Change the UPS battery while it's powered on?

Is it dangerous or not advisable to change the UPS battery while it is plugged in? We have an APC Smart-UPS 1500 and we need to replace its battery. I have the new battery but the UPS powers a few machines that I would rather not turn off for the replacement procedure.

Would something bad happen if I just replace it while it's still plugged in and powered on?

According to the manual:

Replacing the Battery Module

This UPS has an easy to replace, hot-swappable battery module. Replacement is a safe procedure, isolated from electrical hazards. You may leave the UPS and connected equipment on for this proce- dure.

The Smart-UPS 1500 battery is hot-swappable. You do not need to unplug or power down the UPS before changing the battery.

Of course, it is essential to refer to the product documentation and take all appropriate measures to protect yourself from the shock/electrocution hazards associated with live batteries and charging equipment. Under the right (wrong) circumstances, even a 12-volt lead acid battery can deliver a fatal shock.

I "Hot Swapped" 3 APC Smart UPS 1500 batteries at three different power plants here in southern California. These UPS systems are used to power the CAISO RIG (California Independent System Operator Remote Intelligent Gateway). It is a critical system for our electric power grid in the State of California.It took me less than ten minutes to perform this task! This is the first time I ever had to change a battery in a UPS system. The tools I used were just one Phillips screw driver