Vehicle Power Source SOH Control Using Differential SOC-Voltage Signals
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Solution Overview
Problem
Existing power source monitoring systems for hybrid and electric vehicles are inefficient in accurately determining the state of health (SOH) of battery packs, particularly capacitor-assisted batteries, which affects battery capacity utilization and system performance.
Innovation Solution
A state of health (SOH) based control system that includes a control module capable of determining the SOH by analyzing voltage and state of charge (SOC) changes, identifying inflection points and end of charge points through differential signal processing, and performing control operations or countermeasures based on these determinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional voltage monitoring methods are used, then the monitoring system is simple, but the SOH determination accuracy is insufficient
Solution Approach 1:
The patent segments the SOH determination process into multiple stages: voltage signal acquisition, differential signal generation, inflection point detection, and SOH calculation. By dividing the monitoring system into functional modules (voltage sensor, control module with algorithm, differential calculator), it achieves high measurement precision while keeping each component relatively simple and manageable.
Solution Approach 2:
The system performs preliminary actions by pre-storing algorithms and lookup tables in the control module that contain inflection point characteristics and SOH correlation data. This allows the system to quickly determine SOH by comparing real-time differential signals against pre-computed reference data, improving accuracy without requiring complex real-time calculations.
2Measurement precision
If full charge-discharge cycles are used for SOH determination, then accurate SOH can be obtained, but time consumption increases
Solution Approach 1:
The patent applies partial action by determining SOH based on inflection points that occur within partial charge-discharge cycles rather than requiring complete cycles. The system identifies characteristic inflection points (such as the point where dV/dQ reaches maximum) that provide sufficient SOH information without needing to complete full charge-discharge transitions, thus reducing time loss while maintaining accuracy.
Solution Approach 2:
The system replaces the mechanical/time-consuming process of waiting for full charge-discharge cycles with a mathematical/substitution approach: using differential signal analysis and inflection point detection to infer SOH from partial cycle data. The control module substitutes actual full-cycle testing with algorithm-based estimation using stored reference characteristics.
3Speed
If capacitor-assisted batteries are used, then fast response to charging current changes is improved, but SOH monitoring accuracy deteriorates
Solution Approach 1:
The patent introduces an intermediary element: the differential signal dV/dQ. Instead of directly monitoring voltage or current in capacitor-assisted batteries where fast changes occur, the system computes the differential of voltage with respect to charge. This intermediary transformation smooths out the rapid fluctuations caused by capacitor action while preserving the underlying SOH-related trends, thereby maintaining monitoring accuracy despite the fast-response characteristics of capacitor-assisted systems.
Data Source
AI summary
A state of health (SOH) based control system includes: a memory configured to store an algorithm including instructions for determining a SOH of a power source; and a control module configured to receive a voltage signal indicating a voltage of the power source and execute the instructions. The instructions include: determining a state of charge (SOC) of the power source; generating a differential signal based on a change in the voltage and a change in the state of charge; determining an inflection point and an end of charge point of the differential signal; determining the SOH of the power source based on the inflection point and the end of charge point; and performing at least one of a control operation or a countermeasure based on the SOH.