Dynamic Cell Over Voltage Protection for Battery Packs
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Solution Overview
Problem
Existing battery pack charging systems fail to effectively prevent overcharging and maintain balanced state of charge (SOC) among cells, leading to accelerated degradation and performance issues.
Innovation Solution
A charging control device with a controller that dynamically adjusts the cell over voltage protection (COVP) voltage based on the charging current, entering a full-charging limit mode when specific conditions are met, to intercept overcharging and balance SOC among cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed reference voltage is used for cell over voltage protection (COVP), then the protection threshold is simple to implement, but overcharged cells are generated when SOC among cells is imbalanced, accelerating degradation
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed COVP reference voltage to a dynamic reference voltage that varies with charging current. The reference voltage is adjusted in real-time based on the magnitude of charging current, allowing the protection threshold to adapt to different charging stages and cell states, thereby preventing overcharging while maintaining system reliability.
Solution Approach 2:
The patent implements parameter changes by modifying the COVP reference voltage parameter according to charging current levels. During constant current charging, a first reference voltage is used, while during constant voltage charging, a second reference voltage is applied. This parameter adjustment prevents overcharging without significantly increasing device complexity.
2Productivity
If constant current-constant voltage (CC-CV) charging method is used, then charging efficiency is improved, but SOC imbalance among cells occurs leading to overcharging
Solution Approach 1:
The patent applies feedback by continuously monitoring cell voltages during CC-CV charging and comparing them against the dynamic reference voltage. When a cell voltage approaches the reference voltage, the charging current is adjusted or terminated for that specific cell, preventing overcharging while maintaining overall charging efficiency. This feedback mechanism addresses SOC imbalance without sacrificing productivity.
3Reliability
If cell over voltage protection is activated at fixed threshold, then safety accidents are prevented, but degraded cells cannot be protected effectively
Solution Approach 1:
The patent enhances adaptability by making the COVP reference voltage dynamic rather than fixed. For degraded cells with lower capacity, the reference voltage is adjusted to account for their different charge characteristics. This allows the protection system to adapt to both healthy and degraded cells, providing effective safety protection across different cell conditions without requiring separate protection circuits.
Data Source
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AI summary
Described is a charging control device includes: a battery state detector for detecting a cell voltage of at least one cell configuring a battery and a charging current between the battery and a charging device; and a controller for performing a cell over voltage protection function on the battery based on a cell over voltage protection voltage, and varying the cell over voltage protection voltage in response to the charging current.