Muistiefektistä

Muistiefektistä, often translated as the "memory effect" or sometimes "ghost effect," refers to a phenomenon observed in certain types of rechargeable batteries, most notably Nickel-Cadmium (NiCd) and to a lesser extent Nickel-Metal Hydride (NiMH) batteries. It describes a situation where a battery that has been repeatedly partially discharged and then recharged can "remember" its previous discharge level. Consequently, when this partially discharged battery is then fully discharged, it may behave as if its capacity has been reduced, stopping at the remembered discharge point instead of reaching its true minimum voltage.

This effect is primarily a result of the formation of large crystalline structures within the battery's electrodes. During repeated partial discharge and recharge cycles, these crystals can grow, impeding the normal electrochemical reactions required for full capacity. When the battery is then discharged, the voltage drops prematurely as the battery reaches the limit imposed by these larger, less reactive crystals, leading to the perception of reduced capacity.

The memory effect is significantly less prevalent in modern Lithium-ion batteries, which are the dominant rechargeable battery technology today. These batteries do not exhibit the same crystalline growth issues and are generally more resistant to capacity degradation from partial cycling. For NiCd and NiMH batteries, the best way to mitigate the memory effect is to perform a full discharge and recharge cycle periodically, a process sometimes referred to as "conditioning" the battery.