Smart-UPS SUA2200XL Acting up

[Anonymous user]

I have a Smart-UPS SUA2200XL which was acquired in 2009. About a month ago the ups started sounding off the alarm about a bad battery. I took out the batteries and found two out of four that were not charging more than 9V while the other two stay at 13.24V steady. The two working 12V batteries are 18ah and I purchased two 12V 20ah. The 2ah difference shouldn't be a problem it just means the other two 12V batteries would last longer. So I installed the two new batteries and the UPS seems to work fine. I let it run and charge for 24 hours, the battery light shows to full charge on the UPS and as soon as I do a self-test using the powerchute business web app, the battery light drops to one light and the replace battery light comes up. I removed all four batteries and check their voltage and all four are registering 12.84V steady. I left the batteries out for 24 hours and still holding the same voltage value. I don't know how I can determine whether this UPS is broken or if the batteries are bad. I don't know what else to do, but if the UPS is bad I need to return the two new batteries I bought because I now have no use for them 😞

Any suggestions? Thank you!