Choosing the right charger is important. The three basic types of chargers are trickle, timer, and smart chargers. Trickle chargers give batteries a constant low charge, they're compact and inexpensive. Timer based chargers are the next step up, as they are faster; however, they will turn off after set amount of time whether or not batteries are fully charged. Smart chargers are the best type: they detect when cells are fully charged and will automatically switch to trickle mode. Universal chargers can charge AA, AAA, C, D and 9V batteries; universal chargers can be smart or timer based. The chargers below represent a variety of charger types for multiple applications and battery sizes.