Battery Monitor Modules for High-Voltage Stack Safety
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Solution Overview
Problem
Existing battery monitoring systems face challenges in accurately measuring the voltage, impedance, and state of charge of individual cells in a high-voltage battery stack while minimizing the need for costly isolation devices and ensuring simultaneous measurement of cell voltages and stack current.
Innovation Solution
A battery monitoring system utilizing low-voltage monitor modules interconnected in a daisy-chain configuration, where each module is referenced to a subset of cells, allowing for simultaneous measurement of cell voltages and stack current using differential switched capacitor integrators, and eliminating the need for multiple isolation devices by connecting control and readout signals serially through the modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple isolation devices such as optical isolators are used to ensure safety in high-voltage battery monitoring, then system safety is improved, but device complexity and cost increase
Solution Approach 1:
The battery stack is divided into multiple segments, each monitored by a separate monitor module. Each module handles a subset of cells and operates at a reduced voltage level, eliminating the need for isolation devices across the entire high-voltage stack. The segmentation allows low-voltage circuitry to safely monitor high-voltage batteries without requiring multiple isolation barriers.
Solution Approach 2:
Monitor modules serve as intermediary devices between the high-voltage battery stack and the low-voltage control system. These modules electrically connect to the high-voltage cells but internally reference their measurements to a low-voltage potential, acting as a mediator that translates high-voltage signals into safe, low-voltage readout signals without requiring optical isolators.
2Measurement precision
If simultaneous measurement of all cell voltages is performed, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The monitoring function is segmented across multiple independent monitor modules, where each module simultaneously measures a subset of cell voltages. This distributed architecture achieves system-wide simultaneous measurement without requiring a single complex centralized circuit, as each module operates independently with simplified circuitry.
Solution Approach 2:
Each monitor module performs measurements on only a partial subset of the total cells, rather than all cells simultaneously. This partial action approach reduces the complexity of each individual module while the collection of all modules provides complete simultaneous coverage of the entire battery stack.
3Reliability
If low-voltage circuitry is used to monitor high-voltage battery stacks, then device safety and cost are improved, but measurement capability deteriorates
Solution Approach 1:
The monitor modules act as intermediary devices that electrically interface with high-voltage cells but internally reference all measurements to a low-voltage potential. This mediation allows the low-voltage circuitry to accurately measure high-voltage cell potentials by measuring the voltage difference between each cell and the referenced low-voltage potential, then calculating the absolute cell voltage.
Solution Approach 2:
The system changes the reference parameter from which voltages are measured. Instead of measuring each cell voltage against a common high-voltage reference, each monitor module measures against a low-voltage reference potential. This parameter change in the reference level allows safe low-voltage operation while maintaining measurement accuracy through mathematical reconstruction of the high-voltage potentials.
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
Enables accurate and simultaneous measurement of all cell voltages in a high-voltage battery stack with reduced isolation requirements, providing accurate impedance measurements and minimizing power loss, while maintaining module safety and efficiency.
Implementation Method 1
Each monitor module provides a readout signal that represents the sampled cell voltages. The readout signal from the first monitor module is connected to an input of the voltage-to-current converter.
Implementation Method 2
simultaneous measurement of cell voltages and stack current using differential switched capacitor integrators
Data Source
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AI summary
A battery monitoring system is provided to monitor a battery stack (12) having multiple cells connected in series. The monitoring system includes monitor modules (30,32) to monitor respective subsets of the cells of the battery stack (12), each monitor module (30,32), in response to one or more control signals, measuring cell voltages of the respective subset of cells and providing at least one readout signal that represents the sampled cell voltages, the monitor modules (30,32) being electrically connected in a stack (12) such that each monitor module (30,32) is referenced to the voltage of the respective subset of cells, and the control signals and the readout signal are connected through the monitor modules of the stack (12), and a system control unit to provide the control signals to the monitor modules (30,32) and to receive the readout signals from the monitor modules (30,32).