SOC Optimizing Device for Assembled Battery Cell Balancing
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Solution Overview
Problem
Conventional state of charge (SOC) equalization processes for assembled batteries, such as those in hybrid vehicles, fail to adequately account for variations in full charging capacities and temperature distribution, leading to inefficient performance due to non-uniform SOC levels among cells, which are exacerbated by infrequent equalization opportunities when the battery is not in use.
Innovation Solution
A state of charge optimizing device that sets equalization target values based on full charging capacities to uniformly adjust the SOC of cells, ensuring that the difference in charge levels is consistent among all cells, thereby optimizing performance by balancing discharge and charge characteristics around a predetermined SOC range (40-60%) using a charging and discharging unit, an amount of charge difference calculating unit, and an optimization target value setting unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional equalizing process is used with fixed target value, then equalization can be performed, but cells with different full charging capacities cannot maintain uniform SOC levels, leading to performance degradation
Solution Approach 1:
The patent changes the equalization target value from a fixed voltage or average SOC to a dynamic target that varies according to each cell's full charging capacity. The control unit calculates individual target values based on measured full charging capacities, enabling cells with different capacities to reach a balanced state simultaneously, thus resolving the contradiction between SOC uniformity and battery performance.
2Reliability
If equalization is performed frequently, then SOC uniformity can be maintained, but the battery must be stopped more often, reducing operational efficiency
Solution Approach 1:
The patent performs preliminary measurement of full charging capacities for each cell and uses this information to set appropriate equalization target values in advance. This allows the equalization process to be more efficient and accurate, reducing the frequency needed while maintaining SOC uniformity, thus minimizing operational time loss.
3Ease of manufacture
If equalization targets are set based on average SOC, then the process is simple, but cells with different full charging capacities do not achieve optimal performance
Solution Approach 1:
The patent applies local quality by setting individual equalization target values for each cell based on its specific full charging capacity rather than using a uniform average target. The control unit calculates and applies cell-specific targets, ensuring that each cell is equalized according to its unique characteristics, thereby optimizing battery efficiency while maintaining manageable control complexity.
Data Source
AI summary
A state of charge optimizing device according to the present invention optimizes a state of charge of each of a plurality of cells which are connected in series to form an assembled battery, and conducts the optimization by discharging or charging a part or all of the plurality of cells so that the differences between the amount of charge after the optimization and the amount of charge in a predetermined state of charge become uniform.