Hardware How to count Watt? How does it work? (Physics)

MeAndHax

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I just wanted to know if it was THEORATICALLY possible to run a PC through a Power Station that has 220Wh/60.000mAh. I know that it's not possible but I want to know how to calculate it and how quick the PC would turn off.

I tried to calculate it but I got really confused

A standart PC needs 1000 Watt per second so in an hour we have 60.000 Watt

but how exactly can I compare it to Wh?
 
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That's not how watt-hours work. Wh is a measure of capacity, while watts are a measure of power draw. 100W power draw over one hour equals 100Wh. The power draw is not measured per second, it's a constant 1000W (as example) over any period of time. You don't multiply it unless you want to know how much power it would use over a number of hours/days/weeks/whatever. Basically, watts * hours = watt-hours (this also applies to other types of measurements that are the combination of two different units - the dash means multiply the two together)

220 Wh might power your average mid-range gaming PC for an hour of gaming. Power supplies might be rated way above that, but actually the full capacity is only needed at power on, when all the...

emcintosh

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You’ve confused some units there.
Power is rate of transfer of energy and is measured in W, like for lightbulbs : ).
Energy stored would be power times time, so the unit you want here is Wh.
If your computer draws, say 60W, the 220Wh power bank should run it for 220/60= 3 & 2/3 hours. If it took 100W, it would last 220/100 = 2 & 1/5 hours.
Your computer shouldn’t be drawing 1000W - that’s the sort of power of a heater, and you’d notice the computer heating the room.
The mAh figure is the charge stored, and is related to the energy by the voltage the power bank supplies. 220Wh / 60 000 mAh = 3.7V. You would have difficulty powering a computer from that. AIUI USB power delivery is 20V. To supply even 60W at 3.7V, you’d draw a current of 16A. Toasty...
 

The Real Jdbye

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That's not how watt-hours work. Wh is a measure of capacity, while watts are a measure of power draw. 100W power draw over one hour equals 100Wh. The power draw is not measured per second, it's a constant 1000W (as example) over any period of time. You don't multiply it unless you want to know how much power it would use over a number of hours/days/weeks/whatever. Basically, watts * hours = watt-hours (this also applies to other types of measurements that are the combination of two different units - the dash means multiply the two together)

220 Wh might power your average mid-range gaming PC for an hour of gaming. Power supplies might be rated way above that, but actually the full capacity is only needed at power on, when all the capacitors charge up at the same time. The GPU is often the most power hungry part of a PC, easily drawing over 300W for the high end ones, the rest of the system might only draw something like 100-200W under heavy (artificial) load depending on what CPU you have, plus any spinning drives you have which can draw quite a bit. In gaming the CPU is not used as much so the GPU will be consuming most of the power. All this is not taking into account the efficiency of the PSU, which might be somewhere between 80%-94% but is most efficient at around half load. So add another 10-20% to those numbers.

But powerbanks aren't rated for that kind of power draw. That's why UPSes exist. Your average "cheap" UPS probably wouldn't have much more capacity than that powerbank but be much bulkier. As far as I understand, that's largely due to the circuitry needed to convert however many volts DC into 110/220V AC. As well as that, I believe they use lead acid batteries which are much less energy dense than lithium, but are still used because they can provide the amps needed, and are cheaper to make. Lithium batteries can provide high amperage (single cells can be found that are rated all the way up to 35A and maybe higher, mind you this is at 3.0-4.2 volts or thereabouts, 35A at 3 volts is only 105W so you would need a bunch to power a desktop PC, or you could use lipo packs which can be found in all sorts of ratings but are generally speaking a bigger fire hazard)
Just doesn't really make sense to use lithium batteries for something stationary that's gonna be hidden away underneath a desk or something where it doesn't matter that it's about the size of a printer and weighs a lot.

Also, you can get powerbanks that can power a PC. Any of the numerous one supporting USB-PD over USB-C can charge many laptops that support charging over USB-C and there are also ones that have a 12V or 18V or whatever output that's capable of charging laptops that don't have USB-C charging. And there are also powerbanks with actual AC outlets on them, though some of these are probably not designed for that sort of power draw, only the bigger bulkier ones that can actually power a desktop PC for any decent length of time would be rated for that and likely primarily used by people glamping and construction workers who don't have access to power to power their tools and such and for whatever reason don't want to use a generator. People have also made their own by combining numerous li-ion cells with a charge circuit and power inverter which is likely the cheapest option by far, as manufactured ones are not exactly in high demand, being something only people with special needs would buy, thus there are not that many manufacturers making them and they are free to set the price high as the people that need them will still buy them.

If you have a need for portable power for your desktop for some reason, a generator is probably the cheapest option and also can run indefinitely (until it breaks) as long as you keep topping it up. And those can easily provide thousands of watts in a relatively portable form factor as a cart on wheels which may even have a shelf you can stick all your PC hardware on when you move it around. But apart from having a LAN party in the woods or glamping, I can't really think of a reason any normal person would want that (if you can consider people LAN partying in the woods as normal, but hey, pretty cool)
 
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FAST6191

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"A standart PC needs 1000 Watt"

What sort of thing do you call a standard PC? Even before things calmed back down on that front after the core2 era I would have struggled to get that high -- some kind of 3 graphics card skulltrail monster might not even get that high.
Or are you counting a plasma TV in it all and trying to run it from an inverter?

As others mentioned though you have your units, and possibly concepts, confused.

But yeah each component within a computer will draw some power. Manufacturers and/or test sites will list how much this is. You get to add all this up and select a suitable power supply to handle it.
Most of the lists of power are for things running at their maximum power, and might have a safety factor on top of that (say the maximum it will ever run at is 20W they might give an extra 10% or even 20% and call that the power rating). To that end if you know what you are doing you can possibly buy a lower rated power supply than the theoretical maximum of the all the parts added together, or run it from an inverter, mains ring or generator rated below that maximum value.

If you multiply power by time you get watt hours (or possibly kilowatt hours if you use kilowatts or convert to it). As most electricity suppliers price their electricity in units (1 unit = 1 kilowatt hour) you can simply figure out how much it costs to run per hour, or possibly how long batteries might last if you are running it from batteries (you are not thinking about some kind of DC-DC conversion to make rails and run from car batteries are you?).

"how quickly it will turn off" is a different matter entirely and will depend upon what you are doing on the PC, the temperature of the supply, the supply itself (it might say 220W but be able to deliver more for a short period -- this will be something called duty cycle), the parts you put in it and more besides.
If you want to measure it running normally with a power meter (they are quite cheap nowadays -- they make them to see how much energy people use, you can even turn everything else off in your house and measure it with just the computer running from the meter that governs the house itself) then you can
You might also be able to offset it somewhat -- many uninterruptible power supplies will have a brownout protection but we are getting crazy right now.


Or if you prefer then short version.
If you only have 220W to play with then buy a bloody laptop.
 

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