[APML] Deep Cycle Batteries - (was Leonid plans)

[Jon Kolb <jkolb@mindport.com>]

Jerry,

> Total ------------- 7.5 amp hours.
> 
> The camera motors all have their own batteries, so that's not 
> a problem.  I 
> have a 75 amp hour deep-cycle marine battery. That should last from 
> midnight to dawn.

If this is a typical wet-acid deep cycle battery (sealed or not) beware of
discharging past 50% of rated capacity, or 5 hours with the load you
describe.  Go past 50% and you'll start to damage the plates, reducing the
capacity after it's recharged and shortening the life of the battery.  The
same goes for car (starting) batteries, which is why I never draw off them
unless the truck is running.  You can still go past 50%, just know that the
battery will be degraded in the future.

Newer technology batteries like gell-cells and Absorbed Glass Mat (AGM)
models can be discharged down to dead and in the better ones will recharge
to full capacity. From what I've read, AGMs seem to tolerate this abuse
better than gell-cells.  Lifeline and Trojan are two brands that come to
mind.  Lifeline claims that their AGM can sit dead for up to 30 days and
take a full recharge to rated capacity, and they also claim something like
1000 recharge cycles as the life of the battery - more nights than I'll ever
get out.  I'd like to get one of these myself and quit worrying about when
I'm getting close to 50%.

Hmmm...how about an 8D (255 Ah) permanently mounted in the bed of the truck,
with a solar panel on top of the cap, and a telescoping wind generator
mounted on the back of the cab.  That oughta do it. 

Sincerely,
Jon Kolb
Adventures in Astrophotography
http://home.datawest.net/jkolb/
jkolb@mindport.com

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