Battery Module Impedance Measurement via Serial Switching
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Solution Overview
Problem
Existing methods for determining the ohmic internal resistance of battery modules, crucial for battery management, require offline measurements that disrupt normal operation and are not suitable for continuous monitoring, especially in dynamic conditions like those in electric or hybrid vehicles.
Innovation Solution
A method involving repeated connection and disconnection of battery modules under load current, with simultaneous measurement of voltage levels before and after switching, allowing for impedance spectroscopy during operation and enabling continuous monitoring of battery health.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offline pulse charging/discharging measurements are performed to determine internal resistance, then measurement accuracy is improved, but normal battery operation is disrupted and continuous monitoring is not possible
Solution Approach 1:
The patent applies periodic switching of battery modules on and off during normal operation to generate current pulses for impedance measurement. Instead of performing separate offline pulse tests, the system periodically connects and disconnects battery modules in the string, creating repeated current variations that enable continuous impedance spectroscopy while maintaining overall system operation.
Solution Approach 2:
The patent enables continuous monitoring of battery impedance by performing measurements during normal operational phases. By utilizing the natural switching between charging/discharging phases and performing impedance measurements during these phases, the system maintains continuous surveillance of battery health without requiring separate test periods or disrupting overall battery system operation.
2Measurement precision
If current pulses lasting one or more seconds are applied for impedance measurement, then impedance values can be determined, but voltage measurements differ over time and operational disruption increases
Solution Approach 1:
The system uses periodic switching of battery modules with controlled pulse durations. By repeatedly connecting and disconnecting modules at specific intervals during operational phases, the system generates a series of current pulses that enable impedance determination while keeping individual pulse durations optimized to minimize operational disruption.
Solution Approach 2:
The patent performs impedance measurements during naturally occurring operational phases before they would otherwise be interrupted. By utilizing the transition periods between charging and discharging phases, the system captures impedance data at optimal moments without requiring additional time beyond the normal operational cycle.
3Productivity
If battery modules are repeatedly connected and disconnected during operation for impedance spectroscopy, then continuous monitoring is enabled, but switching complexity increases
Solution Approach 1:
The patent makes the battery module coupling units serve dual functions: their primary function of connecting/disconnecting modules for charging/discharging operations, and a secondary function of enabling impedance measurements through the same switching mechanism. This multi-functionality eliminates the need for separate measurement hardware and reduces overall system complexity.
Solution Approach 2:
The system uses its own operational switching actions to generate the current pulses needed for impedance measurement. The normal connect/disconnect operations of battery modules during charging/discharging cycles automatically create the current variations required for impedance spectroscopy, eliminating the need for external test equipment or additional dedicated measurement hardware.
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 quasi-continuous monitoring of battery module states, allowing for early detection of aging or defects, minimizing disruptions and extending the life of battery systems by identifying changes in impedance profiles.
Implementation Method 1
This enables impedance spectroscopy on a battery module of a battery module string during operation.
Implementation Method 2
determining an ohmic internal resistance of a battery module from measurements of voltage levels
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for determining the internal ohmic resistance of a battery module (100) comprising at least one battery cell, for example a lithium-ion battery cell of the type used in traction batteries of electric or hybrid motor vehicles, that is, in motor vehicles comprising drives that are at least partly or intermittently electrically driven. The invention also relates to a motor vehicle and a battery management system (160). The disclosed method comprises the determination of the internal ohmic resistance from measurements of voltage intensities. The invention is characterised in that the method comprises the serial connection of the battery module (100) to at least one other battery module (100) that is subject to a load current and comprises the measurement of voltage intensities in the battery module (100) before and after said connection. This allows a measurement of current and voltage intensities to take place significantly closer to real time and thus almost simultaneously, which in turn allows the determination of the actual wear condition of the battery module (100) to be improved and the durability of individual battery cells or of battery modules (100) to be predicted.