DynLiB: Maximizing Energy Availability of Hybrid Li-Ion Battery Systems

Abstract

Battery-powered devices commonly use Li-ion batteries due to their high energy density. Unfortunately, low ambient temperature and high discharge current significantly affect the available capacity of Li-ion batteries at runtime. One solution to handle this issue is to construct a hybrid energy storage (HES) system, taking advantage of the different performance characteristics of various Li-ion batteries. Conventional HES techniques often configure systems without considering the hardware overhead and capacity loss of batteries. Moreover, dynamic energy management in HES was not considered adequately due to severe power leakage. In this article, we propose DynLiB, a reconfigurable HES architecture that provides high energy availability in various runtime environments. DynLiB constructs HES with only two types of batteries, the main battery and the auxiliary battery, to reduce the operational cost of the hardware. The capacity of each battery is determined based on the application profile that characterizes the runtime factors. DynLiB supports energy transfer between batteries so that the available energy is maximized by dynamically transferring energy between the batteries, depending on the runtime environment. We implemented a prototype system to validate the efficacy of DynLiB. The experimental results showed that DynLiB achieved an average energy gain of 27.2% compared to a single-type battery system in various runtime environments.