Fw: Battery Bussing [RE-wrenches]

[Tom Elliot]

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
>
> - - - -
> To send a message: RE-wrenches at topica.com
>
> Archive of previous messages: http://www.topica.com/lists/RE-wrenches/
>
> List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm
>
> Check out participant bios: www.mrsharkey.com/wrenches/index.html
>
> Hosted by Home Power magazine
>
> Moderator: michael.welch at homepower.com
>
>
>
>
>

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

==^================================================================
EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9
Or send an email To: RE-wrenches-unsubscribe at topica.com
This email was sent to: michael.welch at homepower.com

T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^================================================================