Effects of Charging Lithium-Ion Cells with Zero Termination Current on the State of Health (SoH) for Energy Storage Systems

Abstract

Lithium-ion (Li-Ion) cells have their own charging method, which is known as Constant Current-Constant Voltage charging method. In this method, all Li-Ion cells are charged by the constant current; after the cells reached the pre-defined charge cell voltage, the constant voltage period begins and lasts until the cells' current drawing is under the current level specified in the datasheet. Nowadays, a battery management system (BMS) controls this charging method for Li-Ion cells. In addition to this, BMS ensures that all Li-Ion cells in the battery pack work in a safe operating area. However, in an energy storage system (ESS), the DC bus bar system is used because there may be different current sources such as solar, wind, etc. As a result of this, there will be a continuous current flow over this DC bus system. Therefore, it will be possible to charge the Li-Ion cells with a value below the charge termination current or with zero charge termination current. In this paper, the effect of applying different charge termination currents to the Li-Ion cells on state of health (SOH) is investigated. We present results about how effect the changes both in charge voltages and charge termination current the life of the cell. As a result of this research, it is aimed to prepare a document that can be used by researchers who want to find information on this subject by presenting the data on the SoH with visuals and graphics.