iCharge: User-Interactive Charging of Mobile Devices.

Charging mobile devices \"fast\" has been the focus of both industry and academia, leading to the deployment of various fast charging technologies. However, existing fast charging solutions are agnostic of users' available time for charging their devices, causing early termination of the intended/planned charging. This, in turn, accelerates the capacity fading of device battery and thus shortens the device operation. In this paper, we propose a novel user-interactive charging paradigm, called iCharge, that tailors the device charging to the user's real-time availability and need. The core of iCharge is a relaxation-aware (R-Aware) charging algorithm that maximizes the charged capacity within the user's available time and slows down the battery's capacity fading. iCharge also integrates R-Aware with existing fast charging algorithms via a user-interactive interface, allowing users to choose a charging method based on their availability and need. We evaluate iCharge via extensive laboratory experiments and field-tests on Android phones, as well as user studies. R-Aware is shown to slow down the battery fading by more than 36% on average, and up to 60% in extreme cases, when compared to existing fast charging algorithms. This slowdown of capacity fading translates to, for instance, an up to 2-hour extension of the LTE time for a Nexus 5X phone after its use for 2 years, according to our trace-driven analysis of 976 device charging cases of 7 users over 3 months.