The 12V socket, also known variously as a car cigarette lighter or 12V auxiliary power outlet, is the primary method by which power is delivered to portable electronics in cars, trucks, boats, and a handful of other contexts. While these sockets were originally designed to heat up cigarette lighters, they quickly gained popularity as a de facto automotive electrical outlet.

Today, it is possible to power anything from a cutting edge phone or tablet computer to a tire compressor with the same exact socket that was once used only as a car cigarette lighter.

Some vehicles come with multiple sockets for the express purpose of powering multiple accessory devices, although it is uncommon for more than one to be capable of accepting a cigarette lighter. Accordingly, the specifications for these power sockets that are contained in ANSI/SAE J563 include two variants: one that works with cigarette lighters and one that doesn’t.

The History of Automotive Accessory Power

When the first automobiles hit the road, the idea of an automotive electrical system didn't exist yet. In fact, the first cars didn’t even include electrical systems of any kind. Since they used magnetos to provide a spark, just like your lawnmower does today, and lighting (if any was included at all) was provided by either gas or kerosene lamps, an electrical system simply wasn’t required.

The first automotive electrical systems made use of DC generators, which (unlike modern alternators) didn’t require any voltage input to operate.

These generators were belt-driven (just like modern alternators), and they provided the necessary DC power to run accessories like lights. With the addition of lead acid batteries, it suddenly became possible to add other “accessories” that we take for granted today — like electric starter motors.

Although early electrical systems that included both a DC generator and a lead acid battery technically made electrical accessories possible, the widely variable voltage produced by these generators created issues.

Mechanical devices were used to regulate the voltage, but automotive electrical systems didn’t arrive in the modern era until the introduction of alternators.