Back-ups 1500 shutoff on full battery on outage

[Macmaster28]

I have a backups 1500 thats about 3 months old. 

I have about 40 watts of equipment for my home network (router, modem, AP) to keep my network up in the event of an outage. The estimated time shown is always around 250-300 minutes. 

After a recent power outage, I noticed my network went down. I tested the setup by simply pulling the plug on the ups, it switched to battery normally, but after 10 seconds, the display shuts off but the buttons stay illuminated, it then beeps intermittently for 15 seconds, then shuts off completely. Again, there were no error messages and battery level showed 250-300 minutes. 

I even removed all devices plugged it, with the battery time shooting up to 550+ minutes, and then when unplugging the ups from the wall, the same shutdown sequence occurred. I even reset the unit by removing the battery and holding the power button. 

The fact that its brand new, passes all its self tests, and shows no error messages whatsoever, and this sequence of events is not described in the manual, is puzzling and frustrating. 

Any help is welcome. 

[JonPro]

Hi @Macmaster28 

Thank you for reaching out to the SE Community, my name is Jon and I will assist you with this query.

By any chance, is it possible for you to plug additional equipment into the UPS for it to have at least 35% load and then do a pull plug test once more?  May I also ask the exact model of your UPS as well and on what outlets are the loads plugged in on the UPS?

If you have a Microsoft Desktop OS, would it be possible for you to install the PowerChute Personal Edition software?