Rob,
Um, laptops and batteries are both DC devices, and *require* DC to be charged.
The existing chargers you have no doubt take AC in, but they convert to DC before
sending anything on to the devices (either battery or laptop). AFAIK, without an
intervening AC/DC converter, there isn't any battery that will charge directly from AC.
In fact, hooking any battery directly up to an AC source will likely blow it up spectacularly.
You can buy a DC adapter for any laptop made that'll run quite nicely off of a 12V source
(i.e. car batteries). These also charge the batteries. The one I currently have is a "universal"
type, that has different tips for different devices and will work with any laptop (it also runs off
the DC outputs on airplanes, where it sees most of its use).
As for solar chargers, I have one that works like a champ. It's small (about 2' square), and
produces a 14V DC output at about .25 amps. So yes, it takes 4 hours to replace 1 amp hour used. However, since my big 115 AH field battery only runs down about 8-10 amp hours for a night of use,
I can regain 2-3 amp hours by solar charging the next day, and doing so gives me a week's nighttime use out of the battery instead of 2-3 nights. It helps, and no generator or gasoline is required :)
Paul
-----Original Message-----
From: sf-bay-tac-bounces@seds.org on behalf of Rob Hawley
Sent: Sat 4/24/2004 7:55 AM
To: The Astronomy Connection
Cc:
Subject: RE: [TAC] Solar Battery Charger == Some Questions
I looked at solar chargers last year. Basically I could not make the
numbers work. It is not recommended to charge my large battery using DC.
My laptop can only be charged with AC. That means I have to invert the
output of the solar cells and then run my chargers. At 110V the cell only
produces about .29 A and that figure assumes no loss in the inversion.
I ended up buying a quiet generator instead. At CalStar I run it away from
the tents. Generators are only allowed at the entrance of Shingletown.
However last year one was provided at the other end of the runway last year.