Secondary Battery System Internal Resistance Ratio Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing charge-discharge control methods for assembled batteries in electric vehicles do not adequately protect cells from biased current distribution, leading to potential overheating and excessive current flow, which can result in cell deterioration and lithium deposition.
Innovation Solution
A secondary battery system with a current sensor and control device that calculates an internal resistance ratio between blocks, using this ratio to adjust the charge-discharge current, ensuring protection control is performed earlier and more effectively than with actual current values, thereby preventing high-rate deterioration and lithium deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charge-discharge control is performed based on actual current sensor values, then the control system operates with accurate real-time data, but cells are not protected early enough from biased current distribution leading to deterioration
Solution Approach 1:
The control device calculates the internal resistance ratio between blocks in advance and uses this ratio to proactively adjust charge-discharge current limits. By determining the maximum internal resistance ratio and pre-establishing protection current values based on this ratio, the system performs protection control before biased current distribution causes cell damage, rather than waiting for actual current sensor readings to indicate a problem
2Reliability
If the internal resistance ratio is calculated and used to adjust protection current, then cell protection is improved, but the device complexity increases due to additional calculation requirements
Solution Approach 1:
The control device monitors changes in internal resistance values of different blocks and adjusts the protection current parameter dynamically based on the calculated internal resistance ratio. When the ratio exceeds a predetermined threshold, the system modifies the charge-discharge current limits accordingly. This parameter-based approach provides effective cell protection through straightforward mathematical calculations rather than complex control algorithms
Data Source
AI summary
A secondary battery system includes an assembled battery that includes a plurality of blocks that are connected in series to one another. Each of the plurality of the blocks includes same number of cells that are connected in parallel to one another. A control device is configured to calculate an internal resistance ratio and a protection current. The internal resistance ratio is a value obtained by dividing the higher one of internal resistances by the lower one of the internal resistances of two of the plurality of the blocks. The protection current is a value obtained by multiplying the internal resistance ratio by a current value of the assembled battery detected by a current sensor. The control device is configured to perform the charge-discharge control based on the protection current.