Coulombic Efficiency Measurement Circuit for Battery Modules
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Solution Overview
Problem
Rechargeable lithium batteries in electric and hybrid vehicles have limited service life due to parasitic chemical processes, requiring accurate monitoring of aging states, but existing methods require additional power electronics to determine Coulombic efficiency.
Innovation Solution
A circuit arrangement with switching modules and power semiconductor elements allows for selective connection and disconnection of battery modules in a common current path, enabling accurate current regulation during charging and discharging without additional power electronics, using existing power semiconductor elements in linear mode to determine Coulombic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional power electronics are used to determine Coulombic efficiency, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The existing power semiconductor elements in the battery direct converter perform dual functions: normal power conversion and Coulombic efficiency measurement. The control device utilizes the existing current regulation capability to accurately set charging/discharging currents for measurement purposes, eliminating the need for separate measurement electronics. This self-service approach reduces device complexity while maintaining measurement precision.
Solution Approach 2:
The power semiconductor elements are designed to serve multiple functions: they operate in switching mode for normal battery power management and in linear mode for accurate current regulation during Coulombic efficiency measurement. The control device adapts its control strategy based on the operational mode, allowing the same hardware to perform both power conversion and precise measurement functions without additional components.
2Measurement precision
If power semiconductor elements are operated in linear mode for current regulation, then current setting accuracy is improved, but energy loss increases
Solution Approach 1:
The power semiconductor elements operate in linear mode only during periodic measurement cycles rather than continuously. The control device switches between switching mode (for normal operation) and linear mode (for measurement) based on operational requirements. This periodic use of linear mode minimizes energy losses while still providing accurate current regulation when Coulombic efficiency determination is needed.
Solution Approach 2:
The linear mode operation is applied partially - only during the specific measurement phases when accurate current regulation is required, rather than during entire charging/discharging cycles. The control device implements linear mode current regulation only for the duration needed to accumulate sufficient charge quantity data for Coulombic efficiency calculation, thereby limiting energy losses to the minimum necessary period.
Data Source
AI summary
The disclosure describes a method for determining a coulombic efficiency of battery modules of a rechargeable battery using a circuit arrangement connected to the battery modules and that has a plurality of switching modules for selectively connecting every single one of the battery modules in a common current path or for alternatively isolating every single one of the battery modules from the common current path and from at least one power semiconductor element, which can be operated in linear mode, for regulating the current that flows through the current path. The switching modules are used to select at least one of the battery modules and to connect it in the current path while all other battery modules are isolated from the current path by the switching modules. The selected battery module is subjected to at least one discharge process and at least one charging process via the current path.