Fw: Battery Bussing [RE-wrenches]

Tom Elliot telliot at wagonmaker.com
Mon Sep 10 13:54:26 PDT 2001


Heh, if he didn't like it he'd have one hell of a lot of telco installations
to go after.

Tom


----- Original Message -----
From: "jay peltz" <jay at asis.com>
To: <RE-wrenches at topica.com>
Sent: Monday, September 10, 2001 10:42 AM
Subject: Re: Fw: Battery Bussing [RE-wrenches]


> Wow checking your mail while on vacation!!
>
> Thanks for the update, couldn't tell the cable lengths from the photo.
Looks
> good, just for grins what would john wiles say?
>
> jay
>
> Tom Elliot wrote:
>
> > 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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