Sounds like it should work, just don't tell anyone what you're doing,
it's probably not allowed :)

Bob

P.S. My rule of thumb for car batteries is that the advertised capacity
is actually double the real 20 hour rate. So your 50 AH rated battery is
good for 20 hours at 1.25 A when new.

Second rule of thumb is that a car battery takes some damage if you take
more than 1/2 of its useful (25 AH) capacity. So you do some damage
taking over 12.5 AH. A little here, a little there.

16 AH seems a reasonable amount from a new battery. You should be able
to do it a few times and still have a battery good for use in a car for
several years.

Make sure you turn it off every night, charge it soon after the show and
you'll be fine!


On Mon, Oct 14, 2013, at 05:33 PM, Neil wrote:
> Yes, 10.5V is what I've calculated too.  But I'm wondering if the AH =20
> rating is to that voltage, or to a safer voltage.  If I go to 11V, how =20
> much of the 50AH can I get? Is the drain relatively linear from 12.6 =20
> to 10.5V, so I can expect about half of the 50AH?
>=20
> Either way, some of these shows provide electricity, but at this show =20
> I want to power some electronics in a different section of the show, =20
> where they can get me an extra electrical outlet costs for ~$135.  I =20
> can buy a new car battery instead for $70 and dump it (yes turn it in =20
> for the core charge) when I'm done.
>=20
> At this point, I have another bonus:  instead of powering the devices =20
> with 12V and letting the linear regulators in each drop that to 5V, I =20
> can easily run a 12V-5V buck switcher after the battery and drop by =20
> power requirements by about half.  My calcs with this method is now =20
> 16AH required.


--=20
http://www.fastmail.fm - Or how I learned to stop worrying and
                          love email again

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.