Thread: 90W car adaptor connected to Cig Lighter

The fuse will limit the current to the cigarette lighter to a safe level. If you are pulling too much, the fuse will simply blow. The fuse on you cigarette lighter circuit is 15 amps. To figure the amount of watts:

14 volts * 15 amps = 210 watts

So you can probably pull about 200 watts at the maximum.

A mac mini pulls about 30 watts at a reasonable load. If we guess your 19v dc adapter is 60% effiecient (conservative):

30 watts / .6 = 50 watts

The average 7" lcd screen uses around 10 watts.

50 watts (mac mini) + 10 watts (LCD) = approx. 60 watts.

I think you should be OK hooking up to cigarette lighter. If it were me though, to be on the safe side I would put a lesser fuse in, perhaps a 10amp, to give me an early warning that I was running a little bit close to the limit.

Peace.