Control device for secondary batteries

Abstract

This prevents excessive charging current and also prevents prolonged charging times. [Solution] Based on the SOC range (3b~5b) obtained by adding a calculation error to the SOC of a single cell (e.g., "3b") and the battery temperature range (-2a~a) obtained by adding a detection error to the temperature TB (e.g., "a"), the allowable charging current Ilim is calculated from the first map so that the allowable charging current Ilim is the smallest value (the intersection of "5b" and "-2a", which is "As", becomes the allowable charging current Ilim). When the derived SOC (SOCR) and derived battery temperature (TBR) calculated from the specification map based on the internal resistance R of the single cell are included in the SOC range (3b~5b) and the battery temperature range (-2a~a), the allowable charging current Ilim is calculated and changed from the first map based on SOCR and TBR ("As" is changed to "Ah", which is the intersection of "4b" and "0").

Description

Technical Field

[0001] The present disclosure relates to a control device for a secondary battery.

Background Art

[0002] Japanese Patent No. 5223920 (Patent Document 1) describes calculating an allowable input current value for a battery (secondary battery) from the current, temperature, state of charge (SOC: State Of Charge), etc. of the battery. In this Patent Document 1, the input power limit value of the battery is calculated based on an input current limit target value obtained by reducing the allowable input current value by a predetermined amount, and the charging power is limited by the input power limit value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] The detected battery temperature includes an error. The calculated SOC also includes an error. In order to prevent the charging current of the secondary battery from becoming excessive, it is preferable to determine the allowable charging current in consideration of these errors. For example, when calculating the allowable charging current based on the battery temperature and the SOC from a map using the battery temperature and the SOC as parameters, it is desirable to calculate the allowable charging current from the map such that the allowable charging current becomes a small value within the range of assumed errors. Thereby, even if the battery temperature and the SOC include errors, it is possible to suitably prevent the charging current from becoming excessive. However, if the allowable charging current becomes too small, the charging time will be prolonged.

[0005] An object of the present disclosure is to suppress the charging current from becoming excessive and also suppress the charging time from being prolonged.

Means for Solving the Problem

[0006] One aspect of the present disclosure is a control device for a secondary battery, the control device including: an SOC calculation unit for calculating the state of charge (SOC) of the secondary battery; a temperature detection unit for detecting the battery temperature, which is the temperature of the secondary battery; a resistance calculation unit for calculating the internal resistance of the secondary battery; a first map for calculating the allowable charging current of the secondary battery using SOC and battery temperature as parameters; a specification map using SOC, battery temperature, and internal resistance as parameters; and an allowable current calculation unit for calculating the allowable charging current from the first map. The allowable current calculation unit calculates the allowable charging current from the first map such that the allowable charging current is the smallest value, based on an SOC range obtained by adding a calculation error to the SOC and a battery temperature range obtained by adding a detection error to the battery temperature. The allowable current calculation unit calculates the derived SOC and derived battery temperature from the specification map based on the internal resistance. Then, when the derived SOC is included in the SOC range and the derived battery temperature is included in the battery temperature range, the allowable current calculation unit calculates the allowable charging current from the first map based on the derived SOC and derived battery temperature and changes the allowable charging current.

[0007] In this configuration, the allowable current calculation unit of the control device calculates the allowable charging current from the first map based on the SOC range, which is the calculated SOC plus a calculation error, and the battery temperature range, which is the calculated battery temperature plus a detection error. In this case, the allowable charging current is calculated to be a small value within the range of the calculation error and the detection error, so that even if there are errors in the battery temperature and SOC, it is possible to suppress the charging current from becoming excessive. The allowable current calculation unit calculates the derived SOC and derived battery temperature from the specification map based on the internal resistance of the secondary battery. Then, when the derived SOC is included in the SOC range and the derived battery temperature is included in the battery temperature range, the allowable current calculation unit calculates the allowable charging current from the first map based on the derived SOC and derived battery temperature and changes the allowable charging current. When the derived SOC calculated based on internal resistance is within the calculation error range, and the derived battery temperature calculated based on internal resistance is within the detection error range, and the reliability of the derived SOC and derived battery temperature can be ensured, the allowable charging current is changed to the allowable charging current calculated from the first map based on the derived SOC and derived battery temperature. This prevents the allowable charging current from becoming too small. [Effects of the Invention]

[0008] According to this disclosure, it is possible to suppress excessive charging current and to suppress prolonged charging time. [Brief explanation of the drawing]

[0009] [Figure 1] This is an overall configuration diagram of the electric vehicle according to this embodiment. [Figure 2] This flowchart shows an example of the process for calculating the allowable charging current performed by the ECU. [Figure 3] Figures (A) to (C) illustrate the relationship between SOC, temperature TB, allowable charging current Ilim, and internal resistance R. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0011] Figure 1 is an overall configuration diagram of the electric vehicle 1 according to this embodiment. In this embodiment, the electric vehicle 1 is, for example, an electric vehicle. The electric vehicle 1 comprises a motor generator (MG) 10 which is a rotating electric machine, a power transmission gear 20, drive wheels 30, a power control unit (PCU) 40, a system main relay (SMR) 50, a battery 100, a monitoring unit 200, and an ECU (Electronic Control Unit) 300 which is an example of a control device. The electric vehicle 1 may also be a plug-in hybrid vehicle equipped with an internal combustion engine.

[0012] MG10 is, for example, an embedded permanent magnet synchronous motor, and has both motor and generator functions. The output torque of MG10 is transmitted to the drive wheels 30 via a power transmission gear 20, which includes a reduction gear and a differential. When the electric vehicle 1 is braked, the MG10 is driven by the drive wheels 30, and MG10 operates as a generator. The regenerative power generated by the regenerative braking force in MG10 is stored in the battery 100.

[0013] The PCU40 is a power converter that converts power bidirectionally between the MG10 and the battery 100. The PCU40 includes, for example, an inverter and a converter that operate based on control signals from the ECU300.

[0014] The SMR50 is electrically connected to the power line connecting the battery 100 and the PCU40. When the SMR50 is closed (ON) in response to a control signal from the ECU300, power is exchanged between the battery 100 and the PCU40. When the SMR50 is open (OFF), the electrical connection between the battery 100 and the PCU40 is interrupted.

[0015] Battery 100 stores power to drive MG10. Battery 100 is a rechargeable DC power source (secondary battery), and is a battery pack in which multiple single cells 100a are electrically connected, for example. Battery 100 and single cells 100a correspond to the “secondary battery” in this disclosure. Single cells 100a may be lithium-ion batteries.

[0016] The monitoring unit 200 includes a voltage sensor 210, a current sensor 220, and a temperature sensor 230. The voltage sensor 210 detects the voltage VB of a single cell 100a (the voltage VB between each terminal of the single cell 100a). The current sensor 220 detects the current (input / output current) IB that is input to and output to the battery 100 (single cell 100a). The temperature sensor 230 detects the temperature (battery temperature) TB of the single cell 100a. In this embodiment, one temperature sensor 230 is provided for multiple (for example, three) single cells 100a. Each detection unit outputs its detection result to the ECU 300.

[0017] The electric vehicle 1 is equipped with an inlet 60, and the battery 100 can be externally charged using an electric vehicle supply equipment (EVSE) 400. The inlet 60 is configured to accept a connector 420 located at the end of the charging cable 410 of the EVSE 400. The inlet 60 is electrically connected to the power line connected to the battery 100, and external charging of the battery 100 is performed when the charging relay 70 is closed. The state in which the connector 420 is connected to the inlet 60 is also called the "plug-in state," and it is a state in which the battery 100 can be externally charged.

[0018] The ECU 300 includes a CPU (Central Processing Unit) 301 and a memory (including, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory)) 302. The ECU 300 controls each device so that the electric vehicle 1 is in a desired state based on signals received from the monitoring unit 200, signals from various sensors (not shown) (for example, an accelerator opening signal, a vehicle speed signal, etc.), and information such as maps and programs stored in the memory 302. The ECU 300 controls the PCU 40, the EVSE 400, and the like, and controls the input / output current (charge / discharge current) of the battery 100. The ECU 300 may be configured from a plurality of ECUs, for example, a battery ECU, a travel control ECU, and the like.

[0019] The ECU 300 calculates the SOC of the unit cell 100a. The SOC may be calculated from SOC-OCV (Open Circuit Voltage) characteristics, and a Coulomb counting method may be used in combination. The ECU 300 calculates the internal resistance R of the unit cell 100a. The internal resistance R may be calculated from an I-V characteristic (the slope of time-series data of current IB and voltage VB).

[0020] In the unit cell 100a formed of a lithium ion battery, if the charging current is excessive, lithium metal may precipitate on the negative electrode, which may accelerate deterioration. The lower the temperature TB and the larger (higher) the SOC, the more easily lithium metal precipitates. In order to suppress the precipitation of lithium metal, the ECU 300 calculates an allowable charging current based on the temperature TB and the SOC, and limits the charging current during external charging so as not to exceed the allowable charging current. The temperature TB detected by the temperature sensor 230 includes an error. Further, in the present embodiment, since the temperature TB of the plurality of unit cells 100a is detected by the single temperature sensor 230, the temperature TB also includes an error depending on the detection position. Further, the SOC also includes a calculation error. In the present embodiment, the allowable charging current is calculated in consideration of these errors, so as to suppress the charging current from becoming excessive.

[0021] Figure 2 is a flowchart showing an example of the allowable charging current calculation process performed by the ECU 300. This flowchart is repeated at predetermined intervals when the electric vehicle 1 is plugged in. In step 10 (hereinafter, steps are abbreviated as "S"), the temperature TB, SOC, and internal resistance R are obtained. The temperature TB is the value detected by the temperature sensor 230, while the SOC and internal resistance R are calculated by a separate routine in the ECU 300.

[0022] In S11, the allowable charging current Ilim is calculated from the first map. The first map is a calculation map for the allowable charging current Ilim, with SOC and temperature TB as parameters. Figure 3 is a diagram illustrating the relationship between SOC, temperature TB, allowable charging current Ilim, and internal resistance R. Figure 3(A) is the first map (Map1), which shows the relationship between SOC, temperature TB, and allowable charging current Ilim. In Figure 3(A), the horizontal axis is temperature TB and the vertical axis is SOC. In the first map, "*" represents the value of the allowable charging current Ilim, and the lower the temperature TB and the higher the SOC, the smaller the allowable charging current Ilim. The first map is set in advance through experiments, etc., and stored in memory 302.

[0023] In S11, the allowable charging current Ilim is calculated from the first map using "TB-α", which is the temperature TB acquired in S10 plus the detection error α, and "SOC+β", which is the SOC acquired in S10 plus the SOC calculation error β, as parameters. In order to make the allowable charging current Ilim a small value when the detection error α and the calculation error β are taken into account, the allowable charging current Ilim is calculated from the first map using "TB-α" obtained by subtracting the detection error from the temperature TB and "SOC+β" obtained by adding the calculation error β to the SOC as parameters. Note that "TB-α" is an example of the "battery temperature range obtained by adding a detection error to the battery temperature" of the present disclosure, and "SOC+β" is an example of the "SOC range obtained by adding a calculation error to the SOC" of the present disclosure. For example, when the temperature TB acquired in S10 is "a" and the SOC is "3b", as shown in FIG. 3(A), "TB-α" obtained by adding the detection error α to the temperature TB is "-2a", and "SOC+β" obtained by adding the measurement error β to the SOC is "5b". Therefore, from the first map, the allowable charging current Ilim is calculated as "As" which is the intersection of "-2a" and "5b".

[0024] In FIG. 3(B), the vertical axis represents the allowable charging current Ilim, and the horizontal axis represents the SOC. The smaller the SOC and the lower the temperature TB, the smaller the allowable charging current Ilim becomes. Therefore, as shown in FIGS. 3(A) and (B), when the detected temperature TB is "a" and the calculated SOC is "3B", the allowable charging current Ilim is "Ar" if the detection error α and the calculation error β are not considered, but in S11, the detection error α and the calculation error β are taken into account, so that the allowable charging current Ilim becomes "As". Since "As" is a smaller value than "Ar", the allowable charging current Ilim becomes a smaller value, which can suppress the charging current from becoming excessively large, and can suppress the precipitation of lithium metal. However, if "As" becomes too small, there is a concern that the charging time will become longer.

[0025] In S12, it is determined whether the internal resistance R obtained in S10 is within the range of the detection error α and calculation error β in the specification map (MapS). First, based on the internal resistance R, the derived SOC (hereinafter also referred to as "SOCR") and derived battery temperature (hereinafter also referred to as "TBR") are calculated from the specification map. Figure 3(C) is the specification map, with SOC on the horizontal axis and temperature TB on the vertical axis. In the specification map, "*" represents the value of the internal resistance R, and the lower the temperature TB, the smaller the value of the internal resistance R. The specification map is set in advance by experimentation, etc., and stored in memory 302. In S12, first, SOCR and TBR are calculated from the internal resistance R using the specification map. For example, if the internal resistance R obtained in S10 is "Rs", SOCR is calculated as "4b" and TBR is calculated as "0". When the internal resistance R obtained in S10 is "Rh", the SOCR is calculated as "2b" and the TBR is calculated as "a". Then, it is determined whether the calculated SOCR is included in the "SOC range (SOC-β)" used in S11, and whether the calculated TBR is included in the "battery temperature range (TB-α)" used in S11. For example, if the internal resistance R is "Rs", the SOCR is "4b" and is included in "3b~5b", and the TBR is "0" and is included in "-2a~a" (in other words, "Rs" is included in the shaded area shown in the specifications map), so it is determined to be positive in S12. Also, when the internal resistance R is "Rh", the SOCR is "2b" and is not included in "3b~5b" ("Rh" is not included in the shaded area shown in the specifications map), so it is determined to be negative in S12. If it is determined to be positive in S12, the process proceeds to S13, and if it is determined to be negative, the routine ends.

[0026] In S13, the SOCR and TBR calculated from the specification map based on the internal resistance R in S12 are set as the SOCR and TBR for calculating the allowable charging current Ilim.

[0027] In S14, the allowable charging current Ilim calculated in S11 is modified by calculating the allowable charging current Ilim from the first map based on SOCR and TBR. For example, if the internal resistance R is "Rs", then SOCR is "4b" and TBR is "0", so the allowable charging current Ilim is calculated as "Ah" from the first map. Since "Ah" is a larger value than "As", it is possible to prevent the allowable charging current Ilim from becoming too small and thus increasing the charging time.

[0028] According to this embodiment, the allowable current calculation unit of the ECU300 (flowchart in Figure 2) calculates the allowable charging current Ilim from the first map based on the SOC range obtained by adding a calculation error β to the calculated SOC, and the battery temperature range obtained by adding a detection error α to the calculated temperature TB (S11). In the first map, the allowable charging current Ilim is calculated to be a small value within the range of the calculation error β and the detection error α, so that even if there are errors in the temperature TB and SOC, it is possible to suppress the charging current from becoming excessive. Based on the internal resistance R of the single cell 100a, SOCR and TBR are calculated from the specifications map, and when SOCR is included in the SOC range and TBR is included in the battery temperature range, the allowable charging current Ilin is calculated from the first map based on SOCR and TBR and the allowable charging current Ilim is changed (S12~S14). Since SOCR is within the range of the calculation error β and TBR is within the range of the detection error α, the reliability of SOCR and TBR is ensured. Furthermore, since the allowable charging current Ilim is changed to the allowable charging current Ilim calculated based on SOCR and TBR, it is possible to prevent the allowable charging current Ilim from becoming too small and to prevent the charging time from becoming too long.

[0029] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0030] 1 electric vehicle, 10 motor generator (MG), 20 drive transmission gear, 30 drive wheels, 40 PCU, 50 SMR, 60 inlet, 100 battery, 100a single cell, 200 monitoring unit, 210 voltage sensor, 220 current sensor, 230 temperature sensor, 300 ECU, 400 EVSE, 420 connector.

Claims

[Claim 1] A control device for a secondary battery, The control device is The SOC calculation unit calculates the SOC of the secondary battery, A temperature detection unit for detecting the battery temperature, which is the temperature of the secondary battery, A resistance calculation unit for calculating the internal resistance of the secondary battery, A first map for calculating the allowable charging current of the secondary battery using the SOC and the battery temperature as parameters, A specification map with the SOC, battery temperature, and internal resistance as parameters, Includes an allowable current calculation unit that calculates the allowable charging current from the first map, The allowable current calculation unit is: Based on the SOC range obtained by adding a calculation error to the SOC and the battery temperature range obtained by adding a detection error to the battery temperature, the allowable charging current is calculated from the first map such that the allowable charging current is the smallest value. Based on the aforementioned internal resistance, the derived SOC and derived battery temperature are calculated from the specification map. A control device for a secondary battery, which, when the derived SOC is included in the SOC range and the derived battery temperature is included in the battery temperature range, calculates the allowable charging current from the first map based on the derived SOC and the derived battery temperature and changes the allowable charging current.

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