Lighter The lighter is a metal or plastic cylinder containing a thin flat coil of
nichrome metal strip, through which high current (≈10
amperes) passes when the device is activated, usually by pushing it into the socket as though it were a
push-button. When pushed in, the lighter is held against the force of a spring by a clip attached to a
bimetallic strip. The
heating element glows orange hot in seconds, causing the bimetallic strip to bend and release the mechanism. The handle pops out, eliminating the need for the user to time the heating operation. If the lighter is then promptly removed from its socket, it can light a cigarette, cigar, or
tinder. A common feature of Italian cars in the 1960s to the 1970s, such as Alfa Romeos and Ferraris, is the Brico Pram cigarette lighter, which differs from conventional designs in that the lighter does not pop out for removal to light a cigarette, even though it visually resembles the traditional design. Instead, the center of the lighter features a tapered opening for the user to insert a cigarette until it touches the heating element, the rim of the handle is then pressed down to activate the lighter, the heating element then lights the cigarette and disengages the circuit with an audible ping once the desired temperature is reached as per a conventional lighter. The advantage of such a design is in safety as the red-hot heating element cannot be accidentally dropped onto an occupant's lap. Still, it takes away the ability for the lighter to be removed for the receptacle to be used as a power outlet, and it also does not allow cigars to be lit as the opening is not large enough.
Electrical outlet designed for use with auxiliary power outlets In newer cars, the socket is equipped with a plastic cover without the lighter heating element. However, the socket has been repurposed and continues to be used to power
consumer electronics in vehicles. Often, a vehicle may come with several outlets for convenience, some in the rear passenger area of the vehicle or the cargo area, for powering portable devices. These outlets usually have a plastic cap tethered to them, and are usually labeled as being only for DC power, because they are not intended to withstand the heat produced by an electrical cigarette lighter. The use of cigarette lighter receptacles to supply 12 volt DC power is an example of
backward compatibility to a
de facto standard. As a power connector, the lighter receptacle is larger, harder to use and less reliable than other DC connectors. There are two prong threaded plugs to stop the plug from falling out due to vibrations. Cigarette lighter receptacles are in widespread use in many highway vehicles and some boats. Portable cigarette lighter receptacles attached to cables and
alligator clips for connection directly to
car batteries are available for temporary use. In newer vehicles, one or more
USB connectors may also be provided. Plus in newer cars, the power output from the lighter plug is so reliable that it can charge laptops, without any voltage problems. Standardized 12 volt DC automobile plugs are defined in the United States by
UL Standard 2089 regarding vehicle battery adapters. This standard covers plugs and cord sets that insert into cigarette lighter receptacles. In Europe, 12 volt plugs and sockets are not specially regulated and do not require approvals for the
CE mark. The male plug is sometimes used to feed power
into a vehicle to recharge its battery because it usually has no regulatory circuitry between the outlet and the car battery. For instance, portable solar battery maintainers generally connect to a vehicle's battery in this manner.
Trickle chargers also sometimes connect in this way, eliminating the need to leave a vehicle's hood open, as well as eliminating the possibility of reversed polarity. Most cars nowadays are designed with a battery-negative earthing system and therefore have a +12V positive power distribution. In such a case, the centre pin of a plug/socket will be +12V DC and the outer casing 0V. While polarity is not an issue for a cigarette lighter, it is prudent to verify the correct matching of polarities when connecting other kinds of accessories. In some car models, when the ignition key is removed, the cigarette lighter outlet is not powered and charging is not possible, though modification of the fuse box may allow unlocking continuous power output, by establishing a
parallel circuit from a continuously powered fuse slot through a "piggyback" connector. Since the cigarette lighter socket was originally designed only to heat a cigarette lighter, repurposing these sockets as generic power connectors can lead to many problems. In addition to the issues with partially-compatible physical dimensions, the plugs can vibrate out of the socket under normal driving conditions, owing to poor retention. Also, there have been reports of melted plug tips due to poor contact and heat generation from
ohmic resistance. A second problem is that nominally "twelve-volt" power in cars fluctuates widely. The outlet is connected directly to the electrical system of the car. The actual voltage, matching the car battery's voltage, will be approximately 12.5 volts when dormant (less in cold conditions), approximately 14.5 volts when the engine and the alternator/generator are operating (more when cold), and may briefly drop as low as 5–6 volts during engine start due to the high temporary battery current usage. When used,
DC to DC converters will usually compensate for small fluctuations, but reliable power may not be available without an independent battery-powered
uninterruptible power supply. Rarely, more extreme cases of voltage fluctuation can occur when the car battery is disconnected while the engine is running, or when the car receives a
jump start. When the battery is disconnected while the engine is running, its voltage smoothing effect (similar to
capacitors) is unavailable and a
load dump transient can produce very high voltages as the built-in
voltage regulator has been controlling the alternator
field current to charge the vehicle battery and although it will attempt to reduce the field current to keep the output voltage constant, the field winding is highly inductive and setting the current to its new value takes several hundred milliseconds, during which the alternator output voltage will exceed its intended value. The load dump transient may also ruin the
diodes in the
alternator by exceeding their breakdown voltage. A car receiving a jump start from a truck may be subject to a 24 V electrical system used in some vehicles. Also, a "double battery jump-start" is performed by some tow truck drivers in cold climates. Equipment intended to be powered by the receptacle needs to account for intermittent contact, and voltages outside the nominal , such as maximum voltage continuously, or maximum voltage of lasting , lasting , and lasting . An example of protection component ratings tolerance is to . Robust equipment must tolerate temperatures varying between , plus possible high humidity and condensation of water. == See also ==