There are three specific types of battery chargers: a slow charger, rapid charger and fast charger. Slow chargers are generally used for car batteries and slowly induce a charge over the course of 16 hours, while rapid and fast chargers often lessen the charging time by half or more.
A slow charger is the most common type, used on basic toys or smaller electrical devices. These models of chargers are less likely to cause any types of overcharging to occur, but generally do not have a stop point. This means that the charger will continue to work as long as the battery remains connected.
A rapid charger is a lot faster when compared to a slow charger and is also used to charge smaller electronics. However, one stark difference from a slow and rapid charger is the temperature sensor that turns it off when a battery is completely charged.
The fast charger is usually considered the best of the bunch. Incorporating faster charging times, with a lesser chance of overcharging a battery, these units are most commonly used with Li-Ion batteries. A complete charge generally takes under two hours and once the battery is at full power, the charger will switch to a trickle charge mechanism in order to prevent it from overcharging.