Confused in UPS

[Nebula43]

I want to plug my Router, Monitor and pc into a ups. What ups i am looking at is 600W/1000VA. It has 12V/7.2AH x 2 batteries Lead- acid. UPS has efficiency rating of 95% and MY Power supply has a efficiency of 90%. On PC part picker, my pc will consume around 490w. My monitor should consume 40w and my router around 30w. But what i am concerned about is, will the ups be able to handle the load of 560-570w for at least 10min? Can you please help me make the right decision? What other factors should i look for ? When the efficiency rating of ups matters, while running on battery or on mains? 

[AnonymousGuy]

Not quite.

 

watt hour = 12 x7.2 x 2 x .95

 

watt hour / load = 16.2 minutes

 

However you don't get 100% discharge from lead acid batteries so really the capacity is 50% of the rated AH.  (Lithium is 100% but no one really puts those in non-enterprise UPS's)

So you're getting about 8 minutes at 600W.  However, you're unlikely to be maxing your PC out all the time.

[Nebula43]

13 minutes ago, AnonymousGuy said:

Not quite.

 

watt hour = 12 x7.2 x 2 x .95

 

watt hour / load = 16.2 minutes

 

However you don't get 100% discharge from lead acid batteries so really the capacity is 50% of the rated AH.  (Lithium is 100% but no one really puts those in non-enterprise UPS's)

So you're getting about 8 minutes at 600W.  However, you're unlikely to be maxing your PC out all the time.

So, there won't be any overloading issues? The ups is 95% efficient, what does it mean?

[Needfuldoer]

A desktop UPS isn't meant to give you more than a few minutes of run time, so you have a chance to save everything and do a clean shutdown when the power goes out. They're not sized so you can keep gaming for an hour on battery.

 

"Around 490 watts" is also the maximum your PC could theoretically draw if you were running cpuburn, a drive test, and FurMark. It will undoubtedly use a lot less than that when it's idling or under low load. (If I had to guess, well under 100 watts.)

 

Theoretical power draw and guesses are one thing, but if you really want to know how much power your stuff draws you'll need something like a Kill-a-Watt meter. Fancier consumer UPSes have a screen on them that tells you their current load and state of charge, and most good ones will have a USB port so you can monitor it with software.

 

I'd recommend getting at least that 600W/1000VA UPS, shutting down your PC as quickly as you can while on battery (and you expect an outage of more than a few minutes), and saving the rest of the charge for your router and an LED lamp or two. I know from experience you'll get hours and hours of LED lamp run time out of even a mediocre UPS.

 

 

[manikyath]

most UPS manufacturers list run time at 100% capacity and run time at 50% capacity. 

very often runtime at 100% load is just a few minutes, and when your batteries wear out this gets MUCH worse.

you might get 15 minutes initially, but after a few outages you may only get half that.

 

past that... "efficiency" isnt really something you should be shopping for in a UPS. 90+ efficiency is all fine and good, but if the sine wave is horrid, or it doesnt kick in fast enough, it is gonna do more bad than good.

 

also, when running off mains, you're either connected directly to mains, or going trough a transformer. there's no "efficiency" to be had there.

[mariushm]

33 minutes ago, Nebula43 said:

I want to plug my Router, Monitor and pc into a ups. What ups i am looking at is 600W/1000VA. It has 12V/7.2AH x 2 batteries Lead- acid. UPS has efficiency rating of 95% and MY Power supply has a efficiency of 90%. On PC part picker, my pc will consume around 490w. My monitor should consume 40w and my router around 30w. But what i am concerned about is, will the ups be able to handle the load of 560-570w for at least 10min? Can you please help me make the right decision? What other factors should i look for ? When the efficiency rating of ups matters, while running on battery or on mains? 

 

Your computer components only consume as much as they need.  Your video card may consume 200-300 watts only when gaming, your cpu will consume 50-100 watts only when heavily used. 

When you're typing a message in this forum, or watching a Youtube video, your processor will put some cores to sleep or reduce their frequencies, to lower the power consumption - your cpu could consume as little as 5-10 watts. 

Same for the video card, when you're not gaming, it will reduce frequency of both gpu chip and the ram on the card, it will maybe stop spinning the fans if not needed. 

If you're gonna game and you have a power failure, you're gonna hear the UPS beeping and most likely you're gonna pause the game or turn off the game, and therefore your PC's power consumption should drop significantly, under 100 watts.

I doubt your router consumes 30 watts, but 10-15 watts would be within reasonable values.  Read the label of its power adapter, it should say how much power it's rated for. 

The monitor power consumption varies with the brightness levels you set - could be 20-80 watts, depends on how much backlight your have. 

 

So your computer's power supply's efficiency is 90% - that means when it produces 100 watts for components, that 100 watts represents 90% of the power it actually consumed from the mains power.  So : 

100 watts ... 90% 

?  watts  ... 100%  

Therefore ?  =  100% x 100 watts /  90  = 111 watts. 

 

Your UPS is 95% efficient ... that means that if it produces 111 watts to give the power supply of the computer, those 111 watts will be 95% of the amount of power taken from the batteries.  So again ... 100% x 111 watts / 95% = 116 watts. 

 

It's hard to estimate how long it's gonna last, because as the batteries discharge, the conversion efficiency will vary a bit, and as the batteries age they won't last as long. 

Lead acid batteries are fully charged at around 13.8v and can be discharged down to around 10.8-11v  ... so the UPS has those two in series giving it 22v ..28v which then gets boosted to 110v AC or 230v AC with that 95% efficiency. 

The conversion may be 95% efficient at 25-28v to 110/230, when nearly fully charged batteries  but only 92% efficient when the batteries are nearly discharged, at 22-24v.. 

 

But from the start you assume that your computer's gonna have a constant power consumption of 490 watts.  Most of the time when there's a power failure, you'll realize and just pause the game to reduce power - often (if the game is well programmed), just alt-tabbing / minimizing the game is enough to reduce power consumption of your computer a lot. 

 

[Kilrah]

On 7/27/2022 at 10:16 AM, manikyath said:

also, when running off mains, you're either connected directly to mains, or going trough a transformer. there's no "efficiency" to be had there.

The transformer definitely has an efficiency that can be significant. On my UPS there are about 10W of transformer losses even with no load on the output. With its ~80W load it's a bit more and it adds a good 15% overall.

 

But yeah, on a consumer UPS unless it's seriously oversized if you have an outage you wait 30secs to see if it comes back straight away, and if not you shut down (ideally automated by software).

[manikyath]

8 hours ago, Kilrah said:

The transformer definitely has an efficiency that can be significant. On my UPS there are about 10W of transformer losses even with no load on the output. With its ~80W load it's a bit more and it adds a good 15% overall.

i'd hazard a guess that that 10W is used to keep the UPS's functions up and running. if it's a static number of watts no matter the load it's not an efficiency loss, but an inherent power consumption.

[Kilrah]

That power consumption is iron loss in the transformer getting quite warm, electronics are doing/using basically nothing.