Car charger

[Tony Press]

Isn't there something about needing negative earth ?

[Andy Bennett]

Tony
If you use an insulated socket then it doesn't matter as you are just providing a 6v potential difference across the lighter socket. The earth of the socket then simply becomes -6V and in practical terms 0 to the sat nav, and the 'positive earth' of the A7 is providing a potential difference of +6V.
That's why you must use an insulated socket so that you don't put 6v positive from the A7 bodywork to the earth of the socket/sat nav.
As i noted, some have previously noted an initial voltage surge due to the lack of any voltage regulation which can damage the sat nav, but I have not experienced any problems in 10 years.
Andy

[Bob Culver]

I am now out of touch with such matters, but there is a huge amount of radio interfernce under the bonnet of completely unsuppressed cars. Dunno if any spikes find their way thru the bulkhead but a bypass capacito or shielded cable may reduce any spikes.

["Slack Alice" Simon]

Just put a capacitor across the terminals, as close as you can get it to the output socket.

This short circuits anything that isn't direct current - so cuts down the interference.

If you can use a capacitor that will do in (or just outside) the distributor - very good.   A neat way of carrying a spare.

I bought an indicator unit from a well known supplier, along with LED festoon bulbs.

They are lovely and bright, but wouldn't work properly until I put the capacitor across the unit as recommended in the instructions.

Simon

[Roland Alcock]

I use one of these from Amazon. It is insulated. 

Idealeben Dual Car Cigarette Lighter Socket Splitter 12V 24V Charger Power Adapter

£15. 

Roly

[AustinWood]

The socket I have was for use on boats. It's waterproof and has the facility to disengage the charger without removing it from the socket. It also has a cover for when it'd not in use.

[John Mason]

My socket is one for a motorcycle which allows you to mount it on a flat surface without cutting out the large whole in the dashboard. It is also waterproof..

John Mason