Fw: Battery Bussing [RE-wrenches]

[Tom Elliot]

Jay,

When I had the main buss connects made up I had them use 1/0 cable, which
was overkill but smaller than I had on the previous bank.  I am using 48"
connections from each series pair to the main buss with no problems at all.
I could most likely have used #1 with no problems.  (I don't have the specs
with me, I'm on vacation).

With 12 series pairs the system output/input is spread evenly across the 12
pairs.  Even at max draw on a 4024 that doesn't amount to much per series
pair.  All the pairs are connected to the main buss with the same length
cables so that they all "look" the same to the load.

Tom


----- Original Message -----
From: "jay peltz" <jay at asis.com>
To: <RE-wrenches at topica.com>
Sent: Monday, September 10, 2001 7:32 AM
Subject: Re: Fw: Battery Bussing [RE-wrenches]


> Hi Joel, and Tom,
>
> My question is about wire lengths.  In the plumbing world, to truly
parallel
> something, the lengths of pipe,fittings etc must be the same length.
Seems to me
> that the shorter wires will pull more power.  Yes I realize that we are
talking
> really small differences here, but it is going to take the path of least
resistance.
>
> What say you?
>
> jay
>
> peltz power
>
> Joel Davidson wrote:
>
> > Tom,
> > Thank you very much for the pictures and story on your web page. Using a
common
> > bus makes a lot of sense. I wish I had more time and money to do
research and
> > testing. It would be good to put ammeters on the series and parallel
cables to
> > confirm lower current coming from inner batteries. Perhaps your battery
supplier
> > has some test data.
> > Best regards,
> > Joel Davidson
> >
> > Tom Elliot wrote:
> >
> > > Allan,
> > >
> > > I've been following this thread with some interest as I've just gone
through
> > > my own changeover due to (what I consider) premature cell failure in
an L-16
> > > in my original bank.  I've done a write-up on my web page (the
write-up is
> > > at http://www.wagonmaker.com/newbatt.html ).
> > >
> > > As I say on the webpage, the battery people I deal with who do large
telco
> > > installation literally cringed when I said I had a series/parallel
> > > installation.  The cell in my system that failed first was the one
closest
> > > to the positive inverter takeoff.  I didn't have cross-connection on
the
> > > bank, I took the power from one end (I know not the best) but they
told me
> > > it only made a little difference to take power from opposite ends of
the
> > > bank.
> > >
> > > According to what I was told, virtually *any* paralleling of batteries
is a
> > > bad idea.  The center strings add voltage but not much current to the
> > > inverter draw which means that the outside series strings take more of
a hit
> > > than the center strings.  (I'm getting clarification and more
technical
> > > explanation of this from them but it may take time).
> > >
> > > Anyway, when I saw the "battery bussing" subject line I thought folks
would
> > > be talking about the way I've installed my "new" (to me) bank of AGMs.
All
> > > my series strings (pairs, each is 12 volt) have their own connection
to a
> > > main set of buss bars so that each series strings contributes equally
and is
> > > charged equally.  This makes for more cable but an ultimately easier
to
> > > maintain installation.  It also means none of that rotating batteries
in a
> > > bank stuff.  I have a friend who does that also and it seems like a
> > > hellacious waste of time.
> > >
> > > Another great thing about using a main buss bar setup is that you have
no
> > > limits on the number of series strings you can use and it makes it
easier to
> > > use more, smaller, batteries in large systems.  If you get a chance
check
> > > out a large telco installation and see how they do it.  They are often
> > > connecting over 100 batteries to main busses.
> > >
> > > My original set of L-16s failed (at least one cell did) after only 7
years
> > > of use and an excellent maintenance and charge regime.  I expected a
lot
> > > more out of them and if I had done it this way originally they'd still
be
> > > chugging along just fine.
> > >
> > > Telco installations change out their banks much more frequently than
we in
> > > the industry do and they were surprised at my 7 year battery life but
in our
> > > kind of installations and usage patterns longer life should be a bit
issue
> > > and I think eliminating parallel strings would extend battery bank
life.
> > >
> > > Tom Elliot
> > > Guffey Energy Works
> > > http://www.wagonmaker.com
> > >
> > > ----- Original Message -----
> > > From: "Allan Sindelar" <allan at positiveenergysolar.com>
> > > To: <RE-wrenches at topica.com>
> > > Sent: Thursday, September 06, 2001 2:22 PM
> > > Subject: Re: Fw: Battery Bussing [RE-wrenches]
> > >
> > > >
> > > > Re this part of my earlier post on battery interconnects:
> > > > > The point of diagonal tapping is to minimize
> > > > > the effect of cumulative interconnect and terminal resistance from
> > > causing
> > > > > one string to charge and discharge "sooner" than the others; you
could
> > > > also
> > > > > say "more" or "less" than the other strings. The additional
resistance
> > > is
> > > > > very slight with clean connections, but as the amperage can be
very
> > > high,
> > > > > the resultant voltage drop from parallel string to parallel string
can
> > > be
> > > > > significant. A consistent variation in voltage over time leads to
> > > > > incremental premature failure of some strings--and I admit I'm not
sure
> > > if
> > > > > it's the harder-working strings or the less-cycled strings that
would
> > > fail
> > > > > first.
> > > > Can anyone answer my question? How will an unevenly-matched battery
bank
> > > > deteriorate? Which cells will fail first, and why?
> > > > Thank you...
> > > > Allan at Pos E
> > > >
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