Battery Cell SOC Estimation from Partial Charge Voltage
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Solution Overview
Problem
Existing methods for determining the state of charge (SOC) of individual cells in a battery are inefficient, requiring complex discharge curves and characterization libraries, and lack effective means for identifying defective cells and recycling applications.
Innovation Solution
A method that measures voltages across each cell after a partial discharge or recharge, calculates an interpolation coefficient using voltage and discharge/recharge regime parameters, and determines the SOC indicator (QC) for each cell, allowing for the estimation of charge stored in each cell without needing discharge curves or characterization libraries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex discharge curves and characterization libraries are used to determine SOC, then measurement precision may be improved, but device complexity and ease of operation deteriorate
Solution Approach 1:
The patent extracts only the essential information needed for SOC determination by using simple voltage measurements at specific states instead of requiring complete discharge curves and characterization libraries. This removes the unnecessary complexity while retaining the core functionality of SOC estimation.
Solution Approach 2:
Instead of building up complex characterization models from complete discharge curves, the patent inverts the approach by using simple voltage measurements at specific states (fully charged, fully discharged, and partial states) to directly determine SOC through linear interpolation, eliminating the need for complex preliminary characterization.
2Ease of operation
If simple voltage measurement is used to determine SOC, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent performs preliminary actions by measuring the voltage of the battery at specific states (fully charged, fully discharged, and partial states) before the actual SOC determination. These preliminary voltage measurements establish reference points that enable accurate SOC calculation through simple linear interpolation during normal operation.
Solution Approach 2:
The patent changes the measurement parameters by taking voltage measurements at specific, well-defined states (U1 at full charge, U2 at full discharge, U3 at partial state) rather than requiring continuous or complex measurement profiles. This parameter change enables accurate SOC determination through simple linear interpolation while maintaining measurement simplicity.
3Measurement precision
If complete discharge and recharge cycles are performed to determine capacity, then measurement precision is improved, but loss of time and productivity deteriorate
Solution Approach 1:
The patent applies partial action by performing only necessary voltage measurements at specific states (fully charged, fully discharged, and partial states) rather than requiring complete capacity determination through full charge-discharge cycles. This partial measurement approach provides sufficient information for accurate SOC estimation while significantly reducing the time and resource investment required.
Data Source
Figure 1
AI summary
The present description concerns a method for determining, for each cell of a battery of cells connected in series, an indicator QCi representative of the charge stored in the cell, this method comprising: a) after a phase (101) of partially discharging or recharging the battery, measuring (102) the voltage Ui at the terminals of each cell of the battery; b) calculating (103), for each cell, an interpolation coefficient Xi from a value C_rate representative of the discharge or recharge rate of the battery during the partial discharge or recharge phase (101), and the voltages Ui measured in step a); and c) determining (104), for each cell, from the interpolation coefficient Xi calculated for the cell in step b) and a quantity Qcm representative of the charge stored in the battery, the indicator QCi representative of the charge stored in the cell.