There are several different designs of car battery charger on the market. This article gives an overview of some of them.

The majority of car battery chargers connect to the mains electricity supply, and trickle charge (charge at a slow rate using low current) the battery. The current output of this type of charger is usually quite low, frequently up to around 2 Amps. Trickle chargers need to be hooked up and charging the battery for quite a long time, from several hours to days depending on the state of the battery. An advantage of these chargers is that they don't create a lot of heat inside the battery, and are therefore less likely to cause damage to it.

'Fast charger' designs will charge a flat battery in a short period of time. These chargers have a current output of up to several hundred amps, at this setting they can charge a flat battery in less than one hour. These rapid chargers may give rise to big temperature increases inside the battery, and should only be operated by professional mechanics.

The majority of chargers which the public can buy give an output of between 2 and 10 Amps at 12 volts. The charger Amp setting is often able to be varied depending on the charge required.

Another type of charger is the car-to-car charger. This connects the 12v socket of one car to the 12v socket of another car. This allows the car with the dead battery to be started. The principle is similar to jump-starting using jump leads.

A common design of charger is the trickle charger. These are cheap to buy and unlikely to damage the car battery. Most of these have a transformer that is plugged into a mains electricity supply, plus two leads which are connected to the battery. Trickle charging is a slow process, and it may take a few days to completely recharge a dead battery. A different design of trickle charger is the solar car battery charger. These have a built-in solar panel that trickle charges the car battery via the car's 12v socket located in the dashboard.

Some portable car battery chargers are charged by mains supply, then they can be stored in the car until required. This type of charger only needs an electricity supply for charging the onboard battery. Once charged, the charger can be connected to the dead car battery to bring it back to life.