Dynamic Lithium-Ion Charging Algorithm for Capacity and Thermal Management
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Solution Overview
Problem
Fast charging technologies for lithium-ion batteries are inefficient as they take hours to fully charge, are not necessary for all users, increase safety risks due to rapid heating, and accelerate capacity fading, shortening battery life and increasing operational costs.
Innovation Solution
A user-aware charging method that determines a current charging time period and threshold voltage based on available time, ensuring cell relaxation and safe temperature, using a two-phase charging algorithm with constant current and voltage phases to maximize charged capacity within user-specified time while maintaining safe temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If fast charging is used, then charging time is reduced, but cell temperature increases rapidly causing safety risks
Solution Approach 1:
The charging current is dynamically adjusted based on real-time cell temperature monitoring. The system transitions from static fast charging to dynamic charging where the current profile changes continuously to maintain temperature within safe limits while maximizing charging speed.
Solution Approach 2:
The system implements closed-loop feedback control by continuously monitoring cell temperature and adjusting the charging current accordingly. When temperature approaches unsafe levels, the system automatically reduces current to prevent thermal runaway, creating a self-regulating charging process.
2Productivity
If fast charging is used, then charging speed is improved, but capacity fading accelerates shortening battery life
Solution Approach 1:
The charging process incorporates periodic rest intervals where charging is temporarily suspended to allow cell relaxation. This periodic action prevents continuous high-stress charging, reducing capacity fading while maintaining overall charging efficiency through optimized charge-discharge cycles.
Solution Approach 2:
The system performs preliminary assessment of cell state (temperature, voltage, current) before initiating each charging phase. This preliminary action allows the system to pre-adjust charging parameters to optimal levels that balance speed with battery longevity, preventing excessive stress before it occurs.
3Loss of time
If threshold voltage is reduced to enable faster charging, then charging time decreases, but charged capacity is reduced
Solution Approach 1:
The threshold voltage is dynamically determined based on available charging time rather than being a fixed parameter. The system calculates the optimal threshold voltage that maximizes capacity within the user-specified time constraint, adapting to different charging scenarios (quick top-up vs. overnight charging).
4Productivity
If constant current charging is used to maximize speed, then charging efficiency is improved, but cell relaxation time is insufficient increasing capacity fading
Solution Approach 1:
The charging protocol alternates between constant current charging phases and relaxation phases. During CC phases, high current maximizes charging efficiency; during relaxation phases, current is reduced or suspended to allow cell recovery, preventing capacity fading while maintaining overall efficiency.
Solution Approach 2:
The charging process is segmented into distinct phases (constant current, constant voltage, relaxation) rather than using a single continuous charging mode. This segmentation allows optimization of each phase for its specific purpose while combining them to achieve both speed and battery health.
Data Source
AI summary
Lithium-ion cells are widely used in various platforms, such as electric vehicles (EVs) and mobile devices. Complete and fast charging of cells has always been the goal for sustainable system operation. However, fast charging is not always the best solution, especially in view of a new finding that cells need to rest/relax after being charged with high current to avoid accelerated capacity fading. A user aware charging algorithm is proposed which maximizes the charged capacity within a user-specified available charging time (i.e., user-awareness) while ensuring enough relaxation (i.e., cell-awareness) and keeping cell temperature below a safe level.