APC SmartUPS 3000

[PaulAm]

The batteries appeared to have failed on this APC  SmartUPS-3000 I use to run a server rack.  Fine, I order new batteries, they show up, install them, I run a battery calibration and it shuts down after 2 minutes.  I'm running about 20% load (approx 600 VA), it should run for over an hour.  It thinks I have 4 minutes total of capacity.  So I think one of the new batteries must be bad.  I rig up a load tester and run them at 3A, there's a little variation, but the worst is still roughly 15AH.

So, maybe it only shows up under load.  I put them back in the UPS and monitor the battery voltages and current  during a calibration run.  One battery looks a little iffy, but the discharge curves are looking fine (see attached)  At then end of 140 seconds the UPS thinks I only have 2 minutes left.  Now I'm wondering if the monitoring circuitry in the UPS went squirelly.  Or is that one battery really that bad?  Anyone have any idea what to look for?

These are 12V 18AH AGM batteries

[asis]

Hi,
Are you running the calibration over LAN or RS232?
To calibrate, you need to fully charge the batteries and load more than 30% of the rated power of the UPS.
Load up with something extra.
After starting the calibration, the UPS will transfer to batteries and the controller will build a time remaining ramp, after which it will return to mains power. It will take 10-15 minutes.
If the calibration does not give results, it will be necessary to reset the value of register 00 to (FF) through the terminal program and repeat all over again.

[PaulAm]

Batteries are fully charged, I'm using apctest over a smart cable.  I'll try increasing the load and see if that does anything.

[PaulAm]

OK, the issue looks to have been the battery constant had drifted too low for the firmware to reevaluate.  Got it reset and things are working fine again.

[asis]

It is advisable to indicate the date of battery replacement in the appropriate register.

[PaulAm]

Of  course, that was already done.

Been changing batteries on UPSes for 20 years and never had this happen to me.  Did have another 3KVA UPS die on me though.  That one's on the repair queue.