Re: A simple question - beginner stuff

[XURQ03A@prodigy.com ( LEE A HART)]

> what sort of problems do you run into if you [charge] 10 or more 12V
> batteries in parallel?

>From the battery's point of view, it is a good way to charge them. Lead-acid
batteries automatically equalize to the same state of charge when connected in
parallel. It's like connecting siphon tubes between buckets; the water level
automatically balances to the same level (equalizes) in every bucket.

As a practical matter, you're now left with a 12v system when driving (which
means a) low efficiency, b) a boost converter for a controller instead of the
usual buck converter, or c) a mess of series/parallel switches or relays to
reconnect them for some higher voltage.

For charging, you charge them as if they were one big battery. Ten 10 amp-hr
batteries in parallel is the same as a single 100 amp-hr battery. The only
exception is that final equalizing current (the current you supply when the
batteries are up near 15v) should be appropriate for one battery, not the sum
of all of them.

You'll need a high current charger, as David Roden recommended. One source is
the "starting boost" type of automotive charger, though they can't deliver
high current for very long. Another is an RV inverter/charger (made by Heart,
Trace, Statpower, etc.) -- they have good, high current chargers (150 amps or more).

> Also, I think I will have to use buss bars for this setup...

Bus bars are "wires" made out of rigid, solid bars of copper or aluminum.
Batteries are heavy, and their lead terminals are soft. If you connect
batteries with bus bars, you have to put U or S or L bends in the bars to
provide some slack. Otherwise road vibration, potholes, expansion/contraction
due to temperature changes etc. will break the terminals of the batteries,
cause bad connections that overheat, and crack the seals to make the battery leak.

It just occurred to me -- Bob Schneeveiss used a setup that you might
consider. He put his batteries in boxes with a hinged lid. On the lid were big
flat springs with contacts on the ends. When you closed the lid, the springs
made contact with the battery terminals, and connected them all together.

You could have *two* lids, one that puts them in series for driving, and one
that puts them in paralel for charging. Done right, this could solve your
connection problems neatly.

Lee Hart                     If you would not be forgotten
4209 France Ave. N.          Soon as you are dead and rotten
Robbinsdale, MN 55422 USA    Either write things worth the reading
phone (612) 533-3226         Or do things worthy of the writing
e-mail XURQ03A@prodigy.com   (Ben Franklin, Poor Richard's Almanac)