How to start an uninterruptible hp R3000XR?

Question

Uninterruptable power source

All the best!
For a long time, the HP R3000XR rack UPS stood in the basement for storage. Today I plugged in the power cord and waited, the fans rustled, the Utility light flashed green, then I pressed the power on, the load scale appeared on the first diode 25% (which corresponds to 0-25% load) and the Utility LED was constantly shining green, in this state it stood somewhere hour.
Then I tried to connect a switch to the first load group with batteries. The switch booted up, I took out the UPS plug from 220 V and everything went out. At that moment, as I pulled out the cord, the red lamp of the general warning blinked, the red lamp on ~ Utility and it seems like on batteries (I didn’t have time to see it, remember it). As I understand it, the batteries do not pull. According to the manual for a full charge in the region of 3 hours.
I don’t even know how to diagnose and where to start, while I’m studying the English manual. In this case, I'm far away, I'm afraid to harm the ups with my training, that's why I'm asking for advice. Thanks to those who responded in advance.
PS When he left, he turned off the UPS again, waited at least a minute for it to stop circulating currents, pulled out the plug and it made noise for another minute. Does it mean that there is a charge left in the batteries to complete or is it a self-discharge of the accumulated circulation?