... Most cigarette lighters circuits have a 15 to 20 amp fuse on
them. That ought to work fine for charging/using with your computer ...
That amount of current can/will destroy sensitive electronic devices. (20A??? That's more than what an Icom IC-706MKIIG uses at 100W TX power ... )
Personally, I would never run my laptop off a vehicle's charging system while the vehicle is running. You won't find many reputable laptop manufacturers recommending this.
And all power feeds to my radio gear are properly conditioned and filtered.
If I needed to run my laptop for extended periods on a 12VDC system, I would use nothing less than a ...
Tripp Lite PVINT375 (although this model comes with a cigarette lighter plug, that connection has to be one of the electrically most UNreliable for what we are doing - so the plug gets whacked off and the unit is wired directly) ... or
Astron Pi-250W 12VDC-to-120VAC inverter made for such circumstances. Wire it in to your vehicle's 12VDC system, and simply use your existing AC power supply. Immediate benefit is the ability to power/ charge other electronic items you may have using regular AC chargers.
There's no need to know the voltage/current/connectors of the laptop. The laptop's manufacturer already did all that work for you when they supplied the AC adapter.
Another downfall of using the cig lighter circuit for comms: very rarely is that line filtered for noise and such. I mean, who needs that line filtered to heat up a cig lighter? More intelligent cars do have filtered/conditioned "power ports." But I do not leave anything to chance, and make sure my equipment is properly protected.
Then there are folks who run their 100W HF rigs through a cig lighter plug and swear that all's well with the world ...
And so it goes.
Clint Bradford, K6LCS http://www.clintbradford.com 909-241-7666