UPS getting overload when PC is connected

I have a UPS with 600VA.

When I connect it to my small laptop and a monitor, the total wattage amounting to 40W approximately (to the higher side), the ups on backup runs for 40-50 minutes.

**But when I connect my PC instead of laptop but with the same monitor, it runs on AC perfectly but when the power goes off, the UPS makes overload sound and turns off in 2-5 seconds. **

Also, when connected to the PC, the UPS doesn’t cold start. It starts only when plug is connected to power.

The PC is not a powerful one.

Specs:

  1. Motherboard: DH61HO
  2. Processor: i3 2120
  3. Graphics card: GT710 without fan
  4. 2 Rams DDR3 1333 (4gb and 2gb)
  5. 120gb ssd
  6. 1TB HDD 2.5 inch which i took from external hdd
  7. 450W SMPS
  8. Four 80inch fans.

The UPS is not used much on backup but it is 4 years old.

Is this problem because of faulty battery or some internals of the UPS? Or is it due to my PC’s SMPS being faulty?

The UPS was working fine for the PC for 3 years and I suspended using it for 1 year. Then I resumed using it and after 1 year of use and added a GT710 and 3 extra fans. Then this problem started shortly after fans added.

I am really thankful for the time you took to read this. Any ideas will be appreciated with thanks.


It sounds like you might have an issue with power factor correction and be right on the edge of what the UPS can handle - or the 600VA rating of the UPS is "optimistic" or both. The reality is your setup is "on the edge".

600VA is not the same as 600 watts. They would be the same in a DC circuit, but a VA is less then a Watt - how much less depends - but it could be as low as 350 watts. Indeed, a power factor of 0.7 is not uncommon which means that a 450 watt power supply is more then a 600VA UPS may be designed to handle.

That said, although you have a 450 watt PSU, I would think that the actual draw of the power supply should be a lot lower in that system - certainly your component current draw don't add up to anything close to 450 watts. This likely implies a cheap UPS that is failing.