12 volt

An automobile auxiliary power outlet (also known as car cigarette lighter or auxiliary power outlet) in an automobile was initially designed to power an electrically heated cigarette lighter, but became a de facto standard DC connector to supply electrical power for portable accessories used in or near an automobile directly from the vehicle's electrical system. Such include mobile phone chargers, cooling fans, portable fridges, electric air pumps, and power inverters.
In most vehicles, at least one car outlet is present. Some vehicles may have more power outlets: usually one for the front passengers, one for the rear passengers and one for the luggage trunk.
The voltage of the power outlet is usually near 12 V DC, and may be elevated between 13.5 V to 15 V while the engine is running.
The 12 V power circuit is protected by a car fuse, often rated at 10 to 20 amperes, which provides 120 to 240 watts of power. Large appliances such as hair dryers or toasters draw too much power to be fed from an auxiliary power socket. If wired directly rather than through the ignition, an empty car battery can be charged through the outlet from an external power source, which is more convenient albeit slower than currents supported through electrical clamps on the car battery.

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