WIth linear regulators that would be true, re heat dissipation, but these are (I thought) using switching regulators which are pretty efficient.  Also, with linear regulators, unless they are low drop out regulators, you tend to need a bit higher voltage than the regulator's rated voltage or they go out of regulation and start to sag (voltage wise) which can cause all sorts of issues with reliable system operation.

Rick


On Wed, Aug 19, 2009 at 4:57 PM, Dave Hylands <dhylands@gmail.com> wrote:
Hi Dustin,

On Wed, Aug 19, 2009 at 1:23 PM, Dustin Webb<dustinjwebb@yahoo.com> wrote:
> Dave:
>
> Aha! That's the other modification I was talking about last week. That
> wasn't the problem though. On a whim I tried using two 9V batteries in
> parallel and it worked. Now I just need something more robust than these
> little 9V batteries. I'm going to try using two 6 cell NiCD batteries in
> parallel as soon as I make a second connector. Otherwise I might have to try
> to find some RC batteries closer to 9V.

Ahhh - Yeah 9V batteries are typically only rated to a few hundred
milliamps. With Wifi, you definitely want an amp.

You'd actually be better off to pick batteries closer to 5V.
Everything above 5V is wasted as heat in the voltage regulators. A
5-cell NiCad or NiMH will run from around 7V fully charged down to
about 5V when discharged.

A 4-cell pack will go from about 5.6V down to 4V.

Here's a site that shows a typical discharge curve for NiMH and NiCAD.

If you get a DC-DC converter, like this one:
http://www.sparkfun.com/commerce/product_info.php?products_id=9275
then you can use 9V or 12V and the excess won't be wasted as heat, so
you'll get longer battery life.

--
Dave Hylands
Shuswap, BC, Canada
http://www.DaveHylands.com/

------------------------------------------------------------------------------
Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day
trial. Simplify your report design, integration and deployment - and focus on
what you do best, core application coding. Discover what's new with
Crystal Reports now.  http://p.sf.net/sfu/bobj-july
_______________________________________________
gumstix-users mailing list
gumstix-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/gumstix-users



--
Say you can or say you can't, either way you will be right.
Computers are like old testament gods: Lots of rules and no mercy.