*-Aware Charging of Lithium-ion Battery Cells

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. Fast charging for its typical Charge-and-Go scenario does not allow this needed relaxation. In this paper, we propose *-Aware, a novel charging algorithm which maximizes the charged capacity within the user-specified available charging time (i.e., user-awareness) while ensuring enough relaxation (i.e., cell-awareness). We motivate and evaluate *-Aware via extensive measurements over 10 months. *-Aware is shown to improve the charged capacity by 6.9-50.5% over other charging algorithms that also ensure relaxation, and by almost 3x in some extreme cases. Furthermore, *-Aware slows down the capacity fading by 49.55% when compared to fast charging.