AGM battery bank question

[habitek83@yhaoo.com]

I would like to get some help deciphering some battery data. This is a system which we did not install (installed ~ 1998) but have maintained for about 10 years. About 6 years ago we replaced the batteries. 3600 watt PV system with Trace SW 4048.
  Attached is a log of battery info from our last two visits. my concerns are two:
- Voltages of top row of batteries especially at rest. it seems to indicate that Battery #1 is defective?
- Current readings at interconnection and home-run cables. Maybe due to charge controller? I don;t recall if CC was in Bulk or Float at this point.

Thanks, Tom

[Westbranch]

Battery #1 is defective?

Well it sure looks like it is failing...  have you done a controlled discharge test on that one cell?  Contact your batt. maker or rep for their recommendation and values it should meet.  Probably between  .2C to .5C discharge rate.

[habitek83@yhaoo.com]

Hello Westbranch, I have not performed a discharge test on any of the batteries as I wanted to narrow-down the possible culprit. I'm using an OTC Sabre digital tester to determine AH. I know that this is a n automotive-type tester, but I'm not interested in actual AH  as much as uniformity of readings.

[Westbranch]

the discharge test should be something like 3 hrs long where you record the starting V and every 15 or 30 minutes so that you see the drop off point, the voltage and the time it took to get there, and then compare that Voltage to the tables the company has.  Then you can see just how weak your cell is... 

hth