Battery Constant Current Limit Determination via Voltage Feedback
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Solution Overview
Problem
Existing methods for determining constant current limit values for battery cells are inaccurate due to reliance on calculated parameters, which can be affected by inaccuracies in estimating battery voltage and model inaccuracies, potentially leading to battery damage from excessive voltage levels.
Innovation Solution
A method that measures current and voltage values to determine an actual correction voltage, which is used to adjust the constant current limit value calculation, improving accuracy by incorporating actual values into the calculation model and compensating for estimation inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant current limit values are determined using a calculation model with predefined equivalent circuit parameters, then the method provides a systematic approach for current limiting, but the accuracy deteriorates due to inaccuracies in estimating battery voltage and model parameters
Solution Approach 1:
The patent applies feedback by measuring the actual terminal voltage and using it to calculate a correction voltage that adjusts the no-load voltage parameter in the calculation model. This measured feedback loop compensates for estimation inaccuracies and model deviations, thereby improving the accuracy of constant current limit values while maintaining battery safety protection.
Solution Approach 2:
The patent dynamically adjusts the no-load voltage parameter (UB2) by adding a correction voltage (KUB2) derived from actual measurements. This parameter change approach allows the calculation model to adapt to actual battery conditions, resolving the contradiction between using a systematic calculation model and achieving accurate current limit values.
2Device complexity
If the calculation model uses predefined equivalent circuit parameters, then the system structure remains simple, but the manufacturing precision deteriorates due to model inaccuracies affecting current limit determination
Solution Approach 1:
The patent modifies the no-load voltage parameter in the calculation model by adding a correction term (KUB2) that is calculated from actual voltage measurements. This parameter adjustment maintains the simplicity of the predefined equivalent circuit structure while improving the precision of current limit value determination through dynamic parameter adaptation.
Solution Approach 2:
The patent replaces purely model-based parameter estimation with a measurement-based correction approach. By substituting calculated voltage estimates with actual measured voltage values in the correction term, the system achieves higher precision without significantly increasing structural complexity.
Data Source
AI summary
A method for determining a constant current limit value by means of which a first current which flows through a battery cell is limited, wherein the constant current limit value is determined on the basis of a first function which specifies a first profile of the first current, which first profile is dependent on a plurality of parameters. The plurality of parameters include a first voltage which is applied between two terminals of the battery cell, a second voltage which specifies a no-load voltage of the battery cell, and a time variable.