In uk.d-i-y Dave Fawthrop wrote:
On Sun, 14 May 2006 10:23:38 GMT, Lobster
wrote:

|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.
|
|Sounds good in theory, but are there any gotchas? Eg, safety? Does it
|run a car battery down more to power up a laptop via a 240V inverter
|than directly to the cigar lighter? etc etc

Yes! assume your invertor is 80% efficient.

|Can't help feeling an inverter would be much better if wired or plugged
|into the car some other way than via the god-awful universal
|cigar-lighter plug...

Be careful that there is enough charge available to start the car.

There are two sorts of invertor Modified sine wave output as below
snip
These are quite cheap but electronics do not like sharp edges anywhere near
them. You should *check* that they will work *your* laptop. I was warned
off using one of these with a TV Set Top Box by Bill Wright on
uk.tech.digital-tv

FWIW, I've never had a problem running any of ~12 power supplies on MSW
inverters, including laptops, scopes, ...

In practice, there is relatively little difference in stress between
proper sine waves, and MSW inverters.
The diodes typically get slightly hotter, but that's it.
(IME)