Michael,
Here are photos of how it's done in a home situation
http://www.wagonmaker.com/newbatt2.html
What is handy about the buss bar is the ability to use much smaller cable
from each series pair (in this case) to the buss bar, thus less expense in
cables than otherwise and additional expense for the smaller cables is far
better if it produces extended battery life and ease of service than the
alternative. The buss bars themselves are tinned copper bars mounted on
stand-offs.
Thanks to Jamie Surrette for confirming the wisdom of such setups. I would
love to see battery companies beginning to provide hardware for such systems
and educating installers on how to use them.
Tom
--------------------------------------------------
From: "Michael Welch" <[email protected]>
Sent: Wednesday, December 02, 2009 2:00 PM
To: "RE-wrenches" <[email protected]>
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-battery-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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