There are a lot of battery charger sizes because there are many variants. Some are used for cars, others for electronic gadgets and some for appliances. Some measure 2 x 3 x 5 inches, 3 x 5 x 6 inches and 2 x 2 x 5 inches.
These chargers are designed to energize a rechargeable battery or secondary cell. This is achieved by putting an electric current in it. The technology used determines the charge current. The capacity of the charger also has an effect on the current. That is why the current used on mobile phones are different from those used on car batteries.
These function by providing a pulsed DC or constant DC power source to the battery. This charger does change the output based on charge or time. These chargers are cheap, but the quality is inferior compared to the other types. If the battery is left too long in the unit, over-charging can occur. This may destroy the battery or the charger.
There are also many battery charger sizes available for these types. The current is 500–1,500 mA, which is low. These are used for batteries with a capacity of 2–30 Ah. But they can also be used for batteries with capacities of over 30 Ah.
These are the types used on boats, cars, RVs and other vehicles. The charger can be left joined to the battery for a long time. Depending on the technology, it may be left on for an indefinite period.
With this device, the output ends after a specified time period. These devices were widely used in the 1990s for high-capacity Ni-Cd cells. Usually this charger can be purchased with batteries as well. If lower capacity batteries were utilized, they would be over-charged.
This charger is a device that can react to a battery’s condition and change its charging mode if needed. Many of these chargers are made to work with smart batteries. Smart batteries often have a chip that allows it to communicate with a smart charger. But some smart chargers can work with non-smart types.
The battery charger sizes are not indicative of their capability. You can also take some steps to prolong the life of your battery. For instance, the NiCd types only have to be charged fully every now and then. The lithium-ion based batteries last longer if they are charged as often as possible.