B Strachan wrote:
>
> Nathan,
>
> I would suggest if you do this, you check into a battery isolator. You
> can get these at RV stores and such. Without getting into the details,
> it is not a good idea to just connect two car batteries in parallel.
>
Isolators are used to separate the main battery from an auxiliary battery so
that draining the aux batt doesn't drain the main battery. You don't want to
run down the RV's battery while you're out camping and have no way to start the
beast.
Batteries in parallel is standard procedure on almost any 18 wheeler or other
heavy equipment. They'll run two twelve volt batteries in series (to get 24
volts) and then two more in parallel with the first set to boost the cranking
amps. This can cause grief for unwary installers of after market
electronics. They'll poke around on the battery rack and find 12 volts, and
wire up the CB or cellphone or whatever. Hmmmm. Smoke? Yup. You've got 24
volts between your CB's hot lead and ground! (Older trucks might use 6 volt
batteries in a 24 volt series/parallel setup.)
Paralleling batteries is also standard procedure in power backups. AirTouch
Cellular's original Los Angeles system was installed by AT&T in the early 80's.
The battery backup in those original sites was impressive. 1.5 volt lead acid
cells about 2 feet tall and about 12 inches in diameter. Clear
plastic housing so you can see the plates. (For inspection purposes.) And a
wall full (literally) of them in a parallel/series arrangement - enough to keep
the site on the air for 8 hours without A/C. Newer installations are gel cell,
but still in a parallel/series arrangement.
But if you do this, don't skimp on your cabling or connectors.
--
Mark van der Hoek
Houston, for now
"They that can give up essential
liberty to obtain a little temporary
safety deserve neither liberty nor
safety."
-- Benjamin Franklin
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