On Fri, 7 May 2004 17:39:33 -0500, "Bernard Randall"
|If you need a more detailed discussion of parallel batteries have a look at
| http://www.amplepower.com/pwrnews/parallel /, it doesn't outright condem
|parallel connection, but it does show that the problem is not as clear as
|Wes would like us to believe and is very dependent on the type of batteries
Thank you so much for providing this link, although I was already very
aware of Ample Power's web site. You clearly read things differently
than I. To save the other readers from digesting this, and to put you
on point let's use *your* reference for further discussion.
Remember how you got your panties all bunched up about cell shorts?
Ample Power (your reference, remember) says:
"It is our opinion based on reference 1 and 2 that disastrous cell
shorts are not a major failure mechanism, and the consequences are, in
any case, no more than what happens during equalization. Since the
early 1960s when we designed our first battery charger, we have
witnessed no dangerous situation that resulted from a cell short."
"Up to this point, we have attempted to define the scope of the issue,
and examine the failure mechanisms and their consequences to parallel
configurations. We find *nothing alarming* (emphasis added) about such
practice in either liquid or sealed battery systems, as long as the
batteries are properly instrumented and prudently cared for. We do
favor sealed batteries over liquid batteries for parallel systems
because of the consistency of cell chemistry, and the fact that we
can't tamper with it accidentally. We don't promote an unlimited
number of batteries in parallel. One limit is indicated by the answer
to the shorted cell question that was asked above. There are other
features of parallel systems that *are attractive* (emphasis added)."
Earlier you said:
|It is not good practice to directly connect batteries in parallel, as an
|earlier response stated batteries do have internal resistance and unless the
|batteries are exactly matched the higher charged battery will discharge to
|the level of the lower one.
To which I replied:
"So what? Be an optimist, the battery with the lower terminal voltage
has been *charged* to a high voltage. The *total AH capacity remains
the same except* (emphasis added) for the slight I^2R loss."
But *your* reference says:
"First, a parallel system allows more convenient sizes which yields a
greater range of systems. For instance, a 100 Ah battery can be placed
in parallel with a 200 Ah unit to obtain a total of 300 Ah. Charging
proceeds as expected, with each battery receiving its share of the
charge current, and *each reaching a full charge at the same time*
(emphasis added). On discharge, each battery supplies current
according to its relative capacity, and both batteries maintain the
*same percent depth of discharge* (emphasis added)."
As I said before, I stand by my remarks.
Connect the frigging batteries in parallel and stop fretting about it.