Battery State of Charge Determination Using Interpolated Discharge Curves
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Solution Overview
Problem
Conventional methods for determining a battery's state of charge, such as the open circuit voltage method, require the battery to rest before measurement, leading to undesirable fluctuations in estimated charge during discharge, resulting in an inaccurate user experience.
Innovation Solution
An electronic device with a controller and storage medium that determines the battery's mode and uses multiple discharge curves to calculate the state of charge by measuring current C-rate and voltage, selecting appropriate curves for interpolation, allowing direct calculation of SoC during discharge without resting the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the open circuit voltage method is used to measure battery state of charge, then the measurement can be performed without complex algorithms, but the battery must rest for a period of time before measurement which causes time loss and voltage fluctuation during discharge
Solution Approach 1:
The patent changes the measurement parameters by using multiple discharge curves with different C-rates instead of relying on open circuit voltage after resting. By measuring current voltage and C-rate, and selecting appropriate discharge curves based on the current operating conditions, the system can calculate state of charge without requiring the battery to rest, thus eliminating time loss while maintaining measurement accuracy
Solution Approach 2:
The patent performs preliminary action by pre-storing multiple discharge curves with different C-rates in the storage medium before actual measurement. This allows the controller to quickly select and use the appropriate discharge curve based on current operating conditions, eliminating the need for resting time while maintaining accurate state of charge calculation
2Device complexity
If the open circuit voltage method is used during battery discharge, then the calculation is simple, but the voltage drops significantly causing the state of charge to be underestimated and then bounce back after stopping discharge
Solution Approach 1:
The patent changes from using only voltage as the measurement parameter to using both voltage and C-rate parameters. By incorporating C-rate into the measurement approach and selecting discharge curves based on current C-rate, the system maintains simplicity while eliminating the voltage bounce back effect and underestimation problems during discharge
Solution Approach 2:
The patent introduces dynamics by making the measurement approach adaptive to current operating conditions. The controller dynamically selects appropriate discharge curves based on real-time C-rate and voltage measurements, allowing the system to handle both discharge and resting modes accurately without the static limitations of the traditional open circuit voltage method
Data Source
AI summary
A method for determining a state of charge adapted for a battery is provided, the method including: obtaining a plurality of discharge curves; determining that the battery is in a discharge mode; measuring a current C-rate and a current voltage of the battery in the discharge mode; selecting a first discharge curve and a second discharge curve from the plurality of discharge curves, wherein a first C-rate corresponding to the first discharge curve is greater than the current C-rate, and a second C-rate corresponding to the second discharge curve is less than the current C-rate; and calculating a state of charge of the battery according to the first discharge curve and the second discharge curve.