Choosing A Charger
Broadly speaking there are three types of charger on the market: basic (cheap) chargers, smart chargers and fast chargers. The first type is best avoided altogether as they are often cheaply produced and feed a continuous current as long as they are switched on, which can lead to overcharging and damaged batteries. In addition, cheap chargers generally have no way of automatically shutting down should there be a problem, which can make them inherently dangerous.
Smart chargers will cost you a little more money but are well worth the extra expenditure. These types of chargers will monitor your batteries as they are charging and will automatically shut down once the battery has reached its optimum charge, or of there is a problem. In addition, some smart chargers can automatically drain partially charged batteries before fully charging them in order to preserve their longevity. The main downside with smart chargers is that they tend to be slow, which means you may well have to organise yourself and charge your batteries overnight.
If your primary need is speed then a fast charger might be your best bet. These typically charge suitable batteries in around an hour to an hour and a half. The main issue with fast chargers though is that the batteries can get very, very hot while charging. For this reason avoid any fast chargers that don't have a cooling fan built in, or which don't have any protection circuits should something go wrong. Last but not least, also be aware that fast chargers shorten the life of your batteries much more so than smart chargers do.