[1][2] It describes the situation in which nickel-cadmium batteries gradually lose their maximum energy capacity if they are repeatedly recharged after being only partially discharged.
[4] This long-term, repetitive cycle régime, with no provision for overcharge, resulted in a loss of capacity beyond the 25% discharge point.
In a follow-up program, 20-ampere-hour aerospace-type cells were used on a similar test régime; memory effects were observed after a few hundred cycles.
[5] Phenomena which are not true memory effects may also occur in battery types other than sintered-plate nickel-cadmium cells.
In particular, lithium-based cells, not normally subject to the memory effect, may change their voltage levels so that a virtual decrease of capacity may be perceived by the battery control system.
[citation needed] These can clog the plates, increasing resistance and lowering the voltage of some individual cells in the battery.
Nickel–metal hydride batteries, for example, are known to experience this form of capacity loss [citation needed] often mistakenly attributed to memory effect.
To prevent overdischarge, battery should be brought back to room temperature and recharged to 50% SoC once every six months or once per year.