Battery State Determination Device Using Voltage Gradient Analysis
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Solution Overview
Problem
Existing methods for determining micro-short circuits in rechargeable batteries based on voltage measurements during 0% to 60% depth of discharge have low accuracy, making it difficult to distinguish between non-defective and defective products.
Innovation Solution
A battery state determination device that includes a voltage detector, current detector, and a determination unit to calculate the absolute value of the voltage gradient from 0% to 40% state of charge, comparing it with a predetermined upper limit value to determine micro-short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If voltage measurement is used to determine micro-short circuits in rechargeable batteries during 0% to 60% depth of discharge, then the determination method is simple and quick, but the determination accuracy is low and false positives/negatives occur
Solution Approach 1:
The patent changes the parameter from simple voltage measurement to voltage gradient calculation. By computing the rate of change of voltage with respect to depth of discharge (dV/dDOD), the system transforms a simple threshold comparison into a more sensitive derivative-based detection method. This parameter transformation enables accurate identification of micro-short circuits while maintaining operational simplicity, as the voltage gradient exhibits distinct characteristics for defective versus healthy batteries during controlled discharge.
2Ease of manufacture
If voltage threshold comparison is used for battery abnormality detection, then the method is easy to implement, but it cannot distinguish between normal voltage drop in final discharge stage and actual abnormalities
Solution Approach 1:
The patent segments the discharge process into specific depth of discharge ranges (0% to 60%) and applies gradient analysis only within this window. By focusing the determination on a specific segment of the discharge curve where micro-short circuit effects are most pronounced, the method avoids confusion from normal voltage behavior in other regions (such as the final discharge stage), thereby improving reliability while maintaining implementation simplicity.
3Device complexity
If only voltage value is measured without considering discharge rate, then the measurement is simple, but the state of charge detection accuracy is insufficient for accurate determination
Solution Approach 1:
The patent introduces the voltage gradient (dV/dDOD) as an intermediary parameter that bridges simple voltage measurement and complex battery state analysis. The gradient serves as a mediator that captures dynamic discharge behavior without requiring complex multi-parameter measurements. By using this intermediary derivative parameter, the system achieves precise state of charge detection and micro-short circuit identification while keeping the measurement system relatively simple.
Data Source
AI summary
This battery state determination device (10) is provided with: a voltage detection unit (13) that detects the voltage (V) of a rechargeable battery (M) to be evaluated; a current detection unit (12) that detects the current of the rechargeable battery (M); a charge state detection unit (11) that detects the state of charge (SOC) of the rechargeable battery (M); and a determination unit (11) configured so as to calculate the absolute value of the voltage gradient (G), which indicates the change in voltage with respect to the discharge amount (Ah), when the state of charge (SOC) of the rechargeable battery (M) is less than 40%, compare the absolute value of the voltage gradient (G) to a pre-set upper limit value (Gmax), and, when the absolute value of the voltage gradient (G) is greater than the upper limit value (Gmax), determine that a small short circuit has occurred in the rechargeable battery (M).