, a first variable impedance network coupled between the first energy storage system and an output terminal, the first variable impedance network having a first adjustable impedance, a second variable impedance network coupled between the second energy storage system and the output terminal, the second variable impedance network having a second adjustable impedance, and a control system configured to selectively (1) signal the first variable impedance network to adjust the first adjustable impedance to change a level of a first current delivered by the first energy storage system to the output terminal, and (2) signal the second variable impedance network to adjust the second adjustable impedance to change a level of a second current delivered by the second energy storage system to the output terminal. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a model of a battery cell. [Figure 2] 1 is a plot of direct current internal resistance ("DCIR") and open circuit voltage as a function of state of charge of an exemplary battery cell. [Figure 3] FIG. 1 is a schematic diagram of a model of a battery cell under DC load conditions. [Figure 4] 1 is a graph of a family of voltage versus state-of-charge characteristic curves, each curve representing a different level of battery current for an exemplary single battery cell. [Figure 5] FIG. 1 is a schematic diagram of a model of multiple battery cells coupled in series. [Figure 6] FIG. 1 is a schematic diagram of a simplified model of multiple battery cells coupled in series. [Figure 7]1 is a graph of a family of voltage versus state of charge characteristic curves for an exemplary battery cell stack, with each curve taken at a different cell stack current level. [Figure 8] FIG. 1 is a schematic diagram of a model of a battery cell stack coupled together with a variable impedance network. [Figure 9] FIG. 1 is a circuit block diagram in which a variable impedance network includes multiple switchable diodes coupled in series. [Figure 10] 10 is a graph demonstrating an example of the effect on a family of voltage versus state-of-charge characteristic curves of an exemplary battery cell stack as a result of introducing multiple switchable diodes coupled in series. [Figure 11] FIG. 1 is a circuit block diagram in which a variable impedance network includes multiple switchable resistive elements coupled in parallel. [Figure 12] 1 is a graph demonstrating an example of the effect on a family of voltage versus state-of-charge characteristic curves of an exemplary battery cell stack as a result of introducing a resistive element. [Figure 13] FIG. 1 is a block diagram of an energy delivery system. [Figure 14] FIG. 1 is a block diagram of an energy delivery system configured in accordance with an embodiment of the present disclosure. [Figure 15] FIG. 15 is a schematic diagram of a model of the energy delivery system of FIG. [Figure 16] FIG. 15 is a schematic diagram of a model of the energy delivery system of FIG. 14 in which multiple switchable diodes are coupled in series in a variable impedance network. [Figure 17] FIG. 1 is a flow chart diagram configured in accordance with an embodiment of the present disclosure. [Figure 18] FIG. 1 is a block diagram of an energy delivery system configured in accordance with an embodiment of the present disclosure. [Figure 19] FIG. 1 is a block diagram of an energy delivery system configured in accordance with an embodiment of the present disclosure. [Figure 20] 1 is a graph of an exemplary family of voltage versus state-of-charge characteristic curves during discharge for two battery cell stacks having different chemical compositions; [Figure 21] 1 is a plot of the discharge of two different battery cell stacks. [Figure 22] FIG. 1 is a block diagram of an energy delivery system configured in accordance with an embodiment of the present disclosure. [Figure 23] 1 is a graph of a family of voltage versus state-of-charge characteristic curves for two different battery cell stacks having different chemical compositions. [Figure 24] 1 is a plot of the discharge of two different battery cell stacks. DETAILED DESCRIPTION OF THE INVENTION

[0011] It will be understood that the specific embodiments described herein are shown by way of example and not as limitations on embodiments of the invention, and that the principal features of this invention can be employed in various embodiments without departing from the scope of the invention.

[0012] Embodiments of the present disclosure are described with respect to electrochemical storage systems (e.g., battery technology) due to their improved energy density and expanded range of applications and uses compared to other types of energy storage and mechanical devices. However, embodiments of the present disclosure are not limited to the use of battery cells for energy storage systems, and various embodiments of the present disclosure described herein may be applied to the use of any type of energy storage system, such as the energy storage systems disclosed herein, including, but not limited to, potential energy storage systems and kinetic energy storage systems.

[0013] Embodiments of the present disclosure provide an energy delivery system that combines multiple energy storage sources / systems of different chemical compositions or physical structures with a common control system configured to deliver energy from the systems according to the different performance characteristics of each system, thereby optimizing various operating characteristics of the combined system. According to certain embodiments of the present disclosure, an energy delivery system is provided that combines two or more batteries or other energy storage systems coupled in parallel and connected to a common load. Each of the combined energy storage systems includes battery cells of distinctly different chemical compositions, structures, or operating methods. According to embodiments of the present disclosure, the control system is configured to utilize separate variable impedance circuitry for each energy storage system to adjust the relative output current or discharge rate of each energy storage system to optimize, for example, the cycle life, depth of discharge, temperature, delivered power, and / or perceived safety of each energy storage system. For example, according to embodiments of the present disclosure, an energy delivery system may include two or more battery cell stacks, each having a different battery chemistry. Such multiple chemical systems may include two or more individual groups of cells connected in series / parallel to form two or more battery stacks under the control of a common control system to provide an energy delivery system. In such a non-limiting example, each battery stack can have its own distinct performance characteristics determined by the chemical composition of the cells. Two or more separate battery stacks may be combined in parallel to create a battery system that will deliver output power to a combined load. According to certain embodiments of the present disclosure, the series cell count of each battery stack may be predetermined to optimally match the total stack voltage of each stack. According to certain embodiments of the present disclosure, the parallel cell count of each battery stack may be predetermined to optimize the watt-hour capacity of each battery stack required by the end-use application.

[0014] Lithium-ion battery cells can generally be divided into two classes related to their energy or power capabilities. Lithium-ion “energy cells” are described as having maximized volumetric or gravimetric energy density and have an internal chemical composition that maximizes lithium-ion storage, but have high internal impedance that limits their ability to deliver large currents above 3C (where “C” refers to battery capacity). Such energy cells are utilized in applications such as laptop computers and mobile phones, where energy is slowly extracted over periods of hours or days. Lithium-ion “power cells” are described as having maximized current delivery capabilities and have an internal chemical composition that minimizes internal impedance to allow unimpeded lithium-ion mass transfer, thus enabling very large pulsed or continuous currents to be delivered without reducing the cell terminal voltage to its cutoff limit. Power cells can have discharge rates greater than 8C and up to 50C. Power cells typically have thicker current collectors than energy cells. These internal structural and chemical differences result in lower energy storage capacity and cycle life capabilities compared to energy cells. Power cells are typically used in applications such as cordless drills and other tools where high amounts of energy must be delivered over short periods of time and all of the stored energy is withdrawn over a discharge time, such as one hour or less. Within each cell classification (power or energy), there can be a wide range of cell part numbers, including different energy densities and different internal resistance values.

[0015] Lithium-ion batteries are available in a wide range of chemical compositions and construction techniques, each with specific relative advantages and disadvantages in performance related to cycle life, cost, safety, and energy density, as listed in the following table (Table 1). [Table 1]

[0016] Each of the listed battery types may be said to have a chemical composition that is substantially different from the others. If a designer were tasked with designing an energy storage system with a required cycle life of 5,000 charge and discharge cycles, it is clear from this table that lithium iron phosphate (LFP) or lithium titanium oxide (LTO) would be a better choice, while lithium nickel manganese cobalt (NMC) would be a less suitable choice due to its relatively shorter cycle life. It is also clear that LFP and LTO are the two highest-cost options available, so the relative cost of the system would be higher. Furthermore, the energy density of these two cell types is relatively lower, so more cells would be required to achieve any given system capacity in watt-hours.

[0017] Interpreting the foregoing exemplary information regarding the different relative properties of various energy storage sources / energy storage systems, for a large subset of possible energy storage performance requirements, there are combinations of two or more cell chemistries that can be configured into a single energy delivery system, thereby enhancing at least some properties of the system beyond those achievable using cells of only one chemistry.

[0018] To demonstrate the advantages of embodiments of the present disclosure, an exemplary energy delivery system will now be described, including an energy storage system of a first battery stack including LFP cells and a second battery stack including NMC cells, combined in a watt-hour capacity ratio of approximately 60% LFP and 40% NMC. This energy delivery system takes advantage of the relatively longer lifespan and enhanced safety characteristics of LFP, but is configured at a lower cost point and smaller size due to the lower relative cost and higher energy density characteristics of NMC. According to exemplary embodiments of the present disclosure, the performance and characteristics of the system may be further configured by adjusting the cell chemistry and cell types used, as well as the ratio in which they are combined. While the exemplary embodiments described hereinafter provide a system based on two stacks of energy storage elements, each based on different chemistries of lithium-ion batteries, according to various embodiments of the present disclosure, other energy storage systems, such as a system based on a first stack of battery cells and a second stack of ELDC, may also be utilized, which can be optimized for peak pulse power and enable faster recharges than would be possible using batteries alone. According to embodiments of the present disclosure, three or more energy storage systems (including at least two or more of such systems configured with different chemistries or energy storage technologies (e.g., selected from any potential energy storage system, chemical energy storage system, and / or kinetic energy storage system)) may be included to further customize the overall system performance and / or characteristics of the energy delivery system.

[0019] A battery cell can be modeled as an electronic network as shown in FIG. 1 (see, for example, R. Rao et al., "Battery Modeling for Energy-Aware System Design," Computer, Vol. 36, No. 12, pp. 77-87, December 2003, which is hereby incorporated by reference). A commonly accepted model is the open circuit voltage (herein referred to as "OCV" or "V"). oc "), the equivalent of an ideal voltage source representing a current (I s ) flows through the internal series resistance (R s ), and reactive components (R n C n ), where I n is the current flowing through the reactive component. The model considers the large number (i.e., n, where n ≧ Note that the RC element of 1) may also be included.

[0020] The voltage at the battery terminals under direct current ("DC") load conditions ("V batt」 ) is expressed by the following equation: V batt =V oc -R s I s -ΣR n I n

[0021] The battery's internal series resistance (R s +ΣR n ), sometimes called direct current internal resistance ("DCIR"). DCIR varies with the battery's state of charge ("SOC").

[0022] Figure 2 illustrates a graph showing both the battery cell DCIR and OCV as a function of the SOC of a typical NMC battery cell. oc The voltage will be higher and the DCIR will be lower. The DCIR increases at low states of charge, especially when the SOC drops below approximately thirty percent (30%).

[0023] Note that the time-based component can be a major factor in transient response and faradaic contributions during sudden load changes and charge and / or discharge cycles. When considering the overall behavior of a battery cell under DC load conditions where the current does not change with time, the resistive elements can be added and the capacitive elements can be ignored, and therefore the model can be written as: V batt =V oc -R batt I batt can be simplified to

[0024] This simplified cell model is shown in Figure 3. As a result, V batt is different I batt The NMC cell can be characterized by a family of voltage vs. SOC curves (also referred to herein as VI characteristic curves) at various currents taken at different current values. This family of VI characteristic curves for a typical single NMC cell is shown in FIG. 4. (In FIG. 4, and other figures showing graphs of voltage vs. SOC curves, each line represents the voltage at a different current value related to C, i.e., the rated capacity of the battery.)

[0025] Referring to FIG. 5, when a number (n) of identical battery cells are coupled in series, the model is: V batt =n(V oc -R batt I batt ) where n is the number of battery cells in series. A simplified model is shown in Figure 6.

[0026] Referring to FIG. 7, similar to the single battery cell example described above, an exemplary family of VI characteristic curves can be generated for such a series-connected cell system (in this non-limiting example, a typical NMC cell battery stack described above, with 11 cells connected in series).

[0027] Referring to FIG. 8, the battery stack includes a variable impedance circuit (referred to herein as "Z var " or "Z variable Z var The term Z represents the variable impedance of a circuit, which may be configured as a network of switchable elements (hence, variable impedance circuits will also be referred to herein as "variable impedance networks"). For any given output current value, Z var The term "energy source" refers to the energy source (e.g., battery cell stack) so equipped that var By adjusting the value of Z, the position of its normal characteristic voltage curve (i.e., var (discharge curve observed when V = 0) batt This allows the position of the output characteristic curve to be shifted downward.

[0028] Embodiments of the present disclosure may be configured to utilize any suitable circuitry in variable impedance circuits and / or networks. International Patent Application No. PCT / US2017 / 068301 (hereinafter referred to as “PCT / US2017 / 068301”) discloses exemplary implementations of circuitry including switchable elements that may be utilized in variable impedance networks according to various embodiments of the present disclosure described herein. As shown in FIG. 9 , a first implementation disclosed in PCT / US2017 / 068301 (FIG. 6 from PCT / US2017 / 068301 is provided as FIG. 9 ) utilizes several series-connected switchable diode circuits 610 a...610 c, which may be selectively inserted or removed from the circuit (using switching elements, e.g., FETs) according to a control algorithm implemented by a control system 602, which may be monitoring the system 600 in real time. 9 shows three series-connected switchable diode circuits 610a-610c, more or fewer such switchable diode circuits may be utilized depending on the exact system configuration and end application requirements. Note that the remaining elements shown in FIG. 9 will not be further described for simplicity, but can be found by reviewing PCT / US2017 / 068301.

[0029] Figure 10 shows the effect on the position of the characteristic curve when several series-connected diodes (in this case, five ideal diodes) are introduced into the circuit. The characteristic curves are shown for each case with no impedance insertion (i.e., Z variable Note that the voltage is shifted downward (decreased) by the same amount relative to Z = 0. In this non-limiting example, variable=5*Vf, where Vf is the forward voltage of an ideal diode. Note that battery current has no effect on the level of this shift; i.e., the curve for each current level shifts by the same amount. The variable nature of this embodiment using series-connected switchable diodes arises from the fact that any number of diodes (i.e., from zero diodes to the maximum number of installed diodes) can be added or removed from the circuit at any time. Thus, the VI characteristic curve associated with an installed battery cell stack can be shifted upward or downward at any time during operation of an energy delivery system configured with such variable impedance circuitry.

[0030] FIG. 11 provides a second exemplary implementation of the circuitry including the switchable elements disclosed in PCT / US2017 / 068301 (FIG. 7 from PCT / US2017 / 068301 is provided as FIG. 11). In this exemplary implementation, the circuitry including the switchable elements is configured as a parallel connection of switchable resistive elements 750a-750d. Each switchable resistive element may be selectively inserted or removed from the circuit (using switching elements, e.g., FETs) according to a control algorithm implemented by control system 702, and the total impedance of the switchable resistor network is determined by the number of switchable resistive elements switched on or off at a given time. In much the same manner as described with respect to FIG. 9, adding or subtracting resistance in such circuitry will result in a shift in the position of the VI characteristic curve of the battery cell stack. Note that the remaining elements shown in FIG. 11 will not be further described for the sake of brevity, but can be found by reviewing PCT / US2017 / 068301.

[0031] Figure 12 was set to a value of 0 ohms (i.e., Z variable =0) and the characteristic curves are based on a circuit configuration that includes a switchable resistive element set to a value of 1 ohm (i.e., Z variable10 shows a comparison with a curve from a circuit configuration including a switchable resistive element (=1 ohm). As can be seen, the resulting characteristic shift is different in nature from that demonstrated for the exemplary implementation when a switchable diode is implemented. Rather than shifting all curves downward by the same amount as shown in FIG. 10, the magnitude of the downward shift of each curve is proportional to the current represented by each curve. This results in the various characteristic curves “spreading apart” rather than all curves shifting downward by a fixed voltage value. The voltage drop across a resistor is current times resistance, while the voltage drop across an ideal diode is a fixed voltage that is independent of current. Thus, in the case of a switchable resistive element network, the effect on the VI characteristic curve is current-dependent (e.g., zero current results in zero voltage drop, one current results in one voltage drop, two currents results in two voltage drops, etc.). This means that the VI characteristic curve at each particular current level will "spread" depending on the resistance; the more resistance inserted, the more spread will result. In the case of switchable diodes, the forward voltage drop is fixed regardless of the amount of current. Therefore, all VI characteristic curves will shift downward by the number of diodes switched into the circuit (i.e., the number of diodes not shorted out by the switch). Regardless of the amount of current present in the diodes, one diode will shift all the curves downward by the same amount (e.g., Vf = 0.75V), two diodes will shift the curve downward by 1.5V, five diodes will shift the curve downward by 3.75V, and so on.

[0032] Referring to FIG. 13, a system 1300 is shown in which a battery stack 1301 includes a plurality of series-connected battery cells and a variable impedance network 1302 controls V oEach cell in the battery stack 1301 exhibits a voltage at its positive terminal. The voltage of each cell in the battery stack 1301 is monitored by an analog front end measurement device (“AFE”) 1303. The AFE 1303 may also collect temperature data and deliver the collected data to a control system (e.g., a microcontroller “MCU”) 1304. The battery stack 1301 is connected to V through a sense resistor (Rsense) 1305. o Each side of the sense resistor 1305 is coupled to a fuel gauge integrated circuit (“IC”) 1306 to detect battery current (i o ) to the fuel gauge IC 1306. The fuel gauge IC 1306 can communicate information regarding the state of charge ("SOC") of the battery stack 1301 to the MCU 1304. The MCU 1304 is coupled to and controls the variable impedance network 1302. The MCU 1304 can implement one or more control algorithms configured to control (e.g., optimize) the operating state of the system 1300 in a predetermined manner. For example, a control algorithm operated by the control system 1304 may determine the state of the battery stack 1301 and operate the variable impedance network 1302 to optimize the V-I characteristic curve of the system 1300 by adjusting the position of the V-I characteristic curve that determines this parameter. o The MCU 1304 may be configured to control (e.g., regulate or modify) the voltage presented to the positive terminal. The MCU 1304 may be configured to communicate data and / or information to an external host system (e.g., via a communication link or bus 1307).

[0033] Referring to FIG. 14, an energy delivery system 1400 configured in accordance with an embodiment of the present disclosure is shown. In the energy delivery system 1400, a first battery cell stack 1401a is coupled in parallel to a second battery cell stack 1401b, where each of the battery cell stacks 1401a and 1401b may be coupled to similar control and monitoring circuitry. The battery cell stacks 1401a, 1401b may be coupled to a common control system (e.g., a microcontroller “MCU”) 1404, which may collect parametric information from each battery stack (e.g., simultaneously) and implement control algorithms to control the operation of either or both of the variable impedance networks 1402a, 1402b. The voltage of each cell in the battery stack 1401a may be monitored by an analog front-end measurement device (“AFE”) 1403a. The AFE 1403a may also collect temperature data and transmit the collected data to the control system 1404. The battery stack 1401a is connected to V through a sense resistor (Rsense) 1405a. o Negative. Each side of the sense resistor 1405a can be coupled to a fuel gauge integrated circuit ("IC") 1406a to provide a voltage representative of the value of the battery current (i1) to the fuel gauge IC 1406a whenever current is present in the sense resistor 1405a. The fuel gauge IC 1406a can communicate information regarding the state of charge ("SOC") of the battery stack 1401a to the control system 1404. The voltage of each cell in the battery stack 1401b can be monitored by the AFE 1403b. The AFE 1403b may also collect temperature data and deliver the collected data to the control system 1304. The battery stack 1401b is connected to V through the sense resistor (Rsense) 1405b. oNegative. Each side of sense resistor 1405b can be coupled to fuel gauge IC 1406b to provide a voltage representative of the (i2) value of the battery current to fuel gauge IC 1406b whenever current is present in sense resistor 1405b. Fuel gauge IC 1406b can communicate information regarding the SOC of battery stack 1401b to control system 1304. Essentially, fuel gauge ICs 1406a, 1406b can be configured to measure the instantaneous current as well as the battery temperature and then calculate the average current, instantaneous state of charge, number of charge / discharge cycles the battery stack has experienced, battery stack resistance, and other parameters from the measured or digitally delivered data.

[0034] According to certain embodiments of the present disclosure, V o Note that the positive output terminal is common between the variable impedance networks 1402a and 1402b. As a result, according to an embodiment of the present disclosure, the variable impedance networks 1402a and 1402b are connected to the terminal V o Rather than controlling the output voltage presented to Positive, the variable impedance networks 1402a, 1402b may be configured to control the level of current flowing through each variable impedance network 1402a, 1402b and delivered to the output terminals under selective control by signals from the control system 1404. Selective control of the variable impedance networks 1402a, 1402b by the control system 1404 may be performed such that each of the battery stacks 1401a, 1401b is maintained within a predetermined output current range in accordance with predetermined performance criteria of the energy delivery system 1400.

[0035] The control system 1404 may be configured to communicate data and / or information to an external host system (e.g., via a communication link or bus 1407). Internal communication between the various components and / or external communication from the control system 1404 may be wired or wireless. Possible communication protocols include, but are not limited to, SMB, I2C, RS232, TTL, Serial, USB, CAN, Network, etc.

[0036] In a non-limiting example, the variable impedance networks 1402a, 1402b may include multiple switchable resistive elements, such as the configuration of switchable resistive elements 750a...750d utilized in the system 700 of FIG. 11. Each switch 710a...710d can be individually opened or closed by the control system 1404 according to a predetermined control algorithm. The resistors 750a...750d can be configured with the same or different resistance values. By altering the number of resistors 750a...750d coupled in parallel by their corresponding switches 710a...710d, the effective resistance of either or both of the variable impedance networks 1402a, 1402b can be adjusted over a predetermined range (e.g., from a predetermined minimum resistance value to a predetermined maximum resistance value).

[0037] The energy delivery system 1400 can be represented by a simplified model shown in FIG. 15, which is represented by the equation: V o Positive=V1-R1*i1-i1*Variable R1 V o Positive=V2-R2*i2-i2*Variable R2 i1+i2=i output It can be described by:

[0038] Consider an exemplary embodiment of the present disclosure in which energy delivery system 1400 includes battery cell stacks having different sets of operating parameters (e.g., due to different materials and / or chemical compositions), where cell stack 1401a includes cells configured with a higher cycle life relative to cell stack 1401b, and cell stack 1401b includes cells configured with a lower cycle life relative to cell stack 1401a, but may include cells with a higher relative energy density. Assume the energy capacities of the two cell stacks are approximately the same. According to an embodiment of the present disclosure, it may be advantageous for the operation of energy delivery system 1400 to have the cell stack with the higher relative cycle life (i.e., cell stack 1401a) deliver the majority of the energy during discharge. For example, according to an embodiment of the present disclosure, control system 1404 may be configured such that during discharge, the current drawn from cell stack 1401a is twice the current drawn from cell stack 1401b, or in other words, the cyclic energy drawn from cell stack 1401a is twice the cyclic energy drawn from cell stack 1401b, to take advantage of the longer cycle life of cell stack 1401a. Under such an exemplary operating scenario, the equation becomes: i1=2*i2 (i1 is always twice i2) V o Positive=V1-R1*2*i2-2*i2*Variable R1, and V o Positive=V2-R2*i2-i2*Variable R2 It can be rewritten.

[0039] The values ​​V1, V2, R1, and R2 can be known from cell characterization curves (such as those shown in FIG. 2) associated with the type of battery cells utilized in the cell stacks 1401a, 1401b, and it is therefore trivial to solve the equations for values ​​of Variable R1 and Variable R2 to maintain the condition i1=2*i2 and therefore configure the variable impedance networks 1402a, 1402b with the appropriate values.

[0040] The energy delivery system 1400 can also be represented by the simplified model shown in FIG. 16, where the variable impedance networks 1402a, 1402b each include a plurality of switchable diodes, such as the configuration of switchable diodes 610a...610c utilized in the system 600 of FIG. 9. Each of the switchable diodes 610a...610c is coupled to a switch (e.g., a FET) that can bypass any current around the diode. The switch can be opened or closed according to a control signal received from the control system 1404 (e.g., similar to the control signals 621a...621c of FIG. 9). Each of the diodes can be configured with the same or different forward voltage drop (Vf) values. The number of diodes whose associated switches are open and therefore contribute to a forward voltage drop for their associated variable impedance networks 1402a, 1402b, and the number of diodes whose associated switches are closed and therefore do not contribute to a forward voltage drop for their associated variable impedance networks 1402a, 1402b, are adjustable by the control system 1404, so that the sum of the voltage drops is variable.

[0041] Similar to the example described with respect to FIG. 15, this system is represented by the equation: V o Positive=V1-V var1 -i1*R1 V o Positive=V2-V var2 -i2*R2 i1+ i2=i output It can be described by:

[0042] Again, as in the previous example, consider an energy delivery system 1400 that includes two different battery cells, for example, where cell stack 1401a includes cells configured with a very high cycle life relative to cell stack 1401b, and cell stack 1401b includes cells configured with a lower cycle life relative to cell stack 1401a, but may include a higher relative energy density. Assume the energy capacities of the two cell stacks are approximately the same. Also, as in the previous example, it is desired that i1 = 2 * i2, so the equation becomes: i1+i2=i output i1=2*i2 (i1 is always twice i2) V o Positive=V1-V var1 -2*i2*R1 V o Positive=V2-V var2 -i2*R2 Consider a rewritable energy delivery system 1400.

[0043] Again, the values ​​V1, V2, R1, and R2 are known from cell characterization curves such as those shown in Figure 3, and therefore V can be adjusted to maintain the condition i1 = 2 * i2. var1 and V var2 It is trivial to solve the equation for the exact value of , and configure the number of active diodes in each impedance network with the appropriate value.

[0044] The values ​​V1, V2, R1, and R2 can be known from cell characterization curves (such as those shown in FIG. 2) associated with the type of battery cells utilized in the cell stacks 1401a, 1401b, and therefore can be adjusted to maintain the condition i1=2*i2. var1 and V var2It is trivial to solve the equation for the value of Vf and therefore configure the number of active diodes in each variable impedance network 1402a, 1402b with the appropriate value. It is important to note that because the value of Vf of each diode is a fixed characteristic value depending on the semiconductor technology and device type, the exact value of each of the variable impedance networks 1402a, 1402b cannot be precisely adjusted, but rather is some fixed multiple of the Vf value.

[0045] According to embodiments of the present disclosure, implementations of the energy delivery system 1400, whether the variable impedance networks 1402a, 1402b are implemented utilizing switchable resistive elements, switchable diodes, or a combination thereof, may utilize control algorithms programmed within the control system 1404, possibly embodying equations described with respect to either FIG. 15 or FIG. 16, to control the switching of resistive elements or diodes within the variable impedance networks 1402a, 1402b. Additionally, according to embodiments of the present disclosure, the battery cell specific values ​​V, V, R, and R may be determined from their individual cell characterization curves. Because such values ​​are highly variable with cell state-of-charge, temperature, and age, such values ​​may be incorporated into any suitable database, such as a look-up table, to incorporate characterized data and create models to estimate aging characteristics.

[0046] According to embodiments of the present disclosure, the control system 1404 may utilize a control algorithm based on successive approximations. For example, the energy delivery system 1400 may be initialized and the initial states of the variable impedance networks 1402a, 1402b may be configured (e.g., by solving a descriptive equation) before any energy discharge begins. Then, once discharge begins, rather than performing continuous equation processing, the control system 1404 may repeatedly loop through a parametric measurement step in which dynamically changing operating conditions of the energy delivery system 1400, such as the voltage, current, and SOC of each cell stack 1401a, 1401b, are measured, followed by a comparison step in which the output current or other selected parameters of each cell stack 1401a, 1401b are compared to each other and to targeted performance, and then a correction step in which the variable impedance networks 1402a, 1402b are adjusted (e.g., in small discrete steps) to move the controlled parameters toward the desired behavior with each adjustment. A delay may be added to the loop to allow the battery parameters to stabilize after each adjustment to either of the variable impedance networks 1402a, 1402b. For example, using the previous example of energy delivery system 1400 described with respect to FIG. 14, control system 1404 may be configured to make i1 and i2 equal, or make i1 a fixed percentage of i2, or constantly maintain i1 a fixed percentage of i2 only when the SOC of cell stack 1401a is above 25% and a different fixed percentage when the SOC of cell stack 1401a is below 25%, or reduce the current of the hottest cell stack to 10% of the current of the coldest cell stack whenever the difference between the temperatures of the cell stacks reaches some threshold. The foregoing examples do not limit the possible variations in possible control algorithms.

[0047] 17 shows a flowchart of a process 1700 including an example control algorithm performed within the control system 1404 of the energy delivery system 1400 according to an embodiment of the present disclosure. As will be further described, the process 1700 may also be performed within the control system 1804 of the system 1800 described with respect to FIGS. 18, 19, and 22.

[0048] The energy delivery system 1400 may be initialized (start). In processing block 1701 (access machine state), the state of the energy delivery system 1400 may be determined. For example, voltage (e.g., of cells in the battery stacks 1401 a, 1401 b via AFEs 1403 a, 1403 b), current (e.g., sensed by sense resistors 1405 a, 1405 b), and temperature (e.g., of cells in the battery stacks 1401 a, 1401 b via AFEs 1403 a, 1403 b) may be measured, and this data may be collected by the control system 1404. Using this data, in processing block 1702, a determination can be made as to whether the energy delivery system 1400 is ready for discharge. If not, some corrective action can be taken in processing block 1710.

[0049] For example, if the collected data determines that one or both of the cell stacks 1401a, 1401b are not fully charged, a charging current may be applied from an external energy source (e.g., see chargers 603, 703 in FIGS. 9 and 11, respectively). If the collected data determines that one or more cells in one or both of the cell stacks 1401a, 1401b are too hot, a cooling system (not shown) may be activated. If a manual interlock is engaged, the energy delivery system 1400 may be configured to wait for it to be cleared. After corrective action is initiated, the process 1700 may return to process block 1701, and this loop may continue until the process 1700 determines within the control system 1404 that the energy delivery system 1400 is ready to discharge energy to a load (not shown).

[0050] Once process 1700 within control system 1404 determines that energy delivery system 1400 is ready to discharge, both variable impedance networks 1402a, 1402b may be set to predetermined initial values. These initial values ​​may be determined from equations (e.g., see equations described with respect to FIGS. 15 and 16) performed within control system 1404 in real time, or may be set from a predetermined lookup table of predetermined initial values ​​based on parameters such as SOC, cell stack voltage, temperature measured in process block 1701, and / or from a predetermined lookup table based on VI characteristic curves associated with cell stacks 1401a, 1401b.

[0051] Once the initial values ​​of the variable impedance networks 1402a, 1402b are set, the process 1700 may, for example, configure the energy delivery system 1400 (e.g., V o Positive terminal and V oNegative terminal) while waiting for the load current to begin discharging. This may involve process 1700 looping back to process block 1701. Once a discharge current is detected in process block 1704, process block 1705 collects parameters (also referred to as “parametric data”) from the battery cell stacks 1401 a, 1401 b, the variable impedance networks 1402 a, 1402 b, and / or other parts of the system 1400 (e.g., voltage, current, temperature, SOC, charge / discharge cycles, resistance, impedance, etc.) using the AFEs 1403 a, 1403 b and current sensors 1405 a, 1405 b. In process block 1706, this data may be analyzed to determine whether continued discharge is acceptable. For example, parameters that may terminate the discharge include cell stack voltage below a safe limit, cell stack current above a safe limit, cell stack temperature outside of a safe limit, engagement of a manual safety interlock, and / or any other failure in the control or measurement systems, etc. If at process block 1706 it is determined that the discharge cannot safely continue, process 1700 may proceed to process block 1710 to take appropriate action.

[0052] If, at process block 1706, it is determined that the discharge can safely continue, then at process block 1707, it may be determined whether adjustments to either or both of the variable impedance networks 1402a, 1402b are necessary. For example, according to non-limiting embodiments of the present disclosure, a control algorithm implemented in control system 1404 may be configured to maintain the average current of operation (e.g., as measured by current sensors 1405a, 1405b over a predetermined period of time) equal in both cell stacks 1401a, 1401b. As a result, if recently collected parametric data indicates that the average current in cell stack 1402a is higher than the average current in cell stack 1401b, the control algorithm implemented by control system 1404 may be configured to take one of two possible actions to apply a correction. The MCU 1404 can either signal the switches in variable impedance network 1402a to increase the value of its total impedance, or the control system 1404 can signal the switches in variable impedance network 1402b to decrease the value of its total impedance. While either option may be acceptable, the control system 1404 may be configured to prioritize one of these corrective actions over the other depending on any one or more predetermined factors. For example, variable impedance network 1402a may already be set near its minimum impedance value, in which case the control system 1404 may be configured to decrease the impedance value of variable impedance network 1402b instead. Because the control system 1404 is configured to know the state of both variable impedance networks 1402a, 1402b, the control system 1404 can be configured to choose the most appropriate action.Once a corrective action is determined in processing block 1707, the control system 1404 sends one or more control signals to one or both of the variable impedance networks 1402a, 1402b to implement the action (i.e., apply the new impedance settings) in processing block 1708. Once the new settings are applied, process 1700 may be configured to implement a delay routine (processing block 1709) to allow one or both of the battery cell stack currents (i1, i2) to stabilize under these new settings. Once this delay has expired, process 1700 may return to processing block 1705. It should be noted that the foregoing algorithm described with respect to processing block 1707 is exemplary and not limiting with respect to embodiments of the present disclosure.

[0053] Embodiments of the present disclosure are further illustrated by the following examples, which are provided to illustrate the presently disclosed subject matter and should not be construed as limiting. The examples describe testing that was performed to confirm that embodiments of the present system are capable of conveying and publishing one or more pieces of information under various conditions that illustrate various environments in which embodiments of the present system may be utilized.

[0054] Referring to FIG. 18 , an energy delivery system 1800 configured in accordance with an embodiment of the present disclosure is shown. In the energy delivery system 1800, a first battery cell stack 1801 a is coupled in parallel to a second battery cell stack 1801 b, where each battery cell stack may be coupled to similar control and monitoring circuitry. The battery cell stacks 1801 a, 1801 b may be coupled to a common control system (e.g., a microcontroller “MCU”) 1804, whereby parametric information from each battery stack may be collected (e.g., simultaneously) and a control algorithm may be implemented to control the operation of either or both of the variable impedance networks 1802 a, 1802 b. The voltage of each cell in the battery stack 1801 a may be monitored by an analog front-end measurement device (“AFE”) 1803 a. The AFE 1803 a may also collect temperature data and transmit the collected data to the control system 1804. The battery stack 1801a is connected to V through a sense resistor (Rsense) 1805a. o Negative. Each side of the sense resistor 1805a can be coupled to a fuel gauge integrated circuit ("IC") 1806a to provide a voltage representative of the value of the battery current (i1) to the fuel gauge IC 1806a whenever current is present in the sense resistor 1805a. The fuel gauge IC 1806a can communicate information regarding the state of charge ("SOC") of the battery stack 1801a to the control system 1804. The voltage of each cell in the battery stack 1801b can be monitored by the AFE 1803b. The AFE 1803b may also collect temperature data and deliver the collected data to the control system 1804. The battery stack 1801b is connected to V through the sense resistor (Rsense) 1805b. oNegative. Each side of the sense resistor 1805b can be coupled to a fuel gauge IC 1806b to provide a voltage representative of the value of the battery current (i2) to the fuel gauge IC 1806b whenever current is present in the sense resistor 1805b. The fuel gauge IC 1806b can communicate information regarding the SOC of the battery stack 1801b with the control system 1804. The control system 1804 can be configured to communicate data and / or information to an external host system (e.g., via a communication link or bus 1807). Internal communication between the various components and / or external communication from the control system 1804 can be wired or wireless. Available communication protocols include, but are not limited to, SMB, I2C, RS232, TTL, Serial, USB, CAN, Network, etc.

[0055] Each variable impedance network 1802a, 1802b includes several diodes along with bypass switches, such as those described with respect to FIG. 16. While the number of diodes and corresponding switches is shown to be the same in each variable impedance network 1802a, 1802b, the actual number may be the same or different between the two. The number of diodes present in each variable impedance network 1802a, 1802b is determined by the number of diodes connected from the high side of each battery cell stack 1801a, 1801b to the output terminal V oA maximum voltage drop to positive is determined, which is the sum of the forward voltage (Vf) drops of all the diodes. According to certain embodiments of the present disclosure, one or more of the diodes can have different parametric characteristics such that a different forward voltage drop is achieved by each diode. The number of active and bypassed diodes in each variable impedance network 1802a, 1802b can be controlled by the control system 1804 to effect a downward shift of a predetermined magnitude in the characteristic curve of each battery stack 1801a, 1801b, and thus affect the load current contribution of each battery stack 1801a, 1801b in the energy delivery system 1800.

[0056] FIG. 18 shows the battery stacks 1801a and 1801b and the output terminal V o 18 shows the energy delivery system 1800 with the switches in both variable impedance networks 1802a, 1802b open so that the full forward voltage drop of all of the diodes in each variable impedance network 1802a, 1802b is realized between the positive and negative terminals. While FIG. 18 discloses a dual battery stack energy delivery system, embodiments of the present disclosure may be configured with three or more battery stacks coupled in various series and / or parallel combinations and monitored and controlled by a control system 1804.

[0057] According to an exemplary embodiment of energy delivery system 1800, battery stack 1801a includes battery cells constructed with a relatively high cycle life battery chemistry (e.g., LFP or LTO) such that its terminal voltage and VI characteristic curve overlap with that of battery stack 1801b including NMC battery cells, as shown, for example, by the exemplary VI characteristic curve in FIG. 20. LFP stack 1801a includes 13 cells and has a typical full charge voltage between 44 V and 46.8 V (3.6 V / cell). NMC battery stack 1801b includes 11 cells and has a typical full charge voltage between 43.3 V and 46.2 V (4.0 V / cell). Both the LFP and NMC battery stacks can be charged to the same voltage at full charge, or alternatively, the maximum charge voltage can be adjusted so that the voltage of one of the battery stacks can be maintained higher than the voltage of the other battery stack. In this embodiment, the LFP cell stack 1801a and the NMC cell stack 1801b are configured to have similar chemical capacities in ampere-hours.

[0058] Referring to FIG. 19, in a default mode of operation, the system 1800 may be configured such that all of the diode switches in both variable impedance networks 1802a, 1802b are closed, bypassing the diodes, so that the VI characteristic curves of each cell stack 1801a, 1801b are V oThe VI characteristic curves will be presented at the positive terminal. Because the two VI characteristic curve families lie on top of each other under most conditions of state of charge, within the load current range of interest, the battery stacks 1801a, 1801b will share the load based on their stack voltages, as determined by their VI characteristic curves, at all times during discharge. At any given moment, the current in each battery stack, i1 in the LFP stack 1801a and i2 in the NMC stack 1801b, will lie on their respective VI characteristic curves corresponding to equal voltages at the battery terminals. The greater the difference in the positions of the VI characteristic curves, the greater the current disparity between the stacks 1801a, 1801b. Referring to the battery stack voltages as a function of state of charge shown in FIG. 20 , from an exemplary discharge of the parallel-coupled LFP battery stack 1801a and NMC battery stack 1801b, it can be seen that at a certain load point, initially, the NMC battery stack 1801b has a higher terminal voltage for approximately the first 10% depth of discharge. During the remaining depth of discharge, LFP cell stack 1801a has a higher terminal voltage and a proportionally greater current share during discharge.

[0059] FIG. 21 shows an example discharge graph of the system 1800 configured in FIG. 19 at a constant power of 100 W (the diode switches in both variable impedance networks 1802a, 1802b are all closed and both are Z var=0, thereby coupling the battery stack voltage directly to the output load). Each battery stack 1801a, 1801b is charged to a starting voltage of 44V. The discharge duration is approximately 1.8 hours. Each battery stack 1801a, 1801b is allowed to discharge and balance current based on the VI characteristic curve of each battery stack. Consistent with the voltage curves in FIG. 20, upon coupling a load to the energy delivery system 1800, FIG. 21 shows that current i1 rises in the LFP stack 1801a and the voltage drops rapidly below that of the NMC stack 1801b. This is due to the steep open-circuit voltage curve of LFP chemistry near the full charge state and the shift in operating point from the light-load VI curve to the higher-current VI curve. The NMC stack 1801b soon achieves a slightly higher terminal voltage relative to the LFP stack 1801a and delivers a significantly larger portion of the load current. After approximately 0.18 hours of discharge, the NMC voltage drops due to its reduced SOC, and its stack voltage begins to droop into the range of the LFP stack 1801a. At this point in the discharge, the LFP stack 1801a begins to deliver a higher percentage of current. From this point on, the LFP stack 1801a maintains a higher voltage and current than the NMC stack 1801b, causing the LFP stack 1801a to drop in SOC faster than the NMC stack 1801b and eventually become depleted. The SOC of the LFP stack 1801a slowly moves from 100% to approximately 5% over a period of approximately 1.4 hours. At this point in the discharge event, the LFP stack 1801a is nearly depleted of energy, causing its terminal voltage to drop below that of the NMC battery stack 1801b. The NMC cell stack 1801b then takes over, increasing its current share to nearly 100% during the last few minutes of discharge.

[0060] 22 illustrates an exemplary embodiment of the operation of processing blocks 1707-1708 of system 1800, the purpose of which is to configure system 1800 to bias energy discharge from NMC stack 1801b to LFP stack 1801a so that LFP current i1 is always higher than NMC current i2 from the start of discharge until the energy in LFP stack 1801a is fully depleted. In this exemplary embodiment, the diode switch in variable impedance network 1802a of LFP stack 1801a is closed to provide Z var =0 is generated, and the diode switch in variable impedance network 1802b for NMC stack 1801b opens, Z var The maximum value of (Z var 23, the VI characteristic curve of the LFP remains the same as in the previous example (see FIG. 20), but this time the VI characteristic curve of the NMC has shifted downward by an amount equal to 3*Vf.

[0061] As expected, based on the configuration of energy delivery system 1800 shown in FIG. 22, the voltage curve for NMC stack 1801b is var The shifted voltage curves are shown in Figure 23. The LFP voltage is higher than the NMC voltage over almost the entire SOC range, and its associated Z var This downward shift in NMC voltage caused by ΔΘ ...

[0062] FIG. 24 shows an example discharge graph of the system 1800 configured in FIG. 22 at a constant power of 100 W. Each cell stack 1801a, 1801b is charged to a starting voltage of 44 V. The discharge duration is approximately 1.8 hours. In this example, the diode switch in the variable impedance network 1802a is closed to set Z var = 0, and the LFP battery stack voltage iso Positive, while the diode switch in variable impedance network 1802b remains open, causing the NMC stack voltage to be offset downward by 3*Vf. The operating points of each of the battery stacks 1801a, 1801b are points on their respective VI characteristic curves such that the output current of the energy delivery system 1800 is biased toward the LFP stack 1801a much more than in the examples of FIGS. 20 and 21. Contrasting the discharge shown in FIG. 24 with the discharge shown in FIG. 21, it can be seen that initially, NMC stack 1801b delivers approximately 20% of the load current due to the lower position of the NMC VI characteristic curve. As the system operating point transitions through the VI characteristic curves according to the changing SOC of the various battery stacks, there is no current “inversion” observed, where the NMC current (i2) initially rises above the LFP current (i1) and then suddenly reverses after a short period of time. LFP stack 1801a maintains a higher proportion of the total discharge current until such time as LFP stack 1801a is nearly depleted. The SOC of LFP stack 1801a slowly transitions from 100% to about 5% over a period of about 1.4 hours. At this point in the discharge event, LFP cell stack 1801a is nearly depleted of energy, and at a low state of charge such as this, the LFP VI characteristic curve drops below the corresponding NMC VI characteristic curve at the much higher NMC SOC, and therefore NMC stack 1801b takes over, steadily increasing its proportion of the total power until the end of discharge.

[0063] By adjusting each variable impedance network 1802 a, 1802 b, and thereby the position of the corresponding VI characteristic curve, the current sharing between the different cell stacks can be shifted to bias the discharge current toward one stack or the other to suit a particular purpose and optimize specific performance characteristics. For example, biasing the discharge current toward a cell stack with a relatively high cycle life and away from a stack with a relatively low cycle life will result in the cell stack with the higher cycle life delivering many times more cycle energy than the other cell stack over hundreds of moderate duration discharge events.

[0064] The total depth of discharge of an energy storage system will depend on the load duration. Cell stacks often only complete a partial discharge, delivering 40% to 70% of their total stored energy. As demonstrated in the example in FIG. 24, for a partial discharge lasting 1.3 hours, the high cycle life LFP cell stack 1801a discharged 95% of its energy (completed 0.95 cycles), while the NMC cell stack 1801b discharged only approximately 40% of its energy (completed 0.40 cycles). If this same discharge were performed 1000 times, the LFP cell stack 1801a would be considered to have completed 950 cycles, compared to the NMC cell stack 1801b, which completed only 400 cycles.

[0065] According to various embodiments of the present disclosure, energy delivery systems 1400 and 1800 may be similarly configured so that the control system, AFE, fuel gauge IC, and sense resistor operate in a substantially similar manner, except for modifications that may be made to either system depending on the type of energy storage system to which they are coupled and the type of configuration utilized within the variable impedance circuitry.

[0066] The digital communication links 1407, 1807 may be configured to transmit specific data from the control systems 1404, 1804 to a host system (not shown). Energy delivery systems such as 1400, 1800 may be embedded in larger systems such as computers, electric bicycles or scooters, electric vehicles, etc. These larger systems are therefore considered hosts to their embedded energy delivery systems and may have other systems, such as motor controllers and user or operator interfaces, that may rely on the latest state of their supporting energy delivery systems for safe operation. In the case of an electric vehicle, such a host system could be a motor control system that may reduce the motor speed if the battery temperature exceeds some threshold or if the available energy falls below some threshold. The digital communication links 1407, 1807 may be configured to deliver an instantaneous description of the state of the energy delivery systems 1400, 1800 upstream to the drive equipment.

[0067] According to embodiments of the present disclosure, the fuel gauge disclosed for energy delivery system 1400, 1800 may be implemented as an integrated circuit, which may be in a package separate from MCU 1404, 1804, although its functional portions may also be integrated within MCU 1404, 1804. The fuel gauge may be configured to receive battery temperature and battery cell voltage information, either by direct measurement or as packets of digital data from the AFE relayed to the fuel gauge by MCU 1404, 1804, and / or may include an analog-to-digital converter configured as a coulomb counter that measures the analog voltage appearing across a current sense resistor and mathematically integrates these measurements continuously in either the digital or analog domain. This voltage developed across the sense resistor is a direct representation of the current flowing into or out of the battery cell stack, where a negative voltage represents current flowing out of the battery cell stack (discharge) and a positive voltage represents current flowing into the battery cell stack (charge). By mathematically integrating these currents over time, the net charge change contained in the battery cell stack can be determined, and by adding the net battery charge change and the known starting SOC at any given time, the current SOC can be determined. The fuel gauge may also be configured to include digital hardware and programmed instructions to compute not just the sum of the net charge change and the current SOC, but also other parameters such as the instantaneous current in the sense resistor, the average current in the sense resistor over some average period of time (such as a few seconds or tens of seconds), the total number of charge and discharge cycles (determined by the total charge passed in each direction beginning with the start of use of the battery cell stack), and the resistance of the battery cells, both individually and / or summed over all the cells.

[0068] According to embodiments of the present disclosure, the battery stacks disclosed for energy delivery systems 1400 and 1800 may include backflow prevention devices managed by a common control system. The function of such backflow prevention devices is to prevent the undesired transfer of energy from one battery stack to another. The operation of such backflow prevention devices is described in PCT / US2017 / 068301.

[0069] According to an alternative embodiment of the present disclosure, a variable impedance network may be constructed from several series-connected resistors and associated switches connected in parallel. An energy delivery system constructed with such variable impedance network may provide the ability to manipulate the VI characteristic curves of separate battery stacks in a similar manner and achieve similar results in biasing discharge currents between battery stacks or energy storage systems.

[0070] In yet another embodiment of the present disclosure, the variable impedance network may be configured with resistors connected in parallel to provide finer resolution in the current-dependent voltage drop than resistors connected in series. The increased resolution in voltage steps can be used to further adjust the output voltage of the energy delivery system 1400, 1800.

[0071] According to alternative embodiments of the present disclosure, one or more of the switchable diodes in any or all of the variable impedance networks may be replaced with a network of parallel switchable resistors. Under such a configuration, the control system may utilize the series diodes for "coarse" adjustments and the parallel resistors for "fine" adjustments. Nevertheless, embodiments of the present disclosure may be implemented with one or more of the variable impedance networks including switchable diodes, switchable resistors, or a combination of both.

[0072] The embodiments of the present disclosure described herein can be utilized in uninterruptible power supply (UPS) systems and energy storage systems where high energy density is required to maximize volumetric energy storage. They also require high cycle life, especially under repetitive deep discharge conditions. Energy storage systems may be configured to undergo a full charge / discharge cycle once per day. However, the depth of discharge of the system will vary based on load demand. Low load demand will reduce the required energy delivered by the energy storage system, first depleting battery stacks designed for high cycle count and not depleting battery stacks designed for power density.

[0073] The embodiments of the present disclosure described herein can be utilized in vehicle applications where long cycle life, long run time are a priority, and where there is a periodic demand for transient high current loads.

[0074] As will be appreciated by those skilled in the art, aspects of the present invention (e.g., control systems 1404, 1804 and process 1700) may be embodied as a system, method, and / or program product. Accordingly, aspects of the present invention (e.g., control systems 1404, 1804, AFE, fuel gauge, variable impedance circuitry) may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which may be generally referred to herein as a “circuit,” “circuitry,” “module,” or “system.” Furthermore, aspects of the present invention (e.g., process 1700) may also take the form of a program product embodied in one or more computer-readable storage media having computer-readable program code embodied therein. (Although any combination of one or more computer-readable media may be utilized, and the computer-readable media may be a computer-readable signal medium or a computer-readable storage medium.)

[0075] It will also be noted that each block of the circuit block diagram and / or the functionality represented in process 1700, and combinations of blocks in the circuit block diagram and / or the functionality represented in process 1700, may be implemented by dedicated hardware-based systems that perform the specified functions or acts, or by a combination of dedicated hardware and computer instructions. For example, the modules (e.g., control systems 1404, 1804, AFE, fuel gauge, variable impedance circuitry) may be implemented as hardware circuits comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, controllers, or other discrete components. The modules (e.g., control systems 1404, 1804, AFE, fuel gauge, variable impedance circuitry) may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, or programmable logic devices.

[0076] The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the present specification. As used throughout this application, the word "may" is used in its permissive sense (i.e., having the potential to) rather than its mandatory sense (i.e., must). Similarly, the words "include," "including," "includes," "contain," "containing," and "contains" mean including, but not limited to.

[0077] Various units, circuits, circuitry, or other components (e.g., control systems 1404, 1804, AFEs, fuel gauges, variable impedance networks) may be described as being “configured” to perform a task or tasks. In such contexts, “configured to” broadly describes structure that generally means “having circuitry capable of” performing that task or tasks during operation. Thus, a unit / circuit / component may be configured to perform a task even if the unit / circuit / component is not currently turned on. Generally, the circuitry forming the structure corresponding to “configured to” may include hardware circuits and / or software (including firmware, resident software, microcode, etc.). Similarly, various units / circuits / components may be described as performing a task or tasks for convenience of description. Such descriptions should be interpreted to include the phrase “configured to.” It is expressly intended that the listing of a unit / circuit / component that is configured to perform one or more tasks does not invoke the interpretation of 35 USC §112, paragraph 6, for that unit / circuit / component.

[0078] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosed subject matter belongs.

[0079] As used herein, the terms "about" and "approximately" are used to provide flexibility with respect to the endpoints of a range of numerical values, by providing that a given value may be "a little above" or "a little below" the endpoint.

[0080] In the description herein, flowchart-style techniques may be described as a series of sequential actions. The order of actions, and the parties performing the actions, may be freely changed without departing from the scope of the teachings. Actions may be added, deleted, or modified in some manner. Similarly, actions may be reordered or looped. Furthermore, while a process, method, algorithm, or the like may be described in a sequential order, such process, method, algorithm, or any combination thereof may be operable to be performed in an alternate order. Furthermore, some actions in a process, method, or algorithm may, at least some time, be performed simultaneously (e.g., actions performed in parallel may also be performed in whole, in part, or any combination thereof).

[0081] Unless expressly stated to the contrary, "or" indicates an inclusive or, not an exclusive or. For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0082] As used herein, the term "and / or," and the use of the " / " character between two words, when used in the context of listing entities, indicates that the entities are present either singly or in combination. Thus, for example, the phrase "A, B, C, and / or D" includes not only A, B, C, and D individually, but also any and all combinations and subcombinations of A, B, C, and D.

[0083] Additionally, the use of "a" or "an" is employed to describe elements and resources described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one, or at least one, unless clearly meant otherwise, and the singular also includes the plural, and vice versa. For example, where a single device is described herein, multiple devices may be used in place of the single device. Similarly, where more than one device is described herein, a single device may be used in place of that one device.

[0084] To the extent not described herein, many details regarding specific materials, process acts, and circuits are conventional and can be found in textbooks and other sources within the fields of computing, electronics, and software. [Explanation of symbols]

[0085] 600 System 602 Control System 610a-610c Switchable diode circuits 621a~621c control signals 702 Control System 710a~710d Switch 750a-750d Switchable resistive elements, resistors 1300 System 1301 Battery Stack 1302 Variable Impedance Network 1303 Analog Front-End Measurement Equipment, AFE 1304 Control Systems, Microcontrollers, MCUs 1305 Sense resistor (Rsense) 1306 Fuel Gauge Integrated Circuit, IC 1307 Communication Link or Bus 1400 Energy Delivery System 1401a First battery cell stack 1401b Second Battery Cell Stack 1402a, 1402b variable impedance network 1403a, 1403b AFE 1404 Common Control System, Microcontroller, MCU 1405a, 1405b Sense resistor (Rsense) 1406a, 1406b Fuel Gauge Integrated Circuit, IC 1700 Processing 1800 Energy Delivery System 1801a First battery cell stack 1801b Second Battery Cell Stack 1802a, 1802b Variable impedance network 1803a, 1803b Analog Front-End Measurement Equipment, AFE 1804 Common Control System, Microcontroller, MCU 1805a, 1805b Sense resistor (Rsense) 1806a, 1806b Fuel Gauge Integrated Circuit, IC 1807 Communication Link or Bus

Claims

1. 1. An energy transfer system comprising: a first energy storage system having a first set of VI characteristic curves; a second energy storage system having a second set of VI characteristic curves, the second energy storage system substantially different in a predetermined property from the first energy storage system, wherein at least one of the first set of VI characteristic curves crosses over at least one of the second set of VI characteristic curves; a first variable impedance network coupled in series between the first energy storage system and an output terminal, the first variable impedance network having a first variable impedance; a second variable impedance network coupled in series between the second energy storage system and the output terminal, the second variable impedance network having a second variable impedance; a control system configured to selectively (1) collect parametric data from each of the first and second energy storage systems; (2) adjust the first variable impedance to shift a position of the first set of VI characteristic curves associated with the first energy storage system relative to a position of the second set of VI characteristic curves of the second energy storage system, thereby changing a level of a first current delivered to the output terminals by the first energy storage system; and (3) adjust the second variable impedance to shift a position of the second set of VI characteristic curves associated with the second energy storage system relative to a position of the first set of VI characteristic curves of the first energy storage system, thereby changing a level of a second current delivered to the output terminals by the second energy storage system. Equipped with and wherein the control system is configured to signal at least one of the first variable impedance network and the second variable impedance network to control a relative proportion of total current supplied by each of the first energy storage system and the second energy storage system to the output terminals in response to the parametric data of the first and second energy storage systems in a predetermined manner to optimize at least one operating characteristic of the energy delivery system.

2. 10. The energy delivery system of claim 1, wherein the first variable impedance network comprises a plurality of switchable resistive elements configured to adjust the effective resistance of the first variable impedance network over a predetermined range under the control of the control system.

3. 10. The energy delivery system of claim 1, wherein the first variable impedance network comprises a plurality of switchable diodes configured to adjust a number of forward diode voltage drops present in the first variable impedance network over a predetermined range under the control of the control system.

4. 10. The energy delivery system of claim 1, wherein the first energy storage system and the first variable impedance network are connected to the output terminals in parallel with the second energy storage system and the second variable impedance network, and the first energy storage system differs substantially from the second energy storage system in at least one of chemical composition, electrode voltage characteristics, optimum temperature range, temperature operating point, and operating current.

5. 5. The energy delivery system of claim 4, wherein at least one of the first set of VI characteristic curves crosses over at least one of the second set of VI characteristic curves at a predetermined state of charge.

6. 6. The energy delivery system of claim 5, wherein the control system is configured to signal at least one of the first variable impedance network and the second variable impedance network to adjust where the at least one of the first set of VI characteristic curves crosses over the at least one of the second set of VI characteristic curves.

7. 5. The energy delivery system of claim 4, wherein the first energy storage system comprises a first battery cell stack of a plurality of battery cells each having a first chemical composition, and the second energy storage system comprises a second battery cell stack of a plurality of battery cells each having a second chemical composition, the first chemical composition being different from the second chemical composition.

8. 8. The energy delivery system of claim 7, wherein the first battery cell stack includes a first number of series-connected battery cells and the second battery cell stack includes a second number of series-connected battery cells, the first number being different from the second number.

9. 5. The energy delivery system of claim 4, wherein the first energy storage system is selected from a first group consisting of a chemical energy storage system, a kinetic energy storage system, and a potential energy storage system, and the second energy storage system is selected from a second group consisting of a chemical energy storage system, a kinetic energy storage system, and a potential energy storage system.

10. the control system updating values ​​of the parametric data for the first and second energy storage systems; 6. The energy delivery system of claim 5, configured to send an updated signal to at least one of the first variable impedance network and the second variable impedance network to maintain the at least one operating characteristic of the energy transfer system at a predetermined level.

11. 8. The energy delivery system of claim 7, wherein the control system is configured to selectively signal the first variable impedance network and the second variable impedance network in response to the parametric data collected from the first energy storage system and the second energy storage system, the parametric data including voltage, current, temperature, and state of charge (SOC) measurements associated with the delivery of the first current by the first energy storage system and the delivery of the second current by the second energy storage system.

12. a first analog front end configured to measure a first cell voltage associated with the first energy storage system and communicate the first cell voltage to the control system; a second analog front end configured to measure a second cell voltage associated with the second energy storage system and communicate the second cell voltage to the control system; a first sense resistor coupled to the first energy storage system; a second sense resistor coupled to the second energy storage system; a first fuel gauge circuit coupled to the first sense resistor, the first fuel gauge circuit configured to determine first information responsive to the first current sensed by the first sense resistor and to communicate the first information to the control system; a second fuel gauge circuit coupled to a second sense resistor, the second fuel gauge circuit configured to determine second information responsive to the second current sensed by the second sense resistor and to communicate the second information to the control system; and Furthermore, the control system is configured to selectively signal the first variable impedance network and the second variable impedance network in response to the first cell voltage, the second cell voltage, the first information, and the second information.

10. The energy delivery system of claim 1.

13. 1. A method for delivering energy to a load, comprising: collecting first parametric data including voltage, current, state of charge, and temperature information related to a supply of a first current to the load by a first energy storage system in an energy transfer system; collecting second parametric data including voltage, current, state of charge, and temperature information related to the supply of a second current to the load by a second energy storage system in the energy transfer system; adjusting the first current with a first variable impedance network in the energy transfer system by shifting a position of a first set of VI characteristic curves associated with the first energy storage system relative to a position of a second set of VI characteristic curves associated with the second energy storage system in response to the collected first parametric data and the collected second parametric data, the first variable impedance network being coupled in series between the first energy storage system and the load; adjusting the second current with a second variable impedance network in the energy transfer system by shifting a position of the second set of VI characteristic curves associated with the second energy storage system relative to a position of the first set of VI characteristic curves in response to the collected first parametric data and the collected second parametric data, wherein the second variable impedance network is coupled in series between the second energy storage system and the load, the first energy storage system and the second energy storage system are coupled in parallel with the load, and the first energy storage system has a different chemical composition or physical structure than the second energy storage system; signaling at least one of the first variable impedance network and the second variable impedance network to shift the relative positions of the sets of VI characteristic curves associated with the first and / or second energy storage systems in response to the first parametric data and the second parametric data in a predetermined manner to optimize at least one operating characteristic of the energy transfer system and to control a relative proportion of total current supplied by each of the first energy storage system and the second energy storage system to an output terminal of the energy transfer system; A method comprising:

14. The method of claim 13, wherein the step of shifting the first set of VI characteristic curves associated with the first energy storage system and thereby adjusting the first current is performed in response to a first control signal received from a control system that collected the first parametric data; 14. The method of claim 13, wherein the step of shifting the second set of V-I characteristic curves and thereby adjusting the second current is performed in response to a second control signal received from the control system that also collected the second parametric data.

15. 15. The method of claim 14, wherein the first variable impedance network comprises a plurality of switchable resistive elements configured to adjust the effective resistance of the first variable impedance network in response to the first control signal, and the second variable impedance network comprises a plurality of switchable resistive elements configured to adjust the effective resistance of the second variable impedance network in response to the second control signal.

16. 15. The method of claim 14, wherein the first variable impedance network comprises a plurality of switchable diodes configured to adjust a number of forward diode voltage drops present in the first variable impedance network in response to the first control signal, and the second variable impedance network comprises a plurality of switchable diodes configured to adjust a number of forward diode voltage drops present in the second variable impedance network in response to the second control signal.

17. 15. The method of claim 14, wherein at least one of the first set of VI characteristic curves crosses over at least one of the second set of VI characteristic curves at a predetermined state of charge, and the control system is configured to signal at least one of the first variable impedance network and the second variable impedance network to adjust at least one of a first variable impedance of the first variable impedance network and a second variable impedance of the second variable impedance network to adjust where the at least one of the first set of VI characteristic curves crosses over the at least one of the second set of VI characteristic curves.

18. 15. The method of claim 14, wherein the first energy storage system comprises a first battery cell stack of a plurality of battery cells each having a first chemical composition, and the second energy storage system comprises a second battery cell stack of a plurality of battery cells each having a second chemical composition, the first chemical composition being different from the second chemical composition.

19. 15. The method of claim 14, wherein the first energy storage system is selected from a first group consisting of a chemical energy storage system, a kinetic energy storage system, and a potential energy storage system, and the second energy storage system is selected from a second group consisting of a chemical energy storage system, a kinetic energy storage system, and a potential energy storage system.

Images