Aqueous Battery Pack Charging for SOC Equalization Without Cell Monitoring
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Solution Overview
Problem
Existing battery pack systems with aqueous battery cells face challenges in simplifying system configuration and reducing gas generation and deterioration due to SOC variation, as they require voltage monitoring and high charged electric charge amounts during SOC correction.
Innovation Solution
A charging method that involves constant-current charging at a first rate until a reference voltage is reached, then switches to a lower constant-current rate of 0.01 C to 0.05 C, continuing until a charge amount of 1% to 5% of the nominal capacity is reached, without monitoring individual cell voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage monitoring of each aqueous battery cell is performed during SOC correction, then SOC variation can be corrected accurately, but system complexity increases
Solution Approach 1:
The patent merges the SOC correction function into a standardized battery pack interface, eliminating the need for individual cell voltage monitoring. The battery pack manufacturer integrates the correction mechanism internally, allowing the storage system to treat each battery pack as a uniform unit with standardized electrical connections, thereby reducing system complexity while maintaining SOC correction capability
Solution Approach 2:
The battery pack is designed to perform self-correction of SOC variation through its internal characteristics during charging. The pack automatically equalizes SOC across cells through its inherent electrical properties and charging behavior, eliminating the need for external monitoring and control systems to track individual cell voltages
2Measurement precision
If constant-voltage charging is performed to correct SOC variation, then SOC equalization is achieved, but gas generation increases and battery deterioration accelerates
Solution Approach 1:
The patent changes the charging parameter from constant-voltage to a controlled constant-current regime with limited charge amount. By setting a maximum charged electric charge amount (1-5% of nominal capacity) and using appropriate current rates (0.01C to 0.05C), the system achieves SOC correction while avoiding the high voltage conditions that cause water electrolysis and harmful gas generation
Solution Approach 2:
The patent applies partial charging action by limiting the charged electric charge amount to a small fraction (1-5%) of the battery pack's nominal capacity. This partial charging is sufficient to equalize SOC variation across cells without overcharging, thereby preventing excessive gas generation and battery deterioration that would result from full constant-voltage charging
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively corrects SOC variation between aqueous battery cells, simplifies system configuration, reduces gas generation, and minimizes battery deterioration by lowering the charged electric charge amount.
Implementation Method 1
A charging method is disclosed for a battery pack in which a plurality of aqueous battery cells each including an aqueous electrolyte, a positive electrode, and a negative electrode are electrically connected in series. This charging method performs constant-current charging at a first charging rate on the battery pack until a voltage of the battery pack becomes a reference voltage
Implementation Method 2
Since constant-voltage charging is performed on the battery pack, electrolysis of water occurs in an aqueous battery cell having a high SOC among a plurality of aqueous battery cells forming the battery pack
Data Source
AI summary
In one embodiment, there is provided a charging method of a battery pack in which a plurality of aqueous battery cells are electrically connected in series. In this charging method, in a case where the battery pack reaches a reference voltage by a constant-current charging at a first charging rate, constant-current charging is performed on the battery pack at the second charging rate lower than the first charging rate and being from 0.01 C or more to 0.05 C or less. Then, this constant-current charging at the second charging rate is continued until a charged electric charge amount from a start timing of the constant-current charging at the second charging rate reaches a reference electric charge amount set from 1% or more to 5% or less of the nominal capacity of the battery pack.