Battery for setting a state of charge limit of a cell stack based on the power state of the cell stack

Abstract

Battery, including: a cell stack comprising a plurality of battery cells connected in series; and a control unit electrically connected to the cell stack, the control unit being configured to: to determine a performance state of the cell stack; and adjust a state of charge (SOC) limit for the cell stack by at least one action selected from a group consisting of increasing a charge limit and decreasing a discharge limit when the determined power state is less than a previous power state.

Description

Overview

[0001] Regulatory agencies set limits on battery capacity or regulate batteries that exceed certain capacity thresholds. For example, the Federal Aviation Administration (FAA) and the Transportation Security Administration (TSA) require that batteries with a capacity of 160 watt-hours (Wh) or more are prohibited from being carried on passenger aircraft. The Department of Transportation (DoT) requires that batteries with a capacity of 300 Wh or more be transported by road and rail as Class 9 hazardous material. As another example, batteries with a capacity of 1000 Wh or more must meet cell spread requirements specified, for example, in Underwriters Laboratories (UL) / International Electrotechnical Commission (IEC) standards (i.e., UL2743, IEC62368).

[0002] As batteries become increasingly more powerful, artificial charge and / or discharge limits (here referred to as the state of charge (SOC) limit) are often imposed on cells / accumulators to prevent batteries from exceeding the capacity thresholds set by regulators. For example, a battery that has a capacity of 309 Wh when fully charged and discharged may have its charge and / or discharge capability limited so that the battery's initial capacity does not exceed 299 Wh. This prevents this battery from being classified as Class 9 dangerous goods during rail transport.

[0003] However, as a battery ages and is repeatedly charged and discharged, its capacity naturally decreases, making it desirable to change the battery's state of charge limits to prevent the battery from exceeding the capacity thresholds set by regulators.

[0004] Therefore, the embodiments described herein provide systems for setting a state of charge limit of a cell stack based on a power state of the cell stack.

[0005] An exemplary embodiment provides a battery comprising a cell stack and a controller electrically connected to the cell stack. The controller is configured to determine a power state of the cell stack and adjust a state of charge (SOC) threshold for the cell stack based on the determined power state.

[0006] Before any embodiments are explained in detail, it is to be understood that the embodiments are not limited in their application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The embodiments may be otherwise implemented and practiced. It is also to be understood that the phraseology and terminology used herein is for the purpose of description and should not be considered limiting. The use of "including," "comprising," or "having" and variations thereof is intended to encompass the elements listed below and their equivalents as well as additional elements.Unless otherwise specified or limited, the terms “attached,” “connected,” “held,” and “coupled,” and their variations, are used in their broadest sense and include both direct and indirect attachments, connections, supports, and couplings.

[0007] Furthermore, embodiments may include hardware, software, and electronic components or modules, which for purposes of explanation may be illustrated and described as if most components were embodied solely in hardware. However, one of ordinary skill in the art will recognize, based on this detailed description, that in at least some embodiments, the electronic aspects may be embodied in software (e.g., stored on a non-transitory, computer-readable medium) that may be executed by one or more processing units, such as a microprocessor and / or application-specific integrated circuits ("ASICs"). Thus, a variety of hardware- and software-based devices, as well as a variety of different structural components, may be used to practice the embodiments.For example, "servers" and "computing devices" discussed in the specification may include one or more processing units, one or more computer-readable media modules, one or more input / output interfaces, and various connections (e.g., a system bus) that connect the components.

[0008] In addition, unless expressly stated otherwise, the illustrated components may be combined or divided into separate software, firmware, and / or hardware. For example, rather than being located in and executed by a single electronic processor, the logic and processing described herein may be distributed among multiple electronic processors. Similarly, one or more memory modules and communication channels or networks may be used, even though the embodiments described or illustrated herein include a single such device or element. Regardless of how they are combined or divided, hardware and software components may be located on the same computing device or distributed among several different devices.Accordingly, in the claims, for example, where an apparatus or system is claimed that includes a controller, a control unit, an electronic processor, a computing device, a logic element, a module, a memory module, a communication channel or a network, or any other element that is arranged in a particular way, for example to perform a plurality of functions, the claim or claim element should be interpreted as referring to one or more such elements, each of the one or more elements being arranged, for example, to perform one or more of the listed functions, such that the one or more elements as a group jointly perform the plurality of functions.

[0009] Further features and aspects will become clear from the following detailed description and the attached drawings. Short description of the drawings Fig. 1 shows a power tool battery according to the embodiments described here. Fig. 2 shows a block diagram of a control unit for the battery from Fig. 1 according to the embodiments described here. Fig. 3 shows a charger for a power tool according to the embodiments described here. Fig. 4 shows a block diagram of a control unit for the charger for a power tool from Fig. 3 according to the embodiments described here. Fig. Figure 5 shows an example of the usable energy in a single cell of a battery when no SOC limit is set for the battery cell to prevent a battery cell capacity from reaching or exceeding a threshold set by a regulator. Fig. 6A to Fig. 6C each show a different approach to setting a SOC limit for a battery cell to prevent a capacity of the battery cell from reaching or exceeding a threshold set by a regulator. Fig. 7 shows an example of adjusting a state of charge limit of a cell stack based on a power state of the cell stack according to the embodiments described herein. Fig. 8 shows an example diagram illustrating how the power state of a cell stack affects the cell stack's set state of charge and the percentage of usable energy of the cell stack, according to the embodiments described herein. Fig. 9 shows an example flowchart for adjusting a state of charge limit of a cell stack based on a power state of the cell stack according to the embodiments described herein. Fig. 10 shows an example diagram illustrating how the power state of a cell stack affects the cell stack's set state of charge limit and the percentage of cell stack energy that is usable according to the embodiments described herein. Detailed description

[0010] Fig. 1 shows a battery pack 100 according to some embodiments. The battery pack 100 includes a battery housing 105 and a power tool interface 110. The power tool interface 110 is configured to couple the battery pack 100 to a power tool device. The battery pack 100 supplies operating power to the power tool via the power tool interface 110.

[0011] A battery control unit 200 for the battery 100 is in Fig. 2. The battery controller 200 is electrically and / or communicatively connected to a variety of modules or components of the battery pack 100. For example, the illustrated battery controller 200 is connected to one or more battery sensors 245, a cell stack 260, and the power tool interface 110.

[0012] The battery control unit 200 includes a plurality of electrical and electronic components that power, operate, and protect the components and modules within the battery control unit 200 and / or the battery 100. For example, the battery control unit 200 includes, among other things, a processing unit 205 (e.g., a microprocessor, an electronic processor, an electronic control unit, a microcontroller, or other suitable programmable device), a memory 225, input units 230, and output units 235. The processing unit 205 includes, among other things, a control unit 210, an arithmetic logic unit (“ALU”) 215, and a plurality of registers 220 (in Fig. 2 as a group of registers) and is implemented using a known computer architecture (e.g., a modified Harvard architecture, a von Neumann architecture, etc.). The processing unit 205, the memory 225, the input units 230 and the output units 235, as well as the various modules connected to the battery control unit 200, are connected via one or more control and / or data buses (e.g., a common bus 240). The control and / or data buses are essentially shown in Fig. 2. The use of one or more control and / or data buses for interconnection and communication between the various modules and components will be known to one of ordinary skill in the art in light of the embodiments described herein.

[0013] The memory 225 is a non-transitory, computer-readable medium and includes, for example, a program storage area and a data storage area. The program storage area and the data storage area may include combinations of various types of memory, such as ROM, RAM (e.g., DRAM, SDRAM, etc.), EEPROM, flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic storage devices. The processing unit 205 is connected to the memory 225 and executes software instructions, which may be stored in a RAM of the memory 225 (e.g., during execution), a ROM of the memory 225 (e.g., substantially permanently), or another non-transitory, computer-readable medium such as another memory or a floppy disk.The software included in the implementation of battery 100 may be stored in memory 225 of battery controller 200. The software includes, for example, firmware, one or more applications, program data, filters, rules, one or more program modules, and other executable instructions. Battery controller 200 is configured to retrieve and execute instructions related to the control operations and methods described herein from memory 225, among other things. In other embodiments, battery controller 200 includes additional, fewer, or different components.

[0014] The battery controller 200 is powered by the cell stack 260 and supplies power (e.g., current and voltage) to the power tool interface 110 using the cell stack 260. The cell stack 260 includes one or more battery cells (e.g., a plurality of battery cells) in a particular configuration (e.g., in series, parallel, or series-parallel). The battery sensor(s) 245 are configured to monitor the charge voltage, charge current, discharge voltage, and discharge current of the battery cell(s) of the cell stack 260 individually or collectively.

[0015] Fig. Figure 3 shows a battery charger 300. The battery charger 300 includes a housing 305 and interface sections 310, 315 for connecting the battery charger 300 to one or more batteries (e.g., battery 100). The battery charger 300 also includes a power cable 320 for coupling to an AC power source.

[0016] Fig. 4 shows a control system for the battery charger 300. The control system includes a charging controller 400. The charging controller 400 is electrically and / or communicatively connected to a variety of modules or components of the battery charger 300. For example, the illustrated charging controller 400 is electrically connected to a fan 405, a battery interface 410 (e.g., interface sections 310, 315), one or more charger sensors or charger sensing circuits 415 (e.g., voltage sensors, current sensors, temperature sensors, etc.), one or more indicators 420, a fan control module or circuit 435, and an AC power source 425.The charging controller 400 includes combinations of hardware and software used to, among other things, control the operation of the battery charger 300, determine a temperature of a heat sink, activate the indicators 420 (e.g., one or more LEDs), and the like.

[0017] The charging controller 400 includes a plurality of electrical and electronic components that power, control the operation of, and protect the components and modules within the charging controller 400 and / or the battery charger 300. For example, the charging controller 400 includes, among other things, a processing unit 440 (e.g., a microprocessor, a microcontroller, or other suitable programmable device), a memory 445, input units 450, and output units 455. The processing unit 440 includes, among other things, a control unit 460, an ALU 465, and a plurality of registers 470 (in Fig. 4 as a group of registers) and is implemented using a known computer architecture (e.g., a modified Harvard architecture, a von Neumann architecture, etc.). The processing unit 440, the memory 445, the input units 450 and the output units 455, as well as the various modules or circuits connected to the controller 400, are connected by one or more control and / or data buses (e.g., the common bus 475). The control and / or data buses are essentially shown in Fig. 4. The use of one or more control and / or data buses for interconnection and communication between the various modules, circuits, and components will be apparent to one skilled in the art in light of the invention described herein.

[0018] The memory 445 is a non-transitory, computer-readable medium and includes, for example, a program storage area and a data storage area. The program storage area and the data storage area may include combinations of various types of memory, such as ROM, RAM (e.g., DRAM, SDRAM, etc.), EEPROM, flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic storage devices. The processing unit 440 is connected to the memory 445 and executes software instructions that may be stored in a RAM of the memory 445 (e.g., during execution), a ROM of the memory 445 (e.g., substantially permanently), or another non-transitory computer-readable medium such as another memory or a disc.The software included in the battery charger 300 implementation may be contained in the memory 445 of the charging controller 400. The software includes, for example, firmware, one or more applications, program data, filters, rules, one or more program modules, and other executable instructions. The charging controller 400 is configured to retrieve and execute instructions related to the control operations and methods described herein from the memory 445, among other things. In other constructions, the charging controller 400 includes additional, fewer, or different components.

[0019] The battery interface 410 includes a combination of mechanical components (e.g., rails, grooves, detents, etc.) and electrical components (e.g., one or more connectors) configured and operable to connect the battery charger 300 to a battery (e.g., battery 100) (e.g., mechanically, electrically, and communicatively). For example, the battery interface 410 is configured to receive power via a power line between the AC power source 425 and the battery interface 410. The battery interface 410 is also configured to establish a communication connection with the charging controller 400 via a communication line 480.

[0020] In some embodiments, the charging controller 400 is configured to determine whether a fault condition of the battery charger 300 exists and to generate one or more control signals related to the fault condition. For example, the charger sensing circuitry 415 includes one or more current sensors, one or more temperature sensors, one or more voltage sensors, and the like. The charging controller 400 is configured to detect an overcurrent condition (e.g., when charging the battery 100), an overtemperature condition, etc. When the charging controller 400 detects one or more fault conditions of the battery charger 300 or determines that a fault condition of the battery charger 300 no longer exists, the charging controller 400 is configured to provide information and / or control signals to another component of the battery charger 300 (e.g., the battery interface 410, etc.).

[0021] Fig. 5 shows an example representation of the usable energy in a single cell of a battery 500 (e.g., a battery cell of the cell stack 260) when no SOC limit is set for the battery cell 500 to prevent the battery capacity from reaching or exceeding a threshold set by a regulatory authority. Fig. 4, the battery cell 500 has a maximum charge voltage of 4.2 V (in other words, the state of charge (SOC) of the battery cell 500 is 100 percent when the battery cell 500 is charged to 4.2 V) and the cell 500 has a minimum discharge voltage of 2.5 V (in other words, the SOC of the battery cell 500 is 0 percent when the battery cell 500 is discharged to 2.5 V). The maximum charge voltage and the minimum discharge voltage are specified by the manufacturers of the battery cells 500. When the SOC of the battery cell 500 is 100 percent, the percentage of energy remaining in the battery cell 500 (measured, for example, in Wh) is 100 percent. When the SOC of the battery cell 500 is 0 percent, the percentage of energy remaining in the battery cell 500 is 0 percent (0 Wh).

[0022] In Fig. 5, the section of the battery cell 500 marked 505 represents the usable energy of the battery cell 500. Section 510 represents the unusable energy contained in the battery cell 500. If the energy represented by section 510 is consumed, the service life of the battery cell 500 may be shortened. Section 515 also represents unusable energy that the battery cell 500 can store. If the battery cell 500 is charged to include the energy represented by section 515, the service life of the battery cell 500 may be shortened or the battery cell 500 may become unsafe. Although the battery cell 500 is made of Fig. 5 does not include a charge limit and / or discharge limit (i.e., SOC limit) to prevent the battery capacity from reaching or exceeding a threshold established by a regulatory authority, the battery cell 500 does, however, have a charge limit and a discharge limit that help prevent the battery cell 500 from becoming unsafe and the life of the battery cell 500 from being shortened. When SOC limits are discussed substantially below, they do not refer to SOC limits that help prevent the battery cell 500 from becoming unsafe and the life of the battery cell 500 from being shortened. When a battery or battery cell is described below as having a percentage of available or usable energy, that energy does not include the energy represented by Section 510 and Section 515.

[0023] Fig. 6A to Fig. 6C illustrate three different approaches to setting a SOC limit for a battery cell to prevent the battery cell capacity from reaching or exceeding a threshold set by a regulator.

[0024] Fig. Figure 6A illustrates the approach of setting a discharge limit (e.g., a SOC limit) for a battery cell (e.g., battery cell(s) 500 of cell stack 260) to prevent the battery cell capacity from reaching or exceeding a threshold set by a regulator. Fig. 6A, the discharge limit for battery cell 500 is 3.2 V or 10 percent above the maximum discharge limit of battery cell 500. Energy contained in battery cell 500 but not usable due to the 3.2 V discharge limit for battery cell 500 is represented by the section of battery cell 500 labeled 600. Due to the 3.2 V discharge limit, the Fig. The battery cell 500 shown in Figure 6A is only discharged to a voltage of 3.2 V and has 10 percent of its energy available after reaching a discharge cut-off point.

[0025] Fig. Figure 6B illustrates the approach of setting a charge limit (e.g., a SOC limit) for a battery cell (e.g., the battery cell(s) 500 of the cell stack 260) to prevent the battery cell capacity from reaching or exceeding a threshold set by a regulator. Fig. 6B, the charge limit set on the battery cell 500 is 3.9 V or 90 percent of the maximum charge limit of the battery cell 500. The energy that the battery cell 500 could store, but does not store due to the 3.9 V charge limit, is shown as a section of the battery cell 500 with the marking 605. Due to the 3.9 V charge limit, the Fig. The battery cell 500 shown in Figure 6B is charged to a voltage of 3.9 V and still has 10 percent of its energy to charge.

[0026] Fig. Figure 6C illustrates the approach of establishing a charge limit and a discharge limit (e.g., SOC limits) for a battery cell (e.g., the battery cell(s) 500 of the cell stack 260) to prevent the battery cell capacity from reaching or exceeding a threshold set by a regulator. Fig. 6C, the discharge limit for battery cell 500 is 2.8 V, or 5 percent above the maximum discharge limit of battery cell 500. Energy contained in battery cell 500 but not usable due to the 2.8 V discharge limit is shown as the portion of battery cell 500 marked 610. Due to the 2.8 V discharge limit, the Fig. The battery cell 500 shown in Figure 6C is only discharged to a voltage of 2.8 V and has 5 percent of its energy available after reaching a discharge cut-off point.

[0027] In Fig. 6C, the charge limit imposed on the battery cell 500 to prevent the capacity of the battery cell from reaching or exceeding a threshold set by a regulatory authority is 4.0 V or 95 percent of the maximum charge limit of the battery cell 500. The energy that the battery cell 500 could store, but does not store due to the 4.0 V charge limit, is shown as a section of the battery cell 500 with the marking 615. Due to the 4.0 V charge limit, the Fig. The battery cell 500 shown in Figure 6B is charged to a voltage of 3.9 V and still has 5 percent of its energy to charge.

[0028] Fig. 7 shows an example of a method 700 for setting a SOC limit of a cell stack 260 based on a performance state of the cell stack 260. In some embodiments, the method 700 may be performed by the battery controller 200, the charging controller 400, or both. In some embodiments, the method 700 begins at block 705 when the controller 200, 400 determines a performance state of the cell stack 260. In some embodiments, the controller 200, 400 sets an initial SOC limit for the cell stack 260 prior to executing block 705. For example, the initial SOC limits may include the maximum charge and discharge limits of the battery cells 500. Additionally, the controller 400, 400 may determine an initial performance state of the cell stack 260 prior to executing block 705.

[0029] In block 705, the controller 200, 400 may determine the power state of the cell stack 260. The power state of the cell stack 260 may be defined as 100 percent multiplied by the maximum energy that the cell stack 260 can store between an SOC of 0 percent and an SOC of 100 percent, divided by a measured energy of the cell stack 260 between an SOC of 0 percent and an SOC of 100 percent.The maximum energy that the battery stack 260 can store between an SOC of 0 percent and an SOC of 100 percent may be the maximum amount of energy that the battery stack 260 can store before it has begun to degrade without exceeding a charge limit imposed on the battery stack 260 to help prevent the battery stack 260 from becoming unsafe and shortening the life of the battery stack 260, or falling below a discharge limit imposed on the battery stack 260 to help prevent the battery stack 260 from becoming unsafe and shortening the life of the battery stack 260.The measured energy of the cell stack 260 between an SOC of 0 percent and an SOC of 100 percent may be the maximum amount of energy the cell stack 260 can store once it has begun to degrade without exceeding a charge limit imposed on it to help prevent the cell stack 260 from becoming unsafe and shortening the life of the cell stack 260, or falling below a discharge limit imposed on the cell stack 260 to help prevent the cell stack 260 from becoming unsafe and shortening the life of the cell stack 260. For example, a new cell stack 260 may store a maximum amount of energy of 100 Wh. As the cell stack 260 ages, the ability of the cell stack 260 to store energy (the capacity of the cell stack 260) may decrease, and the cell stack 260 may have a measured energy of 90 Wh.Therefore, in this example, the power state of the cell stack is 260 = 100% * (90 Wh / 100 Wh) = 90%.

[0030] In one embodiment, the measured energy of cell stack 260 is determined by tracking the total amount of energy charged into or discharged from cell stack 260 and using a mapping of the age of cell stack 260 to the capacity of the cell stack. The mapping may be stored in memory 225, memory 445, or both, for example, when battery pack 100 or battery charger 300 is manufactured. The mapping may be determined in a laboratory environment when measuring the capacity of a cell stack while repeatedly charging and discharging the cell stack.

[0031] In another embodiment, the measured energy of cell stack 260 is determined using coulomb counting. Coulomb counting involves measuring the amount of charge flowing into and out of cell stack 260 during charge and / or discharge cycles. In some embodiments, coulomb counting is performed by integrating current (amperes) over time (seconds) to calculate the total charge transferred to or from cell stack 260. The result of the coulomb counting is a value for the capacity of cell stack 260 in ampere-hours (Ah). This value can be multiplied by the nominal voltage of cell stack 260 to determine the reduced capacity or measured energy of cell stack 260 in watt-hours (Wh). The nominal voltage of cell stack 260 is essentially a constant value.

[0032] In some embodiments, the controller 200, 400 may execute block 705 when a predetermined number of discharge cycles have been performed by the cell stack 260 or the cell stack 260 has been discharged a predetermined number of times since block 705 was last executed by the controller 200, 400. For example, block 705 may be executed every 50 discharge cycles of the cell stack 260.

[0033] In block 710, the controller 200, 400 determines whether the determined performance state of the cell stack 260 is worse than a previous performance state. The previous performance state may be the most recently determined performance state of the cell stack 260. For example, the previous performance state may be the performance state determined in block 705 during the last previous iteration of the method 700. In another example, when the first iteration of the method 700 is performed, the previous performance state may be the initial performance state (described above) determined prior to performing block 705.

[0034] If the controller 200, 400 determines that the determined performance state of the cell stack 260 is worse than a previous performance state, the controller 200, 400 may determine, in block 715, whether an SOC limit is set for the cell stack 260. In some embodiments, block 715 includes determining whether the cell stack 260 has a charge limit of less than 100 percent SOC set, a discharge limit of greater than 0 percent SOC set, or both a charge limit of less than 100 percent SOC and a discharge limit of greater than 0 percent SOC set for the cell stack 260.

[0035] If the controller 200, 400 determines that an SOC limit is set for the cell stack 260, the controller 200, 400 adjusts the SOC limit for the cell stack 260 in block 720. That is, the controller 200, 400 increases the charge limit, decreases the discharge limit, or increases the charge limit and decreases the discharge limit set for the cell stack 260. In some embodiments, the controller 200, 400 adjusts the SOC limit set for the cell stack 260 to maintain a desired amount of usable energy (or a desired capacity) for the cell stack 260. The SOC limit of the cell stack 260 is therefore adjusted based on the determined performance state of the cell stack 260.

[0036] In the embodiments described herein, the controller 200, 400 may also enforce the SOC limit. Specifically, the controller 200, 400 may continuously or periodically monitor the SOC during charging and / or discharging of the battery pack 100. If the SOC of the cell stack 260 reaches or exceeds the charging limit during a charging process of the battery pack 100, the controller 200, 400 stops charging the battery pack 100 or the cell stack 260. For example, the controller 200, 400 opens a charging FET of the battery pack 100 or the cell stack 260 to terminate or stop charging. Similarly, the control unit 200, 400 stops discharging the battery pack 100 or the cell stack 260 when the state of charge of the cell stack 260 reaches or falls below the discharge limit during a discharge process of the battery pack 100.For example, the control unit 200, 400 opens a discharge FET of the battery 100 or the cell stack 260 to terminate or stop charging.

[0037] Fig. 8 shows an example chart 800 illustrating how the performance state of a cell stack 260 affects the SOC limit set for the cell stack 260 and the percentage of usable energy of the battery. In the chart 800, the x-axis represents the number of discharge cycles the cell stack 260 has performed, or the number of times the cell stack 260 has discharged. The y-axis of the chart 800 represents a percentage of the energy or capacity of the battery. The line labeled 805 in the chart 800 represents the performance state of the cell stack 260, the line labeled 810 represents the percentage of the battery energy that is being used, and the line labeled 815 represents the percentage of the cell stack energy that is not being used due to an SOC limit set for the cell stack 260.As shown in diagram 800, when not in use, the cell stack 260 can store 100 percent of the energy it is originally capable of storing, however, due to an SOC limit set for the cell stack 260, only 80 percent of the cell stack's energy can be used. As the number of discharge cycles performed by the cell stack 260 increases, the performance state of the cell stack 260 decreases. However, as the performance state of the cell stack 260 decreases, the SOC limits set for the cell stack 260 are adjusted so that 80 percent of the cell stack's energy remains usable, even if the total capacity of the cell stack, or the amount of energy the cell stack 260 can store, decreases. After 200 discharge cycles, the SOC limits no longer limit the percentage of usable energy of the cell stack.However, as the power state of the cell stack 260 continues to decrease, the percentage of usable energy of the cell stack drops below 80 percent and continues to decrease as the power state of the cell stack decreases.

[0038] In some embodiments, there may be some error associated with a particular performance state of cell stack 260, as measurements used to determine the performance state of cell stack 260 may be subject to some error. Therefore, in embodiments where it is important that a cell stack 260 not store more than a predetermined amount of energy, a tolerance associated with the particular performance state may be considered when adjusting the SOC limit set for cell stack 260.

[0039] In Fig. 8 denotes A: The SOH of the battery gradually decreases with increasing battery cycles. B: The usable energy of the battery remains constant as the battery deteriorates, as long as there is no energy limitation. C: Amount of limited energy is consistent with the degradation of battery energy as long as no energy is limited. D: At this point there is no energy limit, so further battery degradation will not result in less usable energy in the battery.

[0040] Fig. 9 shows an example flowchart of a method 900 for setting a SOC threshold of a cell stack 260 based on a performance state of the cell stack 260, taking into account a tolerance associated with the performance state of the cell stack 260. Like method 700 (described above), method 900 may be performed by battery controller 200, charging controller 400, or both. In some embodiments, method 900 begins at block 905 when controller 200, 400 determines a performance state of a cell stack 260. Block 905 may be similar to block 705 described above with respect to method 700.

[0041] In block 910, the controller 200, 400 determines whether the determined power state of the cell stack 260 is below a previous power state by more than a predetermined amount. The previous power state referred to in block 910 may be similar to the previous power state described above with respect to block 710 of the method 700. In some embodiments, the predetermined amount referred to in block 910 is a tolerance value associated with the power state of the cell stack 260. For example, if the tolerance value associated with the power state is 5 percent, the determined power state is 90 percent, and the previous power state is 100 percent, the method 900 proceeds to block 915. The tolerance value associated with the power state may be set by the manufacturer and stored in the memory 225 of the battery pack 100.

[0042] If the determined power state of cell stack 260 is below a previous power state by more than a predetermined amount, controller 200, 400 determines whether an SOC limit is set for cell stack 260 in block 915. Block 915 is similar to block 715 described above with respect to method 700.

[0043] If an SOC limit is set for the cell stack 260, the controller 200, 400 adjusts the SOC limit in block 920 to maintain a usable energy amount that is less than a desired usable energy amount or a desired capacity by the predetermined amount. That is, the controller 200, 400 increases the charge limit, decreases the discharge limit, or increases the charge limit and decreases the discharge limit to maintain a usable energy amount that is less than a desired usable energy amount or a desired capacity by the predetermined amount. For example, if the desired amount of usable energy is 80 percent and the tolerance value associated with the determined power condition is 5 percent, the amount of usable energy referred to in block 920 is 75 percent.

[0044] Fig. 10 shows an example chart 1000 illustrating how the power state of a cell stack 260 affects the SOC limit set for the cell stack 260 and the percentage of usable energy of the cell stack when considering a tolerance associated with the power state of the cell stack 260. In the chart 1000, the x-axis represents the number of discharge cycles the cell stack 260 has performed, or the number of discharges of the cell stack 260. The y-axis of the chart 1000 represents a percentage of the energy or capacity of the cell stack.The line labeled 1005 in diagram 1000 represents the power state of cell stack 260, the line labeled 1010 represents the percentage of usable energy of the cell stack, the line labeled 1015 represents the percentage of cell stack energy that is not being used due to SOC limits set for cell stack 260, and the line labeled 1020 represents the power state of cell stack 260 when the tolerance associated with the power state is added to the power state (the power state of cell stack 260 + the tolerance). In diagram 1000, the tolerance associated with the power state value is 5 percent, and the desired amount of usable energy is 80 percent.To account for the tolerance associated with the power state, the usable energy amount is maintained at 75 percent or less when the power state of the cell stack 260 + the tolerance is less than or equal to 100 percent, and the SOC limits set for the cell stack 260 are only adjusted when the power state of the cell stack 260 + the tolerance is less than or equal to 100 percent.

[0045] In some embodiments, battery pack 100 may have one or more modes for charging or discharging. For example, in a first mode, no SOC limit is set for the cell stack 260 included in battery pack 100 to prevent the capacity of battery pack 100 from reaching or exceeding a threshold set by a regulatory authority. In a second mode (e.g., a shipping and transport mode), battery pack controller 200 may set SOC limits for the cell stack 260 included in battery pack 100 to prevent the capacity of battery pack 100 from reaching or exceeding a threshold set by a regulatory authority.

[0046] In Fig. 10 denotes E: The maximum error of the SOH estimation is 5%. Q: The tolerance of the SOH measurement is + / -5%; to ensure that the battery never provides more than 80% of the rated energy, the battery must limit the power to 80%-(SOH tolerance). G: SOH only decreases with cycles, so the limited energy is only set when the estimated SOH is less than 100% (SOH tolerance).

[0047] Thus, the embodiments provided herein describe, among other things, systems and methods for adjusting a SOC limit of a cell stack based on a performance state of the cell stack.

[0048] Various features and advantages are set forth in the following claims.

Claims

[1] Battery, including: a cell stack comprising a plurality of battery cells connected in series; and a control unit electrically connected to the cell stack, the control unit being configured to: to determine a performance state of the cell stack; and adjust a state of charge (SOC) limit for the cell stack by at least one action selected from a group consisting of increasing a charge limit and decreasing a discharge limit when the determined power state is less than a previous power state. [2] The battery of claim 1, wherein the SOC limit is adjusted when the determined power state is less than a previous power state by a predetermined amount. [3] The battery of claim 2, wherein the predetermined amount is a tolerance value associated with the determined performance state of the cell stack. [4] The battery of claim 1, wherein the controller is configured to determine a power state of the cell stack using a Coulomb count. [5] The battery of claim 1, wherein the controller is configured to set an initial SOC limit for the cell stack below a maximum usable energy limit for the cell stack, and the SOC limit is adjusted from the initial SOC limit. [6] Battery, comprising: a stack of cells; and a control unit electrically connected to the cell stack, the control unit being configured to: to determine a performance state of the cell stack; and to adjust a state of charge (SOC) limit for the cell stack based on the determined power state. [7] The battery of claim 6, wherein the SOC limit is adjusted when the determined power state is less than a previous power state by a predetermined amount. [8] The battery of claim 7, wherein the predetermined amount is a tolerance value associated with the determined performance state of the battery. [9] A battery according to claim 7, wherein the controller is arranged to adjust the SOC limit to maintain a usable energy amount that is less than a desired usable energy amount by the predetermined amount. [10] A battery according to claim 6, wherein the controller is arranged to determine the power state of the cell stack based on one element selected from a group consisting of a number of discharges of the cell stack and a coulomb count. [11] The battery of claim 6, wherein the controller is configured to adjust the SOC limit for the cell stack by at least one action selected from a group consisting of increasing a charge limit and decreasing a discharge limit. [12] A battery according to claim 6, wherein the controller is configured to set an initial SOC limit for the cell stack below a maximum usable energy limit for the cell stack.

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