[Chaos-l] Where to buy 12V batteries?

[Jim Pressley]

Hi Robert,
I too am very interested in how much extremely cold temperatures will reduce
the operating time for batteries.   I have just installed 4 small gel
batteries into my 12.5" Newt.   Two will power heaters and fans and two will
handle the drives and wireless system.   I'm considering a deep discharge
battery to drive my laptop, but have not yet decided which one to buy.

I've calculated the power drain for my scope and it appears to be fine for
normal (comfortable) temperatures.   However, I don't know how to account
for extremely cold temperatures like those last night and at MASP.    An
experiment will be the best way to know for sure.

We're counting on your empiricism to test this on your system and let the
rest of us know what happens.   Hope to see you folks at Astronomy Days..

Clear skies and *warm nights*, Jim



On Sat, Jan 17, 2009 at 1:36 PM, Robert Nielsen <robertnielsen at nc.rr.com>wrote:

> Michael,
> I did a little experiment with a battery I have (that has a voltmeter
> built-in) and my EM-500 mount, which claims to use the 600 mA in tracking
> mode (more for slewing).   I let it run for 8 hours, THROUGH THE 12V -115V
> INVERTER and checked the meter every 15 minutes ... sure enough, the drain
> on this particular battery (a Kendrick Astro power pack, which is
> essentially a marine-sealed AGM unit) plotted *exactly* as expected, and so
> I think it will do what it says.   It also vindicated the money my folks and
> I paid for my physics degree :-)
>
> Of course, next weekend at Medoc Mountain will probably be COLD ... and I'm
> wondering if the battery's chemistry will work as efficiently at that
> temperature.  I guess we'll find out!
>
> As I said before, I'm really interested in how all this turns out, and
> everyone's empirical experience!
>
>
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