Apparatus for predicting internal electrical resistance of secondary battery and method for predicting internal electrical resistance of secondary battery

Abstract

By focusing on the heat generation of the battery 1, the internal electrical resistance is estimated by simple processing. [Solution] The charge rate (and temperature) of battery 1 is made the same at the start and end of charging / discharging, and the amount of heat transferred (heat transfer amount) from battery 1 to the heat medium 6 that cools battery 1 from the start to the end of charging / discharging is determined, and the internal electrical resistance of battery 1 is determined by dividing the value based on the amount of heat transfer by a value based on the charging / discharging current of battery 1.

Description

[Technical Field]

[0001] The present invention relates to an apparatus for predicting the internal electric resistance of a secondary battery and a method for predicting the internal electric resistance of a secondary battery. [Background technology]

[0002] For example, secondary batteries for electric vehicles deteriorate due to repeated charging and discharging, inappropriate usage environments (high and low temperature environments), overcharging and over-discharging, etc. As deterioration progresses, the internal electrical resistance of the battery increases, so the results of predicting internal electrical resistance can be used as one index for evaluating battery deterioration.

[0003] A known technique for estimating the internal electrical resistance of an electric vehicle battery is to calculate the internal electrical resistance of the battery based on the current values ​​of the discharge current and charge current during a desired driving time (for example, Patent Document 1). The technique in Patent Document 1 is capable of accurately estimating the internal electrical resistance of the battery regardless of the magnitude of the variance in the current values.

[0004] Conventional technology estimates the internal electrical resistance of a battery based on the current value situation, so it is necessary to take into account the current value situation depending on the expected situation, and the reality is that the process for calculating the internal electrical resistance may become complicated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-14216 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an internal electrical resistance prediction device for a secondary battery that can estimate the internal electrical resistance through simple processing, focusing on heat generation in the secondary battery, and an internal electrical resistance prediction method for a secondary battery. [Means for solving the problem]

[0007] In order to achieve the above object, the internal electrical resistance prediction device of the present invention according to claim 1 comprises: a battery temperature detection means for detecting the temperature of the secondary battery; current deriving means for deriving a charge / discharge current of the secondary battery; a heat medium temperature detection means for detecting a temperature of a heat medium for cooling the secondary battery; a heat change amount deriving means for deriving a heat change amount of the secondary battery; a heat transfer index deriving means for deriving a heat transfer index, which is an index relating to the heat transfer between the secondary battery and the heat transfer medium (for example, an index relating to the heat transfer derived from physical properties of the secondary battery (mass, specific heat at constant pressure, voltage, temperature, entropy coefficient, etc.), physical properties of the heat transfer medium (specific heat at constant pressure, thermal conductivity relating to the heat transfer rate, density, viscosity, etc.), a flow rate of the heat transfer medium, etc.); a charging / discharging means for charging / discharging the secondary battery so that the charge rate of the secondary battery is the same at the start of charging / discharging and at the end of charging / discharging; and a control means for inputting information from the battery temperature detection means, the current derivation means, the heat medium temperature detection means, the heat change amount derivation means, the heat transfer index derivation means, and the charge / discharge means, and determining the internal electrical resistance of the secondary battery based on the temperatures of the secondary battery and the heat medium, the charge / discharge current of the secondary battery, the heat change amount, and the heat transfer index from the start of charging / discharging by the charge / discharge means to the end of charging / discharging.

[0008] In the present invention according to claim 1, the charge rate (SOC: charge rate relative to a fully charged state) of a secondary battery (battery, storage battery) is kept the same at the start and end of charge and discharge, and the internal electrical resistance of the secondary battery is determined based on the charge and discharge current of the secondary battery, the amount of heat change in the secondary battery, the temperatures of the secondary battery and the heat medium, and a heat transfer index (e.g., the amount of heat transfer) which is an index related to heat transfer. Because the charge rate of the secondary battery is kept the same at the start and end of charge and discharge, the internal electrical resistance of the secondary battery can be determined without the influence of the reaction heat of the secondary battery due to entropy change.

[0009] Therefore, by focusing on the heat generation of the secondary battery, it becomes possible to estimate the internal electrical resistance through simple processing.

[0010] The internal electrical resistance prediction device for a secondary battery of the present invention according to claim 2 is characterized in that, in the internal electrical resistance prediction device for a secondary battery according to claim 1, it is provided with a temperature adjustment means for adjusting the temperature of the secondary battery at the start of charging / discharging and during the end of charging / discharging state, and the control means has a temperature adjustment function for operating the temperature adjustment means so that the temperature of the secondary battery is the same at the start of charging / discharging by the charging / discharging means and during the end of charging / discharging state.

[0011] In the present invention according to claim 2, the temperature of the secondary battery is made the same at the start of charging / discharging and at the end of charging / discharging (at the end of charging / discharging, when cooling time has elapsed since the end of charging / discharging, etc.), and the increase or decrease in thermal energy due to temperature changes is offset to zero by making the temperatures at the start and end of charging / discharging the same, thereby eliminating the influence of the increase or decrease in thermal energy due to changes in the temperature of the secondary battery, and making it possible to estimate the internal electrical resistance based only on the charge / discharge current of the secondary battery, the temperature between the secondary battery and the heat medium, and the heat transfer index, without requiring the physical properties of the secondary battery (mass, constant pressure specific heat).

[0012] Furthermore, the internal electrical resistance prediction device for a secondary battery of the present invention according to claim 3 is characterized in that in the internal electrical resistance prediction device for a secondary battery according to claim 2, the control means has a heat transfer amount derivation function as the heat transfer index derivation means for determining the amount of heat transfer from the secondary battery to the heat medium based on the heat transfer index, and an internal electrical resistance estimation function for estimating the internal electrical resistance by dividing the amount of heat transfer determined by the heat transfer amount derivation function by the state of the charge / discharge current of the secondary battery (using only the divided value).

[0013] In the present invention according to claim 3, the value obtained by multiplying the square of the charge / discharge current and the internal electrical resistance is the value of heat generation in the secondary battery based on the internal electrical resistance. By estimating the internal electrical resistance as the amount of heat transfer divided by the state of the charge / discharge current (simply dividing the amount of heat transfer by the state of the charge / discharge current), the amount of heat transfer can be determined and the internal electrical resistance can be estimated without the influence of the reaction heat of the secondary battery due to entropy changes and the influence of the increase / decrease in thermal energy of the secondary battery due to temperature changes.

[0014] Furthermore, the internal electrical resistance prediction device for a secondary battery of the present invention according to claim 4 is characterized in that in the internal electrical resistance prediction device for a secondary battery according to claim 3, the amount of heat transfer is derived based on the temperature difference of the heat medium at the inlet and outlet of the heat medium and the flow rate of the heat medium.

[0015] In the present invention according to claim 4, the amount of heat transfer is derived based on the temperature difference between the secondary battery and the heat medium at the inlet and outlet of the heat medium, and the flow rate of the heat medium, so that the detected parameters can be used as they are to determine the amount of heat transfer.

[0016] Furthermore, the internal electrical resistance prediction device for a secondary battery of the present invention according to claim 5 is characterized in that in the internal electrical resistance prediction device for a secondary battery according to claim 3, the amount of heat transfer is derived based on a temperature difference between any point of the secondary battery and the heat medium, and a coefficient related to the rate of heat transfer from the secondary battery to the heat medium.

[0017] In the present invention according to claim 5, the amount of heat transfer is derived based on the temperature difference between the secondary battery and any location (for example, any one location) of the heat medium and a coefficient related to the rate of heat transfer to the heat medium, so that the amount of heat transfer can be derived using a small number of detection parameters.

[0018] In order to achieve the above object, the method for predicting the internal electrical resistance of a secondary battery of the present invention according to claim 6 is characterized in that the charge rate at the start and end of charging / discharging of the secondary battery is set to be the same, the amount of heat transfer from the secondary battery to a heat medium that cools the secondary battery from the start to the end of charging / discharging is determined, and the internal electrical resistance of the secondary battery is determined by dividing a value based on the amount of heat transfer by a value based on the charge / discharge current of the secondary battery.

[0019] In the present invention according to claim 6, the parameter of reaction heat due to entropy change (heat generated due to entropy change when charging and discharging the battery) can be ignored, and the internal electrical resistance of the battery can be easily estimated using extremely little information based on information about the heat medium, without the need for complex processing.

[0020] Therefore, by focusing on the heat generation of the secondary battery, it becomes possible to estimate the internal electrical resistance through simple processing. [Effects of the Invention]

[0021] The device and method for predicting the internal electrical resistance of a secondary battery according to the present invention focus on heat generation in the secondary battery and are capable of estimating the internal electrical resistance through simple processing. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic system diagram of an internal electrical resistance prediction device for a secondary battery according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram of a control means. [Figure 3] FIG. 1 is a conceptual diagram illustrating heat transfer. [Figure 4]1 is a graph showing changes in the SOC and temperature of a battery over time. [Figure 5] FIG. 10 is a conceptual diagram illustrating the progress of processing. [Figure 6] 10 is a graph showing changes over time in SOC and temperature of a battery according to another embodiment. [Figure 7] 10 is a graph showing changes over time in SOC and temperature of a battery according to another embodiment. [Figure 8] FIG. 10 is a formula diagram illustrating an example of heat quantity. [Figure 9] FIG. 10 is a formula diagram illustrating an example of heat quantity. [Figure 10] FIG. 2 is a formula for explaining internal electrical resistance. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of the device for predicting the internal electrical resistance of a secondary battery according to the present invention will be described with reference to Fig. 1. Fig. 1 shows a schematic system for explaining the configuration of the device for predicting the internal electrical resistance of a secondary battery according to one embodiment of the present invention.

[0024] As shown in the figure, there is provided a battery temperature detection means 2 for detecting the temperature (Tb) of a secondary battery (for example, a battery for an electric vehicle) 1. The battery 1 can be a battery for an electric vehicle or a secondary battery (storage battery) for various devices.

[0025] The charging and discharging (charging and discharging) of the battery 1 is controlled via the charging and discharging means 3, and the SOC, which is the charge rate relative to the fully charged state of the battery 1, is controlled. The charging and discharging means 3 is controlled by the control means 4, and the charging and discharging current (I) of the battery 1 is grasped (derived) (current deriving means). The control means 4 controls the charging and discharging means 3 so that the SOC of the battery 1 is the same at the start and end of charging and discharging.

[0026] A cooling means 5 for cooling the battery 1 is provided, and a heat medium (refrigerant: air, water, etc.) 6 for cooling the battery 1 flows through the cooling means 5. The cooling means 5 is provided with heat medium temperature detection means 7 for detecting the temperature of the heat medium 6, and the heat medium temperature detection means 7 are provided on the inlet side and outlet side of the cooling means 5.

[0027] Information on the temperature (Ta, in) of the heat medium 6 on the inlet side of the cooling means 5 and the temperature (Ta, out) of the heat medium 6 on the outlet side, detected by the heat medium temperature detection means 7, is input to the control means 4. Information on the flow rate (ma) and specific heat at constant pressure (Cpa) of the heat medium 6 is also input to the control means 4.

[0028] The control means 4 calculates the amount of heat change of the battery 1 based on the mass, constant pressure specific heat, and temperature (Tb) of the battery 1 (heat change amount deriving means). Also, based on the difference (temperature difference between the inlet and outlet sides) between the temperature (Ta, in) of the heat medium 6 on the inlet side of the cooling means 5 and the temperature (Ta, out) of the heat medium 6 on the outlet side, the flow rate (ma) of the heat medium 6, and the constant pressure specific heat (Cpa), a heat transfer index (for example, an index related to heat transfer derived from the physical properties such as the constant pressure specific heat of the heat medium 6, the flow rate of the heat medium 6, etc.) which is an index of heat transfer between the battery 1 and the heat medium 6 (heat transfer index deriving means).

[0029] As will be described later in detail, the heat transfer amount (Qa) is calculated based on the heat change amount of the battery 1 calculated by the heat change amount calculation means and the heat transfer index calculated by the heat transfer index calculation means. Also, the heat transfer amount (Qa) is calculated based on the heat transfer index calculated by the heat transfer index calculation means (without needing physical properties such as the mass of the battery 1 and the specific heat at constant pressure).

[0030] The heat transfer index, which is an index of heat transfer between the battery 1 and the heat medium 6, can also be calculated by calculating the heat transfer amount from the temperature difference between any point (for example, any one point) between the battery 1 and the heat medium 6 and an index related to the heat transfer speed to the heat medium 6. This makes it possible to derive the heat transfer amount (Qa) using fewer detection parameters.

[0031] Information from the battery temperature detection means 2, current derivation means (charge / discharge means 3), heat medium temperature detection means 7, and heat transfer index derivation means is input to the control means 4. Information on the physical properties of the battery 1 (information on mass, specific heat at constant pressure, etc.) is also input to the control means 4.

[0032] The control means 4 is configured to grasp the internal electrical resistance (r) of the battery 1 based on the temperatures of the battery 1 and the heat medium 6, the charge / discharge current (I) of the battery 1, and the heat transfer index (amount of heat transfer) from the start of charging / discharging by the charging / discharging means 3 to the end of charging / discharging.

[0033] This makes it possible to determine the internal electrical resistance (r) of battery 1 based on the charge / discharge current (I) of battery 1, the temperature between battery 1 and heat transfer medium 6, and the heat transfer index (amount of heat transfer), while keeping the SOC of battery 1 the same at the start of charge / discharge (regardless of the order of charge and discharge) and at the end of charge / discharge.

[0034] Since the SOC of Battery 1 is set to be the same at the start and end of charging / discharging, the internal electrical resistance (r) of Battery 1 can be determined without being affected by the reaction heat of Battery 1 due to entropy changes.

[0035] Furthermore, a temperature adjustment means 9 can be provided to adjust the temperature of the battery 1 to a desired state. The control means 4 controls the temperature of the battery 1 to a desired state at the start of charging / discharging and during the end of charging / discharging state (at the end of charging / discharging, when cooling time has elapsed since the end of charging / discharging, etc.). For example, the temperature of the battery 1 is adjusted to be the same at the start of charging / discharging and at the end of charging / discharging (temperature adjustment function).

[0036] The temperature adjustment means 9 makes the temperature of the battery 1 the same at the start and end of charging and discharging, and by making the temperatures the same at the start and end of charging and discharging, it is possible to cancel out the increase or decrease in thermal energy due to temperature changes and make it zero. Therefore, it is possible to eliminate the influence of the increase or decrease in thermal energy due to temperature changes of the battery 1, and to estimate the internal electrical resistance (r) based only on the charging and discharging current (I) of the battery 1, the temperature of the heat medium 6, and the heat transfer index (amount of heat transfer) without requiring the physical properties of the battery 1 (mass, specific heat at constant pressure).

[0037] In other words, by providing a temperature adjustment means 9 so that the temperature of the battery 1 is the same at the start of charging / discharging and at the end of charging / discharging, the internal electrical resistance (r) can be estimated even without information on physical properties such as the mass of the battery 1 and the specific heat at constant pressure.

[0038] It is also possible to omit the battery temperature detection means 2 by using the temperature adjustment means 9 to eliminate the influence of increases and decreases in thermal energy due to changes in the temperature of the battery 1. Alternatively, it is possible to use the battery temperature detection means 2 only to check the temperature when the temperature adjustment means 9 is adjusting the temperature of the battery 1.

[0039] The function of the control means 4 will be explained based on Fig. 2. Fig. 2 shows a block diagram for explaining the function of the control means 4.

[0040] As shown in the figure, the control means 4 has an SOC adjustment function 11 for adjusting the SOC of the battery 1 (see Figure 1), and also has a temperature adjustment function 12 for operating the temperature adjustment means 9 to control the temperature of the battery 1 to a desired state.

[0041] The amount of heat change of the battery 1 is calculated based on the mass, constant pressure specific heat, and temperature (Tb) of the battery 1, and a heat transfer index (index related to heat transfer), which is an index of heat transfer between the battery 1 and the heat transfer medium 6, is calculated based on the difference between the inlet temperature (Ta, in) and outlet temperature (Ta, out) of the heat transfer medium 6, the flow rate (ma) of the heat transfer medium 6, and the constant pressure specific heat (Cpa).The system has a heat balance derivation function 13 (heat change amount derivation means, heat transfer index derivation means) that derives the amount of heat transfer (Qa) based on the amount of heat change and the heat transfer index.

[0042] That is, the heat transfer amount (Qa) is derived based on the difference between the inlet temperature (Ta, in) and the outlet temperature (Ta, out) of the heat medium 6, and the flow rate (ma) of the heat medium 6. Alternatively, the heat transfer amount (Qa) is derived based on the difference between the inlet temperature (Ta, in) and the outlet temperature (Ta, out) of the heat medium 6, and the flow rate (ma) of the heat medium 6.

[0043] The amount of heat transfer (Qa) and the amount of heat change of the battery 1 derived by the heat balance derivation function 13 are sent to the internal electrical resistance estimation function 14. The internal electrical resistance estimation function 14 determines the internal electrical resistance (r) of the battery 1 based on the amount of heat transfer (Qa), the amount of heat change of the battery 1, and the charge / discharge current (I).

[0044] The situation of determining the internal electric resistance (r) of the battery 1 will be specifically described with reference to Fig. 3. Fig. 3 shows a schematic system for conceptually explaining the heat transfer in the internal electric resistance prediction device.

[0045] The heat generation (Qb) of the battery 1 is expressed by the following equation (1). Qb=(I 2 r) Δτ+(Qe) (1) Qe: Reaction heat due to entropy change during charging and discharging, which can be expressed, for example, by the formula shown in FIG. Δτ: Accumulation time

[0046] The amount of heat change, which is the increase or decrease (Qx) in the thermal energy of the battery 1, is expressed by the following equation (2). Qx = Qb - Qa (2) The amount of heat transfer (Qa) is based on the amount of heat transferred based on the flow rate of the heat medium and the specific heat at constant pressure, and can be expressed by the formula shown in FIG. 9, for example. From equations (1) and (2), Qx=(I 2 r) Δτ+Qe-Qa (3) This becomes:

[0047] According to equation (3), the internal electrical resistance (r) of battery 1 is expressed by the following equation (4). r=(Qx+Qa-Qe) / (I 2 Δτ) (4) That is, the internal electrical resistance (r) can be expressed by the formula shown in FIG.

[0048] The parameters indicated by the symbols in the figure are as follows: Mb: Mass of battery 1 Cpa: specific heat at constant pressure of heat medium 6 Cpb: specific heat at constant pressure of battery 1 Ta: Temperature of heat medium 6 Tb: Temperature of battery 1 ma: mass flow rate of heat medium 6 τ: time U: Voltage dU / dT: Entropy change coefficient

[0049] In this embodiment, since the SOC is the same at the start and end of charging and discharging, Qe (heat of reaction due to the change in entropy during charging and discharging) can be ignored among the parameters in equation (4) (because it becomes zero when the SOC increases or decreases by the same amount), and the internal electrical resistance (r) of battery 1 can be estimated based on the following equation (5). r=(Qx+Qa) / (I 2 Δτ) (5) That is, the internal electrical resistance (r) of the battery can be estimated by simple processing using information on the temperature, mass, specific heat at constant pressure of the battery 1, and the temperature of the heat medium 6.

[0050] Furthermore, in this embodiment, the SOC is set to the same at the start and end of charging / discharging, and the temperature of battery 1 is set to the same at the start and end of charging / discharging. Therefore, among the parameters in equation (4), Qe (heat of reaction due to the change in entropy during charging / discharging) can be ignored (because it becomes zero with an equal increase or decrease in SOC), and Qx (amount of heat change due to a change in the temperature of battery 1: increase or decrease in heat) can be ignored (the start and end temperatures are set to the same, so that the increase or decrease in thermal energy due to temperature change is set to zero), and the internal electrical resistance (r) of battery 1 can be estimated based on the following equation (6). r=Qa / (I 2 Δτ) (6) In other words, the internal electrical resistance (r) of the battery 1 can be easily estimated using extremely little information based only on the temperature and mass flow rate of the heat transfer medium 6, i.e., using extremely little information that does not require information on the mass of the battery 1, physical properties such as the specific heat at constant pressure, and temperature, without requiring complex processing.

[0051] Specifically, when estimating the internal electrical resistance (r), the battery 1 is charged and discharged in a desired state, and the temperature of the battery 1 is adjusted to a desired state. Based on the amount of heat transfer (Qa) and the current (I) in the operating conditions, the internal electrical resistance (r) of the battery 1 is estimated using equation (6).

[0052] Alternatively, the battery 1 is charged and discharged under the desired conditions, and the internal electrical resistance (r) of the battery 1 is estimated using equation (5) based on the increase or decrease in thermal energy (Qx), the amount of heat transfer (Qa), and the current (I) under the operating conditions.

[0053] 4 and 5, a specific example of the operating status of the battery 1 by the internal electrical resistance prediction device (internal electrical resistance prediction method) when estimating the internal electrical resistance (r) of the battery 1 using equation (6) will be described.

[0054] FIG. 4 is a graph showing the SOC of the battery 1 and the temperature change over time, and FIG. 5 shows a concept for explaining the charging and discharging process of the battery 1 and the progress of heat transfer.

[0055] In Fig. 4, the SOC status is shown by a solid line, and the temperature (Tb) status is shown by a dashed line. Fig. 5(a) conceptually shows the status during charging, Fig. 5(b) conceptually shows the status during discharging, and Fig. 5(c) conceptually shows the status during heat dissipation.

[0056] As shown in Figure 4, the process starts at time τ0, charging of Battery 1 in a state of SOC1 is performed, and the temperature of Battery 1 in a state of temperature Tb1 is raised (state in Figure 5(a)). At time τ1, the SOC of Battery 1 becomes SOC2, and discharging of Battery 1 in a state of SOC2 is performed (state in Figure 5(b)).

[0057] At time τ2, the SOC of battery 1 becomes SOC1; that is, the SOC is controlled so that it is the same at the start and end of charging and discharging, and the temperature of battery 1 rises from Tb1 to Tb2. At time τ2, charging and discharging is stopped and heat is dissipated from battery 1 (state in Figure 5(c)). At time τ3, the temperature of battery 1 becomes Tb1; that is, the temperature is controlled so that it is the same at the start of charging and discharging and at the end of charging and discharging (when cooling time has elapsed since the end of discharging).

[0058] The internal electrical resistance (r) of the battery 1 is estimated by equation (6) based on the amount of heat transfer (Qa) and the current (I) in the operating conditions shown in Figure 4. Therefore, the internal electrical resistance (r) of the battery 1 can be easily estimated using extremely little information based on the information about the heat medium 6, without the need for complex processing.

[0059] 6 and 7, another specific example of the operating status of the battery 1 (internal electrical resistance prediction method) by the internal electrical resistance prediction device when estimating the internal electrical resistance (r) of the battery 1 using equation (6) will be described.

[0060] 6(a), 6(b), 7(a), and 7(b) show graphs illustrating other examples of the changes over time in the SOC and temperature of battery 1. As in FIG. 4, the SOC status is shown by a solid line, and the temperature (Tb) status is shown by a dashed line.

[0061] As shown in Figure 6(a), processing begins at time τ0, charging of battery 1 in a state of SOC1 is performed, and the temperature of battery 1 in a state of Tb1 is maintained (heat is dissipated). At time τ1, the SOC of battery 1 becomes a state of SOC2, and discharging of battery 1 in a state of SOC2 is performed. The temperature of battery 1 is maintained at a state of Tb1.

[0062] At time τ2, the SOC of battery 1 becomes SOC1, i.e., the SOC is controlled to be the same at the start and end of charging / discharging, and the temperature of battery 1 is maintained at Tb1, i.e., the temperature is controlled to be the same at the start of charging / discharging and at the end of charging / discharging (when cooling time has elapsed since charging / discharging ended).

[0063] Based on the amount of heat transfer (Qa) and the current (I) in the operating conditions shown in Figure 6(a), the internal electrical resistance (r) of battery 1 is estimated using equation (6). As a result, the reaction heat due to the entropy change of battery 1 can be ignored, and the temperature of battery 1 is controlled to be constant, so that the increase or decrease in thermal energy due to the change in temperature of battery 1 can be reliably offset and its effect can be eliminated.

[0064] As shown in Figure 6(b), processing begins at time τ0, charging of Battery 1 in a state of SOC1 is performed, and Battery 1 in a state of temperature Tb1 is heated. At time τ1, charging of Battery 1 is stopped, the SOC changes to a state of SOC2, and the SOC is maintained. The temperature of Battery 1 changes to a state of Tb2, and the temperature is maintained.

[0065] At time τ2, battery 1, which is in a state of SOC2, begins discharging and dissipating heat, and at time τ3, charging, discharging, and heat dissipation of battery 1 are stopped. At time τ3, the SOC of battery 1 becomes SOC1 and the temperature becomes Tb1. In other words, the SOC is controlled to be the same at the start and end of charging and discharging, and the temperature is controlled to be the same at the start and end of charging and discharging (end of charging and discharging).

[0066] The internal electrical resistance (r) of battery 1 is estimated using equation (6) based on the amount of heat transfer (Qa) and current (I) in a situation where battery 1 is operated so that its temperature is controlled to be the same at the end of charging and discharging, as shown in Figure 6(b). As a result, the reaction heat due to the entropy change of battery 1 can be ignored, and the temperature of battery 1 is controlled to be constant, so that the increase or decrease in thermal energy due to changes in the temperature of battery 1 can be reliably offset and its effects eliminated.

[0067] As shown in Figure 7(a), the process starts at time τ0, and the battery 1, which is at a temperature of Tb1, dissipates heat and drops to Tb2. The SOC of the battery 1 is maintained. At time τ1, the battery 1, which is at SOC1, is charged, and at time τ2, the SOC of the battery 1 becomes SOC2, and the battery 1, which is at SOC2, is discharged.

[0068] At time τ3, the discharge of battery 1 is completed and the SOC becomes SOC1, i.e., the SOC is controlled so that it is the same at the start and end of charge / discharge. Then, the temperature of battery 1 is raised from Tb2 to Tb1, i.e., the temperature is controlled so that it is the same at the start of charge / discharge and at the end of charge / discharge (at the end of charge / discharge).

[0069] Based on the amount of heat transfer (Qa) and the current (I) in the operating conditions shown in Figure 7(a), the internal electrical resistance (r) of battery 1 is estimated using equation (6). As a result, the reaction heat due to the entropy change of battery 1 can be ignored, and the temperature of battery 1 is controlled to be constant, so that the increase or decrease in thermal energy due to the change in temperature of battery 1 can be reliably offset and its effect can be eliminated.

[0070] At the start of the process, the battery 1 is allowed to dissipate heat, so that the internal electrical resistance (r) of the battery 1 can be estimated while preventing the battery 1 from overheating in summer or in hot regions.

[0071] As shown in Figure 7(b), the process starts at time τ0, and Battery 1, which is at a temperature of Tb1, is heated to Tb2. The SOC of Battery 1 is maintained. At time τ1, Battery 1, which is at SOC1, is charged, and at time τ2, the SOC of Battery 1 becomes SOC2, and Battery 1, which is at SOC2, is discharged.

[0072] At time τ3, the SOC of battery 1 becomes SOC1, i.e., the SOC is controlled so that it is the same at the start and end of charging and discharging, and discharging is terminated. At time τ3, battery 1 dissipates heat, and at time τ4, the temperature drops to Tb1, i.e., the temperature of battery 1 is controlled so that it is the same at the start of charging and discharging and at the end of charging and discharging (when the heat dissipation time has elapsed since charging and discharging ended).

[0073] Based on the amount of heat transfer (Qa) and the current (I) in the operating conditions shown in Figure 7(b), the internal electrical resistance (r) of battery 1 is estimated using equation (6). As a result, the reaction heat due to the entropy change of battery 1 can be ignored, and the temperature of battery 1 is controlled to be constant, so that the increase or decrease in thermal energy due to the change in temperature of battery 1 can be reliably offset and its effect can be eliminated.

[0074] At the start of the process, the temperature of the battery 1 is raised, so that the internal electrical resistance (r) of the battery 1 can be estimated without the risk of an internal short circuit occurring when the battery 1 is charged in winter or in cold regions.

[0075] In the above-described embodiment, the charging and discharging states of the battery 1 shown in Figures 4, 6, and 7 (operations in which charging is performed followed by discharging) are merely examples, and it is possible to perform operations such as discharging a fully charged battery 1 and then charging it to a full charge.

[0076] The above-described internal electric resistance prediction device and internal electric resistance prediction method make it possible to estimate the internal electric resistance (r) by simple processing, focusing on the heat generation of the battery 1. [Industrial Applicability]

[0077] The present invention can be used in industrial fields for a system for predicting the internal electrical resistance of a secondary battery and a method for predicting the internal electrical resistance of a secondary battery. [Explanation of symbols]

[0078] 1 battery 2. Battery temperature detection means 3 Charging / discharging means 4. Control Measures 5 Cooling means 6 Heat medium 7 Heat medium temperature detection means 9 Temperature adjustment means 11 SOC adjustment function 12 Temperature adjustment function 13 Heat balance calculation function 14 Internal electrical resistance estimation function

Claims

1. a battery temperature detection means for detecting the temperature of the secondary battery; a current deriving means for deriving a charge / discharge current of the secondary battery; a heat medium temperature detection means for detecting a temperature of a heat medium for cooling the secondary battery; a heat change amount deriving means for deriving a heat change amount of the secondary battery; a heat transfer index deriving means for deriving a heat transfer index which is an index relating to heat transfer between the secondary battery and the heat medium; a charging / discharging means for charging / discharging the secondary battery so that the charge rate of the secondary battery is the same at the start of charging / discharging and at the end of charging / discharging; and a control means for receiving information from the battery temperature detection means, the current derivation means, the heat medium temperature detection means, the heat change amount derivation means, the heat transfer index derivation means, and the charge / discharge means, and for determining the internal electrical resistance of the secondary battery based on the temperatures of the secondary battery and the heat medium, the charge / discharge current of the secondary battery, the heat change amount, and the heat transfer index from the start of charge / discharge by the charge / discharge means to the end of charge / discharge. The internal electrical resistance prediction device for a secondary battery is characterized by:

2. 2. The apparatus for predicting internal electrical resistance of a secondary battery according to claim 1, temperature adjusting means for adjusting the temperature of the secondary battery during the start and end of charge / discharge states; The control means includes: A temperature adjustment function is provided for operating the temperature adjustment means so that the temperature of the secondary battery is the same when the charge / discharge means starts charging / discharging and when the charge / discharge means finishes charging / discharging. The internal electrical resistance prediction device for a secondary battery is characterized by:

3. 3. The apparatus for predicting internal electrical resistance of a secondary battery according to claim 2, The control means a heat transfer amount derivation function as the heat transfer index derivation means for determining the amount of heat transfer from the secondary battery to the heat medium based on the heat transfer index; an internal electrical resistance estimation function that estimates the internal electrical resistance by dividing the amount of heat transfer calculated by the heat transfer amount derivation function by the state of charge / discharge current of the secondary battery; The internal electrical resistance prediction device for a secondary battery is characterized by:

4. 4. The apparatus for predicting internal electrical resistance of a secondary battery according to claim 3, The amount of heat transfer is is derived based on the temperature difference of the heat medium between the inlet and outlet of the heat medium and the flow rate of the heat medium The internal electrical resistance prediction device for a secondary battery is characterized by:

5. 4. The apparatus for predicting internal electrical resistance of a secondary battery according to claim 3, The amount of heat transfer is is derived based on a coefficient relating to a temperature difference between any point of the secondary battery and the heat medium and a coefficient relating to a rate of heat transfer from the secondary battery to the heat medium. The internal electrical resistance prediction device for a secondary battery is characterized by:

6. The charging rate at the start and end of charging / discharging of the secondary battery is made the same, grasping the amount of heat transfer from the secondary battery to a heat medium that cools the secondary battery from the start of charge / discharge to the end of charge / discharge; The value based on the amount of heat transfer is divided by a value based on the charge / discharge current of the secondary battery to determine the internal electrical resistance (r) of the secondary battery. A method for predicting the internal electrical resistance of a secondary battery.

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