Correct size fuse for laptop
 

Not sure what section to put this in...

I ran a wire from the battery to my cig lighter and my GPS worked great, but as soon as I plugged in my laptop it blew the inline fuse I put on as protection.

What size fuse should I be using so my laptop will work ok?

I would think the cig lighter would draw more than a laptop. Anyway I would think a 10A slow blow should be enough. What size is in there?

How are you plugging in the laptop? Direct DC or through a DC->AC inverter? 10A probably won't cut it for most modern laptops. You'll need 15-20A slow blow, especially if going through an inverter first as there will be additional losses.

The output from the power supply on my laptop with 16" screen and Intil Core 2 Duo is listed at 3.4a, I would expect a 10a to be plenty unless your computer has much more screen and power than this.

It is going through a power inverter. Its a brand new Sony Vaio CW27FX i5 /w GT 330M graphics card so its semi-power hungry.

I think it was a 10amp fuse...The wiring was already there (I assume somebody had a phone plugged in before I got the car) along with the fuse so I just extended it to my nonfunctional lighter.

I'll give a 15a fuse a shot.
Thanks guys

Inverters, depends a lot on the efficiency of the inverter as to the amp-draw, cheap ones are ineffient and have lousy output waveforms, your power supply will run HOT and might be damaged eventually.

Try staging them so that you don't get all of the inrush current at once: plug in the inverter, turn it on, plug in the power-supply & laptop, then turn it on.

I don't know what a separate fuse would be protecting, the cigarette lighter is already properly fused.

The wiring had no power hence why I just extended the wire that was already there. I didn't want to tear up the dash chasing the wire...
Either way I like the fact I get constant power instead of it cutting out when the key is off.

Playing games while driving, are we?:P