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Old February 22nd 04, 09:41 AM
Pat O'Connell
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Default WalMart Portable Battery Pack?



Thad Floryan wrote:
Davoud wrote in message ...
I made my first-ever visit to a WalMart today to have a look at the
12V, 18AH battery power pack that some folks here have recommended. No
where on the packaging did I see an indication that this is a
deep-cycle battery. Is it? TIA!


If you have the opportunity to pick up (i.e., lift) a deep-cycle battery, you
would know instantly it's "something different". The first one I attempted
to lift off a shelf at Costco really caught me by surprise; it was the same
physical size as a normal auto battery but weighs considerably more due to
the extra-thick lead plates used in its construction. Such deep-cycle batteries
are designed to be operated until they're nearly discharged, then simply charged
up again with no problems or reduced lifetime.

Though I haven't specifically seen a "WalMart 12V 18Ah" battery, just from those
specs I'd guess it's one of many similar auto "jump start" systems whose battery
is typically a gel-cell. All the deep-cycle batteries I've seen are rated
beginning around 80 or so Amp hours and go up from there. The ones I'm using
presently are 80+ Ah and weigh 44 pounds; I've placed them in marine cases I
purchased from Cabelas and you can see the cases he

http://thadlabs.com/ASTRO/POWER/Cabelas_cases+charger.jpg

I find I need to carry them two at a time (for balance) or put them on a hand
truck if a viewing site is a long distance from my vehicle.

I suspect what you saw at WalMart probably resembles what's in this picture
(the red, yellow and black jump-start systems at the left):

http://thadlabs.com/ASTRO/POWER/battery_packs.jpg

noting I've removed the jump-start cabling from most of them for safety in the
field. Those jump-start systems have 17Ah, 18Ah and 19Ah gel-cell batteries
with "Yuasa" (sp?) being the most common manufacturer of the actual batteries.


In general, I would say everything you've said above is right. However,
I think that for the typically low current draws (.75-1.25 A) for
powering a go to telescope, the gel cell battery packs are OK (and I
have a Target Greatland 12 AH power tank for that purpose).

OTOH I suspect the deep cycle batteries might be better for higher
current drawing equipment, like a dew heater system.

I'm not sure whether a laptop PC would fall into the low current or high
current draw category, but I'll probably be trying that sometime in the
near to medium future with a new laptop (rated at 1.7 A at 120VAC) that
I own...
--
Pat O'Connell
[note munged EMail address]
Take nothing but pictures, Leave nothing but footprints,
Kill nothing but vandals...