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One issue I see is that a 4.4 kW inverter is being fed 7 kW. I don't know
if this would account for all you are seeing. Could the Magnum could be
shutting down on overcurrent? <br><br>
At 09:27 PM 12/16/2014, you wrote:<br>
<blockquote type=cite class=cite cite="">Wrenches,<br><br>
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.<br><br>
Here is what I know so far:<br>
- System is ac-coupled with a Sunny Boy 7000 (7.85kW array), Magnum
MS4448PAE (x2), 3 strings of 4 12v batts (705Ah total)<br>
- Site visit was triggered by the Sunny Boy registering zero output via
online monitoring.<br>
- 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.<br>
- 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.<br>
- Customer reports that he was not aware of any recent prolonged power
outages.<br><br>
The three potential suspects would seem to be:<br>
- 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.<br>
- Magnum equipment: Since there is low-battery-cutout protection, why
would this feature not have activated and prevented the batteries from
draining so low?<br>
- 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?<br><br>
Clearly I am fishing for potential leads here, so any suggestions are
welcome.<br><br>
Thanks!<br>
--<br>
Corey Shalanski<br>
Joule Energy<br>
New Orleans, LA<br>
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