<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><DIV>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. <BR></DIV>
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<B><SPAN style="FONT-WEIGHT: bold">From:</SPAN></B> Dan Fink <danbob@hughes.net><BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> RE-wrenches <re-wrenches@lists.re-wrenches.org><BR><B><SPAN style="FONT-WEIGHT: bold">Sent:</SPAN></B> Tue, April 19, 2011 10:18:48 PM<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re: [RE-wrenches] Batteries in parrallel Failure<BR></FONT><BR>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.<BR><BR>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?<BR><BR>I didn't design or install the system, but I want to know if I have missed something obvious here.<BR><BR>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.<BR><BR><BR>All feedback appreciated!<BR><BR>Dan Fink<BR>Executive Director;<BR>Buckville Energy Consulting<BR>Buckville Publications LLC<BR>NABCEP / IREC / ISPQ accredited Continuing Education Providers<BR>http://www.buckville.com/<BR><A href="mailto:info@buckville.com"
ymailto="mailto:info@buckville.com">info@buckville.com</A><BR>970.672.4342 (voicemail)<BR>970.373.1311 (fax)<BR><BR><BR><BR>Darryl Thayer wrote:<BR>> Batteries in parallel, How to protect from catastrophic failure.<BR>> 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? <BR>> ------------------------------------------------------------------------<BR>> <BR>> <BR>> ------------------------------------------------------------------------<BR>> <BR>> _______________________________________________<BR>> List sponsored by Home Power magazine<BR>> <BR>> List Address: <A href="mailto:RE-wrenches@lists.re-wrenches.org" ymailto="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</A><BR>> <BR>> Options & settings:<BR>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org<BR>> <BR>> List-Archive:
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