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JP-2026075463-A - Battery system

JP2026075463AJP 2026075463 AJP2026075463 AJP 2026075463AJP-2026075463-A

Abstract

[Problem] To accurately estimate the full charge capacity even at low temperatures. [Solution] The ECU performs a process that includes the steps of acquiring parameters (S100), calculating the integrated value Q1 of the charging current if step detection is not confirmed (NO in S102) (S106), acquiring the battery temperature of each cell if step detection is confirmed (YES in S102) (S104), calculating the integrated value Q2 of the charging current until charging is completed (NO in S108) (S114), and calculating the correction coefficient C when charging is completed (YES in S108) (S110), and calculating the full charge capacity (S112). [Selection Diagram] Figure 4

Inventors

  • 小椋 隆史
  • 吉田 寛史
  • 菅生 雄基

Assignees

  • トヨタ自動車株式会社

Dates

Publication Date
20260508
Application Date
20241022

Claims (5)

  1. A battery system comprising a control device for controlling the charging of a battery including a lithium iron phosphate battery, The control device is If a step is detected in the change in the OCV (Open Circuit Voltage) of the battery during charging, a correction coefficient is set using the first integrated value of the current flowing through the battery from the start of charging until the step is detected, and the temperature of the battery. A battery system that calculates the full charge capacity of the battery by adding a predetermined value to a second integrated value of the current flowing through the battery from the time the step is detected until the battery is fully charged, and then multiplying the added value by the correction coefficient.
  2. The battery system according to claim 1, wherein the control device sets the correction coefficient such that the full charge capacity is smaller than the sum of the predetermined value and the second integrated value when the battery temperature is low compared to when the battery temperature is high.
  3. The battery system according to claim 1, wherein the control device sets the correction coefficient using the first integrated value, the battery temperature, and the degree of battery degradation.
  4. The battery system according to claim 3, wherein the control device sets the correction coefficient such that the full charge capacity is smaller than the sum of the predetermined value and the second integrated value when the battery's degradation level is high compared to when it is low.
  5. The battery system according to any one of claims 1 to 4, wherein the predetermined value is a value corresponding to the first cumulative value at room temperature when the battery is not degraded.

Description

This disclosure relates to a battery system. For example, Japanese Patent Publication No. 2003-164006 (Patent Document 1) discloses a technology that calculates the degree of battery degradation from voltage and current values, corrects the capacity adjustment range according to the calculated degree of degradation, and displays the current battery capacity using segments. Japanese Patent Publication No. 2003-164006 This figure shows an example of the overall configuration of an electric vehicle equipped with the battery system according to this embodiment.This figure shows the relationship between OCV and remaining capacity in a single cell of this embodiment.This figure shows an example of how the voltage change with respect to the remaining capacitance changes at different temperatures.This flowchart shows an example of a process performed by the ECU.This shows the relationship between battery temperature, integrated value, and correction factor.This diagram illustrates the relationship between battery degradation and the position of the step. The embodiments of this disclosure will be described in detail below with reference to the drawings. Parts identical or corresponding to those shown in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated. Figure 1 shows an example of the overall configuration of an electric vehicle 1 equipped with the battery system S according to this embodiment. In this embodiment, the electric vehicle 1 is, for example, an electric car. 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 electronic control unit (ECU) 300, which is an example of a control device. The MG10 is, for example, an embedded permanent magnet synchronous motor (IPM motor) that has both motor and generator functions. The output torque of the MG10 is transmitted to the drive wheels 30 via a power transmission gear 20, which includes a reduction gear and a differential. During braking of the electric vehicle 1, the MG 10 is driven by the drive wheels 30, and the MG 10 operates as a generator. As a result, the MG 10 also functions as a braking device that performs regenerative braking, converting the kinetic energy of the electric vehicle 1 into electrical energy. The regenerative power generated by the regenerative braking force in the MG 10 is stored in the battery 100. The PCU 40 is a power conversion device that converts power bidirectionally between the MG 10 and the battery 100. The PCU 40 includes, for example, an inverter and a converter that operate based on control signals from the ECU 300. The converter, when the battery 100 is discharged, boosts the voltage supplied from the battery 100 and supplies it to the inverter. The inverter converts the DC power supplied from the converter into AC power to drive the MG10. The inverter converts the AC power generated by the MG10 into DC power during battery 100 charging and supplies it to the converter. The converter steps down the voltage supplied from the inverter to a voltage suitable for charging battery 100 and supplies it to the battery 100. The SMR50 is electrically connected to the power line connecting the battery 100 and the PCU 40. When the SMR50 is closed (ON) in response to a control signal from the ECU 300, power can be exchanged between the battery 100 and the PCU 40. Conversely, when the SMR50 is opened (OFF) in response to a control signal from the ECU 300, the electrical connection between the battery 100 and the PCU 40 is interrupted. The battery 100 stores power to drive the MG10. The battery 100 is a rechargeable DC power source (secondary battery), and is composed of multiple single cells 100a stacked and electrically connected in series, for example. Each single cell 100a may be, for example, a lithium-ion battery. In this embodiment, a lithium iron phosphate battery (LFP battery) is used as the single cell 100a, with lithium iron phosphate as the positive electrode active material. 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 the single cell 100a (the voltage VB between each terminal of the single cell 100a). The current sensor 220 detects the current IB input and output to the battery 100 (single cell 100a). The current IB may be positive (+) for charging the battery 100 and negative (-) for discharging from the battery 100. The temperature sensor 230 detects the temperature TB of each single cell 100a. The monitoring unit 200 outputs the detection results from each detection unit to the ECU 300. The electric vehicle 1 is equipped with a DC inlet 60, and the battery 100 is capable of rapid charging from an external DC power source, which is a charging device. The DC inlet 60 is co