I have now been close to three battery fires caused by thermal runaway, (the
telecom industry has had many many more. Before they got the controls to fix
the problem.. Here my suggestion is limit the maximum current that can flow in
a parallel circuit between batteries.
________________________________
From: Dan Fink <[email protected]>
To: RE-wrenches <[email protected]>
Sent: Tue, April 19, 2011 10:18:48 PM
Subject: Re: [RE-wrenches] Batteries in parrallel Failure
We almost had a house fire in the neighborhood a couple months ago from a
parallel battery bank failure....an aging 2x8 L16 48v battery bank (16 of
them),
and one bat in bank one got a short and thermal runaway. I teach in my
firefighter safety classes that thermal runaway is really rare, but it sure
happened here fast. How rare is it? Smoke was pouring out of the bat box. Good
thing the homeowner was there. He instinctively hit the main DC buss bar
breakers, which was logical but didn't of course help the fire
situation.....and
the result was that all Outback electronics from charge controllers to the 2
inverter set being fried from too high DC voltage coming in the wrong end.
Was something designed or wired wrong here? What is a high-voltage (up to 150
VDC) off-grid MPPT PV system supposed to do when the battery bank effectively
disappears instantly from the system?
I didn't design or install the system, but I want to know if I have missed
something obvious here.
Wind turbines have had the same issue here -- better hit the turbine shutdown
switch before disconnecting the battery bank, or you'll backfeed high Voc and
fry some expensive electronics.
All feedback appreciated!
Dan Fink
Executive Director;
Buckville Energy Consulting
Buckville Publications LLC
NABCEP / IREC / ISPQ accredited Continuing Education Providers
http://www.buckville.com/
[email protected]
970.672.4342 (voicemail)
970.373.1311 (fax)
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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