Battery Management System OCV Measurement Dynamics
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Solution Overview
Problem
Existing battery management systems face challenges in precisely measuring open circuit voltage (OCV) during short times or before polarization correction, leading to errors in state of charge (SOC) calculation, especially in hybrid vehicles where no-load conditions are not consistently met.
Innovation Solution
A battery management system with a sensing unit and a main control unit (MCU) that measures battery current and voltage, resets OCV during a no-load state period, and estimates SOC using a time-varying determining period to ensure accurate OCV measurement, thereby preventing SOC estimation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If OCV measurement is performed in short time or before polarization correction, then response speed is improved, but measurement precision deteriorates
Solution Approach 1:
The patent applies dynamics by making the determination period time-varying rather than fixed. The period starts short and gradually increases, allowing the system to adapt between speed and precision requirements. This resolves the contradiction by enabling fast initial response while ensuring precision as time progresses.
Solution Approach 2:
The patent changes the parameter of determination period from a fixed value to a time-varying value that increases over time. This parameter change allows the system to transition from speed-priority mode (short period) to precision-priority mode (longer period), effectively resolving the contradiction between response speed and measurement precision.
2Measurement precision
If no-load state period is extended to ensure accurate OCV measurement, then measurement precision is improved, but productivity deteriorates
Solution Approach 1:
The patent makes the no-load state period dynamic rather than static. Instead of requiring a fixed extended period, the system uses a time-varying determination period that adapts based on elapsed time. This allows productivity to be maintained while still achieving measurement precision through progressive time extension.
Solution Approach 2:
The patent performs preliminary measurements during the charging/discharging process itself, rather than waiting for a complete no-load period. By starting measurements during operation and continuing them through a gradually extending no-load period, the system achieves precision without completely stopping productivity.
3Measurement precision
If time-varying determination period is used to ensure accurate OCV measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces a time-varying determination period as a parameter change that can be implemented through relatively simple timing logic. The complexity is managed by using a systematic approach (incremental time periods) rather than complex algorithms, balancing precision improvement with acceptable device complexity.
Data Source
AI summary
Battery management system and a driving method thereof including a sensing unit and an MCU. The sensing unit measures a battery current and a battery voltage. The MCU sets an OCV during a no-load state period at time increments measured from the beginning of the no-load state period, and estimates an SOC corresponding to the set OCV.