Battery Pack SOC Calculation Using Kalman Filter Precision Gating
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Solution Overview
Problem
Existing methods for estimating the state of charge (SOC) of lithium iron phosphate batteries face challenges due to significant OCV measurement errors, especially in platform zones where OCV changes are subtle, leading to inaccurate SOC calculations.
Innovation Solution
A method and device for calculating SOC that utilize a combination of a preset integration algorithm and a filter algorithm, specifically the Kalman Filter, to determine a first and second state of charge, respectively. The method then selects the second state of charge as the target SOC if it satisfies specified precision judging criteria, ensuring more accurate SOC estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the OCV method is used for SOC correction, then SOC precision is improved in non-platform zones, but OCV measurement error may be up to 20mV under the impact of previous operating conditions
Solution Approach 1:
The patent performs preliminary voltage sampling at multiple points before final SOC calculation. By collecting voltage data at different states ahead of time and processing these data points together with the ampere-hour integration results, the system prepares corrected SOC values that are less susceptible to transient OCV measurement errors caused by previous operating conditions.
Solution Approach 2:
The patent implements a feedback mechanism where the OCV measurements are continuously compared and used to adjust the ampere-hour integration results. By using the relationship between OCV and SOC as a feedback reference and incorporating multiple voltage sampling points, the system dynamically corrects SOC estimation errors while accounting for hysteresis effects from previous charge-discharge cycles.
2Device complexity
If a single OCV measurement is used for SOC correction, then the calculation process is simple, but the corrected SOC value may be incorrect due to OCV measurement errors
Solution Approach 1:
The patent merges multiple voltage sampling points with the ampere-hour integration method in a unified calculation framework. By combining the advantages of both methods and incorporating multiple voltage measurements taken at different states, the system achieves accurate SOC correction without requiring complex additional hardware, thus maintaining calculation simplicity while improving accuracy.
Data Source
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AI summary
A method, a device, a vehicle, and a storage medium for calculating state of charge of the battery are provided. The method is applied to a battery pack including battery cells and includes the following steps. Charge information of the battery cells is acquired, which includes a first state of charge and a second state of charge of the battery cells. A determination is made as to whether the charge information satisfies specified precision judging criteria. If the charge information satisfies the specified precision judging criteria, a target state of charge of the battery cells is determined based on the second state of charge. If the charge information fails to satisfy the specified precision judging criteria, the target state of charge of the battery cells is determined based on the first state of charge. When the charge information satisfies the specified precision judging criteria, the total state of charge of the battery pack is calculated on the basis of the second state of charge, which is more accurate than that calculated on the basis of the first state of charge, achieving a more accurate estimation of the total state of charge of the battery pack.