All batteries have limited life span.
A battery's life span is measured by the number of charging and draining cycles it can undergo before it can no longer be charged. The amount of time that your system can be operated by battery power before the battery is drained is referred to as battery run time . Memory Effect A NiMH battery in poor condition may begin to exhibit characteristics of memory effect . Memory effect will occur when a user does not allow the battery to fully drain before charging it again. As a result, during the charging process, the declining battery will only receive a portion of its charge capacity.