Battery SOC Tracking via Relaxation Voltage Estimation
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Solution Overview
Problem
Accurate estimation of battery state of charge (SOC) is challenging, particularly in nickel metal hydride (NiMH) batteries, affecting the determination of maximum and minimum power limits, which is crucial for preventing damage and extending the operational life of battery systems in applications like hybrid electric vehicles and electric vehicles.
Innovation Solution
A battery control module that includes a voltage measuring module, current measuring module, and SOC module, which estimates SOC using relaxation voltage and power ratio approaches, accumulating charge and discharge swings within specific windows and monitoring rest periods to determine the qualified swings for accurate SOC estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SOC estimation methods are used, then the system is simpler to implement, but the measurement precision of SOC is insufficient
Solution Approach 1:
The patent segments the SOC estimation process into distinct phases: charge swing accumulation, discharge swing accumulation, rest period monitoring, and relaxation voltage measurement. Each phase has specific qualification criteria that must be met, breaking down the complex estimation problem into manageable segments that improve accuracy without requiring overly complex continuous monitoring systems
Solution Approach 2:
The system performs preliminary actions by accumulating charge and discharge swing data during qualified periods before actual SOC estimation is needed. The control module pre-qualifies swing periods based on voltage and current thresholds, storing this accumulated data for later use during rest periods when accurate SOC measurement is performed, thereby preparing estimation data in advance rather than calculating in real-time
2Reliability
If the battery system is oversized to ensure adequate power assist and regeneration energy, then power limits are not exceeded, but the weight and cost increase
Solution Approach 1:
The patent implements feedback by continuously monitoring battery voltage, current, and calculated SOC levels, then using this information to dynamically adjust power delivery decisions. The powertrain control system receives SOC feedback and uses it to determine maximum and minimum power limits, allowing the system to operate reliably at optimal battery sizes rather than requiring oversized batteries for safety margins
Solution Approach 2:
The system changes operational parameters by adjusting power delivery thresholds based on real-time SOC measurements. Instead of using fixed conservative power limits that would require oversized batteries, the system dynamically modifies power limits according to the actual SOC state, enabling reliable operation with properly sized batteries while preventing power limit exceedance
3Measurement precision
If SOC estimation is performed continuously, then the SOC accuracy is maintained, but the energy consumption and processing load increase
Solution Approach 1:
The patent employs periodic action by performing SOC estimation only during qualified rest periods rather than continuously. The system monitors for specific conditions (voltage thresholds, current thresholds, minimum rest duration) and executes SOC measurement and estimation only when these conditions are met, reducing energy consumption and processing load while maintaining accuracy through periodic updates at strategically chosen moments
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise estimation of battery SOC, maintaining an optimal power ratio between charging and discharging, reducing the need for oversized battery systems and preventing power limit exceedance, thus extending battery life and ensuring safe operation.
Implementation Method 1
estimates SOC based on relaxation voltage
Data Source
AI summary
A battery control module for a battery system comprises a voltage measuring module that measures battery voltage and a current measuring module that measures battery current. A state of charge (SOC) module that communicates with the current and voltage measuring modules and that estimates SOC based on relaxation voltage.