In uk.d-i-y aussie bongo wrote:

"Lobster" wrote in message
...
I'm thinking of buying an 12V - 240V for the car, to enable me to
charge/run devices such as a laptop / mobile phone(s) / AA batteries for
gameboys & camera etc etc while on the road (one at a time!); they seem to
be as cheap as chips these days and this would enable me to use the
standard mains chargers for all the above devices rather than buying
separate low voltage kit to connect each of them up to the cigar lighter.
snip
i dont know about power usage on a laptop, but,
i do know that 100w drawn from an inverter at 240v, will give you less than
1/2hours usage.

YLMV.

And 100W can never give any meaningful amount of run time without
specifying how long.

My laptop - admittedly a subnote - uses about 40W when charging, and
about 15W running normally.

This runs on a standard car battery for around a day, from an inverter.