The memory effect
occurs at the negative electrode (cadmium) of NiCd batteries
. It can appear under the following conditions of application: in case of frequent partial discharges parts of the electrode substance remain "unused", and as a consequence a crystalline formation appears which makes future discharges of the affected electrode substance very difficult, even blocking it in an extreme case. If the effect is not too pronounced, the process can be reversed by several complete charge and discharge cycles with a processor-controlled fast charger
. In the final state, however, a total capacity loss is suffered. Complete discharge-charge cycles
are still the most reliable protection against the memory effect.