Aging mitigation of power supply-connected batteries

Abstract

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.

Design and Optimization of Supercapacitor Hybrid Architecture for Power Supply-Connected Batteries Lifetime Enhancement

“…We need to calculate the amount of deficient energy from the measured current profile. If the adapter is connected, the battery is fully charged most of time because the reduced capacity adapter is able to provide the average power demand even though it fails to meet the maximum power requirement [6]. Hence, we need to consider the situation that discharging starts from the fully charged battery, which reduces the burden of calculation.…”

“…In case of the Lenovo notebook, the specified power demand exceeds the power provided by the adapter by 4 W, in case of the Apple notebook, the gap is even bigger and comes to 14 W. The users usually expect that the reduced adapter would not affect the built-in battery lifetime of the laptop. However, a recent study [6] shows that the reduced capacity adapter may incur the battery aging even though the adapter is supplying the laptop. With higher power demands, the adapter cannot supply this demand fully, hence the deficient power is drawn from the battery.…”

“…With higher power demands, the adapter cannot supply this demand fully, hence the deficient power is drawn from the battery. The aging caused by the deficient power may be significant and the battery lifetime might be reduced to 23% of the shelf lifetime when the battery is connected to the reduced capacity adapter under normal usage conditions [6]. Note that shelf lifetime is the time it takes until the capacitance of a stored and unused battery has faded to 80% of its initial capacity.…”

“…The recent study [6] uses a hybrid architecture shown in Figure 1 as a solution to battery aging for power adapter connected batteries. It also considers the fact that the terminal voltage of the supercapacitor varies linearly with its state of charge (SOC) (The SOC is the ratio of available charge in the battery to the maximum available charge of a recharged battery.).…”

“…The optimal setup of hybrid architecture change if the deficient power and the daily usage pattern changes. Therefore, we first analyze the deficient energy from the built-in battery current profile, which is measured on a commercial laptop computer running benchmarking programs [6]. Second, we perform a circuit-level simulation with a supercapacitor charge buffer between the power adapter and the device that mitigates the battery aging in battery-connected condition while changing its capacitance.…”