Battery Management System Pre-Charging for Over-Discharged Cells
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Solution Overview
Problem
Lithium-ion batteries in information handling systems can become over-discharged due to leakage current or internal shorts, leading to permanent failure if not properly pre-charged, as the cell voltage drops below normal operating levels, causing copper ions to penetrate the separator and create internal shorts.
Innovation Solution
A battery management system with a controller that detects real-time cell voltage and calculates a capacity-based pre-charge value and time, applying a pre-charge voltage to safely recover the battery before full charging, preventing permanent failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full charging current is applied directly to an over-discharged Li-ion cell, then charging speed is improved, but the cell may suffer permanent failure due to copper ion penetration and internal shorts
Solution Approach 1:
The patent implements a pre-charging process that applies a limited current (e.g., 0.05C to 0.1C) before full charging. This preliminary action raises the cell voltage from deeply discharged levels (e.g., below 2.0V) to a safe threshold (e.g., 2.5V-3.0V) where full charging can safely commence, preventing copper dissolution and internal shorts while enabling subsequent fast charging
2Reliability
If pre-charging is implemented to prevent cell failure, then cell reliability is improved, but charging time increases due to the additional pre-charge step
Solution Approach 1:
The patent dynamically adjusts pre-charge parameters based on real-time cell voltage measurements. The pre-charge current is adjusted according to the cell's actual state, and the transition to full charging occurs automatically when voltage thresholds are met. This dynamic approach minimizes pre-charge duration while ensuring safety, reducing total charging time compared to fixed pre-charge schemes
Solution Approach 2:
The system changes charging parameters (current magnitude, voltage thresholds) based on cell state. Pre-charge uses lower current (e.g., 0.05C-0.1C) that is dynamically adjusted, and automatically transitions to full charging current (e.g., 0.5C-1C) when voltage reaches safe levels. This parameter adaptation optimizes the balance between safety and charging speed
3Measurement precision
If real-time voltage monitoring and capacity-based pre-charge calculation are implemented, then pre-charge accuracy is improved, but device complexity increases
Solution Approach 1:
The battery management controller autonomously performs voltage monitoring, capacity calculation, and charging parameter adjustment without external intervention. It self-determines when to switch between pre-charge and full charging modes based on internal voltage thresholds and capacity algorithms, reducing the need for complex external control systems while maintaining high precision
Data Source
AI summary
A computer-implemented method enables capacity based pre-charging and age based permanent failure detection in a battery. The method comprises detecting, via a controller, a real time cell voltage for at least one cell in the battery. The controller determines if the real time cell voltage is less than a normal operating cell voltage. In response to the real time cell voltage being less than the normal operating cell voltage, a capacity based pre-charge value is calculated based on a full charge capacity and at least one cell parameter of the cell. A pre-charge time is calculated based on the capacity based pre-charge value. A pre-charge voltage is identified. The battery management controller is triggered to pre-charge the battery using the calculated pre-charge time and the identified pre-charge voltage.