Battery Pack Charge End Voltage Control for Capacity and Life Trade-off
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Solution Overview
Problem
Secondary batteries in battery packs used in high capacity or long life modes are prone to over-charging degradation, leading to reduced cycle life and inaccurate state of charge detection when switching between modes.
Innovation Solution
A battery pack with a controlling and computing portion that selectively sets charge end voltages within specific ranges for high capacity and long life modes, calculates the relative state of charge based on discharging current and time, and adjusts charge end voltages to prevent over-charging, ensuring accurate state of charge monitoring across mode changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge end voltage is set at a high value (4.2 V/cell) to achieve high charge capacity, then the charge capacity is increased, but the cycle life becomes short due to over-charging degradation
Solution Approach 1:
The patent applies dynamics by making the charge end voltage adjustable rather than fixed. The controlling and computing portion dynamically changes the charge end voltage between a first value (4.2 V/cell) and a second value (4.0 V/cell) based on the detected operation mode, allowing the system to adapt between high capacity and long life requirements
Solution Approach 2:
The patent applies parameter changes by modifying the charge end voltage parameter according to the operation mode. When the long life mode is detected, the charge end voltage is changed from the first value to the second value, directly altering the charging parameter to extend cycle life while maintaining adequate charge capacity
2Reliability
If the charge end voltage is set at a low value (4.0 V/cell) to extend cycle life, then the cycle life is increased, but the charge capacity is decreased
Solution Approach 1:
The system dynamically adjusts the charge end voltage based on the operation mode. When high charge capacity is required, the charge end voltage is set to the first value (4.2 V/cell), and when extended cycle life is prioritized, it is reduced to the second value (4.0 V/cell), providing flexible adaptation to different operational requirements
Solution Approach 2:
The patent changes the charge end voltage parameter from the first value to the second value when long life mode is detected, allowing the system to optimize for cycle life when needed while maintaining the capability to operate at higher capacity when required
3Quantity of substance
If the charge end voltage is continuously set at 4.2 V in high capacity mode after battery degradation, then the battery is over-charged and degradation is progressed, but maintaining high charge capacity is required
Solution Approach 1:
The patent applies feedback by detecting the operation mode and using this information to adjust the charge end voltage. The controlling and computing portion continuously monitors the operation mode and modifies the charging parameters accordingly, creating a closed-loop system that prevents over-charging degradation while maintaining appropriate charge capacity
Solution Approach 2:
The system takes preliminary anti-action by proactively reducing the charge end voltage from the first value to the second value when long life mode is detected, preventing over-charging degradation before it occurs. This anticipatory adjustment protects the battery from harmful effects while still providing adequate charge capacity
Data Source
AI summary
A controlling and computing portion for controlling charge or discharge of a secondary battery comprises an operation mode setting portion for selectively setting a high capacity mode using a first voltage or a long life mode using a second voltage lower than the first voltage, a remaining capacity calculating portion for calculating a relative state of charge from a remaining capacity of the secondary battery and a full charge capacity, a cycle number calculating portion for calculating a cycle number from a calculation result of the remaining capacity calculating portion, and a charge end voltage setting portion for decreasing the first voltage based on the cycle number, and setting the second voltage at a voltage left by subtracting a predetermined voltage from the first voltage in a case where the first voltage becomes equal to or less than a voltage obtained by adding a predetermined value to the second voltage.