Battery Module Decoupling for Internal Resistance Measurement
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Solution Overview
Problem
Existing methods for determining the internal resistance of battery cells in direct battery converters disrupt the output voltage, making them unsuitable for arbitrary use with inverters and electric machines, and can lead to operational issues.
Innovation Solution
A method where a first battery module is decoupled and connected to the battery string, with a matching number of second modules decoupled to maintain voltage stability, allowing for precise determination of internal resistance without altering the output voltage, using a step-like current excitation and voltage response evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a battery module is connected to determine internal resistance, then measurement precision is improved, but output voltage stability deteriorates
Solution Approach 1:
The control unit proactively compensates for the voltage change caused by connecting a battery module for measurement by simultaneously connecting another battery module in parallel. This preliminary anti-action prevents the output voltage instability before it occurs, allowing accurate internal resistance measurement while maintaining voltage stability.
2Measurement precision
If existing methods are used to determine internal resistance, then measurement capability is improved, but operational reliability deteriorates
Solution Approach 1:
The control unit continuously monitors the output voltage and automatically manages the connection and disconnection of battery modules based on measurement requirements. This feedback mechanism ensures that internal resistance measurements are performed accurately while the system maintains operational reliability by preventing voltage instability that could affect connected electric machines.
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 precise and non-disruptive determination of internal resistance, preventing output voltage changes and ensuring stable operation of electric motors connected to the battery converter.
Implementation Method 1
The battery cells of at least one battery module connected to the battery string are excited by means of a sudden current and the sudden response voltage generated by the excited battery cells is recorded and evaluated to determine the internal resistance
Data Source
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AI summary
The invention relates to a method for determining the internal resistance of battery cells of battery modules (220, 230) of a battery (100) that can be connected to an electric motor (60), said modules being arranged in at least one battery bank (110). In order to generate an adjustable output voltage (UB) for the battery (100), each battery module (220, 230) is designed to be connected in series to the battery bank (110) of the battery (100) and to be decoupled from said bank (110). According to the invention, during the operation of the electric motor (60) at least one first battery module (220) that has been decoupled from the battery bank (110) is connected to said bank (110) and the internal resistance of the battery cells of at least one first connected battery module (220) is determined. In addition, at the same time as the first battery module (220) is connected, a sufficient number of second battery modules (230) that are connected to the battery bank (110) and generate a voltage (UM) corresponding to the voltage (UM) generated by the first connected battery module (220) within predefined tolerance limits are decoupled from the battery bank (110).