UPS battery losing power and not charging fully for unknown reason?

[aardvark]

Hi,

so i have a Backup-ups 850 BE850G2-UK (Serial: 5B2111T00688) that i bought to replace an older ups in may 2021.

All 4 lights are usually solid, meaning 100% charged, but i noticed a few days ago that the end light was flashing (so charging) and powerchute said it was 84% and charging.

it seems to very slowly increase and yesterday was on 91% but not going higher.

I woke up today and its back down to 84% and charging.

so i'm not sure whats going on - there have been no power events, so no discharge that i am aware of.

Passes a self test.

i only have my pc attached to the back up sockets and i turn that off at night, on during the day.

any ideas?

thanks

[aardvark]

ok, now its 100% charged for the first time in a few days.

is this normal behaviour?