[RE-wrenches] reverse return on batteries

[Dana]

Battery cabling and bus bars do follow a similar plumbing schematic of
"reverse return" [first in last out and last in first out] That and keeping
the cables equidistant has kept our installs happy. We here in cooler
country have used cheapo Vaseline for years and it has worked fine. We buff
the metal with copper pipe fitting brushes [ cut the handle off ] in a
cordless drill and wear an organics filtered respirator [ not a dust mask ]
and vacuum the battery tops before proceeding to bolt up and coat the
completed terminals.

Dana Orzel

Great Solar Works, Inc
www.solarwork.com
E - dana at solarwork.com
V - 970.626.5253
F - 970.626.4140
C - 970.209.4076

I will be the shift in how the world uses power! - Dana Orzel


-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Walt
Ratterman
Sent: Wednesday, December 02, 2009 5:47 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Strings and series of batteries

Michael:

The bus bar solution has to do at least partially, with:

 - Equal resistance paths to each string of batteries (need to keep the
circuit cables the same length).
 - Ability to remove (isolate) a string more easily.


With two strings, if the bus bar capacity exists in the hardware of the
inverter system (such as the bus in the flexware) simply bring back a large
battery cable from each of the two strings to the flexware and the bus in
the flexware becomes the bus bar.  (with a fuse in each positive....)

Thanks,

Walt
SunEnergy Power International
www.SunEPI.org

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Michael
Welch
Sent: Wednesday, December 02, 2009 4:00 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Strings and series of batteries


I wish I understood this bus bar use better. Electrically, these seem to be
the same thing. But by using the bus bar, there has to be more cables, cable
ends, and connection points. And cost.

I just drew a battery bank (see below link to graphic), three series strings
in parallel. On the negative side I drew a bus bar. On the positive side I
drew normal parallel cable interconnects.

The bus bar side requires 3 cables with 6 cable ends and 6 interconnection
points.

The cable side requires 2 cables with 4 cable ends and 3 interconnection
points.

How can a bus bar possibly be better? There will always be one more cable,
and 2 more cable ends to connect.

I do not see how either way could cause the current for one battery pass
through another. It is merely using the terminal of the battery as a
connector between two cables. Ditto for any difference in how internal
resistance reacts, they both seem the same to me.

Related question #2:

It also has been noticed that some installers use "cross tie" interconnects
for paralleling batteries in the middle of the series strings where the
positive of one battery connects to the negative of the other -- not just at
the final pos. and neg. outer ends of the strings. In fact, some even
recommend two cables between:
http://www.green-trust.org/wordpress/wp-content/uploads/2008/09/cross-tied-b
attery-bank-300x187.jpg

What's up with that? If it helps make charging equal, is it worth the extra
expenses and connections involved?

Here is a little jpg that illustrates both of these questions:
ftp://ftp.re-wrenches.org/pub/bbvscablewcrossties.jpg



Tom Elliot wrote at 02:19 PM 12/2/2009:
 
>Darryl, The process of paralleling through buss bars means attaching each
serial string to a pair of buss bars rather than to neighboring series pairs
so batteries aren't passing current through each other and aren't affected
by each others internal resistance.  The buss bars then feed the inverter
breaker.  It's standard practice in large telco installations which is where
I got clued into the process.  I got some batteries from a wholesaler who
did those installations and he was aghast at the idea of series/parallel
installations the way off-grid systems have been done traditionally. 


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