The tendency for NiCd batteries to lose the ability to hold maximum charge if they are recharged without being completely discharged. Some experts dispute whether memory effect is possible in “consumer”-level batteries, citing the following requirements:
- The exact same amount of discharge (+/-1%) each time
- Exact 100% recharge, without overcharging
- More than one volt per cell left in the battery before recharging
Some tests have shown that memory effect did not occur after hundreds of computer-controlled discharges and recharges. Other tests have shown that memory effect can occur after a few hundred discharges and recharges.
In many cases, other problems are mistaken for memory effect, such as rapid voltage drop after overcharging or simply the effects of the battery aging.
Memory effect has been shown to exist in specialized NiCd aerospace batteries, which are repeatedly discharged to precisely 25% then recharged to precisely 100% under computer control.