Charging control device

Abstract

A charge control device is provided. The charge control device includes a calculation section that calculates a damage accumulation amount that indicates an accumulation amount of damage to a storage battery due to rapid charging of the storage battery, and a charge control section that permits rapid charging to the storage battery when the damage accumulation amount is less than a threshold value, and restricts rapid charging to the storage battery when the damage accumulation amount is equal to or greater than the threshold value. The calculation section calculates the damage accumulation amount such that the damage accumulation amount increases as a period during which a current value of the storage battery at the time of rapid charging, i.e., a charge current value, is greater than a prescribed value is longer, and the damage accumulation amount decreases as a period during which the charge current value is equal to or less than the prescribed value and a period during which the storage battery is not being charged are longer.

Description

Technical Field

[0001] This invention relates to a charging control device. Background Technology

[0002] There is a known technology that prohibits fast charging when the number of times the battery is fast charged exceeds a certain number in order to suppress the degradation of battery performance (see Japanese Patent Application Laid-Open No. 2001-218378). Summary of the Invention

[0003] As mentioned above, banning fast charging based solely on the number of times it is fast charged may exceed the necessary opportunities to restrict fast charging.

[0004] Therefore, the present invention aims to provide a charging control device that suppresses the performance degradation of a battery caused by fast charging and avoids excessively limiting the opportunity for fast charging.

[0005] The above objective can be achieved by a charging control device comprising: a calculation unit that calculates a damage accumulation amount, which represents the accumulation of damage to the battery caused by fast charging; and a charging control unit that allows fast charging of the battery when the damage accumulation amount is less than a threshold, and restricts fast charging of the battery when the damage accumulation amount is greater than or equal to the case where the damage accumulation amount is less than the threshold. The calculation unit calculates the damage accumulation amount in the following manner: the longer the period during fast charging when the battery current value, i.e., the charging current value, is greater than a predetermined value, the greater the damage accumulation amount; the longer the period during which the charging current value is less than the predetermined value and the longer the period during which the battery is not charging, the greater the damage accumulation amount.

[0006] According to the present invention, a charging control device can be provided that suppresses the performance degradation of a battery caused by fast charging and avoids excessively limiting the opportunity for fast charging. Attached Figure Description

[0007] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which similar reference numerals denote similar parts.

[0008] Figure 1 It is a schematic diagram of the vehicle's components.

[0009] Figure 2A It is a graph showing the rate of increase in resistance corresponding to the number of times the battery is fast-charged.

[0010] Figure 2B It is a coordinate graph showing the shift of the charging current value In during fast charging.

[0011] Figure 3A It is a coordinate graph representing Δd corresponding to the charging current value In.

[0012] Figure 3B It specifies the mapping between the infinite rated current value α and the allowable current value β corresponding to the battery's SOC and temperature during charging.

[0013] Figure 4A This is a flowchart illustrating an example of a control that determines whether fast charging is permitted or restricted.

[0014] Figure 4B This is a flowchart illustrating an example of the calculation and control of the damage accumulation amount QCd.

[0015] Figure 5 This is a time graph showing the progression of the damage accumulation QCd when fast charging is performed while maintaining the charging current value In at the allowable current value β, and then stopping the fast charging.

[0016] Figure 6 It is a time graph showing the accumulation of damage QCd when charging starts with the charging current value In being below the infinite rated current value α and then fast charging is stopped.

[0017] Figure 7 This is a time graph showing the accumulation of damage QCd when the charging current value In is maintained at the allowable current value β and repeated fast charging and discharging are performed.

[0018] Figure 8 This is a time graph showing the accumulation of damage QCd when the charging current value In is maintained at an infinite rated current value α and repeated fast charging and discharging are performed.

[0019] Figure 9 This is a time graph showing the accumulation of damage QCd when the charging current value In is maintained at the allowable current value β and repeated fast charging and discharging are performed, and then charging is stopped.

[0020] Figure 10 This is a time graph showing the accumulation of damage QCd when the charging current In is maintained at an infinite rated current α and repeated fast charging and discharging are performed, and then charging is stopped. Detailed Implementation

[0021] [Brief Composition of Vehicle 100]

[0022] Figure 1This is a schematic diagram of vehicle 100. Vehicle 100 is an electric motor vehicle equipped with a battery 110, which uses the electricity stored in the battery 110 to power an electric generator (hereinafter referred to as "MG (Motor Generator)") 130. It should be noted that vehicle 100 can be a hybrid vehicle that is equipped with an engine in addition to the MG 130, or a fuel cell vehicle that is equipped with a fuel cell in addition to the battery 110, etc.

[0023] The storage battery 110 is an externally charged battery that is charged by power supplied from a charger located outside the vehicle 100. In this embodiment, the case of fast charging of the storage battery 110 using power supplied from the charging station 200 is shown. Fast charging is a charging method that completes charging in a short time by supplying DC power (e.g., several hundred kW) to the storage battery 110 with a power greater than that of normal charging (e.g., tens of kW). With the connector 280 of the charging station 200 connected to the charging port 150 of the vehicle 100, when the vehicle 100 and the charging station 200 indicate that external charging is to be performed, the storage battery 110 of the vehicle 100 is charged from the charging station 200. It should be noted that charging of the storage battery 110 is not limited to the charging station 200; commercial power from a household can also be used.

[0024] In detail, the vehicle 100 includes a battery 110, a system main relay SMR, a power control unit (hereinafter referred to as "PCU (Power Control Unit)") 120, an MG 130, a power transmission gear 135, a drive wheel 140, a charging port 150, a charging relay RY, an ECU 160, an HMI (Human Machine Interface) device 170, and a charging device 180.

[0025] The storage battery 110 is configured to be rechargeable and dischargeable, such as a lithium-ion battery or a nickel-metal hydride battery. It should be noted that a lithium-ion secondary battery is a secondary battery that uses lithium as the charge carrier. In addition to general lithium-ion secondary batteries with liquid electrolytes, it can also be a so-called all-solid-state battery that uses a solid electrolyte.

[0026] The battery 110 is connected to the charging port 150 via the charging device 180 and is externally charged by the charging pile 200 connected to the charging port 150. During driving, the battery 110 supplies the stored power to the MG130 via the PCU 120. Furthermore, the battery 110 is charged by receiving power generated by the MG130 during regenerative braking.

[0027] The system main relay SMR is located between the power lines PL1 and NL1 of the battery 110 and the PCU120. When the vehicle system is started by a starter switch (not shown), the system main relay SMR is turned on by the ECU160.

[0028] PCU120 is a drive unit that drives MG130, and is configured as a power conversion device such as a converter or inverter. PCU120 is controlled by ECU160 and converts the DC power received from battery 110 into AC power for driving MG130. In addition, PCU120 converts the AC power generated by MG130 into DC power and outputs it to battery 110.

[0029] The MG130 is typically an AC rotating motor, such as a three-phase AC synchronous motor with a permanent magnet embedded in the rotor. The MG130 is driven by the PCU120 to generate rotational driving force, which is transmitted to the drive wheel 140 via the power transmission gear 135. On the other hand, during vehicle braking, the MG130 functions as a generator, performing regenerative power generation. The electricity generated by the MG130 is supplied to the battery 110 via the PCU120.

[0030] A charging relay RY is installed in the circuit between the charging device 180 and the battery 110. Specifically, the charging relay RY includes relays K5 and K6. Relay K5 is installed between the power line DCL1 connected to the charging port 150 via the charging device 180 and the power line PL2 connected to the positive terminal of the battery 110. Relay K6 is installed between the power line DCL2 connected to the charging port 150 via the charging device 180 and the power line NL2 connected to the negative terminal of the battery 110. The charging relay RY is turned ON / OFF by the ECU 160.

[0031] Charging port 150 receives charging power supplied from charging pile 200 during external charging. Connector 280 of charging pile 200 is connected to charging port 150. During external charging, DC power output from charging pile 200 is supplied to battery 110 via charging device 180 through power lines DCL1, DCL2, charging relay RY, power lines PL2, NL2, and power lines PL1, NL1. Charging device 180 converts the DC power output from charging pile 200 into the desired charging current to charge battery 110. Charging device 180 can quickly charge battery 110 as external charging according to instructions from ECU 160, as detailed later. ECU 160 is an example of a charging control device, functionally implementing the calculation unit and charging control unit described later.

[0032] The ECU 160 comprises a CPU (Central Processing Unit) 162, a memory (RAM (Random Access Memory) and a read-only ROM) 164, and input / output ports (not shown) for inputting and outputting various signals. The CPU 162 expands the program stored in the ROM onto the RAM and executes it. The program stored in the ROM records the processing of the ECU 160. When the ECU 160 is connected to the connector 280 at the charging port 150, it exchanges various messages with the charging pile 200 via the signal line SL and performs external charging. Furthermore, the ECU 160 is electrically connected to a SOC sensor 111 for detecting the SOC (State of Charge) of the battery 110, a temperature sensor 112 for detecting the temperature of the battery 110, and a current sensor 113 for detecting the current value of the battery 110.

[0033] When the vehicle is in motion, ECU160 activates the system main relay SMR and controls PCU120, thereby controlling the drive of MG130 and the charging and discharging of battery 110. Furthermore, when charging externally, ECU160 activates charging relay RY and exchanges various messages with charging station 200 via signal line SL, thereby executing external charging. Moreover, when the SOC of battery 110 reaches its upper limit, ECU160 sends a charging stop request to charging station 200 via signal line SL and deactivates charging relay RY.

[0034] Charging station 200 is a charging device used to supply power to vehicle 100. Charging station 200, for example, is installed in public facilities and is a charging station capable of supplying DC power (e.g., hundreds of kW) to battery 110 for fast charging, exceeding the required charging power (e.g., tens of kW). It should be noted that when vehicle 100 is connected to charging station 200, they can communicate with each other.

[0035] HMI device 170 is a device that provides various information to users of vehicle 100 or handles operations by users of vehicle 100. HMI device 170 includes a display with a touch panel or speakers, etc.

[0036] [Details on fast charging]

[0037] Next, the fast charging of the battery 110 and the rate of increase in resistance of the battery 110 based on fast charging will be explained. Figure 2A This is a graph showing the rate of increase in resistance corresponding to the number of fast charges performed on battery 110. Figure 2A The diagram shows the rate of increase in resistance of battery 110 corresponding to the number of fast charges performed once to four times a day. Figure 2AIn the diagram, the horizontal axis represents the number of days elapsed, and the vertical axis represents the rate of increase in resistance [%). Figure 2A The image shows the battery 110 being rapidly charged from 0% to 100% SOC.

[0038] like Figure 2A As shown, the more times a fast charge is performed in a day, the higher the rate of increase in resistance becomes over the days. This indicates a decline in the performance of battery 110. Therefore, fewer fast charges per day are preferable, and limiting the number of fast charges can be considered. However, the performance degradation of battery 110 is affected not only by the number of fast charges but also by the current flowing into battery 110 during charging (hereinafter referred to as the charging current value In), the state of charge (SOC) during charging, and the temperature. Generally, the higher the charging current value In, the higher the SOC, and the lower the temperature, the greater the impact on the performance degradation of battery 110.

[0039] Figure 2B This is a graph showing the shift of the charging current value In during fast charging. The horizontal axis represents time, and the vertical axis represents the current value [A]. Figure 2B The diagram illustrates a rapid charging process where the State of Charge (SOC) of battery 110 increases from 0% to 100%, completing the process in approximately 45 to 60 minutes. The charging current In is controlled by ECU 160 based on the SOC. Specifically, initially, when the SOC is low at the start of rapid charging, the charging current In is maintained at a high value. As the SOC rises above a predetermined value, the charging current In gradually decreases, eventually being controlled to zero to complete the rapid charging. Thus, the charging current In is not always constant, minimizing the impact on the performance of battery 110 when the charging current In is low.

[0040] Therefore, in this embodiment, the ECU160 considers the charging current value In, the SOC (supposed later), and the temperature to calculate the damage accumulation amount QCd (Quick Chargedamage), which is an indicator of the impact of fast charging on the performance of the battery 110. Based on the magnitude of the damage accumulation amount QCd, the ECU160 determines either the allowance or restriction of fast charging to the battery 110.

[0041] The amount of damage accumulated, QCd, is calculated as follows.

[0042] QCd n =QCd n-1 +Δd…(1)

[0043] QCd n This represents the current value, QCd. n-1 This indicates the previous value.

[0044] Δd is defined as follows.

[0045] Δd=(In-α) / (β-α)…(2)

[0046] Δd=-E…(3)

[0047] Figure 3A This is a coordinate graph showing Δd corresponding to the charging current value In. The infinite rated current value α represents the maximum current value that flows during charging with minimal impact on the performance of the battery 110. The infinite rated current value α is an example of a specified value. The permissible current value β represents the maximum current value that can flow into the battery 110 during charging. When the charging current value In is greater than the infinite rated current value α but less than the permissible current value β, Δd is calculated according to formula (2). When the charging current value In is less than the infinite rated current value α, Δd is calculated according to formula (3). For example, when the charging current value In is less than the permissible current value β, Δd is calculated as "D" (D>0), and when the charging current value In is less than the infinite rated current value α, Δd is calculated as "-E".

[0048] That is, the longer the period during which the charging current value In is greater than the infinite rated current value α and falls below the allowable current value β, the greater the damage accumulation QCd is increased by adding Δd. Conversely, the longer the period during which the charging current value In falls below the infinite rated current value α, the greater the damage accumulation QCd is decreased by subtracting Δd. Here, during the non-charging period when no charging is performed, the charging current value In is set to 0, and the damage accumulation QCd is calculated based on the above formula (2). That is, in this case, the damage accumulation QCd also decreases by subtracting Δd. It should be noted that "D" is, for example, 1, and "-E" is, for example, -0.2, but is not limited to these.

[0049] Here, the unlimited rated current value α and the permissible current value β are taken as different values ​​according to the SOC and temperature of the battery 110 during charging. Figure 3B It specifies the mapping between the unlimited rated current value α and the permissible current value β corresponding to the SOC and temperature of the battery 110 during charging. Figure 3B In this diagram, two infinite rated current values ​​α are shown as infinite rated current values ​​α1 and α2, and two permissible current values ​​β are shown as permissible current values ​​β1 and β2, respectively. Figure 3BIn the diagram, solid lines represent the allowable current value β1, dashed lines represent the allowable current value β2, a single-dotted line represents the infinite rated current value α1, and a double-dotted line represents the infinite rated current value α2. The infinite rated current value α1 and allowable current value β1 represent the battery 110 at a specified temperature. The infinite rated current value α2 and allowable current value β2 represent the battery 110 at temperatures lower than the infinite rated current values ​​α1 and β1. The infinite rated current value α1 at higher temperatures is higher than the infinite rated current value α2 at lower temperatures, and the same applies to the allowable current values ​​β1 and β2. That is, the lower the temperature of the battery 110, the more likely it is to cause a decline in the performance of the battery 110.

[0050] Furthermore, the higher the State of Charge (SOC), the lower the rated current values ​​α1 and α2, and the lower the allowable current values ​​β1 and β2. Specifically, when the SOC is below a specified value, the rated current values ​​α1 and β1 remain constant; when the SOC is above a specified value, the rated current values ​​α1 and β1 gradually decrease. The rated current values ​​α2 and β2 gradually decrease as the SOC increases from a low value. Therefore, the higher the SOC, the more likely it is to negatively impact the performance of the battery 110.

[0051] Figure 3B The mapping only shows the infinite rated current values ​​α1 and α2 and the permissible current values ​​β1 and β2 for two different temperatures, but in fact, detailed infinite rated current values ​​α and permissible current values ​​β for each temperature are also specified and are pre-stored in the memory 164 of ECU160.

[0052] [Control executed by ECU160]

[0053] Next, we will explain the control over whether ECU160 decides to allow or restrict fast charging. Figure 4A This is a flowchart illustrating an example of control that determines whether fast charging is permitted or restricted. The ECU 160 determines whether the temperature of the battery 110 is above a specified temperature T based on the detection result of the temperature sensor 112 (step S1). The specified temperature T is a temperature that is above a specified tolerance level for the minimum temperature at which fast charging of the battery 110 is permitted.

[0054] If step S1 is "Yes", ECU 160 determines whether the damage accumulation amount QCd is less than the threshold R (step S2). The threshold R is a value that is lower than the maximum value of the damage accumulation amount QCd that will not affect the performance degradation of the battery 110 caused by fast charging, but is not limited to this value. If step S2 is "Yes", ECU 160 allows fast charging (step S3) and ends this control. When fast charging is allowed, the charging current value In can be controlled to be below the allowable current value β to perform fast charging to the battery 110. By maintaining the charging current value In at a high value within the range below the allowable current value β, the charging of the battery 110 can be completed in a short time.

[0055] If either step S1 or S2 is "No", ECU 160 restricts fast charging (step S4) and ends the control. In this embodiment, when fast charging is restricted, fast charging can be performed by limiting the charging current value In to below the infinite rated current value α. By limiting the charging current value In to below the infinite rated current value α, the time required to complete charging is reduced compared to the case without such restriction, but charging can be performed without affecting the performance of the battery 110. For example, if the damage accumulation QCd increases to or exceeds the threshold R during fast charging, and fast charging is restricted, ECU 160 controls the charging device 180 to continue charging by limiting the charging current value In to below the infinite rated current value α. The processing of steps S3 and S4 is an example of the processing performed by the charging control unit.

[0056] Next, we will explain the calculation and control of the damage accumulation amount QCd performed by ECU160. Figure 4B This is a flowchart illustrating an example of the calculation and control of the accumulated damage amount QCd. The ECU 160 determines whether the battery 110 is undergoing fast charging (step S11). For example, if the current value displayed by the current sensor 113 is above a predetermined value, it can be determined that the battery 110 is undergoing fast charging. If step S11 is "yes", the ECU 160 obtains the current charging current value In (step S12) and determines whether the charging current value In is greater than the infinite rated current value α (step S13).

[0057] If step S13 is "yes", ECU160 increases the damage accumulation amount QCd using equations (1) and (2) above (step S14), and ends this control. If either step S11 or S13 is "no", the damage accumulation amount QCd decreases using equations (1) and (3) above (step S15), and ends this control. It should be noted that... Figure 4A and Figure 4BThe control is repeatedly executed at predetermined intervals, thus calculating the accumulated damage amount QCd at any time. Based on the magnitude of the accumulated damage amount QCd, the permissibility or limitation of fast charging is determined at any time. Steps S14 and S15 are an example of the processing performed by the calculation unit.

[0058] As described above, the damage accumulation amount QCd used to determine whether fast charging is permissible or not is calculated based on the magnitude of the charging current value In. Therefore, when fast charging is performed, for example, by setting the charging current value In to a relatively low value, fast charging is less likely to be restricted, and the opportunity for fast charging can be avoided from being excessively limited. Moreover, the damage accumulation amount QCd is calculated considering not only the magnitude of the charging current value In but also the SOC and temperature of the battery 110. Therefore, the damage accumulation amount QCd can be calculated with higher accuracy, and the opportunity for fast charging can be avoided from being excessively limited. Furthermore, when the charging current value In is less than the infinite rated current value α or when fast charging is not performed, the damage accumulation amount QCd decreases. Therefore, the recovery of the battery 110's performance is reflected in the damage accumulation amount QCd, thereby also avoiding the opportunity for fast charging from being excessively limited.

[0059] Next, we will explain in detail the shift in charging current value In and damage accumulation QCd. Figure 5 This is a time graph showing the progression of the accumulated damage QCd after fast charging is stopped, while maintaining the charging current value In at the allowable current value β. Figure 5 The changes in charging current value In, unlimited rated current value α, permissible current value β, and damage accumulation QCd are shown. Figure 3B As shown, the infinite rated current value α and the allowable current value β vary according to the state of charge (SOC). If charging starts from time t0, the charging current value In remains at the allowable current value β, thus the damage accumulation QCd increases rapidly. When charging is completed at time t1, the damage accumulation QCd gradually decreases, and at time t2, the damage accumulation QCd decreases to 0.

[0060] Figure 6 This is a time graph showing the progression of the accumulated damage QCd after charging begins with the charging current In set below the infinite rated current α and then fast charging is stopped. When charging begins at time t0, the charging current In remains below the predetermined value of the infinite rated current α, therefore the accumulated damage QCd is still 0. At time t1, when the infinite rated current α decreases and the charging current In becomes above the infinite rated current α, the accumulated damage QCd begins to increase. Then, the allowable current β decreases while the charging current In remains at the allowable current β. At time t2, when fast charging is complete, the accumulated damage QCd gradually decreases, and at time t3, the accumulated damage QCd decreases to 0.

[0061] like Figure 5 and Figure 6 As shown, fast charging can be completed in a short time by maintaining the charging current value In at the allowable current value β, but the damage accumulation QCd is calculated to be large, so it takes time for the damage accumulation QCd to return to 0.

[0062] [Variation Example]

[0063] In the above embodiments, as a limitation of fast charging, the case where the charging current value In is limited to less than or equal to the infinite rated current value α is described as an example. In this modified example, as a limitation of fast charging, the case where charging is stopped before the damage accumulation QCd becomes 0 is described as an example.

[0064] First, let's explain the situation where fast charging and discharging are repeatedly performed in a short period of time, with the charging current value In limited to less than or equal to the infinite rated current value α, as a limitation of fast charging. Figure 7 This is a time graph showing the progression of the damage accumulation QCd during repeated fast charging and discharging while maintaining the charging current value In at the allowable current value β. Fast charging is performed from time t0 to time t1, and battery 110 is discharged from time t1 to time t2. During discharge, the damage accumulation QCd gradually decreases, but fast charging resumes at time t2, causing the damage accumulation QCd to increase before it can sufficiently decrease. By repeating this process, at time t3, during fast charging, the damage accumulation QCd exceeds the threshold R, fast charging is restricted, and the charging current value In is maintained at the unlimited rated current value α. If, in this state, the damage accumulation QCd decreases below the threshold R, the fast charging restriction is lifted, and the charging current value In is again maintained at the allowable current value β. When the charging current value In is maintained at the allowable current value β, the damage accumulation QCd again exceeds the threshold R, and fast charging is restricted again. Thus, the fluctuation of the charging current value In during charging may affect the performance of battery 110.

[0065] Figure 8 This is a time graph showing the progression of the damage accumulation QCd when the charging current value In is maintained at an infinite rated current value α during repeated fast charging and discharging. Fast charging is performed from time t0 to time t1, and battery 110 is discharged from time t1 to time t2. When this fast charging and discharging is repeated, at time t3, the damage accumulation QCd becomes above the threshold R, and fast charging is restricted. During subsequent discharges, the damage accumulation QCd becomes below the threshold R, and the fast charging restriction is lifted, but fast charging is restricted again due to subsequent fast charging. Therefore, the damage accumulation QCd remains at a high value, which may affect the performance of battery 110.

[0066] In this variation, as a limitation of fast charging, we will take the case where charging is stopped before the damage accumulation QCd becomes 0 as an example. Figure 9 This is a time graph showing the accumulation of damage QCd when the charging current value In is maintained at the allowable current value β and repeated fast charging and discharging are performed, and then charging is stopped. Figure 10 This is a time graph showing the progression of the accumulated damage QCd after repeated fast charging and discharging while maintaining the charging current value In at an infinite rated current value α, and then stopping charging. In all cases, rapid charging and discharging are repeated from time t0. If the accumulated damage QCd reaches a threshold at time t1, charging is stopped before the accumulated damage QCd becomes 0. Specifically, before the accumulated damage QCd becomes 0, ECU 160 keeps the charging relay RY open (OFF). This avoids fluctuations in the charging current value In during charging and prevents the accumulated damage QCd from remaining at a high value, thus suppressing the degradation of the battery 110's performance.

[0067] [other]

[0068] As an example of the limitations of fast charging, the examples illustrate the situation where charging current In is limited to below the infinite rated current value α while charging is permitted, and the situation where charging is stopped before the damage accumulation QCd reaches 0, but this is not the only limitation. For example, charging can also be performed by maintaining the charging current In at a value lower than the specified value in the case where fast charging is not limited.

[0069] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to these specific embodiments. Various modifications and alterations can be made within the scope of the spirit of the present invention as set forth in the claims.

Claims

1. A charging control device, characterized in that, include: a calculation unit that calculates a damage accumulation amount QCd n the damage accumulation amount QCd n indicates an accumulation amount of damage to the storage battery due to rapid charging of the storage battery; and The charging control unit, in the damage accumulation amount QCd n If the value is below a threshold, rapid charging of the battery is permitted, at the level of the accumulated damage QCd. n When the value is above the threshold, the amount of damage accumulated is related to the amount QCd. n Compared to limiting rapid charging of the battery when the value is below the threshold, The calculation unit calculates the accumulated damage amount QCd in the following manner. n The longer the period during which the battery current value (i.e., the charging current value In) is greater than the specified value α during fast charging, the greater the amount of damage accumulated (QCd). n The greater the value of the charging current In, the longer the period during which the charging current value In is below the specified value α, and the longer the non-charging period of the battery, the greater the amount of damage accumulated, QCd. n The more it drops, The calculation unit calculates the damage accumulation amount QCd based on the following equations (1), (2), and (3). n : QCd n =QCd n-1 +Δd…(1) Δd=(In-α) / (β-α)…(2) Δd=-E…(3) Wherein, the amount of damage accumulation QCd n This represents the current value, the amount of damage accumulated, QCd. n-1 Indicates the previous value. When the charging current value In is greater than the specified value α but less than the allowable current value β, Δd is calculated according to equation (2). When the charging current value In is below the specified value α, Δd is calculated according to equation (3). The allowable current value β is a value larger than the specified value α, and is the maximum current value that can flow to the battery during fast charging. -E is a fixed value.

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