Battery Charging Termination Using Depth-of-Discharge Sensing
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Solution Overview
Problem
Lithium-ion batteries often experience under-charging or over-charging, leading to reduced device operating time, faster aging, swelling, and cell failure, especially at low temperatures or in aged batteries, due to the inability of existing charging methods to accurately determine the depth of discharge.
Innovation Solution
A method and system that detect battery voltage and current to determine the depth of discharge (DOD) and control charging termination based on a DOD threshold, using a battery gauge circuit and processor to ensure precise charging termination, thereby improving charging accuracy and preventing under- or over-charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If constant current/constant voltage (CC/CV) or fast charging technology is used, then charging speed is improved, but charging accuracy deteriorates leading to under-charging or over-charging
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring battery voltage and current during charging, calculating depth of discharge (DOD) in real-time, and using this information to dynamically adjust charging termination. The system measures battery parameters, computes DOD based on these measurements, and feeds this information back to control the charging process, ensuring accurate termination regardless of charging speed.
Solution Approach 2:
The patent replaces traditional mechanical/voltage-threshold-based charging termination methods with an electronic calculation system. Instead of relying on fixed voltage thresholds that fail at low temperatures or in aged batteries, the system uses electronic sensors to measure voltage and current, then employs a processor to calculate DOD based on these electrical parameters, providing more accurate and adaptive charging termination.
2Device complexity
If charging termination is based on fixed voltage thresholds, then device complexity is reduced, but reliability deteriorates due to under-charging or over-charging
Solution Approach 1:
The patent changes the fundamental parameter used for charging termination from fixed voltage thresholds to dynamic depth of discharge calculations. Instead of terminating at a predetermined voltage level that doesn't account for battery condition variations, the system calculates DOD based on measured voltage and current, adjusting the termination criterion to account for temperature effects, battery aging, and individual cell characteristics, thereby improving reliability.
Solution Approach 2:
The patent enables the battery management system to self-regulate charging termination by autonomously monitoring its own state through voltage and current sensing, calculating its own DOD, and making independent decisions about charging termination. This self-service approach eliminates the need for complex external control mechanisms while improving reliability through continuous self-monitoring and adaptive control.
Data Source
AI summary
A method includes detecting a voltage of the battery, detecting a current of the battery, determining a depth of discharge of the battery based on the voltage and the current of the battery, and controlling terminating charging of the battery responsive to the determined depth of discharge of the battery reaching a depth of discharge threshold. A system includes a battery gauge circuit and a processor coupled to the battery gauge circuit. The battery gauge circuit has a voltage sense input and a current sense input and is configured to determine a depth of discharge of a battery based on a battery voltage at the voltage sense input and a battery current at the current sense input. The processor is configured to control terminating charging of the battery responsive to the determined depth of discharge reaching a depth of discharge threshold.