Battery SOC Correction Using Capacity-Voltage Fitting Across Temperatures
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Solution Overview
Problem
Existing methods for battery state of charge (SOC) estimation suffer from low accuracy due to temperature mismatches between actual conditions and the temperatures corresponding to the OCV-SOC tables provided by manufacturers.
Innovation Solution
A method that involves obtaining an SOC estimation value, open circuit voltage, and maximum available capacity at current temperature, using a capacity-voltage fitting formula to calculate an SOC target value, which is then used to correct the estimation value, thereby improving accuracy without requiring OCV-SOC tables at all temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If OCV-SOC tables are obtained through battery testing at different temperatures and discharge rates, then SOC correction accuracy is improved, but testing time and complexity increase significantly
Solution Approach 1:
The patent performs battery testing at a preset reference temperature to obtain reference OCV-SOC correspondence relationships in advance. These pre-obtained data are stored and later used for SOC correction at different operating temperatures through temperature compensation calculations, avoiding the need to conduct time-consuming tests at every possible temperature
Solution Approach 2:
The patent changes the temperature parameter from a fixed reference temperature to a variable operating temperature. By establishing temperature compensation models that adjust the OCV-SOC relationship based on the difference between reference temperature and actual operating temperature, the system achieves accurate SOC correction without requiring separate test data for each temperature
2Measurement precision
If OCV-SOC tables are obtained through extensive battery testing at multiple temperatures, then SOC correction accuracy is improved, but device complexity and data requirements increase
Solution Approach 1:
The patent creates a universal temperature compensation model that can handle SOC correction at any operating temperature using a single set of reference test data. The model universally applies the same compensation algorithm regardless of the specific temperature difference, simplifying the data structure and reducing the complexity of managing multiple temperature-specific OCV-SOC tables
3Ease of manufacture
If OCV-SOC tables correspond to several representative temperatures, then manufacturing complexity is reduced, but SOC correction accuracy deteriorates due to temperature mismatch
Solution Approach 1:
The patent dynamically adjusts the temperature parameter in the OCV-SOC relationship by calculating temperature compensation based on the difference between reference temperature and actual operating temperature. This allows the system to maintain high SOC correction accuracy across varying temperatures while keeping the manufacturing process simple, as only reference temperature test data is required
Data Source
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AI summary
A method for estimating an SOC of a battery and related devices. The estimation method includes steps of: obtaining an SOC estimation value of the battery at a current moment (S101); obtaining an open circuit voltage of the battery at the current moment and a maximum available capacity of the battery at a current temperature (S102); obtaining an SOC target value of the battery at the current moment according to the maximum available capacity at the current temperature, the open circuit voltage at the current moment and a capacity-voltage fitting formula; where the capacity-voltage fitting formula is a formula obtained by fitting a remaining available capacity and a corresponding open circuit voltage at a preset temperature, and the remaining available capacity is obtained by multiplying a maximum available capacity at the preset temperature and an SOC value at the preset temperature (S 103); and correct the SOC estimation value of the battery at the current moment using the SOC target value at the current moment (S104). SOC target values corresponding to open circuit voltages at different temperatures are obtained on the basis of the capacity-voltage fitting formula, thereby the accuracy of the battery's SOC correction can be improved.