a 100 Watt system draws a little less than 1 Amp
at 120 VAC and about 8 Amps at 12VDC. there's about
10 times power loss per foot of conductor and per
connection (estimate 1/2 Ohm per connection). Yes,
heavier guage wire is required for a lower voltage
supplying the same power.
for that reason, systems using 12VDC must require
very little power. Via's latest motherboards include
some that draw 20 or 30 Watts and yet have pretty
good processing capabilities. SATA solid state drives
and USB pendrives draw very little power. there are
systems advertised drawing less than 10 Watts (e.g.
gumstix). the XO laptop (OLPC) is a good example of a
fairly powerful computer that requires very little
Wattage.
efficient software design--good algorithms and
small memory footprint--improve benchmark performance
at the feature level. software that must comply with
legacy requirements is at a disadvantage in such
systems. and such systems look to be increasingly
needed, given the increasing green requirements world
wide, not to mention the spotty power availability of
many of the world's remote regions.
i believe manufacturers will be delivering systems
that require less and less power in the near future,
and more and more of them will be battery powered,
not only at 12VDC but with AA and C cell batteries
(e.g. cellphones and PIM devices).
as 12VDC is ubiquitous, we should see more and more
systems designed to work off a cigarette lighter.
they exist today.
On Fri, 2008-04-11 at 21:28 -0700, John R Pierce wrote:
> jim wrote:
> > 12VDC is appropriate for places that don't have
> > other electrical supplies. these places include
> > automobiles and boats as well as remote regions
> > that use windmills, creekmills, solar panels,
> > car batteries, and deep discharge gel batteries,
> > possibly in a mix. typically there's noise and
> > variant voltage levels above the nominal 12VDC;
> > any system should be designed to work with spikes,
> > noise, and higher voltages--most are as a matter
> > of course.
> >
>
> and, of course, you need 10 times the amperage at 12V... For instance, a
> 250 watt system that would draw about 2 amps at 120V will be drawing 20
> amps at 12V. this means that you need much heavier gauge power wiring,
> especially for long runs.
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