System and method for battery self-discharge monitoring

Abstract

The invention relates to a system and method for battery self-discharge monitoring. A self-discharge resistance of the battery is monitored. Exemplary embodiments include methods for monitoring a state of the battery, including: determining a total energy loss in the battery through a plurality of charge cycles and a plurality of discharge cycles based on a battery voltage and a battery current; determining an energy loss due to an internal resistance of the battery during the plurality of charge cycles and the plurality of discharge cycles; determining a self-discharge energy due to a self-discharge resistance of the battery based on a difference between the total energy loss and the energy loss due to the internal resistance of the battery; and generating a signal indicative of the self-discharge resistance of the battery based on the self-discharge energy.

Description

Background Art

[0001] Rechargeable batteries, such as lithium-ion batteries, are used in a variety of applications. Many types of rechargeable batteries contain volatile and / or toxic components, such as flammable materials and oxidants, which can be damaged by external and / or internal forces. Examples of such internal forces include internal damage, which can lead to dangerous accidents. Furthermore, rechargeable batteries are used in many different applications that are particularly sensitive to damage, such as medical devices worn on and / or implanted in the human body.

[0002] Early detection of such internal damage in a rechargeable battery may allow such failure and / or hazard to be mitigated or avoided before such failure and / or hazard becomes severe enough to cause the battery to fail and / or be endangered. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] To describe in detail example embodiments, reference will now be made to the accompanying drawings, in which:

[0004] Figure 1 shows a schematic block diagram of a battery charging and monitoring system according to the present disclosure;

[0005] Figure 2 shows a schematic block diagram of a battery state controller;

[0006] Figure 3 shows a graph with curves representing battery voltage as a function of state of charge (SOC) under open circuit conditions, charging conditions, and discharging conditions;

[0007] Figure 4 shows a graph showing charging energy loss and discharging energy loss and available energy as a function of SOC;

[0008] Figure 5 shows a graph showing charge energy loss, discharge energy loss and self-discharge energy loss and available energy as a function of SOC;

[0009] Figure 6 A flowchart outlining method steps according to at least some embodiments is shown.

[0010] definition

[0011] Various terms are used to refer to specific system components. Different companies may refer to a component by different names—this document is not intended to distinguish between components that differ in name but function identically. In the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended manner, and thus, these terms should be interpreted to mean "including, but not limited to..." Additionally, the terms "coupled" or "coupled" are intended to mean either an indirect connection or a direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect connection via other devices and connections.

[0012] “Controller” shall mean, alone or in combination, an individual circuit component, an application specific integrated circuit (ASIC), a microcontroller with control software, a reduced instruction set computer (RISC) with control software, a digital signal processor (DSP), a processor with control software, a programmable logic device (PLD), a field programmable gate array (FPGA), or a programmable system on a chip (PSOC) that is configured to read inputs and drive outputs in response to those inputs.

[0013] In the context of electrical devices, the terms "input" and "output" refer to electrical connections to the electrical device and should not be considered verbs requiring operation. For example, a controller may have a gate output and one or more sense inputs. DETAILED DESCRIPTION

[0014] The following discussion relates to various embodiments of the present invention. Although one or more of these embodiments may be preferred, the disclosed embodiments should not be interpreted or otherwise used to limit the scope of the present disclosure, including the claims. In addition, it should be understood by those skilled in the art that the following description has broad application, and the discussion of any embodiment is merely an example of that embodiment and is not intended to indicate that the scope of the present disclosure, including the claims, is limited to that embodiment.

[0015] Exemplary embodiments relate to systems and methods for monitoring the state of a battery. The disclosed systems and methods can provide early detection of aging, damage, and / or degradation conditions in batteries, such as lithium-ion batteries, which can indicate impending failure and / or potentially dangerous conditions of the battery. Figure 11 shows a schematic block diagram of a battery charging and monitoring system 10. The system 10 includes a battery 12 and a load device 14 connected to the battery via a first conductor 16 and a second conductor 18. The battery 12 includes one or more rechargeable battery cells. In some embodiments, the battery 12 may include lithium-ion battery cells. However, the systems and methods of the present disclosure may be used with other battery chemistries. The system 10 also includes a battery state controller 20 that is configured to monitor the state of the battery 12. The battery state controller 20 is connected to each of the first conductor 16 and the second conductor 18 to measure a battery voltage V across the battery 12. batt The load device 14 may include, for example, a controller such as a microcontroller or a system-on-chip device.

[0016] In some embodiments, the load device 14 may include a controller in a medical device (such as a portable medical device). In some embodiments, the system 10 may be included in a medical device that may include one or more sensors and / or actuators to dispense medication or provide other medical treatments, such as electrical stimulation for specific medical purposes. For example, the system 10 may be included in a blood glucose sensor and / or an insulin pump used by a diabetic patient. Additionally or alternatively, the system 10 may be included in a pacemaker or implantable cardioverter-defibrillator (ICD) device for monitoring and treating cardiac conditions. However, the system 10 of the present disclosure may be used in a variety of different devices and applications.

[0017] The current sensor 22 is configured to measure the battery current i in the second conductor 18 dd The current sensor 22 is shown as a shunt resistor, which may have a very low resistance, such as a few milliohms. The battery state controller 20 is connected to the second conductor 18 on either side of the current sensor 22 to measure the voltage across it and, thereby, the battery current. However, the current sensor 22 may use a different configuration, such as a contactless inductive sensor. Alternatively or additionally, the current sensor 22 may be located elsewhere in the circuit with the battery 12, such as in the first conductor 16.

[0018] In some embodiments, and as Figure 1 As shown, the second conductor 18 may be connected to a ground plane, such as chassis ground. The current sensor 22 is connected between the negative terminal 32 of the battery 12 and the connection to the ground plane to accurately and completely measure the battery current i dd .

[0019] The temperature sensor 24 is thermally coupled to the battery 12 to measure the temperature of the battery 12. The battery state controller 20 is connected to the temperature sensor 24 for monitoring the temperature of the battery 12.

[0020] The battery 12 includes a positive terminal 30 connected to the first conductor 16 and a negative terminal 32 connected to the second conductor 18. Figure 1 As shown, battery 12 also includes model features 34, 36, and 38 that represent real-world characteristics of the battery. As shown, battery 12 includes an electrochemical cell 34 connected in series with an internal resistance 36. A self-discharge resistance 38 (also referred to as a self-leakage resistance) is connected in parallel with electrochemical cell 34. The parallel combination of self-discharge resistance 38 and electrochemical cell 34 is connected in series with internal resistance 36 between positive terminal 30 and negative terminal 32 of battery 12. The combination of internal resistance 36 and self-discharge resistance 38 can represent all resistive effects of battery 12, with electrochemical cell 34 representing an idealized model with no resistance.

[0021] When the battery current i dd When having a non-zero value, internal resistance 36 may account for a majority of the energy lost by battery 12 during charging and discharging. Self-discharge resistance 38 may have a relatively small effect on energy loss in battery 12 during charging and discharging. However, as battery 12 ages or is otherwise damaged and / or degraded, self-discharge resistance 38 may decrease, thereby having a greater effect on energy loss. In some cases, self-discharge resistance 38 may reach a value that causes a hazard, such as a thermal runaway condition, in battery 12.

[0022] In some embodiments, and as Figure 1 As shown, the battery state controller 20 provides a plurality of status signals 26, 27, and 28 to the load device 14. The status signals 26, 27, and 28 may include a battery warning signal 26 to warn of a dangerous condition in the battery 12. The status signals 26, 27, and 28 may include a state-of-health (SoH) signal 27 indicating the health of the battery 12. The status signals 26, 27, and 28 may also include a state-of-charge (SoC) signal 28 indicating the charge state of the battery 12. The status signals 26, 27, and 28 may be generated and transmitted by the battery state controller 20 as separate signals, which may be transmitted as discrete or analog voltage or current signals. Additionally or alternatively, one or more of the status signals 26, 27, and 28 may be transmitted using digital signals over a digital communication interface, such as a serial peripheral interface (SPI), an inter-integrated circuit (I2C) interface, a controller area network (CAN bus) interface, or the like.

[0023] The battery state controller 20 includes a processor 42 coupled to a storage device memory 44. The storage device memory 44 stores instructions, such as program code, in an instruction storage device 46 for execution by the processor 42. The storage device memory 44 also includes a data storage device 48 for storing data used by the processor 42. The data storage device 48 may record, for example, the battery voltage V batt , battery current idd The value of and / or the result of a function calculated by processor 42.

[0024] Figure 1 Also shown are a DC power source 50 , which may be referred to as a charging power source, and a charging switch 52 configured to selectively conduct current from the DC power source 50 to the first conductor 16 for charging the battery 12 .

[0025] Figure 2 FIG. 2 shows a schematic block diagram of the battery state controller 20. As shown in the figure, the battery state controller 20 includes a voltage monitor 60 connected to the first conductor 16 and configured to generate a voltage representative of the battery voltage V batt The battery state controller 20 also includes an SOC calculator 62 configured to calculate the battery state based on the battery voltage V batt The battery state controller 20 also includes an RSOC calculator 64 configured to calculate the state of charge (SOC) of the battery 12. The RSOC calculator 64 is configured to calculate the state of charge (SOC) of the battery 12 based on the battery voltage V batt The RSOC signal 65 is generated to represent a relative state of charge (RSOC) of the battery 12. The RSOC signal 65 may indicate the state of charge of the battery 12 as a fraction of a full charge or a predetermined charge capacity.

[0026] The battery state controller 20 also includes an energy loss detector 66 that is configured to detect the battery voltage V batt and the battery current i dd The battery state controller 20 also includes a self-discharge monitor 68 configured to generate a self-discharge energy E SD The self-discharge energy signal 101 corresponds to the energy loss in the battery 12 due to the self-discharge resistor 38. The battery state controller 20 also includes a run timer 70 that provides a timer indicating the amount of time T that has elapsed during each of the plurality of charge cycles and the plurality of discharge cycles. run The running time signal 71.

[0027] The battery state controller 20 also includes an analog-to-digital converter (ADC) 72 and a temperature calculator 74. The ADC 72 is coupled to the temperature sensor 24 and is configured to generate a raw signal representing the temperature measured by the temperature sensor 24 and provide the raw signal to the temperature calculator 74. The temperature calculator 74 is configured to generate a temperature signal 75 representing the temperature (Temp) of the battery 12 as measured by the temperature sensor 24. For example, the temperature calculator 74 may calculate the temperature signal 75 by applying a scaling factor and / or an offset to the raw signal from the ADC 72.

[0028] like Figure 2 As shown, the energy loss detector 66 includes a current calculator 80 connected to the current sensor 22 and configured to determine the battery current i dd For example, the current calculator 80 may determine the voltage difference across the current sensor 22 and then calculate the battery current i by applying a scaling factor and / or an offset to the voltage difference across the current sensor 22. dd .

[0029] The energy loss detector 66 also includes a charge / discharge detector 82 that receives a current calculator 80 indicating the battery current i dd The charge / discharge detector 82 is based on the battery current i dd The charge / discharge detector 82 may generate a charge status signal 83 indicating the charge status of the battery 12 based on the value of the battery current i. The charge status signal 83 may include a Boolean value having one logic level indicating that the battery 12 is being charged and a different logic level indicating that the battery 12 is not being charged. For example, the charge / discharge detector 82 may be responsive to the battery current i dd The charge / discharge detector 82 may be responsive to the battery current i dd A second threshold current is above which indicates that the battery 12 is no longer being charged, driving the charge status signal 83 to a low logic level.

[0030] The energy loss detector 66 also includes a multiplexer 84, a charge energy accumulator 86, and a discharge energy accumulator 88. The multiplexer 84 receives a current from the current calculator 80 indicating the battery current i dd The multiplexer 84 converts the battery current i dd The signal is provided to only one of the charging energy accumulator 86 or the discharging energy accumulator 88. For example, when the charging state signal 83 indicates that the battery 12 is being charged, the multiplexer 84 may provide a signal representing the battery current i to the charging energy accumulator 86. ddWhen the state of charge signal 83 indicates that the battery 12 is not charged, the multiplexer 84 may provide a signal representing the battery current i to the discharge energy accumulator 88. dd signal, and provides a different signal, such as a zero or empty signal, to the charging energy accumulator 86.

[0031] The energy loss detector 66 also includes a cycle counter 92 that receives the charge state signal 83 and is configured to maintain a count of the number of charge cycles and / or the number of discharge cycles. In some embodiments, the energy loss detector 66 may provide data regarding the total energy loss in the battery only after a predetermined number of charge cycles and / or discharge cycles have occurred. Additionally or alternatively, the cycle counter 92 may be configured to determine when an equal number of charge cycles and discharge cycles have occurred, and the energy loss detector 66 may update the difference energy signal E only when the number of charge cycles and discharge cycles is equal. Diff .

[0032] The charging energy accumulator 86 is configured to generate an accumulated charging energy signal E C , the accumulated charging energy signal represents the amount of energy provided to the battery 12 over a plurality of charging cycles. C The charging energy accumulator 86 uses the battery voltage V from the voltage monitor 60 batt The signal from the multiplexer 84 represents the battery current i when the battery 12 is being charged. dd In some embodiments, the charging energy accumulator 86 may also use the running time signal T from the running timer 70. run To generate the charging energy signal E C .

[0033] The discharge energy accumulator 88 is configured to generate an accumulated discharge energy signal E D , the accumulated discharge energy signal represents the amount of energy discharged from the battery 12 over a plurality of discharge cycles. D The discharge energy accumulator 88 uses the battery voltage V from the voltage monitor 60 batt The signal from the multiplexer 84 represents the battery current i when the battery 12 is not charged. dd In some embodiments, the discharge energy accumulator 88 may also use the run time signal T from the run timer 70. run To generate the discharge energy signal E D .

[0034] The energy loss detector 66 also includes a difference calculator 90 configured to calculate a difference energy signal E Diff , and the difference energy signal represents the total energy loss in the battery 12 through multiple charging cycles and multiple discharging cycles. For example, the energy loss detector 66 can obtain the energy loss from the charging energy signal E C Subtract the discharge energy signal E from D To determine the difference energy signal E Diff . Difference energy signal E Diff The difference energy signal E Diff A portion of may represent a difference in available energy in the battery 12 due to a difference in state of charge. However, in situations where there is no difference in available energy in the battery 12, such as where the number of charge cycles is equal to the number of discharge cycles, this portion may be low or zero. Additionally, and for a sufficiently long evaluation period, such as over a few hundred charge cycles and a few hundred discharge cycles, the difference energy signal E may be small or zero. Diff The portion of , representing the difference in energy available in battery 12 , is negligible compared to the energy losses attributable to internal resistance 36 and self-discharge resistance 38 .

[0035] like Figure 2 As shown, the battery state controller 20 also includes a warning generator 110 configured to generate a battery warning signal 26 based on the self-discharge warning signal 107 from the self-discharge monitor 68. The battery state controller 20 also includes a SoH calculator 112 configured to calculate the battery warning signal 26 based on the self-discharge energy signal E from the self-discharge monitor 68. SD To generate the SoH signal 27. For example, the SoH calculator 112 may use the number of charge cycles and discharge cycles, the charge energy loss E loss_C and / or discharge energy loss E loss_D The SoH calculator 112 may determine the initial SoH estimate based on the self-discharge energy signal E from the self-discharge monitor 68. SD to adjust the initial SoH estimate to generate the SoH signal 27. Thus, the SoH calculator 112 of the present disclosure may provide an improved estimate of the state of health when compared to conventional devices.

[0036] The initial SoH estimate may include a SoH value (SOH), which may be determined as set forth in equation (1):

[0037]

[0038] where Q0 is the rated capacity of the battery 12 (which may also be referred to as the nominal charge capacity), and where Q maxis the maximum charge capacity of the battery 12 under its current conditions.

[0039] The SoH calculator 112 of the present disclosure may generate a SoH signal 27 representing a refined SOH value that accounts for self-discharge losses in the battery 12 and may be determined according to equation (2):

[0040]

[0041] The self-discharge loss capacity represents the reduction in the charge storage capacity of the battery due to the self-discharge resistor 38. The SoH calculator 112 may be based on the self-discharge energy signal E from the self-discharge monitor 68. SD To calculate or otherwise determine the self-discharge loss capacity.

[0042] The battery state controller 20 also includes an initial inventory charge controller (IIC) 114 that is configured to generate the SoC signal 28 based on several signals about the battery 12, such as the battery voltage V batt , battery current i dd , an SOC signal 63 from the SOC calculator 62 , an RSOC signal 65 from the RSOC calculator 64 , and a temperature signal 75 from the temperature calculator 74 .

[0043] The initial RSOC estimate can be determined as set forth in equation (3):

[0044]

[0045] where Q 充电 is the amount of charge stored in the battery 12 under its current condition. The IIC 114 may generate a SoC signal 28 representing a refined RSOC value that accounts for self-discharge losses in the battery 12 and may be determined according to equation (4):

[0046]

[0047] The self-discharge monitor 68 is configured to generate one or more signals indicative of the self-discharge resistance 38 of the battery 12. The self-discharge monitor 68 includes a circuit configured to calculate the self-discharge energy E SD The self-discharge calculator 100 is also configured to calculate a self-discharge loss percentage (SD%) representing energy loss due to the self-discharge resistor 38 as a percentage of the total energy provided to the battery 12.

[0048] The self-discharge calculator 100 can calculate the internal resistance R representing the internal resistance 36 of the battery 12, the charging energy loss E loss_C and discharge energy loss E loss_DAs input. Charging energy loss E loss_C represents the energy loss in the battery 12 due to the internal resistance 36 of the battery 12 and throughout the plurality of charge cycles during which the battery state controller 20 is active, and the discharge energy loss E loss_D = represents the energy lost in the battery 12 due to the internal resistance 36 of the battery 12 and over a number of discharge cycles during which the battery state controller 20 is active. The internal resistance value R may be based on the battery voltage V batt and how it changes with the battery current i during charging and / or discharging dd The charging energy loss E is determined by the function of loss_C and discharge energy loss E loss_D Each can be based on the battery voltage V over a period of time batt , battery current i dd and internal resistance R. For example, the charging energy loss E loss_C and discharge energy loss E loss_D can be used by the difference calculator 90 to calculate the difference energy signal E Diff The multiple charge cycles and discharge cycles of the same are determined within the charge.

[0049] The self-discharge calculator 100 can calculate the internal energy loss E in the battery 12 due to the internal resistance 36. loss_CD Determined as charging energy loss E loss_C and discharge energy loss E loss_D The self-discharge monitor 68 can be configured to monitor the total energy loss in the battery 12 through multiple charge cycles and multiple discharge cycles by calculating the difference energy E. Diff Subtract internal energy loss E loss_CD To calculate the self-discharge energy E SD .

[0050] The self-discharge monitor 68 also calculates the self-discharge energy E SD The total energy E supplied to the battery 12 总 The self-discharge ratio between the total energy E 总 The self-discharge monitor 68 can be based on the battery voltage V batt and the battery current i dd to calculate or otherwise determine the total energy supplied to the battery 12. In some embodiments, the total energy supplied to the battery 12 may be determined by a source external to the self-discharge monitor 68, such as the original inventory charge controller 114.

[0051] For example, the self-discharge monitor 68 can monitor the self-discharge energy E SD Divide by the total energy E总 The self-discharge monitor 68 may provide a self-discharge percentage SD based on the self-discharge ratio multiplied by 100. ％ .

[0052] The self-discharge monitor 68 also includes a self-discharge comparator 106 configured to convert the self-discharge percentage SD ％ is compared with the self-discharge threshold, and in response to determining the self-discharge percentage SD ％ A high self-discharge condition warning is generated indicating that the battery 12 exceeds the self-discharge threshold. SD For example, the self-discharge comparator 106 may be responsive to determining the self-discharge percentage SD ％ A self-discharge warning signal 107 is generated when a self-discharge threshold of 1.0% is exceeded. The self-discharge threshold may have different values depending on, for example, the intended application or the details of the construction or chemistry of the battery 12. For example, a lower self-discharge threshold may be used for batteries in safety-critical applications, such as implantable medical devices, compared to other applications with lower safety requirements.

[0053] Figure 3 Graphs are shown with curves 200 , 202 , 204 representing battery voltage as a function of state of charge (SOC) under open circuit conditions, charging conditions, and discharging conditions, respectively. Figure 3 A first curve 200 is included that represents the battery voltage of the battery 12 as a function of the state of charge (SOC) under open circuit conditions, where the battery current i dd Basically zero. Figure 3 Also included is a second curve 202 representing the battery voltage of the battery 12 as a function of the state of charge (SOC) under charging conditions, and a third curve 204 representing the battery voltage of the battery 12 as a function of the state of charge (SOC) under discharging conditions.

[0054] refer to Figure 3 , the first curve 200 representing the open circuit voltage condition may not be affected by temperature or battery aging, while the internal resistance 36 will be affected by temperature and / or battery aging (the internal resistance 36 will increase with higher temperature or aging). Therefore, the second curve 202 and the third curve 204 will each be affected by temperature and / or battery aging, even with the same battery current i dd Therefore, based on the battery voltage V batt The total energy loss in the battery through a plurality of charge cycles and a plurality of discharge cycles is determined in conjunction with one of the SOC signal 63 and / or the RSOC signal 65 , which may be designated as SOC / RSOC (block 302 ).

[0055] Thus, determining energy loss during charging and / or discharging may include: determining SOC / RSOC; determining the open circuit voltage at SOC / RSOC; batt The voltage difference ΔV is determined by subtracting the open circuit voltage at SOC / RSOC from the measured value of ΔV; and the energy loss E is calculated according to equation (5): 损失 (which may include charging energy losses E loss_C and / or discharge energy loss E loss_D ):

[0056] E 损失 =ΔV×I dd ×Time (5)

[0058] The method for determining energy loss during charging and / or discharging may include updating the SOC / RSOC as it increases or decreases over time.

[0059] Figure 4 A graph showing charging and discharging energy losses and available energy as a function of SOC is shown. Figure 4 The graph includes curves 200 , 202 , 204 representing battery voltage as a function of state of charge (SOC) under open circuit conditions, charging conditions, and discharging conditions. Figure 4 A first region 212 is shown between the first curve 200 and the second curve 202 and represents the charging energy loss E due to the internal resistance 36 when the battery 12 is being charged. loss_C . Figure 4 A second region 214 is also shown between the first curve 200 and the third curve 204 and represents the discharge energy loss E due to the internal resistance 36 when the battery 12 is being discharged. loss_D . Figure 4 A third region 216 below the third curve 204 is also shown and represents an estimate of the energy available in the battery 12. This estimate of available energy represented by the third region 216 does not take into account any energy losses due to the self-discharge resistor 38.

[0060] Figure 5 Another graph showing charge energy loss, discharge energy loss, and self-discharge energy loss, as well as available energy as a function of SOC is shown. Figure 5 The graph is similar to Figure 4 , including curves 200, 202, and 204. However, Figure 5 A fourth region 220 is also included that is located directly below the third curve 204 and represents energy losses due to the self-discharge resistor 38 . Figure 5A fifth region 222 is also included below the fourth region 220 and represents an improved estimate of the energy available in the battery 12, accounting for energy losses due to the self-discharge resistor 38. This improved estimate of the energy available in the battery 12, represented by the fifth region 222, is determined in accordance with the present disclosure and is useful when compared to alternative estimates, such as those provided by Figure 4 When compared to the estimate represented by the third region 216 shown in FIG, a more accurate estimate of the available energy in the battery 12 can be provided.

[0061] Figure 6 A flowchart outlining the steps of a method for monitoring the status of a battery according to at least some embodiments is shown. Specifically, the method begins (block 300) and includes determining the total energy loss in the battery over a plurality of charge cycles and a plurality of discharge cycles based on the battery voltage and the battery current (block 302). For example, the processor 42 may execute instructions to implement the energy loss detector 66 and thereby determine the total energy loss in the battery 12 over a plurality of charge cycles and discharge cycles.

[0062] The method also includes determining the energy loss due to the internal resistance of the battery during the plurality of charge cycles and the plurality of discharge cycles (block 304). For example, the processor 42 may execute instructions to implement the self-discharge calculator 100 and calculate the internal energy loss E in the battery 12 due to the internal resistance 36. loss_CD Calculated as charging energy loss E loss_C and discharge energy loss E loss_D The sum of .

[0063] The method also includes determining the self-discharge energy due to the self-discharge resistance of the battery based on the difference between the total energy loss and the energy loss due to the internal resistance of the battery (block 306). For example, the processor 42 may execute instructions to implement the self-discharge calculator 100 for calculating the self-discharge energy by calculating the self-discharge energy from the difference energy E Diff Subtract internal energy loss E loss_CD To calculate the self-discharge energy E SD .

[0064] The method also includes generating a signal indicating the self-discharge resistance of the battery based on the self-discharge energy (block 308). For example, the processor 42 may execute instructions to implement the self-discharge calculator 100 to generate a signal indicating the self-discharge energy E and the self-discharge resistance E, respectively. SD and self-discharge percentage SD ％ signals 101, 102.

[0065] In some embodiments, the method may further include generating a state-of-health signal indicative of the state of health of the battery. In some embodiments, the step of generating a signal indicative of the self-discharge resistance of the battery (block 308) includes adjusting the state-of-health signal based on the self-discharge energy. For example, the processor 42 may execute instructions to implement the SoH calculator 112 for adjusting the state-of-health signal based on the self-discharge energy signal E from the self-discharge monitor 68. SD To generate the SoH signal 27.

[0066] In some embodiments, the method may further include generating a state of charge signal that represents the state of charge of the battery. In some embodiments, the step of generating a signal indicative of the self-discharge resistance of the battery (block 308) includes adjusting the state of charge signal based on the self-discharge energy. For example, the processor 42 may execute instructions to implement the IIC 114 for generating the SoC signal 28 according to equation (4) and representing a refined RSOC value that accounts for self-discharge losses in the battery 12. Alternatively or additionally, the processor 42 may execute instructions to implement the IIC 114 for adjusting the SOC signal 63 based on the self-discharge loss capacity and thereby generating a signal that accounts for the self-discharge energy E SD The adjusted absolute SOC is the SoC signal 28 .

[0067] In some embodiments, the signal indicating the self-discharge resistance of the battery comprises a warning signal indicating that the battery has a degraded condition. For example, the processor 42 may execute instructions to implement the warning generator 110 for generating the battery warning signal 26 based on the self-discharge warning signal 107 from the self-discharge monitor 68.

[0068] In some embodiments, the method may further include: determining a self-discharge metric based on the self-discharge energy; and determining that the self-discharge metric exceeds a threshold value. In some embodiments, the step of generating a signal indicative of the self-discharge resistance of the battery (block 308) includes generating a warning signal based on the self-discharge metric exceeding the threshold value. For example, the processor 42 may execute instructions to implement the self-discharge comparator 106 to convert the self-discharge percentage SD ％ is compared with the self-discharge threshold and in response determines the self-discharge percentage SD ％ Exceeding the self-discharge threshold generates a self-discharge warning signal warning SD .

[0069] In some embodiments, the method may further include determining the total energy delivered to the battery; and calculating a self-discharge ratio between the self-discharge energy and the total energy delivered to the battery. In some embodiments, the self-discharge metric includes a self-discharge ratio. For example, processor 42 may execute instructions to implement self-discharge calculator 100 for calculating a self-discharge loss percentage (SD%) representing energy loss due to self-discharge resistor 38 as a percentage of the total energy delivered to battery 12.

[0070] In some embodiments, the method may further include measuring the battery current using a current sensor. In some embodiments, the step of determining the total energy loss in the battery through a plurality of charge cycles and a plurality of discharge cycles (block 302) includes determining the total energy loss in the battery based on the battery voltage and the measured battery current. For example, the processor 42 may execute instructions to implement the current calculator 80 for determining the battery current i based on the voltage difference across the current sensor 22. dd .

[0071] In some embodiments, the method may further include determining an estimated battery current based on the battery voltage. In some embodiments, the step of determining the total energy loss in the battery through a plurality of charge cycles and a plurality of discharge cycles (block 302) includes determining the total energy loss in the battery based on the battery voltage and the estimated battery current. For example, the processor 42 may execute instructions to determine the total energy loss in the battery based on the battery voltage V batt and one or both of the SOC signal 63 and / or the RSOC signal 65 to calculate the battery current i dd estimated value.

[0072] In some embodiments, the method may further include measuring the temperature of the battery. In some embodiments, the step of determining the estimated battery current includes determining the estimated battery current based on the battery voltage and based on the temperature of the battery. For example, the processor 42 may execute instructions to further refine the battery current i based on the temperature signal 75 from the temperature calculator 74. dd estimated value.

[0073] In some embodiments, the self-discharge resistance of a battery can be determined while the battery is connected to a load system and remains connected to the load system throughout multiple charge cycles and multiple discharge cycles. For example, the systems and methods of the present disclosure provide for measuring the self-discharge resistance of a battery without disconnecting the battery from its load. This differs from conventional techniques, which may require the battery to be disconnected from any external load in order to measure the self-discharge resistance. The systems and methods of the present disclosure may be particularly advantageous for many applications, such as medical devices, where the battery is required to remain connected to the load at all times.

[0074] The systems and methods of the present disclosure detect increases in self-discharge resistance, which can indicate abnormal conditions within the battery and can provide early warning of battery cell failure and / or potentially dangerous conditions in the battery. Thus, the systems and methods of the present disclosure can avoid or mitigate such potential hazards by removing, replacing, or otherwise adjusting the use of the battery.

[0075] The above discussion is intended to illustrate the principles and various embodiments of the present invention. Once the above disclosure is fully understood, many variations and modifications will become apparent to those skilled in the art. The following claims are to be interpreted as intending to include all such variations and modifications.

Claims

1. A method for monitoring a battery status, the method comprising: determining a total energy loss in the battery through a plurality of charge cycles and a plurality of discharge cycles based on the battery voltage and the battery current; determining energy loss due to an internal resistance of the battery during the plurality of charge cycles and the plurality of discharge cycles; determining a self-discharge energy due to a self-discharge resistance of the battery based on a difference between the total energy loss and the energy loss due to the internal resistance of the battery; as well as A signal indicative of the self-discharge resistance of the battery is generated based on the self-discharge energy.

2. The method of claim 1 , further comprising generating a state-of-health signal indicative of a state-of-health of the battery, Wherein generating the signal indicative of the self-discharge resistance of the battery includes adjusting the state-of-health signal based on the self-discharge energy.

3. The method of claim 1 , further comprising generating a state of charge signal indicating a state of charge of the battery, Wherein generating the signal indicative of the self-discharge resistance of the battery includes adjusting the state of charge signal based on the self-discharge energy. 4 . The method of claim 1 , wherein the signal indicative of the self-discharge resistance of the battery comprises a warning signal indicating that the battery has a degraded condition.

5. The method according to claim 4, further comprising: determining a self-discharge metric based on the self-discharge energy; as well as determining that the self-discharge metric exceeds a threshold, Wherein generating the signal indicative of the self-discharge resistance of the battery includes generating the warning signal based on the self-discharge metric exceeding the threshold value.

6. The method according to claim 5, further comprising: determining a total energy supplied to the battery; as well as calculating a self-discharge ratio between the self-discharge energy and the total energy supplied to the battery, Wherein the self-discharge metric comprises the self-discharge ratio.

7. The method of claim 1 , further comprising measuring the battery current using a current sensor, Wherein determining the total energy loss in the battery through the plurality of charge cycles and the plurality of discharge cycles comprises determining the total energy loss in the battery based on the battery voltage and the measured battery current.

8. The method of claim 1 , further comprising determining an estimated battery current based on the battery voltage, Wherein determining the total energy loss in the battery through the plurality of charge cycles and the plurality of discharge cycles comprises determining the total energy loss in the battery based on the battery voltage and the estimated battery current.

9. The method according to claim 8, further comprising measuring the temperature of the battery, Wherein determining the estimated battery current includes determining the estimated battery current based on the battery voltage and based on the temperature of the battery.

10. The method of claim 1, wherein the battery is connected to a load system and remains connected to the load system throughout the plurality of charge cycles and the plurality of discharge cycles.

11. A system for monitoring a status of a battery, the system comprising: A controller configured to: determining a total energy loss in the battery through a plurality of charge cycles and a plurality of discharge cycles based on the battery voltage and the battery current; determining energy loss due to an internal resistance of the battery during the plurality of charge cycles and the plurality of discharge cycles; determining a self-discharge energy due to a self-discharge resistance of the battery based on a difference between the total energy loss and the energy loss due to the internal resistance of the battery; as well as A signal indicative of the self-discharge resistance of the battery is generated based on the self-discharge energy.

12. The system of claim 11 , wherein the controller is further configured to generate a state-of-health signal indicative of a state-of-health of the battery, and Wherein generating the signal indicative of the self-discharge resistance of the battery includes adjusting the state-of-health signal based on the self-discharge energy.

13. The system of claim 11 , wherein the controller is further configured to generate a state of charge signal indicating a state of charge of the battery, and Wherein generating the signal indicative of the self-discharge resistance of the battery includes adjusting the state of charge signal based on the self-discharge energy.

14. The system of claim 11, wherein the signal indicative of the self-discharge resistance of the battery comprises a warning signal indicating that the battery has a degraded condition.

15. The system of claim 14, wherein the controller is further configured to: determining a self-discharge metric based on the self-discharge energy; and determining that the self-discharge metric exceeds a threshold, and Wherein generating the signal indicative of the self-discharge resistance of the battery includes generating the warning signal based on the self-discharge metric exceeding the threshold value.

16. The system of claim 15, wherein the controller is further configured to: determining a total energy supplied to the battery; and calculating a self-discharge ratio between the self-discharge energy and the total energy supplied to the battery, and Wherein the self-discharge metric comprises the self-discharge ratio.

17. The system of claim 11, further comprising: a current sensor configured to measure a battery current, and Wherein determining the total energy loss in the battery through the plurality of charge cycles and the plurality of discharge cycles comprises determining the total energy loss in the battery based on the battery voltage and the measured battery current.

18. The system of claim 11 , wherein the controller is further configured to determine an estimated battery current based on the battery voltage; and Wherein determining the total energy loss in the battery through the plurality of charge cycles and the plurality of discharge cycles comprises determining the total energy loss in the battery based on the battery voltage and the estimated battery current.

19. The system of claim 18, further comprising: a temperature sensor configured to measure a temperature of the battery, and Wherein determining the estimated battery current includes determining the estimated battery current based on the battery voltage and based on the temperature of the battery.

20. A device for monitoring a status of a battery, the device comprising: processor; and a memory comprising instructions that, when executed by the processor, cause the processor to: determining a total energy loss in the battery through a plurality of charge cycles and a plurality of discharge cycles based on the battery voltage and the battery current; determining energy loss due to an internal resistance of the battery during the plurality of charge cycles and the plurality of discharge cycles; determining a self-discharge energy due to a self-discharge resistance of the battery based on a difference between the total energy loss and the energy loss due to the internal resistance of the battery; as well as A signal indicative of the self-discharge resistance of the battery is generated based on the self-discharge energy.

21. The apparatus of claim 20, wherein the instructions causing the processor to generate the signal indicative of the self-discharge resistance of the battery further cause the processor to adjust at least one signal based on the self-discharge energy, and wherein the at least one signal comprises at least one of a state of health signal and a state of charge signal.

22. The apparatus of claim 20, wherein the signal indicative of the self-discharge resistance of the battery comprises a warning signal indicating that the battery has a degraded condition.

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