Battery Cell Bypass Control for Safe Li-Ion Charging
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Solution Overview
Problem
Lithium ion batteries require strict charge and discharge criteria to ensure optimal performance and safety, particularly to prevent abusive conditions such as overload and short circuits, which existing technologies have not adequately addressed.
Innovation Solution
A battery management system (BMS) with a central microcontroller and individual control circuits for each cell, including temperature sensors, shunt resistors, and fuse protection, that monitors and controls charging and discharging to prevent excessive conditions, allowing continuous charging of remaining cells when one reaches maximum voltage and shutting down to prevent minimum voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If individual monitoring and control circuits are implemented for each battery cell, then safety and performance optimization are improved, but device complexity increases
Solution Approach 1:
The battery management system is divided into a central control unit and multiple independent control circuits, each assigned to monitor and control specific battery cells. This segmentation allows individual cell monitoring while distributing system complexity across modular components rather than requiring a monolithic complex system.
Solution Approach 2:
The control circuits are designed with multi-functionality to perform voltage monitoring, charging control, discharging control, and communication functions within a single integrated circuit. This reduces the overall number of separate components needed, thereby managing device complexity while maintaining comprehensive safety monitoring.
2Measurement precision
If shunt resistors are used for current monitoring during charging, then charging control precision is improved, but power loss increases
Solution Approach 1:
The system dynamically adjusts the shunt resistor values based on charging conditions and cell states. By changing resistance parameters adaptively rather than using fixed high-precision resistors, the system achieves adequate measurement precision while minimizing power loss through optimized resistance values for different operating conditions.
3Productivity
If bypassing individual cells is implemented when maximum voltage is reached, then charging efficiency is improved, but device complexity increases
Solution Approach 1:
The control circuits dynamically switch cells in and out of the charging circuit based on real-time voltage monitoring. When a cell reaches maximum voltage, its bypass switch is activated to exclude it from further charging, allowing the charging process to continue efficiently for remaining cells. This dynamic adaptation improves charging efficiency without requiring permanent complex circuitry for each cell.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures optimal performance and maximum safety during charging and discharging by preventing abusive conditions, allowing for modular adaptation to different cell configurations and providing flexible communication options.
Implementation Method 1
temperature sensors for continuous monitoring of the temperature in the device
Implementation Method 2
current monitoring by means of a shunt resistor
Implementation Method 3
establishing a shunt across the individual battery cell for allowing a continued charging of the remaining battery cells
Data Source
AI summary
A method and apparatus are disclosed for a Battery Management System (BMS) for the controlling of the charging and discharging of a plurality of battery cells (12). Each battery cell has an associated plurality of control circuits (32, 36) which monitor and control the charging of individual battery cells. These units are controlled by a central microcontroller (14) which shunts current around the battery cell if fully charged and stops discharge if a battery cell is fully discharged in order to prevent damage to the other cells.