[RE-wrenches] Batteries in parrallel Failure

Wed Apr 20 11:50:09 PDT 2011

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<mailto: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<mailto: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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