Question why power cut caused my ups to turn off my computer during gaming?

Oct 4, 2021
I was playing Assassin's Creed Valhalla on my pc and with my new UPS which was connected in normal mode. Suddenly I faced load shedding/power cut during gameplay and I saw that my pc got turned off. Then when electricity came I again played the same game and with ups in normal mode, then during gameplay I intentionally disconnected the UPS from my power board and this time with backup mode my pc was not turned off, and I was able to play the game with UPS backup.
I would like to know why ups turned off my pc during a natural power cut/load shedding event where it was able to keep my pc on after my intentional power cut?
Should i be worried about this problem? If yes, then how can I solve this issue? I am asking this very important question because earlier I fried my gigabyte rtx 3060 ti while I was not using ups back then(see this post of mine : ),so this time with new GPU, I brought a new ups so that I am out of trouble but still seems like luck is not on my side :(
My pc specifications :
  • Noctua NH-D9L, premium CPU Cooler with NF-A9 92mm Fan(bronze)
  • western digital 1TB Blue desktop HDD
  • MSI Radeon RX 6500 XT MECH 2X 4G OC GDDR6 Graphics Card
  • MaxGreen A363BK ATX Casing
  • amd ryzen 5 3600x
  • samsung 970 evo plus nvme m.2 250gb ssd
  • Gigabyte p650B 650w 80 plus bronze certified non-modular power supply # gp-p650b
  • corsair vengence LPX 8GB 3200MHz ddr4 desktop ram(ram slot B2)
  • corsair vengence LPX 8GB 3200MHz ddr4 desktop ram(ram slot A2)
  • Havit KB585GCM Gaming Wireless Keyboard & Mouse
  • SAMSUNG LF22T350FHW 22 inch 75Hz full hd ips led monitor
  • Power Guard PG650VA-CS 650VA Offline UPS with Plastic Body (
my UPS acted like IPS and i don't know why(was my pc turned off very quickly before UPS went to back up mode? Is this possible?)
blame could be with your PSU, in PSU parameters you should be able to find out what hold up time it has
its a time for how long PSU can run without any power, its should be 16ms+ per ATX specs

here you can see AC loss to power ok is only 11.5ms, which is below industry standart and ATX specs

now when power cuts out, UPS needs time to switch to battery, this time needs to be lower than your PSU AC loss hold up time
i cant find switch time for your UPS unit but since your PC is shuting down, then it could be at industry 15ms

anyway its a 390watt UPS, that might be low during gaming, dont you think?
if PC components draws 300watts from PSU at 90% efficiency, it will take 330 watts from wall (or UPS)
did you check with wattmeter that your UPS can handle your PC under load?