Battery Management System Internal Resistance Estimation
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Solution Overview
Problem
Existing battery management systems face challenges in precisely detecting battery internal resistance, which affects the state of health (SOH) and lifespan of rechargeable cells in hybrid vehicles, especially due to variations in internal resistance with temperature and state of charge (SOC).
Innovation Solution
A battery management system incorporating a sensing unit and micro control unit (MCU) that measures battery temperature and current, estimates SOC, calculates internal resistance within a predetermined SOC area where its variation is minimized, and determines SOH using equations for maximum discharge current and power values, with threshold comparisons to assess battery health.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If battery internal resistance is measured across the entire SOC range, then measurement coverage is improved, but measurement precision deteriorates due to large variations in internal resistance
Solution Approach 1:
The patent divides the SOC range into multiple predetermined SOC areas (e.g., first SOC area, second SOC area, third SOC area). Each area is associated with different predetermined internal resistance values. This segmentation allows the system to select the appropriate internal resistance value based on the current SOC, improving measurement precision within each segment while maintaining comprehensive coverage across the entire SOC range.
Solution Approach 2:
The patent changes the parameter of internal resistance values based on the SOC parameter. By establishing a relationship between SOC and internal resistance, and selecting different predetermined internal resistance values corresponding to different SOC areas, the system adapts the internal resistance parameter to match the actual battery state, thereby improving measurement accuracy across varying SOC conditions.
2Device complexity
If a single internal resistance value is used for all SOC conditions, then device complexity is reduced, but measurement precision deteriorates due to temperature and SOC variations
Solution Approach 1:
The patent introduces multiple predetermined internal resistance values corresponding to different SOC areas and temperatures. The MCU selects the appropriate internal resistance value based on the current SOC and temperature conditions, allowing the system to adapt to varying operating conditions without requiring complex real-time measurement circuits.
Solution Approach 2:
The system uses the battery's own SOC and temperature information to automatically select the appropriate internal resistance value. The MCU estimates SOC based on battery current and uses this estimation along with temperature data to determine which predetermined internal resistance value to apply, enabling the system to self-adjust without external intervention.
3Measurement precision
If SOC estimation is continuously updated using battery current, then SOC accuracy is improved, but calculation complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the MCU continuously estimates SOC based on battery current measurements. This estimated SOC is then fed back to determine which predetermined internal resistance value to use, creating a closed-loop system that improves accuracy while maintaining manageable complexity through iterative refinement.
Solution Approach 2:
The patent pre-calculates and stores multiple predetermined internal resistance values corresponding to different SOC areas and temperature conditions. This preliminary preparation allows the MCU to quickly select the appropriate value based on current conditions without performing complex real-time calculations, reducing computational complexity while maintaining accuracy.
Data Source
AI summary
A battery management system and a driving method thereof includes a sensing unit and a micro control unit (MCU). The sensing unit measures a battery temperature and a battery current. The MCU receives the battery temperature and current, detects battery internal resistance corresponding to an estimated state of charge (SOC) and the battery temperature when the estimated SOC is included within an SOC area corresponding to the transmitted battery temperature, and estimates a battery state of health (SOH) by using the battery internal resistance. In the SOC area, a variation of the battery internal resistance is minimized.