Re: fitting additional cigarette socket
Replace the fuse with a multimeter and see what current draw you have on the "unused" fuse. Only thing you may have a problem with is if it goes above 10amps as most handheld meters on DC don't go much higher. However in reply to the how much power does a phone charger use question I can state "bugger all". Most phone chargers work at 5volts at 500mA that equals 5 times 0.500 which equals 2.5watts. If you divide 2.5 watts by 12 volts you get 0.208 amps assuming no losses. IIRC the standard batteries are rated at 70Ah so you'll get 336 hours of charge ie 14 days doing nothing but charging your phone!
The point of a fuse is to protect the wiring and devices connected, ie you don't have 2.5mm wire and a 100Amp fuse as the wire is only good for about 32 amps! This is what protects against electrical fires, if all you want to do is a feed to a phone charger use 1mm wire and fuse it with a 5 amp fuse. That equates to 60 watts at 12 volts. If you use good quality wire 1mm is good for 18 amps and a 15 amp fuse.
Last edited by rhett71; 24-05-09 at 22:58.