Battery RSOC Estimation Using Available Capacity Tracking
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Solution Overview
Problem
Existing methods for estimating the relative state-of-charge (RSOC) of lithium batteries are inaccurate, leading to sudden power-offs due to sharp drops in RSOC at the end of discharge, causing various operational issues.
Innovation Solution
A method and apparatus for calculating RSOC by measuring battery parameters such as voltage, current, and temperature, estimating state-of-charge (SOC) and non-dischargeable capacity, and updating RSOC based on a ratio to available SOC (AvSOC), using discharge simulations and correction thresholds to smooth RSOC variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SOC estimation methods are used, then the estimation process is simple, but the RSOC accuracy deteriorates causing sharp drops at end of discharge
Solution Approach 1:
The patent segments the battery capacity into dischargeable capacity and non-dischargeable capacity components. By dividing the total capacity estimation into these distinct segments and tracking them separately, the method achieves more accurate RSOC estimation without requiring overly complex unified models.
Solution Approach 2:
The patent performs preliminary discharge simulations to establish SOC-OCV data and capacity characteristics before actual battery operation. This pre-characterization allows the estimation algorithm to use pre-computed reference data, improving accuracy while keeping real-time computation relatively simple.
2Reliability
If simple SOC estimation is used, then the calculation process is fast, but sudden power-offs occur due to RSOC plunge
Solution Approach 1:
The patent implements feedback mechanisms where the estimated SOC and capacity values are continuously updated and used to correct previous estimation errors. The system monitors the difference between estimated and actual battery behavior, adjusting the RSOC calculation to prevent sharp drops and sudden power-offs.
Solution Approach 2:
The patent dynamically changes estimation parameters based on battery state, including adjusting the weight given to different measurement inputs (voltage, current, temperature) and modifying the discharge simulation parameters based on operating conditions. This adaptive parameter adjustment maintains reliability without requiring excessively complex real-time calculations.
3Measurement precision
If discharge simulation is performed for accurate non-dischargeable capacity estimation, then the capacity estimation accuracy is improved, but the computational burden increases
Solution Approach 1:
The patent performs computationally intensive discharge simulations in advance to build reference data and capacity characteristics. These pre-computed results are stored and reused during actual battery operation, achieving accurate non-dischargeable capacity estimation without repeating full simulations in real-time, thus reducing computational energy consumption.
Data Source
AI summary
A method of calculating a relative state-of-charge (RSOC) of a battery according to the disclosure includes measuring at least one parameter of the battery, based on the at least one parameter, estimating a state-of-charge (SOC) of the battery, based on the SOC, SOC-open circuit voltage (SOC-OCV) data of the battery, and the at least one parameter, estimating a non-dischargeable capacity of the battery, based on the non-dischargeable capacity of the battery, the SOC, and intrinsic capacity of the battery, estimating an available SOC (AvSOC) of the battery, based on the SOC and the AvSOC of the battery, determining the RSOC of the battery, and based on a ratio of the RSOC to the AvSOC, updating the RSOC of the battery.