Multiplexer-Based Battery Cell Voltage Monitoring
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Solution Overview
Problem
Existing methods for monitoring the state of charge of battery cells in series-connected battery packs are costly and inefficient, leading to potential cell damage from improper charging and incomplete charging, particularly with sensitive lithium-ion batteries.
Innovation Solution
A multiplex arrangement is introduced between the battery cells and the electronics unit, allowing cyclic tapping and transmission of voltage values to a single measurement arrangement, enabling accurate voltage determination with reduced costs and preventing overcharging or undercharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate measuring arrangement is connected to each battery cell in series, then the voltage of each cell can be monitored individually, but the device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent merges multiple measuring arrangements into a single shared measuring unit that sequentially measures the voltage of each battery cell through a multiplexer. Instead of having separate amplifiers and A/D converters for each cell, one measuring arrangement serves all cells by switching between them, thereby reducing component count and complexity while maintaining individual cell monitoring capability
Solution Approach 2:
The single measuring arrangement is designed to perform multiple functions by measuring the voltage of different battery cells at different time instances. The multiplexer enables the measuring unit to be universally applied to all cells in the series connection, making one component serve multiple purposes rather than requiring dedicated components for each cell
2Measurement precision
If multiple measuring arrangements are used for each battery cell, then individual cell voltage can be determined accurately, but the manufacturing cost increases
Solution Approach 1:
The patent combines multiple measuring arrangements into a single shared unit that sequentially measures all battery cells. By merging the amplifiers and A/D converters into one shared resource controlled by a multiplexer, the bill of materials is reduced, directly lowering manufacturing costs while preserving the ability to accurately determine individual cell voltages
Solution Approach 2:
Instead of physically duplicating expensive measuring components for each cell, the system uses a single measuring arrangement that is time-multiplexed across all cells. The sequential measurement approach creates a functional copy of the measurement capability for each cell without the physical overhead of duplicate hardware, reducing component costs
3Device complexity
If battery cells are charged without individual voltage monitoring, then the charging process is simpler, but cells may be overcharged or undercharged leading to cell damage
Solution Approach 1:
The patent implements a feedback mechanism where the single measuring arrangement continuously monitors the voltage of each battery cell through the multiplexer. The measured voltage values are fed back to the charging control system, which uses this information to regulate the charging current for each cell, preventing overcharging and ensuring complete charging while maintaining manageable system complexity
Data Source
AI summary
The pack has rechargeable battery cells e.g. lithium cells connected in a rechargeable battery housing and arranged in series. An electronic unit for controlling voltage of the cells is connected with the cells. A multiplex arrangement is provided between the cells and the unit. The multiplex arrangement measures voltage values of the cells cyclically one after another and then provides received values to the unit. An independent claim is also included for a method of controlling voltages of rechargeable battery cells that are arranged in series in a rechargeable battery pack.