Secondary Battery SOC Unevenness Detection via V/K Analysis
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Solution Overview
Problem
Existing methods for estimating battery capacity in secondary batteries, such as those described in Japanese Unexamined Patent Application Publication No. 2016-157565 A, fail to accurately determine SOC unevenness on the electrode surface, leading to inaccurate capacity estimation.
Innovation Solution
A diagnostic apparatus and method that acquire the electricity storage amount and V/K (change in open circuit voltage with respect to temperature) to determine SOC unevenness on the electrode surface, using reference information and inflection points in graphs of electricity storage amount and V/K to assess and reduce SOC unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If battery capacity is estimated using SOC and heat separation method, then capacity estimation is achieved, but accuracy deteriorates when SOC unevenness occurs on electrode surface
Solution Approach 1:
The patent performs preliminary detection of SOC unevenness by measuring the relationship between electricity storage amount and V/K before conducting capacity estimation. This preliminary action identifies inflection points that indicate SOC unevenness, allowing the system to prevent inaccurate estimation from occurring in the first place.
Solution Approach 2:
The patent introduces V/K (temperature coefficient of open circuit voltage) as an intermediary parameter to detect SOC unevenness. By measuring how OCV changes with temperature and analyzing the relationship with electricity storage amount, the system can indirectly detect electrode surface conditions without directly measuring SOC distribution.
2Measurement precision
If SOC unevenness detection is added to improve accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent uses the battery's own inherent properties (open circuit voltage and its temperature coefficient) to detect SOC unevenness. No external sensors or additional measurement devices are required - the system leverages existing electrical characteristics that naturally reveal information about electrode surface conditions.
Solution Approach 2:
The patent transforms the detection approach by using V/K (temperature coefficient) as a derived parameter from OCV measurements. By analyzing how this parameter changes with electricity storage amount and identifying inflection points, the system detects SOC unevenness through parameter transformation rather than direct measurement.
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 accurate detection and reduction of SOC unevenness, thereby improving the estimation of battery capacity and deterioration state with high precision.
Implementation Method 1
V/K indicating the magnitude of change in open circuit voltage (OCV) of the secondary battery with respect to temperature change of the secondary battery
Data Source
AI summary
A diagnostic apparatus for a secondary battery includes a control device. The control device acquires an electricity storage amount that is the amount of electricity stored in the secondary battery, and V/K indicating the magnitude of change in OCV of the secondary battery with respect to temperature change of the secondary battery. The control device determines whether or not an SOC unevenness occurs in an electrode surface of the secondary battery by using the acquired electricity storage amount and V/K.