Battery Charging Current Derating for Uneven Cell Voltages
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Solution Overview
Problem
Uneven voltage division among electrochemical cells in a battery charged in series leads to overcharging, causing swelling and performance degradation.
Innovation Solution
A battery charging method that derates the charging current when the highest voltage approaches the upper limit of a single cell's voltage, ensuring all cells remain below their charging limit, using a derating current determined from a preset sequence or table lookup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constant current charging is used to improve charging efficiency, then charging speed increases, but some electrochemical cells may be overcharged due to uneven voltage division
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the voltage of each electrochemical cell during charging. When the voltage difference between cells exceeds a preset threshold, the system automatically adjusts the charging current to prevent overcharging, thereby maintaining both charging efficiency and battery safety.
Solution Approach 2:
The charging current is dynamically adjusted based on the real-time voltage state of electrochemical cells. The system transitions from a static constant current charging mode to a dynamic charging mode where the current varies to accommodate uneven voltage division, preventing overcharging while maintaining efficient charging.
2Loss of time
If higher charging current is applied to reduce charging time, then charging speed increases, but voltage division becomes more uneven among cells
Solution Approach 1:
The system performs preliminary detection of cell voltages before initiating high-current charging. When uneven voltage division is detected, the system pre-adjusts the charging current to an appropriate level, preventing excessive voltage differences from developing during charging, thus maintaining both speed and uniformity.
Solution Approach 2:
The patent changes the charging current parameter dynamically based on voltage division characteristics. By adjusting the current parameter in response to voltage differences, the system optimizes the balance between charging speed and voltage distribution uniformity throughout the charging process.
Data Source
AI summary
A method includes: obtaining a current charging current and voltages of n electrochemical cells; if a difference between a highest voltage in the voltages of the n electrochemical cells and a preset upper limit of a single electrochemical cell charging voltage is less than or equal to a preset difference, determining a derating current, where the preset difference is greater than or equal to 0, the highest voltage is less than or equal to the upper limit of the single electrochemical cell charging voltage, and the derating current is less than the current charging current; and indicating to charge the battery with the derating current.