Smart2: Smart Charging for Smart Phones

Abstract

In this paper, we present Smart 2 , an advanced smartphone charger that mitigates battery's capacity fading, which until now has usually been ignored. Smart 2 exploits the fact that many users charge their phones over night. Since the overnight charging duration is unnecessarily long, the battery is subjected to a high average state of charge (SOC), which accelerates battery aging. Therefore, we delay the charging adaptively to be done shortly before the phone is unplugged. With this scheme, clearly when averaged over the duration of the night, the average SOC is lower and hence aging is reduced. Indicators are a set alarm clock and/or statistics of previous usage. Similarly, we lower the maximum target SOC. To enable this, the main challenges are firstly to find a solution that does not negatively influence the usability and secondly to quantify the achieved savings in terms of aging mitigation. Towards this, we propose a novel charging scheme which can be implemented in the smartphone's firmware. Furthermore, we propose a modified battery charging device that can be used with almost all existing smart phone models. Using our proposed techniques, the average battery cycle life can be nearly doubled from 3.7 to 6.6 years.

Intelligent Chargers Will Make Mobile Devices Live Longer

“…Several prior studies have dwelt on battery-health-aware charging [2], [3], [4], [5], [6]. However, commercial solutions are not yet mature.…”

“…Control knobs presented in related literature that mitigate battery aging during the charging process are (i) delayed charging [2] also in combination with (ii) reduced charging current [4], [5] and (iii) voltage relaxation periods [6]. So far a joint optimization of delay length, charge current, charge duration and voltage relaxation phase length has not yet been proposed.…”

“…Cycle life gains reported are up to 46.2% [4] with optimal charging current and delay, and 36% on an average for adjusted voltage relaxation [6]. If the charge delay is combined with adjusted SOC then the cycle life is almost doubled [2]. These significant gains show the potential of intelligent chargers.…”

Design space exploration of drone infrastructure for large-scale delivery services

“…If it is known when a battery will be discharged, in our case when the battery will be used for a delivery task, charging could be delayed as much as possible. A similar idea to extend the battery life has been proposed for smartphones [15]. Charging speed could also be a control knob for optimization.…”

“…As we have stated in Section 4, the calendar aging also plays a significant role and is largely affected by the average SOC of a battery. Thus, it would be a good direction to search for a better runtime algorithms, which makes use of delayed charging similar to a smartphone usage case [15], or charging the battery to just the appropriate amount. The electricity cost remains almost the same, as the actual amount of energy required for the deliveries does not change.…”