Battery Cell Balancing With Minimum-SOC Reference Thresholds
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Solution Overview
Problem
Existing battery systems face challenges in reducing cell deviation due to varying internal resistance and state of charge (SOC) in battery cells, leading to overcharging or overdischarging, which shortens the battery pack's lifespan and reduces capacity.
Innovation Solution
A battery system that includes a cell monitoring IC, current sensor, and main control circuit to estimate SOC, determine a balancing reference value, and perform cell balancing based on the minimum SOC, classifying SOC sections and setting section reference values to accurately identify and address cell imbalance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cell balancing is performed based on a fixed balancing reference value, then the cell balancing process is simple, but the cell balancing accuracy is insufficient when cell SOC varies significantly
Solution Approach 1:
The patent applies dynamics by making the balancing reference value changeable according to cell SOC. Instead of using a fixed reference value, the system dynamically adjusts the reference value based on the actual cell SOC state, allowing the balancing process to adapt to different charge levels and improve accuracy across the entire SOC range.
Solution Approach 2:
The patent changes the parameter of balancing reference value based on cell SOC. By establishing a correspondence between cell SOC and balancing reference value, the system adjusts the reference value parameter according to the actual charge state, enabling more accurate balancing decisions under varying SOC conditions.
2Reliability
If cell balancing is performed for all battery cells regardless of SOC, then cell deviation can be reduced, but cells with very small or very large SOC experience excessive voltage change and insufficient balancing
Solution Approach 1:
The patent applies local quality by implementing differentiated balancing strategies for different cell SOC ranges. Cells with very small or very large SOC are handled differently from cells with moderate SOC, with specific adjustments to balancing reference values and timing to prevent excessive voltage changes while ensuring adequate balancing effectiveness for each local SOC condition.
3Productivity
If cell balancing current is increased to reduce cell deviation faster, then productivity improves, but cells with large or small SOC experience excessive voltage drop and insufficient balancing
Solution Approach 1:
The patent makes the balancing current application dynamic by adjusting it according to cell SOC. For cells with very small or very large SOC, the system reduces the balancing current to prevent excessive voltage drops, while for cells with moderate SOC, higher current can be applied to achieve faster balancing, thus optimizing both speed and accuracy.
Data Source
AI summary
The present invention relates to a cell balancing method and a battery system providing the method. The battery system according to one example of the present invention includes: a battery including a plurality of battery cells; a cell monitoring integrated circuit (IC) that measures a cell voltage of each of the plurality of battery cells; a current sensor that measures a battery current flowing in the battery; and a main control circuit that estimates a cell state of charge (SOC) of each of the plurality of battery cells based on the cell voltage and the battery current, extracts a minimum cell SOC among cell SOCs of the plurality of battery cells, determines a balancing reference value corresponding to the minimum cell SOC, and determines a need for cell balancing for each of the plurality of battery cells based on the balancing reference value.