Battery SOC Calibration via Capacity and Time Thresholds
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Solution Overview
Problem
Current methods for tracking battery state of charge (SOC) in battery packs, such as coulomb-counting and fixed maximum capacity calculations, suffer from cumulative errors due to inaccuracies in current measurements and runtime readings, leading to decreased accuracy over time.
Innovation Solution
A system and method for calibrating battery SOC by monitoring accumulated capacity and time after an initial SOC calibration, charging the battery when these values exceed a predetermined threshold to reset the SOC calibration, using a battery management system with sensors and a controller to track ampere-hours discharged and time periods, and adjusting thresholds based on SOC accuracy and sensing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coulomb-counting method is used to track battery state of charge, then continuous monitoring capability is achieved, but cumulative errors accumulate over time reducing accuracy
Solution Approach 1:
The patent implements periodic SOC calibration by monitoring accumulated capacity and time thresholds, then performing full charge cycles at intervals to reset cumulative errors. This periodic intervention maintains long-term accuracy without requiring continuous calibration.
Solution Approach 2:
The system continuously monitors accumulated capacity and time, comparing against thresholds to determine when calibration is needed. This feedback mechanism dynamically adjusts calibration timing based on actual usage patterns, optimizing both accuracy and efficiency.
2Ease of operation
If fixed maximum capacity value and runtime counter are used for SOC calculation, then simple calculation is achieved, but accuracy decreases due to cumulative errors in runtime readings
Solution Approach 1:
The patent segments the SOC tracking into two parts: continuous simple monitoring using fixed capacity values, and periodic calibration using accumulated capacity tracking. This segmentation maintains operational simplicity while eliminating cumulative errors through structured calibration intervals.
3Measurement precision
If SOC calibration is performed frequently to maintain accuracy, then measurement precision is improved, but productivity and battery cycle life are reduced
Solution Approach 1:
The calibration frequency is made dynamic rather than fixed. The system adapts calibration intervals based on accumulated capacity and time thresholds, adjusting the calibration schedule to match actual battery usage patterns. This dynamic approach maintains accuracy while minimizing unnecessary calibrations that would reduce productivity and battery life.
4Measurement precision
If accumulated capacity monitoring is implemented to trigger calibration, then calibration timing accuracy is improved, but device complexity increases
Solution Approach 1:
The battery management system performs multiple functions using the same monitoring infrastructure: it tracks both real-time SOC and accumulated capacity, monitors time intervals, and triggers calibrations based on either metric exceeding thresholds. This multi-functionality approach improves calibration timing accuracy without proportionally increasing system complexity.
Data Source
AI summary
The present disclosure is directed to a system and method for calibrating state-of-charge (SOC) of an energy storage device. The method includes monitoring, via a battery management system, at least one of an accumulated capacity of the energy storage device after a first SOC calibration or a time period after the first SOC calibration. Another step includes determining, via the battery management system, whether at least one of the accumulated capacity or the time period is above a predetermined threshold. If at least one of the accumulated capacity or the time period is above a predetermined threshold, then the method includes charging, via the battery management system, the energy storage device for a specified duration until the energy storage device reaches a second SOC calibration.