Effects of periodically changing load on Li-ion battery cells

Abstract

The aim of our research is to identify the effect of periodically changing load on the available capacity and state-of- health of a selected battery cell. In this paper the discharge current changed between 1C and 2C, so the profile was created by the switch of the load. Two different measurements were performed, with both periodically changing resistance and current. For comparison a reference cell was also measured with constant resistance and discharging current. In case of the constant current it was 1C while the constant resistance was calculated so that the current of the cell was around 1C. The effects of the ambient temperature were the same to both cells, and to obtain more information on the behavior of measured cells, it was recorded as well. During the measurement, effects of four different switching frequencies were examined on the available capacity and state-of-health. Altogether ten measurements were performed in case of each switching frequency, each of them preceded by a reference measurement with 1C discharge to compare the capacity change of the reference and measured cell. As the discharge capacity is affected by the charging current both cells were charged in the same way with 1C constant current-constant voltage method.