The Battery effect, lazy battery effect, memory effect or battery memory can occur when an accumulator is incompletely discharged very often. The frequent partial discharging of the accumulator causes an earlier voltage drop, which reduces the capacity of the accumulator. The accumulator seems to "remember" the required amount of energy and over time only covers the previously required energy demand.
Modern accumulators (e.g. lithium accumulators) no longer reproduce this effect to such an extent. It is no longer necessary to fully discharge the battery before each charging process, but it is still advisable to perform a full discharge at regular intervals (e.g. every 50 charging cycles). Then it is quite possible that the battery life can even be increased by frequent partial discharging.