Power storage amount estimation device

Abstract

To enable estimation of the amount of power stored in a secondary battery by detecting changes in stage of a negative electrode without having to detect a voltage of the secondary battery.SOLUTION: A power storage amount estimation device provided herein is configured to acquire changes in temperature during charging or discharging of a secondary battery, determine whether a rate of change in temperature has changed or not, and estimating that the amount of power stored in the secondary battery has reached a predetermined level when it is determined that the rate of change in temperature has changed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a device for estimating a stored charge amount of a secondary battery. [Background technology]

[0002] A known method for estimating the state of charge of a secondary battery is described in Patent Document 1. In Patent Document 1, a map of voltage change rate and SOC (State Of Charge) is stored for each charge rate and discharge rate, and voltage steps caused by negative electrode stage changes are detected according to the voltage change rate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 010475 Summary of the Invention [Problem to be solved by the invention]

[0004] The estimation method described in Patent Document 1 is applicable when the charging current and discharging current are constant, but is not applicable when the charging current and discharging current change depending on the SOC, such as in a vehicle.

[0005] Although the most accurate method for detecting the behavior of changes in the negative electrode stage structure is to detect voltage detection, the negative electrode potential cannot be detected directly, and it is necessary to estimate the positive electrode potential and then subtract it from the CCV voltage.

[0006] However, although the positive electrode potential can be kept constant, the CCV voltage fluctuates due to the influence of resistance changes, polarization, etc., and therefore it is not possible to accurately estimate the negative electrode potential obtained by subtracting the positive electrode potential from the CCV voltage.

[0007] As described in Patent Document 1, if you want to detect stage changes from potential changes, you need to estimate the potential by keeping the current constant. However, even if the current is constant, if the current value is large, there is a problem that the potential step of the negative electrode cannot be detected due to the electrode characteristics. This tendency is more pronounced in LFP batteries than in ternary batteries.

[0008] Therefore, an object of the present disclosure is to estimate the amount of stored electricity in a secondary battery by detecting a change in the stage of the negative electrode without detecting the voltage in the secondary battery. [Means for solving the problem]

[0009] The present disclosure relates to a secondary battery storage capacity estimation device, which includes a temperature acquisition unit that acquires temperature changes when the secondary battery is being charged or discharged, a change determination unit that determines whether the rate of change of the temperature change has changed, and a storage capacity estimation unit that, when it determines that the rate of change of the temperature change has changed, estimates that the storage capacity of the secondary battery has reached a predetermined storage capacity. [Effects of the Invention]

[0010] According to the present disclosure, the amount of stored electricity in a secondary battery can be estimated by detecting a change in the stage of the negative electrode without detecting the voltage in the secondary battery. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram for explaining the overall configuration of an electric vehicle according to this embodiment. [Figure 2] FIG. 2 is a flowchart for explaining the processing of the EVECU shown in FIG. [Figure 3] FIG. 3 is a diagram for explaining the charge / discharge characteristics of the battery pack shown in FIG. [Figure 4] FIG. 4 is a diagram for explaining the amount of stored electricity when the battery pack shown in FIG. 1 deteriorates over time. [Figure 5] FIG. 5 is a diagram for explaining the relationship between the amount of stored electricity and the temperature in a battery cell. [Figure 6] FIG. 6 is a flowchart for explaining the processing of the EVECU shown in FIG. [Figure 7] FIG. 7 is a flowchart for explaining the processing of the EVECU shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0013] 1 is a schematic diagram illustrating the overall configuration of an electric vehicle 2 according to this embodiment. In this embodiment, an example will be described in which the electric vehicle 2 is an electric vehicle (BEV: Battery Electric Vehicle), but the electric vehicle 2 is not limited to a BEV and may be, for example, a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle), a hybrid electric vehicle (HEV: Hybrid Electric Vehicle), a fuel cell electric vehicle (FCEV: Fuel Cell Electric Vehicle), or the like.

[0014] The electric vehicle 2 includes an EVECU (Electric Vehicle Electronic Control Unit) 21 , a battery pack 22 , a boost converter 23 , an inverter 24 , a motor generator 25 , a transmission gear 26 , and drive wheels 27 .

[0015] The battery pack 22 is mounted on the electric vehicle 2 as a drive power source that is a power source for the electric vehicle 2. The battery pack 22 is configured by stacking a plurality of cells 221, which are single cells, and connecting them in series. The cells 221 are configured by, for example, rechargeable iron phosphate lithium ion batteries (LFP batteries). Note that the battery pack 22 may also be configured by stacking a plurality of cells 221 to form a cell stack and connecting a plurality of cell stacks in series.

[0016] The battery pack 22 further includes a current sensor 224, a temperature sensor 223, a voltage sensor 222, and a battery pack ECU (Electric Vehicle Electronic Control Unit) 225.

[0017] The current sensor 224 detects the battery current Ib, which is the input / output current to and from the multiple cells 221. The temperature sensor 223 detects the battery temperature Tb, which is the temperature of the multiple cells 221. Note that multiple temperature sensors 223 may be provided so that the temperatures of the multiple cells 221 can be accurately measured. The voltage sensor 222 detects the battery voltage Vb, which is the voltage between the terminals of each of the multiple cells 221. In this embodiment, the same number of voltage sensors 222 as the number of cells 221 are provided.

[0018] The battery pack ECU 225 receives detection values ​​output by the current sensor 224, the temperature sensor 223, and the voltage sensor 222. These detection values ​​include the battery current Ib, the battery temperature Tb, and the battery voltage Vb. The battery pack ECU 225 outputs the battery voltage Vb, the battery current Ib, and the battery temperature Tb to the EVECU 21.

[0019] The battery pack 22 is connected to the boost converter 23 via system main relays 28a and 28b. The boost converter 23 boosts the output voltage of the battery pack 22. The boost converter 23 is connected to an inverter 24. The inverter 24 converts the DC power from the boost converter 23 into AC power.

[0020] The motor generator (three-phase AC motor) 25 receives AC power from the inverter 24 and generates kinetic energy for propelling the electric vehicle 2. The kinetic energy generated by the motor generator 25 is transmitted to the drive wheels 27. On the other hand, when the electric vehicle 2 is decelerated or stopped, the motor generator 25 converts the kinetic energy of the electric vehicle 2 into electrical energy. The AC power generated by the motor generator 25 is converted into DC power by the inverter 24 and supplied to the battery pack 22 via the boost converter 23. This allows regenerative power to be stored in the battery pack 22. In this way, the motor generator 25 is configured to generate driving force or braking force for the vehicle by exchanging power with the battery pack 22.

[0021] It is possible to omit the boost converter 23. When a DC motor is used as the motor generator 25, the inverter 24 can be omitted.

[0022] If the electric vehicle 2 is configured as a PHEV further equipped with an engine as a power source, the output of the engine can be used as driving force for traveling in addition to the output of the motor generator 25. It is also possible to use a motor generator that generates electricity using engine output to generate charging power for the battery pack 22.

[0023] The electric vehicle 2 has an external charging function for charging the battery pack 22 using an external power source 55. The electric vehicle 2 has a charger 30 and charging relays 29a and 29b. In the present disclosure, charging the battery pack 22 using the external power source 55 is referred to as "external charging."

[0024] The external power source 55 is a power source provided outside the vehicle, such as a commercial power source. The charger 30 converts power from the external power source 55 into charging power for the battery pack 22. The charger 30 is connected to the battery pack 22 via charging relays 29a and 29b. When the charging relays 29a and 29b are on, the battery pack 22 can be charged with power from the external power source 55.

[0025] The external power source 55 and the charger 30 can be connected by, for example, a charging cable 50. When the charging cable 50 is connected to the external power source 55, the external power source 55 and the charger 30 are electrically connected, and the battery pack 22 can be charged using the external power source 55. Alternatively, the electric vehicle 2 may be configured so that power is transmitted contactlessly between the external power source 55 and the charger 30. For example, the battery pack 22 can be charged by the external power source 55 by transmitting power via a power transmitting coil (not shown) on the external power source side and a power receiving coil (not shown) on the electric vehicle side.

[0026] When AC power is supplied from the external power source 55, the charger 30 is configured to have a function of converting the power supplied from the external power source 55 (AC power) into charging power (DC power) for the battery pack 22. When the external power source 55 is a DC power source, the charger 30 adjusts the magnitude of the DC power from the external power source 55 and supplies it to the battery pack 22. The manner of external charging of the electric vehicle 2 is not particularly limited.

[0027] The EVECU 21 has, as electrical components, a microcomputer (hereinafter also referred to as "mc"), a data transfer circuit, a power supply circuit, and a power supply detection circuit. The mc includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a flash memory. The EVECU 21 has, as functional components, a drive control unit 211, a charge / discharge control unit 212, a temperature acquisition unit 213, a change determination unit 214, a power storage amount estimation unit 215, and an SOC estimation unit 216. The EVECU 21 receives signals output from various sensors such as an accelerator position sensor (not shown) and a vehicle speed sensor (not shown), as well as on / off signals corresponding to the operation of a power switch (not shown) for starting / stopping the EVECU 21.

[0028] The drive control unit 211 performs various calculations based on various signals input to the EVECU 21 and controls the operation of various devices such as the boost converter 23, the inverter 24, and the system main relays 28a, 28b. When a power switch (not shown) is switched from off to on, the drive control unit 211 switches the system main relays 28a, 28b from off to on, thereby activating the boost converter 23 and the inverter 24. When the power switch (not shown) is switched from on to off, the drive control unit 211 switches the system main relays 28a, 28b from on to off, thereby stopping the boost converter 23 and the inverter 24.

[0029] The charge / discharge control unit 212 controls the charger 30 and the charge relays 29a, 29b to perform external charging of the battery pack 22. When the start switch (power switch) is switched from off to on, the charge / discharge control unit 212 switches the system main relays 28a, 28b from off to on.

[0030] The temperature acquisition unit 213 is a part that acquires temperature changes during discharging or charging of the battery pack 22. The temperature acquisition unit 213 acquires temperature changes during discharging or charging of the battery pack 22 based on the battery temperature Tb output from the battery pack ECU 225. The temperature acquisition unit 213 also acquires the ambient temperature of the area where the battery pack 22 is placed. The ambient temperature may be acquired from an ambient temperature sensor (not shown) or may be estimated from weather data.

[0031] The change determination unit 214 is a unit that determines whether the rate of change in temperature during discharging or charging of the battery pack 22 is equal to or greater than a predetermined rate. The stored power estimation unit 215 is a unit that estimates the stored power of the battery pack 22 when the rate of change in temperature during discharging or charging of the battery pack 22 is equal to or greater than a predetermined rate. The SOC estimation unit 216 is a unit that estimates the SOC (State Of Charge) of the battery pack 22.

[0032] Next, the stored power amount estimation process in the EVECU 21 will be described with reference to Figure 2. While Figure 2 illustrates the process during charging, the estimation process can be performed similarly during discharging. In step S01, the temperature acquisition unit 213 acquires the ambient temperature and determines whether the rate of change in the ambient temperature is less than a predetermined value. This is to prevent changes in the ambient temperature from affecting the determination of the stored power amount, which is estimated based on changes in the battery temperature from step S02 onwards.

[0033] If the rate of change of the ambient temperature is less than the predetermined value (step S01: YES), the process proceeds to step S02. If the rate of change of the ambient temperature is not less than the predetermined value (step S01: NO), the process of step S01 is repeated.

[0034] In step S02, the temperature acquisition unit 213 acquires the battery temperature Tb of the battery pack 22. The temperature acquisition unit 213 continues to acquire the battery temperature Tb at predetermined time intervals. In step S03 following step S02, the temperature acquisition unit 213 determines whether there has been a change in the rate of change of the battery temperature Tb.

[0035] If there is a change in the rate of change of the battery temperature Tb (step S03: YES), the process proceeds to step S04. If there is no change in the rate of change of the battery temperature Tb (step S03: NO), the process proceeds to step S02.

[0036] In step S04, the stored power amount estimation unit 215 estimates the amount of stored power in the battery pack 22. In step S05 following step S04, the stored power amount estimation unit 215 executes a process of updating the amount of stored power in the battery pack 22. This amount of stored power may be used as the amount of power that can be discharged by the battery pack 22, and may be used to calculate the distance that can be traveled.

[0037] Next, a method for estimating the amount of stored power in the battery pack 22 by the stored power amount estimating unit 215 will be described with reference to FIGS.

[0038] FIG. 3 is a diagram showing the charge / discharge characteristics of an example secondary battery. In FIG. 3, the vertical axis represents battery voltage VB, and the horizontal axis represents SOC. In FIG. 3, the solid line illustrates the SOC-OCV characteristics of the secondary battery. The dashed-dotted line illustrates the charge characteristics (charge curve) when charging at a large current (e.g., charge rate: 2C). The dashed-two-dotted line illustrates the discharge characteristics (discharge curve) when discharging at a large current (e.g., discharge rate: 2C).

[0039] The SOC-OCV characteristic shows the correlation between the SOC and the OCV, which is the open-circuit voltage of a battery. For some secondary batteries, as shown in Figure 3, the first stage transition S1 and the second stage transition S2 are clearly visible, and the first flat region F1, the second flat region F2, and the third flat region F3 are clearly recognizable. However, when the charge / discharge current is large, the sharp change in the battery voltage VB during the stage transition may not appear, as indicated by the dashed-dotted line or the dashed-two-dotted line in Figure 3.

[0040] Furthermore, depending on the secondary battery, the SOC-OCV characteristics may not show clear stage changes as shown in Figure 3. In any case, there are cases where it is not possible to accurately estimate the SOC by simply measuring the battery voltage VB.

[0041] The SOC is expressed as the ratio of the actual amount of charge to the amount of charge when fully charged. The amount of charge when fully charged changes depending on the deterioration of the secondary battery. The relationship between the change in the amount of charge when fully charged and the change in the stage will be explained with reference to Figure 4.

[0042] FIG. 4 is a diagram showing the relationship between OCV and the amount of stored energy in an example secondary battery. In FIG. 4, the vertical axis is OCV, and the horizontal axis is the amount of stored energy [Ah]. In FIG. 4, the solid line illustrates the relationship between OCV and the amount of stored energy when the secondary battery is new. The dashed line illustrates the relationship between OCV and the amount of stored energy when the secondary battery has deteriorated. As shown in FIG. 4, even if the amount of stored energy at full charge (full charge capacity) decreases due to deterioration of the secondary battery, the amounts of stored energy Q1 and Q2 at the time of stage change do not change, and are approximately the same value when the secondary battery is new and when it has deteriorated.

[0043] In this embodiment, even if the battery pack 22 deteriorates, the amount of stored power at the time of the stage change is estimated by focusing on the fact that the amount of stored power at the time of the stage change remains approximately the same. However, as described with reference to Fig. 3, the stage change of the battery pack 22 cannot be determined by simply measuring the battery voltage VB. Therefore, in this embodiment, the stage change is estimated by focusing on the temperature change of the battery pack 22 and utilizing the fact that the behavior of the maximum value of the temperature change corresponds to the stage change.

[0044] Fig. 5 is a diagram showing the relationship between the temperature and the amount of stored electricity in the cells 221 that make up the battery pack 22. In Fig. 5, the vertical axis represents the temperature [°C] of the cells 221, and the horizontal axis represents the amount of stored electricity [Ah]. Fig. 5 shows the temperature change for cells 1 and 2, which are examples of cells included in the cells 221 that make up the battery pack 22.

[0045] 5, although the temperature behaviors of cells 1 and 2 do not completely match, the temperature change rate changes at a point corresponding to the amount of stored power Q1, exhibiting a local maximum value. Therefore, based on the determination of whether or not there is a change in the rate of change of battery temperature Tb in step S03, the stored power estimation unit 215 determines that if there is a change in the rate of change of battery temperature Tb in step S03, the amount of stored power at that time corresponds to the amount of stored power Q1 and corresponds to the first stage change S1.

[0046] Next, the SOC estimation process in the EVECU 21 will be described with reference to FIG. 6. In step S21, the SOC estimation unit 216 determines whether the relationship between the SOC and the battery voltage VB is in a flat region. In the example of FIG. 3, for example, the relationship between the SOC and the battery voltage VB is in a flat region between the first flat region F1 and the third flat region F3. In the example of FIG. 3, for example, the relationship between the SOC and the battery voltage VB is not in a flat region when the SOC is lower than the third flat region F3 or higher than the first flat region F1, and the relationship between the SOC and the battery voltage VB has a steep slope.

[0047] If the relationship between the SOC and the battery voltage VB is in the flat region (step S21: YES), the process proceeds to step S22. If the relationship between the SOC and the battery voltage VB is not in the flat region (step S21: NO), the process proceeds to step S23.

[0048] In step S22, the SOC estimation unit 216 estimates the SOC of the battery pack 22 using the current integration method. When the processing of step S22 is completed, the process proceeds to step S24. In step S23, the SOC estimation unit 216 estimates the SOC of the battery pack 22 using the OCV method. When the processing of step S23 is completed, the process proceeds to step S21.

[0049] In step S24, the SOC estimation unit 216 determines whether or not the stored power amount Q1 has been updated. The update of the stored power amount Q1 is the update of the stored power amount Q1 performed by the stored power amount estimation unit 215 in step S05 in FIG.

[0050] If the amount of stored power Q1 has been updated (step S24: YES), the process proceeds to step S25. If the amount of stored power Q1 has not been updated (step S24: NO), the process proceeds to step S21.

[0051] In step S25, the SOC estimation unit 216 acquires the full charge amount Qfull. As described with reference to Fig. 4, the full charge amount decreases as the battery pack 22 deteriorates, so the full charge amount Qfull is the most recently updated full charge amount of the battery pack 22.

[0052] In step S26 following step S25, the SOC estimation unit 216 calculates the amount of stored electricity Q1 / the amount of fully charged electricity Qfull, and estimates the current SOC.

[0053] Next, another example of the stored power amount estimation process in the EVECU 21 will be described with reference to Fig. 7. Although Fig. 7 describes the process during charging as an example, the estimation process can be performed similarly during discharging. In step S41, the temperature acquisition unit 213 acquires the ambient temperature and determines whether the rate of change of the ambient temperature is less than a predetermined value.

[0054] If the rate of change of the ambient temperature is less than the predetermined value (step S41: YES), the process proceeds to step S42. If the rate of change of the ambient temperature is not less than the predetermined value (step S41: NO), the process of step S41 is repeated.

[0055] In step S42, the temperature acquisition unit 213 acquires the battery temperature Tb of the battery pack 22. Since the battery pack 22 is provided with a plurality of temperature sensors 223, the temperature acquisition unit 213 acquires the battery temperature Tb from each temperature sensor 223. The temperature acquisition unit 213 continues to acquire the battery temperature Tb at predetermined time intervals.

[0056] In step S43 following step S42, the temperature acquisition unit 213 determines whether there has been a change in the rate of change of the battery temperature Tb in the first cell 221. As described above, the battery pack 22 is provided with multiple temperature sensors 223. The temperature changes of the multiple cells 221 are not uniform, and the behavior of the temperature change differs depending on the location of the cell 221, etc. The location where the temperature sensor 223 is provided is a location that represents the temperature changes of the multiple cells 221. Therefore, when there is an initial change in the rate of change of the temperature of the battery temperature Tb output from the multiple temperature sensors 223, it is determined that there has been a change in the rate of change of the battery temperature Tb in the first cell 221.

[0057] If there is a change in the rate of change of the battery temperature Tb in the first cell 221 (step S43: YES), the process proceeds to step S44. If there is no change in the rate of change of the battery temperature Tb (step S43: NO), the process proceeds to step S42.

[0058] In step S44, the charge / discharge control unit 212 limits the charge current to the battery pack 22. The charge / discharge control unit 212 limits the charge current to an extent that allows detection of a voltage step in the cell 221 that constitutes the battery pack 22. This voltage step is a voltage fluctuation that allows identification of a stage change in the negative electrode of the cell 221.

[0059] In step S45 following step S44, the stored power estimation unit 215 executes a process of detecting a voltage step in the cells 221 constituting the battery pack 22 other than the cell 221 in which the temperature change was detected in step S43.

[0060] In step S46 following step S45, the stored energy estimation unit 215 determines whether or not a voltage step has been detected in all cells 221 constituting the battery pack 22 (excluding the cell 221 in which a temperature change was detected in step S43).

[0061] If a voltage step has been detected in all of the cells 221 constituting the battery pack 22 (excluding the cell 221 in which a temperature change was detected in step S43) (step S46: YES), the process proceeds to step S47. If a voltage step has not been detected in all of the cells 221 constituting the battery pack 22 (excluding the cell 221 in which a temperature change was detected in step S43) (step S46: NO), the process proceeds to step S45. In step S47, the charge / discharge control unit 212 cancels the process of limiting the charging current to the battery pack 22.

[0062] In step S48 following step S47, the stored power amount estimation unit 215 estimates the stored power amount of the battery pack 22. The stored power amount estimation in step S48 is based on the estimated stored power amount in each cell 221. This estimation is performed by appropriately performing numerical processing such as the average value or median value of the estimated stored power amount in each cell 221. In step S49 following step S48, the stored power amount estimation unit 215 executes processing to update the stored power amount of the battery pack 22.

[0063] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise.

[0064] [Note] Notes 1 to 3 below can be combined in any way as long as there is no technical contradiction.

[0065] [Appendix 1] A device for estimating a stored charge amount of a secondary battery, a temperature acquisition unit 213 that acquires temperature changes during charging or discharging of the secondary battery; a change determination unit 214 that determines whether the rate of change of the temperature change has changed; The device further includes a stored power amount estimation unit 215 that estimates that the amount of stored power in the secondary battery has reached a predetermined amount when it is determined that the rate of change in temperature has changed.

[0066] In this embodiment, a battery pack 22 and a cell 221 are exemplified as the secondary battery. An LFP battery is exemplified as a specific example of the cell 221, but a so-called ternary battery may also be used. It is preferable to use a secondary battery having SOC-OCV characteristics with a flat region in which the rate of change of open circuit voltage with respect to the charge rate is equal to or less than a predetermined value. In this embodiment, the EVECU 21 is exemplified as the storage capacity estimation device, but it may be another ECU or may be configured with multiple ECUs as long as it can function as a storage capacity estimation device.

[0067] According to Supplementary Note 1, when it is determined that the rate of change of temperature change has changed, it is estimated that the amount of electricity stored in the secondary battery has reached a predetermined amount of electricity. Therefore, it is possible to detect a change in the negative electrode stage without relying on voltage detection, and the amount of electricity stored in the secondary battery can be estimated.

[0068] [Appendix 2] 10. The storage capacity estimation device according to claim 1, When the rate of change of the temperature change indicates an endothermic reaction of the secondary battery, the change determination unit 214 determines that the rate of change of the temperature change has fluctuated.

[0069] As explained with reference to Figure 5, when the battery pack 22 and the cell 221 are charged, an endothermic reaction occurs near Q1, where the amount of charge is approximately 60%, and the temperature change rate exhibits a maximum value. On the other hand, an exothermic reaction occurs near Q2 (see Figure 4), where the amount of charge is approximately 30%, and the temperature change rate does not exhibit a maximum value. According to Supplementary Note 2, Q1, which is the predetermined amount of charge, can be accurately detected, improving the accuracy of estimating the amount of charge stored in the secondary battery.

[0070] [Appendix 3] 3. The storage capacity estimation device according to claim 1, Further provided is a charge / discharge control unit 212 that controls the charge / discharge of the secondary battery, A plurality of secondary batteries are provided and connected in series, After the change determination unit 214 detects the rate of change of the temperature change of the first secondary battery, the charge / discharge control unit 212 limits the charge / discharge current of the other secondary batteries, The stored power amount estimation unit 215 detects voltage steps in a plurality of secondary batteries and estimates the stored power amount based on the voltage steps.

[0071] According to Supplementary Note 3, after detecting the rate of change of the temperature change of the first secondary battery, the charge / discharge control unit 212 limits the charge / discharge current of the other secondary batteries, so that the charge / discharge current of the other secondary batteries is reduced and voltage steps can be easily detected. The stored energy amount estimation unit 215 detects voltage steps in multiple secondary batteries and estimates the stored energy amount based on the detected voltage steps, thereby improving the accuracy of estimating the stored energy amount. [Explanation of symbols]

[0072] 2: Electric vehicles 221: Cell 222: Voltage sensor 223: Temperature sensor 224: Current sensor 25: Motor generator 26: Transmission gear 27: Drive wheel 28a, 28b: System main relay 29a, 29b: Charging relay 50: Charging cable 55: External power supply

Claims

1. A device for estimating a stored charge amount of a secondary battery, a temperature acquisition unit that acquires a temperature change during charging or discharging of the secondary battery; a change determination unit that determines whether a rate of change of the temperature change has changed; and a storage capacity estimation unit that estimates that the storage capacity of the secondary battery has reached a predetermined storage capacity when it is determined that the rate of change of the temperature change has changed.

2. The storage amount estimation device according to claim 1 , wherein the change determination unit determines that the rate of change of the temperature change has fluctuated when the rate of change of the temperature change indicates an endothermic reaction of the secondary battery.

3. a charge / discharge control unit that controls charging / discharging of the secondary battery; A plurality of the secondary batteries are provided and connected in series, After the change determination unit detects a rate of change in temperature of a first secondary battery, the charge / discharge control unit limits the charge / discharge current of the other secondary batteries; The storage capacity estimation device according to claim 1 or 2, wherein the storage capacity estimation unit detects voltage steps in the plurality of secondary batteries and estimates the storage capacity based on the voltage steps.

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