COACH BATTERIES

[Don Bradner]

On 8/11/2008 at 7:58 PM Michael wrote:

>Bottom line is for most people who will not take the time to do the
>proper maintenance, invest big dollars in expensive
>monitoring/charging systems, or have special needs, then 12v parallel
>systems ARE superior to their 6v counter parts. So if you're looking
>for "bang per buck", 12v lead acid is the way to go.. in MY opinion!
>
>Hope I didn't put too much fuel on the fire?

Nope, but once again you brought a lot of theory to a situation where practical
often doesn't have to compete with theoretical best.

We have people here at the oldest end with single batteries, where 6-volt is not
an option without engineering significant changes. So 12-volt is the best not
for any of the reasons supplied in terms of redundancy, connections, etc.

We have people here at the newest end who have 8Ds, or perhaps even 12Ds. 6-volt
is not an option there, either, again for none of the theoretical reasons, but
simply for supplier availability.

Then we have all of us in the middle, with 4 or more conventional batteries,
always an even number. That tends to make a lot of the theoretical reasons
against 6-volt moot.

My case is typical. The battery tray was designed for 6 Group 24 batteries, all
in parallel. That is a lot of connections, no matter how you do it - figure at
least a dozen cables. Depending on brand, a Group 24 is 75-80AH and can be had
in anything from deep-cycle to high CCA starting batteries.

Now assume you want more capacity. I do, and it is not for running air
conditioners going down the road. I boondock one 1+ month continuous every year,
plus additional shorter periods. I run a *lot* of electronics. I want to run the
generator as little as possible, with a high charge rate, into those batteries.

In the space I have, I challenge anyone to find an off-the-shelf solution that
will exceed the capacity of 6 6-volt batteries. At 210-220AH each depending on
brand, giving 630-660AH in the same footprint as the above 450-480AH.

Now guess what? This is accomplished with FEWER cables and connections! Don't
believe me? work it out. Three less cables, 6 less connections.

Finally, while our engineer says that a manufacturer can produce the same
deep-cycle characteristics in 12-volts that they (all) do in 6-volts, I just
don't see anything like that actually being manufactured. Perhaps it is true in
a 4D or larger, but there isn't space for plates that thick in any "standard"
size below a 4D.

Don Bradner
90 PT40 "Blue Thunder"
My location: http://www.bbirdmaps.com/user2.cfm?user=1