I had a motorcoach that we upgraded to a magnum inverter, (strangely from a dimensions inverter)
the guy called me one day and told me the batteries were at at 9 V, when I got there they were flat and by that I mean they made a pancake look high ! As it turned out the low-voltage disconnect gets bypassed by the smoke and carbon monoxide detectors in the motorcoach End result was six very discharged golf cart batteries that I don't think ever fully recovered Might there be something like that loading the batteries when nobody is looking? Bob Ellison > On Dec 17, 2014, at 2:13 PM, Dan Fink <danbo...@gmail.com> wrote: > > Interesting mystery, and great discussion. > I'm leaning towards a battery cell problem too. Corey mentions 3 strings of 4 > "12v" batteries -- what are these 12v batteries exactly? > I've seen issues in the past that convince me a couple parallel battery > strings are a good thing (but not too many strings); in an open-cell failure > mode the parallel string keeps the battery bank from 'disappearing.' > > > > Dan Fink > Buckville Energy > IREC Certified Instructor™ for: > ~ PV Installation Professional > ~ Small Wind Installer > NABCEP / IREC / ISPQ Accredited Continuing Education Providers™ > 970.672.4342 > > > >> On Wed, Dec 17, 2014 at 11:17 AM, Ray Walters <r...@solarray.com> wrote: >> I've never seen an inverter not disconnect on low voltage. My understanding >> is that they just can't operate below a certain threshold. >> However, I have seen behavior as described caused by DC loads that did not >> have a LVD in place. Were there any other DC connections to the battery >> bank besides the inverter? >> Once the whole bank gets low enough, even the charge controllers will not >> reconnect, and the entire bank is quickly ruined. >> This is why I rarely use DC direct loads anymore, and If I do, I always >> recommend a LVD. >> Any chance of a short circuit in the cabling before the inverter? >> The only other thing I could think of is a shorted cell in one of the >> batteries, that then drained the rest of the batteries. >> >> >> R.Ray Walters >> CTO, Solarray, Inc >> Nabcep Certified PV Installer, >> Licensed Master Electrician >> Solar Design Engineer >> 303 505-8760 >>> On 12/17/2014 10:36 AM, Corey Shalanski wrote: >>> Clarification and Update: >>> - I believe I may have inadvertently thrown Magnum under the bus in in my >>> initial post. >>> ᐧ >>> While on site yesterday I did speak with Magnum's customer support about my >>> findings and they advised to try to trickle charge the batteries up to the >>> minimum threshold at which the Magnum inverters would turn back on. From >>> there we will hopefully be able to run some more determinate tests. My >>> question about the low-battery-cutout was more intended to explore whether >>> others have ever experienced any similar issues with this protection >>> feature. I am finding out that the feature is only relevant during >>> inverting (not charging) mode and so would imply that the utility feed had >>> been cut, which does not appear to be the case. >>> - Our battery distributor has lent us a 12-circuit trickle charger - one >>> set of alligator clips per battery. I am planning to re-visit the jobsite >>> later today to put each battery on a trickle charge, which I am told will >>> take 1-2 weeks for any lasting change to take effect. The distributor >>> advised to reverse the leads on the batteries with negative voltage, hoping >>> that they may be recoverable as "reversed pole" batteries thenceforth. >>> >>> -- >>> Corey >>> >>> >>> On Tue, Dec 16, 2014 at 8:27 PM, <cshalan...@joule-energy.com> wrote: >>>> >>>> >>>> Wrenches, >>>> >>>> I visited a customer today whose grid-tied battery backup system suffered >>>> some sort of catastrophic failure, and now I'm trying to play detective to >>>> figure out what happened and whose equipment/design is to blame. >>>> >>>> Here is what I know so far: >>>> - System is ac-coupled with a Sunny Boy 7000 (7.85kW array), Magnum >>>> MS4448PAE (x2), 3 strings of 4 12v batts (705Ah total) >>>> - Site visit was triggered by the Sunny Boy registering zero output via >>>> online monitoring. >>>> - SPST Solid state relay installed on Sunny Boy output, controlled via >>>> Magnum router, serves as secondary overcharge protection to Magnum's >>>> frequency shift feature. Technician who initially responded claims he >>>> measured 240v across the relay's terminals - relay manufacturer claims this >>>> is "100% impossible". We removed the relay from the circuit, and the Sunny >>>> Boy is again operational. >>>> - On arrival I found the Magnum display showing a "Low Battery Charge" >>>> message with the bank measuring ~4Vdc. The individual batteries were in >>>> various states of charge, ranging from high of 6.3v to low of -2.6v. These >>>> measurements were taken at rest, all battery cables disconnected, and yes >>>> three of the batts were registering a negative voltage. >>>> - Customer reports that he was not aware of any recent prolonged power >>>> outages. >>>> >>>> The three potential suspects would seem to be: >>>> - SS relay: The customer is convinced that this is the weak link in the >>>> system and somehow triggered this failure. I am not so >>>> convinced but would >>>> be interested to hear recommendations for properly testing its >>>> functionality. >>>> - Magnum equipment: Since there is low-battery-cutout protection, why would >>>> this feature not have activated and prevented the >>>> batteries from draining >>>> so low? >>>> - Batteries: I am not very familiar with modes of failure, but our >>>> distributor suggested that an internal short could be a possibility - what >>>> might have triggered this? >>>> >>>> Clearly I am fishing for potential leads here, so any suggestions are >>>> welcome. >>>> >>>> Thanks! >>>> -- >>>> Corey Shalanski >>>> Joule Energy >>>> New Orleans, LA >>> >>> >>> _______________________________________________ >>> List sponsored by Redwood Alliance >>> >>> List Address: RE-wrenches@lists.re-wrenches.org >>> >>> Change listserver email address & settings: >>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>> >>> List-Archive: >>> http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html >>> >>> List rules & etiquette: >>> www.re-wrenches.org/etiquette.htm >>> >>> Check out or update participant bios: >>> www.members.re-wrenches.org >> >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> List-Archive: >> http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html >> >> List rules & etiquette: >> www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> www.members.re-wrenches.org > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org >
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