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.
Short drive range due to limited battery capacity and high battery depreciation costs persist to be the main deterrents to the wide adoption of Electric Vehicles (EVs). High power battery packs consisting of a large number of battery cells require extensive management, such as State of Charge (SOC) balancing and thermal management, in order to keep the operating conditions within a safe and efficient range. In this paper, we propose a novel State of Health (SOH)-aware active cell balancing technique, which is capable of extending the cycle life of the whole battery pack. In contrast to the state-of-the-art active cell balancing techniques, the proposed technique reduces the load current of cells with low SOH using the active cell balancing architecture. Based on the observation that assigning the smallest possible load current to cells with lower SOH extends cycle life, the technique identifies the most beneficial charge transfers. We find that with our proposed scheme, aging could be mitigated by up to 23.5% over passive cell balancing and 17.6% over active SOC cell balancing.
Battery-operated portable electronics, from smartphones to notebook computers, are generally sold with a dedicated power supply. The power supply operates the device and also charges the built-in battery. Most users are concerned about the battery aging while the device is operated by the built-in battery. This is the first paper to our knowledge that discovers, analyzes and mitigates the built-in battery aging when the device is operated with the provided power supply. We focus on the fact that in an effort to reduce size and weight, the capacity of the power supply is optimized for the average power demand rather than the maximum power demand. Such a reduced-capacity power supply brings advantages in terms of size, weight and cost but it accelerates the battery aging because the aging progresses even when the device is operated by the power supply, which is different from the expectation of most users. We quantitatively analyze such battery aging with various operating scenarios based on standard benchmark programs. We show that the battery experiences significant aging, i.e., the battery lifetime can be reduced to 23% of its shelf lifetime. Finally, we propose a cost-effective supercapacior hybrid to mitigate such battery aging when the device is operated using the power supply. The simulation results show that 10, 1 and 0.1 mF supercapacitors can reduce the battery aging by 68.6%, 55.1% and 4.6%, respectively.
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