Go Gentle into the Good Night via Controlled Battery Discharging

Abstract

Prevalent battery management approaches for mobile devices treated a battery's residual capacity as a given budget and tried to make the best of this budget by turning off lower-priority tasks. In contrast, the research reported in this paper aims to maximize the quantitative value of a battery's residual capacity by operating the battery according to its discharge characteristic curves (DCC), which describes a battery's discharging dynamics in terms of the correlation among its voltage level, capacity and discharging current. According to the DCC theory, it is possible to increase a battery's effective capacity in terms of Ampere hours by capping the discharging current in a certain way after its capacity falls below a threshold. This paper describes a DCC-based Battery Discharging (or DBD) technique that is capable of automatically deriving a battery's DCC, using the DCC to determine a suitable instantaneous discharge current budget, and limiting the total discharge current under that budget. Measurements on an operational prototype show that DBD is capable of extending a battery's residual capacity by more than 20% after its SOC is reduced to 30%.