Study of imbalanced internal resistance on drop voltage of LiFePO4 battery system connected in parallel

The purpose of this research focuses on the effect of imbalanced internal resistance for the drop voltage of LiFePO 4 18650 battery system connected in parallel. The battery pack has been assembled consist of two cell battery LiFePO 4 18650 that has difference combination of internal resistance. Battery pack was tested with 1/C constant current charging, 3,65V per group sel, 3,65V constant voltage charging, 5 minutes of rest time between charge and discharge process, 1/2C Constant current discharge until 2,2V, 26 cycle of measurement test, and 4320 minutes rest time after the last charge cycle. We can conclude that the difference combination of internal resistance on the battery pack seriously influence the drop voltage of a battery. Theoretical and experimental result show that the imbalance of internal resistance during cycling are mainly responsible for the drop voltage of LiFePO 4 parallel batteries. It is thus a good way to avoid drop voltage fade of parallel battery system by suppressing variations of internal resistance.