Nickel Cadmium (ni-cad)
Warning! Charging batteries without due care can cause the battery to swell and even explode. The information presented here is basic and should only be used as a rough guide in combination with other sources. When in doubt, set your charge rates low and increase only through successful experience.
The original consumer rechargeable battery, nicad has largely been replaced in the home by its more powerful and efficient cousin nimh. Nicad batteries do have some interesting characteristics though that give them some unique advantages. The most prominent is their extremely high discharge rate abilities. You can also charge them at faster speeds (depending on the model) than other types. This make them very useful in battery power tools. They can be quickly recharged and used again in a short span, while possessing the raw power needed in such tools. More recently thoughli-ion batteries have improved enough to leverage their high energy density to become the battery of choice in battery power tools.
Refer to the nimh as charging is very similar.
Very bad for self-discharge compared to other chemistries. You can use a trickle charge equal to the self-discharge rate to keep the batteries ready to go. Beware of the memory effect in these batteries. This phenomina occurs when the battery is constantly discharged to the same level. It causes the battery to 'remember' that level and capacity beyond it is reduced. The most common avoidance tactic is to ensure the battery is always fully discharged prior to charging.