Laptop power - 12v converter to 240V or to 19v 4.2ma?

[Stemar]

Cheap mains inverters aren't usually pure sine wave and can upset some computers - maybe damage them, but I don't know enough to be sure.

 

[Refueler]

The cheap square wave inverters basically throw out the regulated power supplies ... they cannot regulate properly.

Its rare for it to affect the computer ... apart from not working !

Some mains power bricks for computers have a default that can mean leaving it for some time before plugging into a clean domestic supply. Not sure how it works - but my a couple of my Inspectors in the past had this ...
The 'power adaptor' would start then shut down with the cheap inverter. If they plugged straight away in mains - nothing. Wait 5 minutes and all worked fine in the mains again.

 

[PhillM]

Thanks everyone.

 

[EugeneR]

As stated above, a DC to DC converter will be the most efficient. It is less likely to have a noisy fan like an inverter, and less likely to pull too much amps that will make your supply trip.

Buy a reputable brand from a reputable source. I recently bought a new, "original" Dell 12v to laptop voltage converter off Ebay. It did look original but the plug was 1/2mm too big to go into the boat's 12v socket so ended up being useless.

 

[Ningaloo]

I have both inverter and a dedicated 12v cigarette lighter converter. The inverter appears to draw 2A with nothing plugged in, obviously more when things are plugged in.
The 12v converter is much more efficient. I got a no brand one off eBay. Usually comes with voltage selector and a range of different size plugs.
Like you I need to work whilst living aboard for the season.