Symmetra LX 16000 RM battery fault - how to identify faulty battery?

[Anonymous user]

I'm looking for help with Symmetra LX which is reporting a faulty battery module but I'm struggling to find which one it is that needs replaced.  There was an external power problem which the UPS logged as 'Unacceptable utility voltage rate of change', all the UPS's showed changing to battery power very briefly before changing back to mains power and running normally.  The Symmetra LX didn't return to normal and switched to bypass mode, the display shows a 'battery module fault' and to replace batteries, the web interface shows the same with two critical alerts (and no others) - Battery Fault and Replacement Battery Needed.  It shows the battery capacity at just 41% (and hasn't risen in the last couple of days) and it won't come out of bypass mode.

The unit has four batteries in the main frame and two frames attached with three batteries in each (10 in total) but the web interface shows all 10 batteries to be good and the interface on the device also shows each battery to be ok.  I've removed each battery and checked the status to see if it changed but while the unit recognised each time a battery had been removed it still showed the battery module fault each time even when all the battery modules had been removed (although that may be an error generated by the fact there are no battery modules present).  The raw data looks quite different for the second frame:

Battery Frame
Main Frame:	00 0000 04/04 000F 0000 0000 0000 00 00 000.0 00.0 0000 0000
Battery Frame 1:	00 0000 04/04 000F 0000 0000 0000 00 00 000.0 00.0 0000 0000
Battery Frame 2:	00 0000 03/03 0007 0000 0000 0000 00 00 077.3 -0.2 0666 1951

While I don't know what the raw status codes mean the second battery frame looks suspiciously different so I tried removing its communication cable which the main unit recognised (showing the number of battery frames had decreased) but it still showed the battery module error.  I tried swapping over the communications cables so only the other one was connected then tried removing both but the system still showed the battery module error so I'm stumped what to check next. I've found a couple of other users who sound like they've had the same issue with this unit but there were no confirmed solutions on those threads.

Any other suggestions to narrow down the faulty battery would be appreciated.