It's 4.4 (x2) I parallel so should be ok. Usually if the battery based inverter 
is too small the SB would "push" the voltage around until the SB disconnects.

Gary Baxter
Product Manager
Magnum/Dimensions

On Dec 18, 2014, at 9:52 AM, Drake 
<drake.chamber...@redwoodalliance.org<mailto:drake.chamber...@redwoodalliance.org>>
 wrote:

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 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
[[]] ???
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