Multi-Stage Battery Charging Method for Lithium-Ion Cells
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Solution Overview
Problem
Existing battery charging methods, such as the step constant current (CC)/constant voltage (CV) method, generate linear stress and additional deterioration in batteries due to non-linear resistance characteristics, leading to uneven cell performance and reduced battery pack lifespan.
Innovation Solution
A battery charging method that applies a series of stepwise voltages determined by the battery's internal resistance characteristics, switching between different voltage levels based on charging current thresholds to reduce stress and match the characteristics of each cell in the battery pack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If step constant current/constant voltage charging method is used, then charging speed is maintained, but battery lifespan is reduced due to linear stress and non-linear resistance characteristics
Solution Approach 1:
The charging process is divided into multiple constant voltage stages (first constant voltage, second constant voltage, third constant voltage) with different voltage levels and time periods. Each stage is designed to correspond to different resistance characteristics of the battery during charging, thereby reducing linear stress while maintaining charging efficiency.
2Ease of operation
If constant current charging is applied throughout, then charging simplicity is maintained, but cell performance becomes uneven leading to over-charging and over-discharging
Solution Approach 1:
The charging method dynamically adjusts voltage levels based on the charging process stage and battery resistance characteristics. By switching between different constant voltage levels (first voltage < second voltage < third voltage) at different time periods, the system adapts to changing battery conditions, ensuring uniform cell performance while maintaining operational simplicity.
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 extends battery lifespan by reducing stress and ensuring each cell receives an appropriate electric current, resulting in improved battery pack performance and longevity without affecting charging time.
Implementation Method 1
Resistance of a battery has a non-linear characteristic that varies during a charging process, according to a C-rate, a state of charge (SOC), temperature, and/or the like
Data Source
AI summary
A method of charging a battery, wherein the battery comprises a plurality of battery cells, includes charging the battery with a first voltage for a first time period, which charging is first charging, charging the battery with a second voltage for a second time period, which charging is second charging, and charging the battery with a third voltage for a third time period, which charging is third charging, wherein lengths of the first to third time periods are determined in correspondence with a magnitude of charging current of the battery.