Battery SOC Estimation Using Internal Resistance and Charging Efficiency
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Solution Overview
Problem
Conventional methods for estimating the state of charge (SOC) of electric vehicle batteries are inaccurate due to battery aging, especially when temperature and internal resistance variations are not considered.
Innovation Solution
A method and device that estimate the SOC of a battery based on its internal resistance and charging efficiency, using a controller to determine entry conditions, generate initial and second SOC values, and calculate storage capacities to accurately predict the battery's state of charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional OCV map method is used to estimate SOC, then the estimation process is simple, but the SOC value cannot be accurately estimated due to battery aging
Solution Approach 1:
The patent changes the estimation parameters from only open circuit voltage (OCV) to include both OCV and internal resistance (IR). By measuring multiple parameters (voltage, current, temperature, and calculated internal resistance), the system compensates for battery aging effects that cause OCV-SOC relationship degradation, thereby improving SOC estimation accuracy without excessive complexity
Solution Approach 2:
The patent replaces the simple lookup table approach (mechanical/OCV map) with an electronic calculation system that uses measured voltage, current, and temperature data to compute internal resistance and estimate SOC through mathematical relationships, enabling more accurate tracking of battery state despite aging
2Measurement precision
If battery aging is not considered, then the estimation method remains simple, but temperature and internal resistance variations cause inaccurate SOC estimation
Solution Approach 1:
The patent introduces internal resistance as an intermediary parameter that mediates between directly measurable quantities (voltage, current, temperature) and the target parameter (SOC). By measuring voltage, current, and temperature, then calculating internal resistance using these intermediaries, the system achieves accurate SOC estimation that accounts for aging and environmental effects
Solution Approach 2:
The patent implements feedback by continuously monitoring voltage, current, and temperature to calculate internal resistance, which then feeds back into the SOC estimation process. This closed-loop approach allows the system to adapt to changing battery conditions and aging effects, improving accuracy over time
Data Source
AI summary
A method for estimating a state of charge (SOC) value of a battery may include determining, by a controller, whether an entry condition for estimating the SOC value of the battery is satisfied based on state data of the battery; generating, by the controller, an initial SOC value of the battery using an internal resistance value of the battery when the state data satisfies the entry condition; generating, by the controller, a first storage capacity of the battery to generate using the initial SOC value; generating, by the controller, a second storage capacity of the battery using the first storage capacity and a charging efficiency of the battery; and estimating, by the controller, the SOC value of the battery using the second storage capacity.