Some 12V compressors are equipped with alligator clips, allowing direct connection to a car battery.
There are several different types of portable air compressors, some of which are designed to run on 12-volt direct current (DC). These devices are primarily designed to inflate low-pressure objects such as sports balls and air mattresses, although many are also capable of inflating car tires. Unlike most air compressors, these units typically lack any type of pressurized container to store compressed air. Instead, a 12V compressor typically pumps air directly onto an object. These compressors are typically less powerful than portable alternating current (AC) powered units, though the fact that they can run on 12-volt electrical systems found in cars and boats often makes them more useful when traveling.
Air compressors are devices that use various methods to pressurize air. Most air compressors pump air into some type of sealed container to pressurize it, although others are capable of pumping air directly into an inflatable object. The 12V compressor is a prominent example as most of these devices do not have any type of pressurized vessel. A motor inside the 12V compressor sucks in air and pumps it directly onto an object. This can limit the effectiveness of some pumps, as car tires and similar objects often require a large volume of air to reach the required pressure.
Compressors that have tanks only need to run until the pressure vessel is full. The engine will automatically start when the pressure drops below a certain level. As 12V compressors do not normally have any kind of reservoir, they must run continuously. This makes it important to turn them off from time to time during use, especially when inflating large volume items such as car tires. Long-term use without interruption can burn out a 12V compressor motor, which is why most manufacturers set a time limit for continuous operation.
Aside from not having a pressure vessel to store compressed air, the other big difference between a 12v compressor and other portable units is the power supply. Most compressors run on AC power, while 12V compressors are designed to work with the 12V DC systems found in most automotive and marine electrical systems. These units usually come equipped with plugs that are designed to plug into cigarette lighter sockets, although others have alligator clips that can be plugged directly into a car battery. This can make these units very useful on the road, allowing them to inflate tires and other inflatables in situations where AC power is not available.