> >         Well a PC needs four voltages, +5 at around 10-12 amps,
> +12 at 5-7 amps, -5
> > at under an amp, and -12 at under around 500ma, (please note, these
> > amperages vary greatly, and are just guesses really).
>
> but does this also hold for the screen/monitor?

        I suppose it depends on the monitor, never actually opened one and noted
what the voltages present in it were.

>
> > For a 12V car battery,
> > +5 and +12 are easy, you've already got that, it's the -5 and
> -12 which is a
> > problem.
>
> You may take a second battery and put the ground to the other outlet, to
> get the negative potentials.

        Yes that would work quite well, but you would need a second battery which
might be a problem, I don't know.