Battery State Detection from Negative-Electrode Voltage Slope
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Solution Overview
Problem
Existing methods for determining the state of rechargeable batteries, particularly nickel-metal hydride batteries, cannot accurately assess the negative electrode capacity without conducting a destructive test, leading to undetected deterioration and reduced performance.
Innovation Solution
A battery state determination device and method that includes a voltage detector, current detector, and state of charge detector to calculate the absolute value of a voltage slope during discharge, comparing it with preset limits to determine both micro-short-circuits and negative electrode capacity without destructive testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacity check test (full charge and discharge) is performed to detect negative electrode capacity, then the negative electrode capacity can be measured, but the battery must be fully charged and discharged which is time-consuming and cannot be done during normal operation
Solution Approach 1:
The patent extracts the negative electrode capacity detection function from the traditional full charge-discharge test by using a simplified voltage slope measurement method during normal discharge operation. This allows the specific detection need to be separated from the time-consuming complete capacity check procedure.
Solution Approach 2:
Instead of performing a complete charge-discharge cycle to measure capacity, the patent uses a partial measurement approach by measuring the voltage slope during a portion of the discharge process (when SOC is between 10% and 40%). This partial action provides sufficient information to detect negative electrode capacity degradation without requiring full cycle testing.
2Reliability
If the battery state determination device only checks for micro-short-circuits at the positive electrode, then the positive electrode quality can be assessed, but the negative electrode capacity degradation remains undetected
Solution Approach 1:
The patent makes the voltage slope detection method universal by applying it to detect both positive electrode micro-short-circuits (when voltage slope is abnormally high) and negative electrode capacity degradation (when voltage slope is abnormally low). This single measurement approach serves multiple detection functions.
Solution Approach 2:
The patent inverts the detection logic by establishing that a too-low voltage slope (rather than just a too-high slope) indicates negative electrode capacity degradation. This complementary approach detects the opposite extreme of the same parameter to identify different failure modes.
3Measurement precision
If a destructive test is performed to directly measure negative electrode capacity, then accurate measurement can be achieved, but the battery becomes unusable
Solution Approach 1:
The patent replaces the destructive mechanical disassembly and direct measurement process with an electrical measurement method (voltage slope detection during discharge). This substitutes a non-invasive electrical measurement for the destructive physical testing process.
Solution Approach 2:
The patent creates an electrical signature (voltage slope characteristic) that copies or represents the negative electrode capacity information without physically accessing or damaging the electrode. This electrical copy allows indirect measurement of the capacity parameter through observable voltage behavior.
Data Source
AI summary
A method for determining a negative electrode capacity of a rechargeable battery is performed by a measurement device that includes a voltage detector that detects a voltage value of the rechargeable battery, a current detector that detects a current value of the rechargeable battery, and a state of charge detector that detects a state of charge of the rechargeable battery. The method includes calculating an absolute value of a voltage slope indicating a voltage change amount with respect to a discharge amount when the state of charge of the rechargeable battery is less than 40%, comparing the absolute value of the voltage slope with a preset lower limit, and determining that the negative electrode capacity of the rechargeable battery has decreased when the absolute value of the voltage slope is less than or equal to the lower limit.