Battery Equalization Using Voltage Variation Rate
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Solution Overview
Problem
Olivine-type lithium-ion iron batteries with graphite-based negative electrodes face challenges in equalizing capacities due to voltage variations, especially in the plateau region where voltage remains constant, leading to incomplete charging or discharging and inefficient capacity utilization.
Innovation Solution
An electric storage device management apparatus with a voltmeter, discharging circuit, and controller that measures voltage variations and elapsed time periods to control discharging, allowing for capacity equalization by determining specific discharging times based on reference values, even in the plateau region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage information is used to equalize capacities in the variation region, then equalization control can be performed, but the SOCs reach about 100% or 0% before capacities are equalized, causing charging or discharging termination
Solution Approach 1:
The patent changes the parameter used for equalization control from voltage to unit time variation of voltage. This allows the system to identify batteries that have not yet reached full capacity even when voltage appears constant in the plateau region, enabling continued equalization without premature termination.
Solution Approach 2:
The patent introduces dynamic monitoring of unit time variation in voltage during the plateau region, allowing the system to detect subtle changes that indicate remaining capacity. This dynamic approach enables the equalization process to continue beyond what static voltage thresholds would allow.
2Ease of operation
If voltage information is used to estimate capacities in the plateau region, then measurement is simplified, but capacities cannot be properly equalized due to constant voltage despite SOC changes
Solution Approach 1:
The patent changes the measurement parameter from static voltage to unit time variation of voltage. This maintains the simplicity of voltage measurement while adding temporal dimension to detect capacity differences in the plateau region where voltage remains constant.
Solution Approach 2:
The patent implements continuous monitoring and feedback of unit time variation in voltage during charging or discharging. This feedback mechanism allows the control system to identify batteries with different capacities even in the plateau region and adjust equalization accordingly.
3Productivity
If discharging is performed to equalize capacities, then capacity utilization is improved, but time is required for equalization process
Solution Approach 1:
The patent performs preliminary identification of capacity differences using unit time variation measurement during normal charging or discharging operations. This allows the system to pre-identify which batteries need equalization and plan the equalization process more efficiently, reducing overall time loss.
Data Source
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AI summary
An electric storage device management apparatus is provided for monitoring an electric storage device assembly including a plurality of electric storage devices connected in series. The apparatus includes a voltmeter, a discharging circuit, and a controller. The discharging circuit is configured to discharge the electric storage devices individually. The controller is configured to: determine whether a unit time variation in voltage of a first electric storage device has increased to a reference value and a unit time variation in voltage of a second electric storage device has increased to the reference value; measure an elapsed time period since the unit time variation of the first electric storage device has increased to the reference values and control the discharging circuit to discharge the electric storage devices based on the elapsed time period such that capacities of the electric storage devices are equalized.