The problem may be with the UPS and not the battery. The problem is likely one of three things: Also, most of our UPS' have an option to reset error state. I think you may need to perform that reset manually to clear certain faults. Some of our UPS' may not clear a fault state automatically.
I do have a 5yrs old DELL UPS 4200R. Few months ago the battery just died and I did replace them with similar specification. Unfortunately, this UPS is no longer warranty and can't raise this with Dell support to assist me. Now, after replacing the batteries it is showing an error message saying Battery disconnected even though the battery is connected. I am thinking this is due to old firmware and I wanted to upgrade the UPS. However I can't seems to access the GUI interface of this UPS. I can ping the IP address but when I tries to access it via web browser I got the error message below: Can’t connect securely to this page
Dell UPS 4200R Firmware Upgrade