Here is one connector I don’t like and sometimes hate: The cigarette lighter receptacle in an automobile, initially designed to power an electrically heated cigarette lighter. It has became a de-facto standard DC connector to supply electrical power for portable accessories used in or near an automobile. It is commonly used as a means of powering other equipment in a vehicle, such as mobile phone chargers, CD players etc.
While the cigarette lighter receptacle is a common feature of automobiles, using these sockets as power connectors can lead to many problems. The basic design has the disadvantage of a poor contact stability: plugs can vibrate out of the socket under normal driving conditions, owing to poor retention. One reason it for problems is that this connector design is very old. In the United States cigar lighters started appearing as standard equipment in automobiles in 1925/26.
The cigar lighter outlet has even enjoyed some popularity outside of automobiles, such as boats, and even non-vehicular applications on AC adapters that convert to 12 volt DC. Note that the same connector is used on 12V systems in cars and 24V systems in lorries – this requires care not to damage the equipment!
The plugs and cord sets that insert into cigarette lighter receptacles are standardized in the United States by the “UL standard 2089″ and ANSI/SAE J563 specification. The center connection in connector is positive. The sprung ‘wings’ on the sides which hold the plug into the socket and the jack casing are negative.
In Europe, 12 volt plugs and sockets are not specially regulated and does not require approvals for CE mark. This leads to fact that there are plugs with incompatible sizes and even poorer retention than original (especially on many multi-outlet / extension cables). Equipment intended to be powered by the receptacle needs to account for intermittent contact, but many modern equipment do not take those without problems.
For car electronics DC powering there should be a better more reliable plug available in cars. Either a new locking mechanism option to the original design or some new standardized proper 12V connector to new cars. I am starting to be bored on playing with this nearly 100 years old crappy connector.
In some new cars USB standard 5-volt outlets are being offered in tandem with cigar lighter outlets in newer vehicles. USB connector will solve problems with smart phone charging and powering low power digital gadgets more reliably, but does not solve the powering of devices that need more power.