Mark Trueman wrote:
Hi,

What is the best way to power a laptop from a car ciggy lighter socket.
The transformer for the laptop outputs 19volts, 3.16 amps.

The best way is a special power supply designed for your laptop.
The slightly less better way is to simply buy a 100W inverter, and plug
your laptop PSU into this.

What about powering a desktop printer. Is this possible or do i need a
generator.

It depends.
Laser printers can use up to a kilowatt of power, which isn't practical
for most inverters, certainly not the cigar lighter socket.

Inkjets mainly 20W or so, so could share the above inverter.
If using them at the same time often, I'd go up to 150W or so rating.

This will drain the car battery in about 3-5 hours, so a secondary
battery, or having the engine running may be a better option.