Battery SOC Estimation Using OCV-Impedance Error Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing SOC estimation algorithms, such as the ampere-hour integration method, often result in inaccurate SOC estimation, leading to vehicle breakdowns, poor user experience, and safety issues due to errors in determining the state of charge of battery systems.
Innovation Solution
A method and apparatus that utilize correlations between open-circuit voltage (OCV) and impedance with the SOC, along with the operating current, to determine a correction coefficient, which corrects the estimated SOC, improving accuracy by eliminating error accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ampere-hour integration method is used for SOC estimation, then the SOC can be determined continuously during battery operation, but the estimation accuracy deteriorates due to error accumulation
Solution Approach 1:
The patent implements feedback by using the measured terminal voltage and current to continuously update and correct the SOC estimation. The correction term in the SOC calculation formula incorporates real-time voltage measurements, creating a feedback loop that eliminates error accumulation by constantly comparing estimated SOC with actual voltage-based SOC indicators.
Solution Approach 2:
The patent changes the parameter used for SOC estimation from solely relying on ampere-hour integration to a hybrid approach that incorporates terminal voltage measurements. By introducing voltage as an additional parameter and deriving a correction term from voltage-SOC correspondence, the system transforms the estimation method to maintain accuracy over extended periods.
2Measurement precision
If correction coefficient determination is added to improve SOC accuracy, then the SOC estimation precision improves, but the device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing the correspondence between terminal voltage and SOC, and between impedance and SOC, before actual battery operation. These pre-determined relationships are stored and directly applied during operation to determine correction coefficients, avoiding the need for complex real-time calculations and reducing computational complexity.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A state of charge (SOC) determination method and apparatus for a battery system are disclosed. Based on a correspondence between impedance and SOC, a correspondence between OCV and SOC, and an operating current at a previous data collection moment, a correction coefficient at a current data collection moment can be determined(S101). After the SOC estimated at the current data collection moment is corrected based on the correction coefficient(S102-S103), the accumulation of errors in the SOC can be eliminated, and the accuracy of the determined SOC is thereby improved.