Computer suddenly draws more watts?

[JohnSmith2]

I have an i7 5960x (8-core, 16 threads) and two GTX 970s that are all running at full load 24/7. The total system power usage is typically around 450-550 watts when everything is under load. It has a 1000 watt power supply and is plugged into a UPS with a battery backup that is rated for 810 watts.

 

When the electricity in our house goes out or lights start flickering briefly (common in the spring/early summer), the UPS starts emitting a constant tone. However, rather than continuing to power the computer like I would expect, the computer still shuts off anyway, defeating the purpose of the battery backup in the UPS. I looked up what the constant tone means in the manual and it says this is because the 810 watt capacity was exceeded (so it shut off power to the computer), even though under full load the system only draws 450-550 watts (the UPS tells me this). So how does that happen?

 

Whenever the house has some kind of electricity problem (like it going out or lights flickering) because of a storm or whatever, is it possible that the computer can suddenly draw more watts than the 810 watt capacity? I just have no idea why this happens given the machine never gets close to 810 watts even under full GPU + CPU load when the electricity in the house is stable. It is a Thermaltake Toughpower 1000W Gold power supply and a CyberPower 810 watt battery backup UPS.

[jaslion]

Is the ups old?

 

Can easily be that due to a degraded battery or circuit it cannot handle the load anymore.

[mariushm]

Is it Cyberpower 810  watts or 810 VA  ?

 

If it's VA, you're probably overloading the UPS ... you should not go above 50-60% of the VA rating of any UPS, or around 4-500w if you ups has a rating of 800va

 

Other explanations could be the UPS takes too long time to switch to battery and start giving the full 500 watts or so, which causes the internal capacitors in the power supply to discharge and shut down the psu. Maybe the internal lead acid batteries are aged and have a much higher internal resistance and can't keep up pushing so much power all of the sudden.

 

Also, a power supply may pull more current when it's fed with simulated sine wave or whatever AC output the UPS does ... normally more expensive UPSes output pure sine wave AC, but cheaper models do a simulated sine wave output or almost square wave output.

The power factor correction circuits in power supply sometimes have issues with these not so pure sine wave AC inputs and it can result in pulses of higher power consumption (like for example power supply pulling 700w for 10 ms then 300w for 20ms and so on, averaging at 500-550w)

 

[dkoudijs]

On 6/14/2021 at 8:04 AM, mariushm said:

Is it Cyberpower 810  watts or 810 VA  ?

 

If it's VA, you're probably overloading the UPS ... you should not go above 50-60% of the VA rating of any UPS, or around 4-500w if you ups has a rating of 800va

 

Other explanations could be the UPS takes too long time to switch to battery and start giving the full 500 watts or so, which causes the internal capacitors in the power supply to discharge and shut down the psu. Maybe the internal lead acid batteries are aged and have a much higher internal resistance and can't keep up pushing so much power all of the sudden.

 

Also, a power supply may pull more current when it's fed with simulated sine wave or whatever AC output the UPS does ... normally more expensive UPSes output pure sine wave AC, but cheaper models do a simulated sine wave output or almost square wave output.

The power factor correction circuits in power supply sometimes have issues with these not so pure sine wave AC inputs and it can result in pulses of higher power consumption (like for example power supply pulling 700w for 10 ms then 300w for 20ms and so on, averaging at 500-550w)

 

This is a pretty good way of explaining it. I would think that yes when tripping to UPS mode, the PC is pulling more power thus, tripping the unit.

I know in data centers they normally go with your UPS should be hovering around 50-60% of your load. This way the batteries can stay when you switch over to battery power.

 

Also could you test your UPS with something small, like just your monitor/lamp/fan? Just to see if the UPS does deliver power at all?

[Forbidden Wafer]

Some UPSs do not behave normally due to power factor correction from power supplies. If it never worked for you, that may be the case. It may be good for lower powered computers (e.g. laptops), as those don't have that kind of stuff.

[JohnSmith2]

On 6/14/2021 at 7:04 AM, mariushm said:

Is it Cyberpower 810  watts or 810 VA  ?

 

If it's VA, you're probably overloading the UPS ... you should not go above 50-60% of the VA rating of any UPS, or around 4-500w if you ups has a rating of 800va

 

Other explanations could be the UPS takes too long time to switch to battery and start giving the full 500 watts or so, which causes the internal capacitors in the power supply to discharge and shut down the psu. Maybe the internal lead acid batteries are aged and have a much higher internal resistance and can't keep up pushing so much power all of the sudden.

 

Also, a power supply may pull more current when it's fed with simulated sine wave or whatever AC output the UPS does ... normally more expensive UPSes output pure sine wave AC, but cheaper models do a simulated sine wave output or almost square wave output.

The power factor correction circuits in power supply sometimes have issues with these not so pure sine wave AC inputs and it can result in pulses of higher power consumption (like for example power supply pulling 700w for 10 ms then 300w for 20ms and so on, averaging at 500-550w)

 

Thanks, this helps. The UPS is 6 years old now. This is the exact model: https://www.cyberpowersystems.com/product/ups/lx1325g/

[mariushm]

Ok, it's simulated wave output and can output up to 810 watts (but lasts only 3 minutes at that output)

The batteries probably have to be replaced... the page says 2 lead acid 12v 8ah batteries ... these should be standard but just to be sure, open the ups

You'll want to get vrla batteries ... sealed lead acid batteries optimized for ups and not car batteries, those are optimized for current and fast discharge (to push current into spark plugs and cranking the motor)

[LogicalDrm]

-> Moved to Power Supplies