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The main objective of this article is determination of the charging and discharging efficiency of the Li-ion battery depending on the value of the charging and discharging current. An automated workplace allows us to measure the capacity of cells, temperature and other parameters required for assessing the performance of batteries. A dependence of the energy storage efficiency on the charging and discharging current was found out. Consequently this measured dependence was approximated with an analytical expression. The obtained analytical result can be used e.g. in predictive models of EVs action radius etc.

Deep discharging or over-charging of Li-ion cells must be avoided to ensure sufficient life-time and sometimes also the operation safety of these batteries. BMS circuits co-operating with the charger and forbidding deep discharging of the cells are necessarily present in battery packs. However, deep discharging can appear in a case of BMS failure or poor user care of the batteries. Then the battery can be discharged to zero voltage. Battery manufacturers do not allow such operation and battery behavior in this situation is not described in their datasheets. Experimental deep discharging was performed. After discharging, the battery was left in a fully discharged state (zero voltage) for various time intervals before it was fully recharged again. Consequently, capacity decrease or internal resistance increase was checked.

This article deals with the thermal calculation of a battery pack made up of 480 Li-Ion batteries. The used battery pack is based on using a phase-change material to achieve lower cells temperature and to increase safety when some battery is damaged. The calculation is performed as a transient thermal analysis using ANSYS software. The simulation results are verified by laboratory measurement on the made battery pack prototype.