Battery Control Device Using Dynamic Temperature Mode Switching
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Solution Overview
Problem
In batteries with temperature distribution, the input temperature is not uniquely determined, leading to errors in internal resistance estimation, which increases SOC estimation errors and can cause battery control to deviate from its operational range.
Innovation Solution
A battery control device with a first SOC calculation unit based on battery voltage and temperature, and a second SOC calculation unit based on current, which switches between modes for high and low temperature calculations to improve estimation accuracy by using multiple temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a representative temperature is set to one point to estimate internal resistance, then the device complexity is reduced, but the measurement precision of internal resistance deteriorates
Solution Approach 1:
The battery pack is divided into multiple temperature zones with sensors placed at different positions (header, middle, footer). Each zone's temperature is measured independently, allowing the system to capture temperature distribution rather than using a single representative temperature, thus improving internal resistance estimation accuracy without excessive complexity increase
Solution Approach 2:
The system dynamically selects which temperature measurement to use based on real-time temperature distribution. When temperature difference exceeds a threshold, the system switches to using the maximum temperature for SOC calculation, otherwise uses average temperature. This dynamic adaptation improves measurement precision while keeping the control logic manageable
2Speed
If the SOC calculation uses a single temperature value, then the calculation speed is improved, but the reliability of SOC estimation deteriorates
Solution Approach 1:
The SOC calculation unit dynamically switches between different temperature selection modes based on the temperature distribution state. When the temperature difference between maximum and minimum exceeds a predetermined threshold, the system uses the maximum temperature for calculation; otherwise, it uses the average temperature. This dynamic approach maintains calculation speed while improving reliability
Solution Approach 2:
The system changes the temperature parameter used in SOC calculation based on the temperature distribution condition. By switching between maximum temperature and average temperature as the input parameter, the system adapts to different thermal states, improving estimation reliability without significantly impacting calculation speed
3Measurement precision
If multiple temperature measurements are used for SOC calculation, then the measurement precision of SOC improves, but the device complexity increases
Solution Approach 1:
The battery pack is divided into multiple temperature zones with sensors placed at header, middle, and footer positions. This segmentation allows capturing temperature distribution to improve SOC estimation accuracy
Solution Approach 2:
Instead of using the average temperature (conventional approach), the system inverts the logic by using the maximum temperature when temperature difference exceeds the threshold. This inversion addresses the issue of temperature distribution effects on SOC estimation, improving precision while maintaining manageable system complexity through clear decision logic
Data Source
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AI summary
Provided is a battery control device which can suppress a battery degradation caused by an influence of an SOCv estimation error. The battery control device includes an SOCv calculation unit 151 which calculates the state of charge SOCv on the basis of a temperature and a voltage value of a battery and an SOCi calculation unit 152 which calculates the state of charge SOCi on the basis of a current value of the battery, and controls the charging/discharging of the battery on the basis of the state of charge SOC based on the state of charge SOCv and the state of charge SOCi. Then, the temperature includes a plurality of temperatures which are measured at plural positions of the battery. The SOCv calculation unit 151 switches a first mode in which the SOC calculation of the battery is performed on the basis of the first temperature on the high temperature side of the battery and a second mode in which the SOC calculation of the battery is performed on the basis of the second temperature on the low temperature side of the battery on the basis of the amplitude of the second temperature.