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'[OT] Solar Panel / Battery hybrid power for palmto'
I'm building a solar array to charge a battery pack, and run a small
palmtop I have.
Can I ask some good questions off-list of someone who's done this sort
of thing? Please e-mail me if willing & able <G>
Mark, Maxim's Engineering Journal, vol 27, has an article on using
solar cells with 0.8 to 4.5V outputs to generate a 5V, 500ma supply.
I also ran across an excellent article about using solar arrarys
recently but I can't find it. I thought it was from Maxim or Linear but
it may have been in EDN. I have'nt searched those yet.
At 11:12 PM 3/8/99 -0800, Mark Willis wrote:
> I'm building a solar array to charge a battery pack, and run a small
>palmtop I have.
> Can I ask some good questions off-list of someone who's done this sort
>of thing? Please e-mail me if willing & able <G>
I'm after 10V to 10.5V, 1.3A peak (800mA works, though, and the
palmtop has an internal battery. Probably can get by on 400-500 mA most
of the time, give or take.) I want a small Lead-Acid battery pack
probably (Want a package the size of a regular laptop or so, but 2/3 of
it'll be batteries, and the solar cells stow safely for carrying.) I
want a lot <G> Thanks, please keep looking!
Tom Handley wrote:
|Hi again Mark
There have been some adds in Nuts & Volts for flat pack lead acid gel
batteries. I will try to locate something and scan it for you. There was
also an article in EDN Feb 4/99 Design Feature- Solar Power. Sorry I have
recycled mine but perhaps some good soul would send you the article (Page
120 or so).
Home power Magazine has done some of these projects and may have some info
on their website http://www.homepower.com/hp/. HP may be a little too grass
roots for you.
Your panel will have to be a good size. A 6v panel will not usually put out
as high as 10-10.5v so a 12v panel may be the most cost effective, unless
maybe you want to mount up cells to make your own custom panel. You will
probably end up with better than 1 square foot for your panel and more if
you go with amorphous.
The batteries, I'm assuming gel, love to be equalized fairly often and
there is evidence that shows prolonged life with pulsed charging. There may
be a spot for a PIC in the battery management system. Sounds like a fun
solar,wind,tide, TEG renewable energy
| From: Mark Willis <NWLINK.COM> mwillis
| To: MITVMA.MIT.EDUPICLIST
| Subject: Re: [OT] Solar Panel / Battery hybrid power for palmtop
| Date: Tuesday, March 09, 1999 2:04 AM
| I'm after 10V to 10.5V, 1.3A peak (800mA works, though, and the
| palmtop has an internal battery. Probably can get by on 400-500 mA most
| of the time, give or take.) I want a small Lead-Acid battery pack
| probably (Want a package the size of a regular laptop or so, but 2/3 of
|On Tue, 9 Mar 1999 06:51:35 -0800 WIL REEDER <BC.SYMPATICO.CA> teachtech
> a 12v panel may be the most cost effective,
>maybe you want to mount up cells to make your own custom panel. You
>probably end up with better than 1 square foot for your panel and more
>you go with amorphous.
Always use a larger panel and battery than you think you need. Panels
with an open-circuit voltage of about 17V are common and a good match for
charging a 12V lead-acid battery without a regulator. In a small system
like this one, you're better off to buy more / larger panels than to try
and get a few percent more power using a regulator.
For any sort of high-performance application (and wanting this much power
from a portable system is high-performance), don't use amorphous panels.
They only output their specified power in full sunlight, and fall off
very rapidly with less light. Crystalline ones will continue to produce
useful power on cloudy days, which in most areas happen quite frequently.
I'd go farther and say don't use amorphous panels, period, but for those
few who happen to live in a desert and can get the panels for almost
free, they may be practical.
>The batteries, I'm assuming gel, love to be equalized fairly often and
>there is evidence that shows prolonged life with pulsed charging.
The most important thing for battery life is to not overdischarge. The
load should turn itself off when the battery voltage drops to 10.5V (for
a 12V nominal battery). Second most important is to keep the battery
temperature in the "room temperature" range, hard to do when it is set
out in the sun. Probably overcharging won't be much of a problem, when
it does happen it will act as an equalize. If you use a battery type
that is commonly found as inexpensive surplus, it won't be too bad to
replace it every couple of years. Don't expect a sealed lead-acid to
work more than 5 years even if you treat it perfectly.
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