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I had another frustrating experience with technology yesterday. I had recently bought a Coleman Powermate PMB8110 Emergency Car Starter rechargable battery pack, which has a cigar lighter plug and socket, and built-in recharging circuitry. I intend to use it for ham radio work, but plugging a cord into it proved difficult—and removing it almost impossible. I purchased both the Powermate and the cigarette lighter plug at Radio Shack, so you’d think they should work together, right?

Wrong. The Coleman device seems to have a socket that doesn’t conform to the conventions used for cigarette lighter sockets. And yes, I mean conventions, not standards. Since this type of socket was never intended as an electrical connection, nobody ever produced a specification for the geometry of the connections. This is why not all plugs fit all sockets. There are apparently two common sizes of sockets (21.0mm and 22.2mm), however, and the Powermate’s is just 20.5mm—too narrow by 0.5mm—just enough to let me insert the larger Radio Shack plug, but not quite enough to get it out without a sweat.

So why do manufacturers still use these horrid connectors? They don’t even carry DC power well. I think it is high-time for the automotive, computer, and personal electronics industries to agree on a better standard—preferably one that is genderless, so that connections can be made without adapters.

Here are a few standard DC connectors that are better than the cigar lighter interface:

Andersen PowerPole
Used by the ham radio community. There is no concrete standard for polarity, but they are genderless and can handle 30 amps.
Jastek Powerlet
Used on BMW motorcycles, John Deere equipment, and some Unimogs.
EmPower (ARINC 628) airline in-seat-power connector
Used by most airlines to provide power for laptops and DVD players. American Airlines, however, uses one of the two sizes of cigarette lighter sockets. 15 volts DC at up to 8 amps (though airlines typically limit this to 75W, and the FAA limits it to 100W). (General Dynamics Advanced Information Systems)

Author: Peter Sheerin

Peter Sheerin is best known for the decade he spent as the Technical Editor of CADENCE magazine, where he was the acknowledged expert in Computer-Aided Design hardware and software. He has a long-standing passion for improving usability of software, hardware, and everyday objects that is always interwoven in his articles. Peter is available for freelance technical writing and product reviews, and is exploring career opportunities in interaction design. His pet personal project is exploring the best ways to harmonize visual, tactile, and audible symbols for improving the effectiveness of alerting systems.

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