Yes, it is possible. See here, for example, but it basically depends on the UPS model. You have to read up on that beforehand. Here for an APC Smart UPS 750VA, the battery is used and it is possible with the UPS. Link: https://www.apc.com/shop... (Search for ongoing, it's quicker.)
Hello The replacement battery is for an emergency power supply that I had to take out of service to change the battery. However, I have a switch at the output of the emergency power supply where I can switch from emergency power to mains power so that the connected systems are temporarily supplied with mains power and thus continue to operate.