Re: [RE-wrenches] Magnum System - Discharged Battery Bank

[Allan Sindelar]

Corey, In a somewhat similar situation years ago: a client had installed a generator/inverter/battery system at an off grid cabin. The system was intended to use the Trace SW4024 inverter to maintain AC to support the generator's battery charger; then send an autostart signal to the gennie, which would recharge the batteries. It was a perilous design, destined to fail, and it did. Once the generator failed to start, the inverter reached low voltage disconnect and some remaining DC load dropped the battery voltage further, to where the inverter couldn't be booted up to recharge the batteries. And of course, without the charger the generator was useless. From the Don't Try This at Home Dep't. Archives: I brought two old 12V batteries with me to the site and set them up in series next to the dead bank. I started the generator, disconnected one battery cable at the bank, ran jumpers from the cables to the two I brought, booted up the inverter, started the charging process, reconnected the disconnected cable, and removed the two old batteries. The inverter continued to recharge the dead bank, although the batteries were permanently weakened, of course, and were soon replaced (and some trickle-charge PV added). Basically I jump-started the dead batteries as you would do with an automobile. I suspect that you could do the same with the Magnum in your situation, and it would be much more effective than 1-2 weeks of slow charging - as in one trip, and the chance to focus your time and effort on the causes of the problem. Allan Allan Sindelar al...@sindelarsolar.com NABCEP Certified PV Installation Professional NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Founder (Retired), Positive Energy, Inc. 505 780-2738 cell   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

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