Battery SOC Equalization via Capacity-Aware Discharge Control
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Solution Overview
Problem
Existing electrical storage systems face inefficiencies in equalizing state of charge (SOC) variations among multiple cells due to full charge capacity variations, leading to frequent and wasteful discharging processes.
Innovation Solution
An electrical storage system with a controller that calculates and corrects SOC differences using full charge capacity data, distinguishing between SOC variations caused by full charge capacity changes and self-discharge, and only discharging for variations due to self-discharge to prevent unnecessary energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If equalizing process is carried out whenever SOC variations occur, then SOC uniformity is improved, but energy waste increases due to discharging for capacity-related variations
Solution Approach 1:
The system performs preliminary action by calculating the expected SOC difference based on full charge capacity variations before deciding whether to execute the equalizing process. This allows the system to distinguish between SOC variations caused by capacity differences (which don't require equalization) and those caused by self-discharge or other factors (which do require equalization), thereby avoiding unnecessary discharging and energy waste.
2Measurement precision
If equalizing process is frequently carried out, then SOC accuracy is improved, but productivity decreases due to frequent interruptions
Solution Approach 1:
The system calculates the expected SOC difference based on full charge capacity data before executing equalization, allowing it to predict when equalization is truly necessary. This preliminary calculation prevents frequent unnecessary equalizing operations that would interrupt system productivity while still maintaining accurate SOC levels when actually needed.
Solution Approach 2:
The system uses feedback from full charge capacity measurements to adjust equalization decisions. By continuously monitoring capacity variations and comparing expected SOC differences with actual SOC differences, the system can intelligently determine when equalization is necessary, balancing SOC accuracy maintenance with system productivity.
3Device complexity
If equalizing process is carried out without considering full charge capacity variations, then device complexity is reduced, but measurement precision deteriorates due to inaccurate SOC equalization
Solution Approach 1:
The system performs preliminary calculation of expected SOC differences using stored full charge capacity data before executing equalization. This approach maintains relatively simple control logic while significantly improving SOC equalization accuracy by accounting for capacity variations among different storage elements.
Data Source
AI summary
An electrical storage system includes electrical storage elements connected in series with each other and being charged or discharged; discharge circuits respectively connected in parallel with the electrical storage elements and discharging the corresponding electrical storage elements; and a controller controlling operations of the discharge circuits. The controller calculates a first SOC difference using a full charge capacity of each electrical storage element. The first SOC difference is a difference in SOC between the electrical storage elements and arises due to a difference in full charge capacity between the electrical storage elements. The controller calculates a second SOC difference that is a difference in SOC between the electrical storage elements at the moment the second SOC difference is calculated. When the second SOC difference is larger than the first SOC difference, the controller brings the second SOC difference close to the first SOC difference through a discharge with the discharge circuits.