[RE-wrenches] Batteries in parrallel Failure

Wed Apr 20 15:08:42 PDT 2011

I have been using buss bars for 12 years or so and about 8 years ago started
to add a class “T” fuse to the connection at each buss bar in most systems.

I have seen thermal runaway hit the industrial batteries I service. 

It would be best to avoid it in a battery box if at all possible.

Do a search for buss bars or battery interconnector straps and you can
locate them. I am lucky that I have a supplier that I visit and he had some
lying around that he gave me. Drill them to fit the fuses and attach the
cables to the fuses.

If you are using a battery with a terminal you can bolt to, you can put the
fuse there also.

I attach the buss bars to the battery boxes with electric fence insulators
as much as a standoff as anything else. 

I also use a board between them so there is no way to get contact between
the 2 bars when working in the box. Trust me, they will spark rather well if
you keep putting off wrapping the ends of the wrenches
..  Also watch the
ends of the cables as you’re whipping them around in there too, best to wrap
them with tape and pull it off when you’re ready to connect them. As we all
know there are lots of exposed terminals in a battery bank and only ½ of
them are friendly.

Using the buss bars has stopped the end cell failures that I used to see
from all the batteries going to the major pos and neg terminals.

I am on a useless dial up at the moment but will try a search for the buss
bars when I get back to the real world.

Later,

Bob

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Brian
Teitelbaum
Sent: Wednesday, April 20, 2011 2:50 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Batteries in parrallel Failure

Does anyone know of a manufacturer or supplier of fused battery buss bars or
battery string combiners (preferably using Class-T fuses) that are UL Listed
for use in residential or commercial applications?

Brian Teitelbaum

AEE Solar

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Tom Elliot
Sent: Wednesday, April 20, 2011 11:36 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Batteries in parrallel Failure

What?  No royalties?  Damn...(but thanks for the props)  Sorry I
misunderstood what you meant.

My installs of buss bars back in the day had cable pairs of the same length
but different pairs could be of different lengths with the consideration
being bank construction.  I’d use slightly oversized cables to minimize
resistance differences.  Since the cables from each string only carried
current from that string it also made for easier installation.  In these
days of grid-tie I’m seeing less and less discussion of batteries, good to
see another one happening even if it was prompted by a failure, though I
guess that’s how we learn.

Tom

From: R Ray Walters <mailto:ray at solarray.com>  

Sent: Wednesday, April 20, 2011 8:16 AM

To: RE-wrenches <mailto:re-wrenches at lists.re-wrenches.org>  

Subject: Re: [RE-wrenches] Batteries in parrallel Failure

Tom; 

That's exactly what Daryl and I were suggesting: all strings paralleled to a
central combiner box with breakers on each series string.

The only thing I left out was that each cable set should be the same length
( which Daryl was already suggesting).

You need to reread what we were talking about.  We got this idea from you
many years ago, so the record is not broken;

its been pirated, reposted for Free download on all sorts of unsavory sites,
and you aren't getting a royalty check....

Imitation is the sincerest form of flattery, and this list listens to and
appreciates you.

Thanks,

R. Walters

ray at solarray.com

Solar Engineer

On Apr 19, 2011, at 10:16 PM, Tom Elliot wrote:

The broken record will now repeat himself yet again.  Bussbars are the way
to go, not across battery terminals but individual strings connected to a
central positive and negative buss from which the inverter connection then
runs.  This allows fusing of each individual connection and also allows for
smaller positive cables and no need to have identical length parallel cables
since each string is independently connected.  It’s what telecom
installations use.  The Telecom guys who showed me how to do it literally
laughed when told about paralleling across battery terminals.  They then
told me they considered it profoundly stupid and dangerous and since I had
just avoided a meltdown myself by catching a bad cell before complete
failure I got the message pretty quick.

Really guys, this is amazingly simple and yes, it may mean a bit more
cabling and another component but from a safety standpoint those
considerations are pretty minor and cheap insurance against disaster.

Tom

From: R Ray Walters <mailto:ray at solarray.com>  

Sent: Tuesday, April 19, 2011 6:01 PM

To: RE-wrenches <mailto:re-wrenches at lists.re-wrenches.org>  

Subject: Re: [RE-wrenches] Batteries in parrallel Failure

I like the fused parallel idea; could save the system, and would make
battery troubleshooting nice. 

I would suggest #6 jumpers with 50 to 60 amp breakers,  so the system could
be operated on just a few strings if needed.

R. Walters

ray at solarray.com

Solar Engineer

On Apr 19, 2011, at 8:29 PM, Darryl Thayer wrote:

Batteries in parallel, How to protect from catastrophic failure.

I just got contacted to commission a solar system off grid not of my design.
Eight battery strings in parallel, AGM batteries, 24 volts @ 120 AH each
string (two 12 volt in series)  New system, new batteries, Silent POwer
Inverter.  Two kW DC array.  generator to charge through Silent power.
(present installer is not sure how to do final set up and testing) 

I am most concerned about 8 batteries in parallel, (especially since last
week a set of AGM burned up having 5 in parallel Owner had no way to break
the paralleling of the batteries, she could only stop the chargeing)   What
I am proposing for your review is requireing the installtion of  two
combiner boxes Midnight solar with a breaker in each battery string, using
about 3' of #10 to connect each battery string to the combiner box.  This
way if a battery failed and the paralled strings were to "dump" into the
failed battery it would trip the breaker.  I was thinking of using a 30 amp
breaker in each string. The main breaker is set at 240 amps. 

Ideas Please?  

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