Li-Ion Battery Deep Discharge Degradation

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.