I recently recieved an old UPS from my mothers work and purchased new batteries for it and it seems to be working fine other than the fact that after 10 seconds it automatically switches to battery even though it is plugged in, any help would be appreciated.
I would like to ask if the UPS goes back to Online mode. If not, what do you usually do to put it back to online? Is the UPS switching back and forth from Online to On Battery?
One thing that I can recommend is for you to change the sensitivity of the UPS to a much more lower setting. Depending on the model, you can look at the back of the UPS and look for the Sensitivity button. Here is a kbase that would show you how to change the sensitivity.
[What are the different sensitivity settings of a Smart-UPS?|http://nam-en.apc.com/app/answers/detail/a_id/62/kw/smart-ups%20sensitivity]