Automatic battery conditioning
NiMH batteries perform best when they are conditioned through a discharge/charge cycle. Many chargers do this automatically. On some smart chargers you simply press a button for the conditioning to begin.
Charge batteries in a couple of hours. If the batteries and charger are specifically designed for quick charging, battery life should not be prematurely reduced.
Dual charging units
Charge two different sets of batteries simultaneously; eg: NiMH AA and NiHM AAA.
World voltage capable
Some chargers have a built-in 100~240V 50/60 Hz power supply. They can be used in other countries with a only an electric plug adapter.
Battery charger plugs
Transformer – Battery chargers with transformers can be less expensive than others, but are not convenient if you want to carry the charger in your camera bag.
Fold in – Plugs fold into the charger when not in use. They are compact and easy to pack in a camera bag. If you use this type of charger, check the instructions. Some must be removed from the outlet once batteries are fully charged.