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?
At 09:27 PM 12/16/2014, you wrote:
Wrenches,
I visited a customer today whose grid-tied
battery backup system suffered some sort ofÂ
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
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