APC Back-UPS BX1100C-IN 1100VA / 660W, 230V, UPS System, An ideal Power Backup & Protection for Home Office, Desktop PC & Home Electronics

This UPS does fail my PC sometimes when load on my GPU and CPU is high and Mains electricity fails again and again within seconds.That is a rare occurrence. It fails with UPS being “overloaded” when electricity fails. Now before you guys start telling me I should go for a larger UPS, the recommended PSU for my combo of CPU and GPU (ryzen3500 and GTX 1060) is less than 450 watts. And adding maximum losses from 80PLUS PSU, it still does not ask for more than 540 watts. UPS is 660 watts. As a matter of fact I can Cold Start my UPS when Mains electricity is OFF and I can load my PC maximally (both GPU and CPU) for a few minutes on battery backup without problem.So too much load is not the problem. It is momentary overload when electricity fails . I will explain it in a bit more detail ahead.

Anyway I will not return this unit because this is the best I can get for this amount of money from a big brand. Now let me explain to the extent of my understanding why it sometimes fails in rare circumstances.

It is most basic model of UPS from APC. Anything above it from APC costs considerably more both in initial purchase and later in Battery replacement costs. Today in era of APFC PSUs, Sine-wave UPS are preferred, but sine-wave UPS are basically not available in India or are priced too highly. So I will settle for this. Even APC itself suggests Sine-wave UPS for APFC PSUs, and if you have a decent PC bought in last 10 years it most probably has APFC PSU.

Now for those who don’t know about “Transfer Time”, most of the UPS in market do not provide power backup upon Mains electricity failure “INSTANTLY”. There is a Tiny time delay in switching on battery power of UPS. This Delay is “Transfer time.” PSUs are supposed to handle this “Transfer time” to extent of about 15ms. PSUs have some energy in their capacitors. So Max of 12ms from this UPS should be acceptable. But not all PSUs are good enough. Even branded PSUs of huge brands fall short on this parameter by a little bit. So it is always better for UPS transfer time to be lower. If PSUs capaitor are unable to handle “Transfer time”, PC will restart in most cases. This does not happen for me.

Also during this delay of “Transfer time” capacitors in PSU gets discharged, causing a larger than normal current to charge capacitors when power is resumed after the tiny delay. This current is Inrush current and can cause UPS to shutdown because of overload. This probably is the case for me. Less the transfer time, less the capacitor is discharged and less is the Inrush current. So , again, it is always better for UPS transfer time to be lower.

Many other brands are offering Transfer time in 4-8ms in this price range. But they are less reputed than APC, so I will stick with APC. But I expect even basic model from brand like APC to have better “Transfer time”. It is a critical parameter of UPS. In the era of APFC PSUs all UPS from a big brand must be Sine wave. But alas that is not the case.

If you need 100 percent reliability you can sure go for expensive models with Less “Transfer Time” or preferably Less “Transfer Time” and Sine-wave. If your work is really important and money is no limit, go for “Online topology” UPS which have ZERO “Transfer time”, but will need more battery costs, and even consume a bit more energy.