Battery Pack Charging Control Using Open Circuit Voltage
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Solution Overview
Problem
Conventional battery pack charging methods using the CC/CV method may result in overcharge before reaching the C/20 current threshold, leading to reduced stability and lifespan due to the determination of charge completion time based on charging voltage rather than the battery's actual state.
Innovation Solution
A battery pack that utilizes an open circuit voltage (OCV) measurement to determine charge completion time by interrupting charging after a set time period, measuring OCV, and comparing it with set voltages to prevent overcharging, even at maximum permissible charging voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the charge completion time is determined by the conventional C/20 current threshold method, then the charging process is simple to implement, but the battery pack may be overcharged before reaching the C/20 threshold, reducing stability and lifespan
Solution Approach 1:
The patent implements feedback control by continuously monitoring the charging current and comparing it against dynamic thresholds. The system measures actual charging progress and adjusts the charging process accordingly, using feedback from current sensors and voltage measurements to determine when to terminate charging, thereby preventing overcharge while maintaining system reliability.
Solution Approach 2:
The patent changes the charging control parameter from a fixed current threshold (C/20) to a time-based control method where the charging duration is precisely calculated based on battery capacity and charging rate. This parameter change allows the system to terminate charging at the optimal moment before overcharge occurs, improving battery stability and lifespan without requiring complex real-time current threshold adjustments.
2Productivity
If the maximum permissible charging voltage is applied to charge the battery pack quickly, then the charging speed is improved, but the battery pack may already be fully charged before the charging current reaches C/20, causing overcharge
Solution Approach 1:
The patent applies preliminary action by pre-calculating the exact charging duration required to reach full charge based on the battery's capacity and the applied charging rate. Before initiating charging, the system determines the precise time when charging should terminate, allowing it to apply maximum permissible voltage for optimal speed while ensuring charging stops exactly when full, preventing any overcharge condition.
Solution Approach 2:
The patent replaces the conventional current-threshold-based termination mechanism with a time-based termination mechanism. Instead of relying on mechanical/electrical current monitoring to detect full charge, the system uses precise time measurement and calculation to control charging duration, substituting the detection mechanism with a more accurate time-based control approach that prevents overcharge while maintaining high charging speed.
3Measurement precision
If the charging current is reduced to C/20 to ensure complete charging, then the charge completion detection is simplified, but the charging time is extended and the battery may still be overcharged
Solution Approach 1:
The patent applies preliminary action by pre-calculating the exact charging duration before charging begins. Instead of extending charging time to C/20 threshold detection, the system determines in advance the precise time when full charge will be achieved based on battery capacity and charging rate, then terminates charging exactly at that moment. This eliminates both the time extension and overcharge risk associated with conventional methods.
Data Source
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AI summary
A method of charging a battery pack including at least one secondary battery includes charging the secondary battery using a constant current-constant voltage method, measuring a charging voltage applied to the secondary battery, interrupting the charging the secondary battery when the charging voltage of the secondary battery is equal to or higher than a first set voltage, measuring an open circuit voltage (OCV) of the battery pack in during or after a second time period after the charging has been interrupted, and terminating the charging of the battery pack when the measured OCV is equal to or higher than a second set voltage.