Technical Details
The sockets and mating plugs are defined in the ANSI/SAE J563 specification. For the 12 volt systems, the "contact point", which is the center part of the plug when viewed end-on, carries the positive voltage, whereas the "can" part, which is the outer part of the connector, carries the negative voltage (which is the "ground" connection for most automobiles, which have a negative ground electrical system).
12 volt auto connectors are made to comply with a standard by Underwriters Laboratories for safety. UL2089 was developed to cover the requirements for portable adapters rated 24 V DC or less that are intended to be supplied from the battery powered electrical system of a vehicle. Products covered by the standard include cord assemblies of a plug that mates with the standard cigarette receptacle found in automobiles.
- 6-volt cigar lighter receptacle and plug
- Receptacle inside diameter: 21.34 - 21.46 mm (median 21.4 mm)
- Plug body diameter: 21.08 - 21.23 mm (median 21.155 mm)
- 12-volt cigar lighter receptacle and plug, size A
- Receptacle inside diameter: 20.93 - 21.01 mm (median 20.97 mm)
- Plug body diameter: 20.73 - 20.88 mm (median 20.805 mm)
- Most often used in American automobiles.
- 12-volt cigar lighter receptacle and plug, size B
- Receptacle inside diameter: 21.41 - 21.51 mm (median 21.455 mm)
- Plug body diameter: 21.13 - 21.33 mm (median 21.18 mm)
- Most often used in European automobiles, and sometimes as a second socket in American automobiles expressly for DC power connections.
Plugs often include a pilot light to indicate a connection has been made.
Read more about this topic: Cigarette Lighter Receptacle, Use As An Electrical Outlet
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