Battery State of Health Estimation for Mobility Devices
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Solution Overview
Problem
Existing battery indicators in electrically powered mobility devices, such as wheelchairs, often provide inaccurate information about the remaining charge due to random fluctuations, rendering them essentially useless for effective route planning.
Innovation Solution
A method that estimates the remaining driving distance by determining the state of charge and state of health of the battery, using actual consumed ampere hours and nominal ampere hours, and filtering the state of health to compensate for rapid changes, thereby providing a more accurate estimation of the battery's capacity and travel distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing battery indicators are used to display remaining charge, then users can see charge status, but the information provided is inaccurate and fluctuates randomly
Solution Approach 1:
The system continuously monitors battery parameters (voltage, current, temperature) and uses this feedback to dynamically calculate and update the state of charge and state of health. This closed-loop feedback mechanism allows the system to detect and compensate for measurement errors and battery degradation, providing accurate and stable charge status information without random fluctuations.
Solution Approach 2:
The patent replaces simple visual battery indicator mechanisms with an electronic calculation system that processes multiple battery parameters. Instead of relying on basic voltage-threshold indicators, the system uses microprocessor-based calculations involving state of charge (SOC) and state of health (SOH) to determine remaining driving distance, substituting mechanical/simplified indication with electronic computation for improved accuracy.
2Productivity
If calculated consumed ampere hours are used based on motor load, then current consumption can be estimated, but the entire power consumption of the mobility device is not reflected
Solution Approach 1:
The system implements a universal monitoring approach that tracks multiple sources of power consumption simultaneously. Instead of only monitoring motor load, the system also monitors auxiliary device consumption (lights, display, control systems) and combines these measurements to provide a comprehensive view of total battery usage, ensuring all power drains are accounted for in the state of charge calculation.
3Device complexity
If state of charge alone is used to estimate remaining driving distance, then calculation is simple, but estimation accuracy is insufficient due to battery degradation
Solution Approach 1:
The system performs preliminary characterization of the battery during manufacturing or initial use to establish baseline capacity and degradation patterns. This preliminary action creates a reference model of the battery's state of health (SOH) that is stored and used throughout the battery's life. By having this pre-established baseline, the system can accurately interpret current state of charge readings in the context of battery aging without requiring complex real-time adjustments.
Data Source
AI summary
A method of estimating the remaining driving distance available from a current charge of a battery of an electrically powered mobility device, wherein the method comprises: a) determining a state of charge of the battery based on a measured battery-related parameter, b) determining a state of health of the battery based on the state of charge, and c) estimating the remaining driving distance that the mobility device can travel with the current charge based on the state of charge and the state of health, wherein step b) involves determining the state of health based on actual consumed ampere hours of the battery.