Mobile power supply WAS: Re: SFD volunteers in Concord, NH

[VirginSnow at vfemail.net]

> Date: Mon, 18 Aug 2008 17:25:31 -0400
> From: mike ledoux <mwl+gnhlug at alumni.unh.edu>

> On Mon, Aug 18, 2008 at 05:05:23PM -0400, Bill McGonigle wrote:
> > On Aug 18, 2008, at 14:38, Ben Scott wrote:
> > 
> > > 12 VDC from a car works but is suboptimal.
> > 
> > Who knows anything about hooking up a laptop directly to a car or  
> > marine battery, with perhaps a DC/DC transformer in the mix?
> 
> If you've got a 12Vdc adapter for the laptop, you don't need
> a(nother) transformer in the mix, just wire a power socket to the
> battery terminals and plug into that.  Ratshack has one that should
> work well enough:

If you're going to do your own wiring, remember to put a fuse in
series with your masterpiece. :)

If you buy one of those cigarette lighter adapters, make sure to check
its max current capacity... many of them (intended for small devices
like cell phones, etc.) can carry only 500mA.  If you exceed that
load, they go into automatic shutdown.  (Many of the store-bought
adapters also have an replaceable internal fuse.)  You might be able
to find adapters for sale in local electronics/marine shops that can
carry as much as 1.5A.

Using gel cell or deep cycle marine *is* recommended.  However, a
DC-AC inverter may or may not perform well.  I tried powering a mini
tower (with an AT power supply) off a deep cycle marine battery this
way.  I was disappointed and a bit surprised when it didn't work.
You'd think the power inverter would have been designed with laptops
in mind. ;)