Ciggy lighter

Seconded, it's not that hard to find or even run a heavy wire from the battery through a dedicated fuse straight to your appliance.

You '70w' hair straighteners may average 70w but may well take way over that at startup.

I was running a small PC setup off a 2KW petrol generator once, no problems at all. Then we turned the laser printer on - stalled it. Tried again and it ran, but every 30 seconds or so the printer gave another pulse to it's heater wire and the genny coughed and stuttered briefly every time.

Depends how long you're stood idle & what you're doing. From experience, don't try comissioning Mac esterior lanterns that way as the battery life drops from 2 hours to 15 minutes with the supplied USB device & software. Which seems bizarre & may mean I need a new battery, but the Scorpio suffered the same fate.

Given the price of inverters & the price of laptops & given mine eats

I can't see why I need to bother with that. I've been successfully running a 150W inverter from lighter sockets regularly for about 6 years in multiple vehicles.

John

A Scorpio I'd guess has a 70 amp/hour battery or thereabouts. To flatten it in ten minutes means theoretically drawing about 400 amps, but in practice anyway far more than a cigar lighter and wiring could do without burning out.

Because large current draw items should not be run through temporary connections - there can be problems with heat generation from bad electrical contacts, wear an tear etc. Not a problem on a low-draw appliance as it will not cause a fire if shorted or poorly contacted. A higher draw appliance may cause excessive heating even way before the fuse blows. I've actually had a set of fog lights wired through a 15A fuse set fire to the front of my car when the temporary connector arc'd

- fuse never blew but the heat generated was enough to ignite the paint on the bumper, cable seemed fine.

Thing is its *probably* fine but to be safest you'd want it properly wired in. The whole point of the OPs question was why dont they provide high-draw sockets as standard - its because high draw appliances are safest when run through their own fused and properly switched live. Adding that to a car could cost upward of =A32 per car. =A32 on a car that sells 1 million is =A32million. We all know the story of the guy for ford who saved them something stupid like 2p per car and got a massive bonux. The guy who suggests a =A32 expense would be fired :-)

But a 150w inverter is not a high draw appliance IMO.

Assuming it was new & fully charged you'd be right. But given the age & the usage it wasn't, & to be fair it lasted just over an hour. The bit I don't understand is how the usb port can guzzle that much power. Fortunately the genny in the boot solved the problem.

Ok if the engine isn't running, but I wouldn't like to directly expose an expensive laptop to the noisy environment of a running car's electrical system ;)

Lee