SMT2200IC strange battery capacity (SoC) drops

[JustAnotherSteve]

Hello,

I added a Smart UPS 2200 "SMT2200IC" to the fleet. It's the first UPS here with a AP9640 card (we don't use the cloud thing).

This new UPS, in use since September 13 2022, so far had 3 moments where the battery capacity (SoC or State Of Charge) suddenly and instantly dropped from 100% to 97 ish percent.

We monitor our UPS'ses (all APC Smart UPS's, ranging from 3000VA to 1500VA models, all equiped with AP9631 cards) with PRTG and it takes a measurement of a AP9xxx card every 15 seconds.

When it happens, we see the "ups high prec battery capacity" PRTG metric (APC Sensor) dive down from 100% to 97-ish % within a 15 second measurement-interval.

Since September 13th, when this UPS was installed, these events happened:

20.09  19:33   SoC 100 % to 96.9 %
27.09  12:42   SoC 100 % to 97.8 %
04.10  13:26   SoC 100 % to 97.7 %

We have never ever seen this happen, in al the many years we use APC UPS'ses and those NMC cards. But this is the first AP9640 card for us.

After such a "SoC drop", the battery requires many hours to get back to 100% which is also something we are not used to.

The battery temperature, when the SoC is at 100%, hovers around 27 degrees C.

The software versions in both UPS and NMC cards are all up2date.

When such a drop happens, there are no self-tests going on. In fact, there are 0 / Zero log entries of any kind that show that something happened. As far as the Logs (incl. remote syslog) are concerned, nothing happened at all.

Has anyone else seen such behaviour maybe?

Kind regards,

Steve