NiMH Battery Charge Reserve Capacity Control Under SOC Variation
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Solution Overview
Problem
Existing nickel-metal hydride battery systems face performance deterioration due to inaccurate calculation of negative electrode reserve capacity, leading to premature safety valve activation and electrolyte loss, which affects the battery's overall performance.
Innovation Solution
A battery system and method that calculates the charge reserve capacity by considering the battery temperature, discharge electricity amount, and state of charge (SOC) variation range, using correlations obtained from preliminary tests to accurately determine the reserve capacity and control charging and discharging to prevent performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the negative electrode reserve capacity is calculated based only on battery temperature, then the calculation is simple, but the accuracy of calculating the charge reserve capacity is insufficient
Solution Approach 1:
The patent extends the calculation parameters from only temperature to include temperature, discharge electricity amount, and SOC variation range. This multi-parameter approach significantly improves the accuracy of charge reserve capacity calculation while maintaining computational feasibility through pre-established correlation maps.
2Reliability
If the safety valve opens to prevent abnormal internal pressure rise, then the internal pressure safety is improved, but the electrolytic solution is discharged together with gas causing performance deterioration
Solution Approach 1:
The system performs preliminary calculation and monitoring of the charge reserve capacity using multiple parameters (temperature, discharge electricity amount, SOC variation range) to predict when the negative electrode will deteriorate to the point of causing safety valve activation. By detecting the degradation trend early, the system can take preventive actions such as adjusting charging/discharging rates before the safety valve opens, thereby preventing electrolytic solution loss while maintaining pressure safety.
3Reliability
If the charging and discharging power is restricted when the negative electrode reserve capacity decreases, then the progress of deterioration is suppressed, but the battery performance is reduced
Solution Approach 1:
The patent implements dynamic control of charging and discharging power based on real-time calculation of the charge reserve capacity. Instead of fixed power restrictions, the system continuously adjusts the charging/discharging rates according to the calculated reserve capacity and its degradation trend. This dynamic approach suppresses deterioration when necessary while maximizing battery performance when the electrode is in good condition.
Data Source
AI summary
A battery system includes a nickel-metal hydride battery and an ECU that controls charging and discharging of the nickel-metal hydride battery. The ECU calculates a discharge electricity amount showing an integrated value of a current discharged from the nickel-metal hydride battery, and further calculates ΔSOC of the nickel-metal hydride battery in a prescribed time period. The ECU calculates a charge reserve capacity of the nickel-metal hydride battery based on a temperature of the nickel-metal hydride battery, the discharge electricity amount, and the ΔSOC.