Online cellphone battery entropy measurement for SoH estimation

The widespread use of batteries requires knowledge of their state of health (SoH). In this paper we present a method to use entropy evolution as an aging indicator for batteries. Voltage, current and temperature are monitored in battery cells used in cellphones and in real-time operation. Irreversible entropy is estimated from irreversible energy dissipation in the battery for long periods of use. Simple open circuit battery voltage U
_ocv
models were evaluated and compared to lab measured U
_ocv
. It was found that the entropy generation rate is always increasing during battery operation and that irreversible entropy is a fingerprint of aging for batteries.