Battery Full Charge Capacity Calculation via Polarization Wait
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Solution Overview
Problem
The existing methods for calculating the full charge capacity of electrical storage devices, such as batteries, face accuracy issues due to voltage variations caused by polarization during charging and discharging, which affect the estimation of state of charge and subsequently the full charge capacity.
Innovation Solution
An electrical storage system that includes a voltage sensor, current sensor, and a controller, which temporarily stops charging to detect voltage values and calculate state of charge based on open circuit voltage correlations, ensuring accurate full charge capacity calculation by minimizing the impact of polarization-induced voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the SOC is calculated based on the detected voltage value during charging, then the calculation process is simple and fast, but the estimation accuracy of SOC and full charge capacity decreases due to polarization-induced voltage variations
Solution Approach 1:
The system performs a preliminary waiting period after charging starts before detecting voltage, allowing polarization-induced voltage variations to subside. This preliminary action ensures that voltage measurements are taken when the battery voltage is more stable and closer to its true open-circuit voltage, thereby improving SOC estimation accuracy without significantly impacting overall calculation speed
Solution Approach 2:
The system implements periodic voltage detection during charging, where voltage is measured at specific intervals (after waiting periods) rather than continuously. This periodic measurement approach balances the need for accurate SOC estimation with computational efficiency, obtaining sufficient data points to calculate full charge capacity while avoiding excessive processing requirements
2Speed
If voltage detection is performed immediately during charging, then real-time monitoring is achieved, but voltage variation due to polarization causes inaccurate SOC estimation
Solution Approach 1:
Before performing voltage detection, the system implements a preliminary waiting period to allow polarization effects to diminish. This ensures that voltage measurements reflect the true battery state rather than transient polarization effects, improving measurement accuracy while maintaining acceptable response timing
Solution Approach 2:
The system continuously monitors charging state and uses feedback from previous voltage measurements to determine appropriate detection timing. By analyzing voltage trends and charging conditions, the system dynamically adjusts when to perform measurements, balancing real-time monitoring requirements with accuracy needs
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
This approach ensures accurate estimation of full charge capacity even with polarization, by stabilizing voltage variations and using accumulated current values, thereby improving calculation precision.
Implementation Method 1
When polarization occurs as a result of charging or discharging of the battery pack, a voltage value of the battery pack, which is detected by a voltage sensor, (referred to as detected voltage value) includes a voltage variation resulting from the polarization.
Data Source
AI summary
An electrical storage system includes an electrical storage device, a voltage sensor, a current sensor and a controller. The electrical storage device is configured to be charged with electric power from an external power supply. The controller is configured to detect a first voltage value with the use of the voltage sensor in a state where external charging is temporarily stopped, and calculate a first state of charge corresponding to the first voltage value, when an elapsed time from when external charging at a predetermined electric power is started is longer than or equal to a predetermined time. The predetermined time is a time required until a convergence of a voltage variation resulting from polarization during external charging. The controller is configured to detect a second voltage value with the use of the voltage sensor, when the charging is resumed at the predetermined electric power after the charging is temporarily stopped and then the charging is stopped again, and calculate a second state of charge corresponding to the second voltage value. The controller is configured to calculate a full charge capacity from an accumulated value of the current value in a period from when the charging is resumed to when the charging is stopped and a variation between the first state of charge and the second state of charge, when a difference between a rate of change corresponding to the first voltage value and a rate of change corresponding to the second voltage value is smaller than or equal to an allowable value. The rate of change is identified from the correlation, and indicates the ratio of a variation in open circuit voltage to a variation in state of charge.