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UPS runtime
I would like to calculate the approx runtime for my UPS.
I did a search, but found conflicting formulas. 12 volt 18 Ah Total use of computer, monitor, and router is about 200 watts. Thanks. |
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#2
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UPS runtime
Andy wrote on 3/31/2020 9:31 PM:
I would like to calculate the approx runtime for my UPS. I did a search, but found conflicting formulas. 12 volt 18 Ah Total use of computer, monitor, and router is about 200 watts. The simplest and most efficient way is to plug two lamps with 100 watt bulbs into your UPS and unplug everything else. Next unplug the UPS and note the time. When the bulbs start to fade, the up time is calculated by again noting the time and subtracting. The use of engineering formulas isn't very accurate. There are a bunch of highly nonlinear factors at play especially near situations were the battery is almost used up. I think that even UPS manufactures supplement theory with pull-the-plug-under-known load tests. Of course there loads are more accurately known than the light bulbs I suggested but you'll get a reasonable estimate fairly quickly. -- Jeff Barnett |
#3
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UPS runtime
Andy,
I did a search, but found conflicting formulas. 12 volt 18 Ah Neither is a formule, just some numbers. Just for the record, next time please include those formulas. They simply might include factors that are outside of a quick calculation (which we could than point out to you). But, onto the quick calculation: 12 volt times 18 Ah = 216 watt-hour. 216 watt-hour divided by 200 watts = a few minutes more than an hour Than again, that ignores any kind of conversion losses, the fact that when the battery goes near empty its voltage will drop (possibly causing the UPS to cut out early), and that VA's are not the same as watts. YMMV. Regards, Rudy Wieser |
#4
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UPS runtime
Andy wrote:
I would like to calculate the approx runtime for my UPS. I did a search, but found conflicting formulas. 12 volt 18 Ah Total use of computer, monitor, and router is about 200 watts. Thanks. To start with, you can characterize the load better, with a Kill-O-Watt power meter. They're cheap and reusable for all sorts of projects. (Model has "Watts" and "VA") http://www.p3international.com/products/p4400.html For example, my PC might range from 96W to 370W. The 370W would be with Furmark and Prime95 running. The UPS will not drain the battery flat. It has a cutoff threshold it uses. The battery spec of 18Ah, should be taken with a grain of salt. It does not take too many cycles of draining those batteries flat, to damage them. By keeping that in mind, I was able to get ten years out of my battery. Generally speaking, you should use the cabling interface provided with the UPS, to automatically shut down the PC cleanly when the power fails. It would take a pretty large rack of batteries, to make riding out all power outages possible. A Tesla powerwall (~$10K magnitude) is one pre-packaged way to do it. The longest conventional power failure I've had here, was 24 hours, for a relatively minor issue. The longest unconventional failure might have been three days (nuclear reactors all scrammed). During the ice storm more than ten years ago, some rural sites were without power for two weeks. Maybe a $100K worth of Powerwalls could handle that. At some point, it becomes absurd to prop up the PC :-) Paul |
#5
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UPS runtime
R.Wieser wrote:
Andy, I did a search, but found conflicting formulas. 12 volt 18 Ah Neither is a formule, just some numbers. Just for the record, next time please include those formulas. They simply might include factors that are outside of a quick calculation (which we could than point out to you). But, onto the quick calculation: 12 volt times 18 Ah = 216 watt-hour. 216 watt-hour divided by 200 watts = a few minutes more than an hour Than again, that ignores any kind of conversion losses, the fact that when the battery goes near empty its voltage will drop (possibly causing the UPS to cut out early), and that VA's are not the same as watts. YMMV. Regards, Rudy Wieser With modern "Active PFC" ATX supplies, the power factor is around 0.99 or so. This means that roughly "VA equals Watts" on those. With the older supplies, the PF was around 0.7 or 0.65 or so, meaning a Kill-O-Watt meter might come in handy for characterizing the load. The Kill-O-Watt meter is good enough at what it does, to nail the "off" power (like when the PC sleeps). Many other measurement methods can be off by a factor of ten (when you believe them). For example, using the Kill-O-Watt, my machine with 8 DIMMs draws 7.5W at S3 sleep, and the machine with 4 DIMMs draws 5W at S3 sleep. If the 8 DIMM machine is in Soft Off state, power drops to 1.3W and some of that is USB devices on 5VSB. Some UPS do not behave well, when on battery and driving extremely light loads. Throwing a couple 3W lights onto the UPS, might keep it running with such a light load. (Preferably 3W incandescent, or even power resistors, if you have the skills to wire some of the correct value up.) If your UPS continues to run down to zero load, then... great :-) And some UPS, if you switch them off using the switch, then switch them on, they won't go back onto battery. They're refuse to do anything until the power comes back. If you were thinking "I'll just switch this off so in an hours time I can do X", they don't necessarily accept your request when asked. They can be temperamental. Paul |
#6
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UPS runtime
On Wednesday, April 1, 2020 at 3:08:08 AM UTC-5, R.Wieser wrote:
Andy, I did a search, but found conflicting formulas. 12 volt 18 Ah Neither is a formule, just some numbers. Just for the record, next time please include those formulas. They simply might include factors that are outside of a quick calculation (which we could than point out to you). But, onto the quick calculation: 12 volt times 18 Ah = 216 watt-hour. 216 watt-hour divided by 200 watts = a few minutes more than an hour Than again, that ignores any kind of conversion losses, the fact that when the battery goes near empty its voltage will drop (possibly causing the UPS to cut out early), and that VA's are not the same as watts. YMMV. Regards, Rudy Wieser Thanks. Andy |
#7
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UPS runtime
On Wednesday, April 1, 2020 at 1:07:39 AM UTC-5, Jeff Barnett wrote:
Andy wrote on 3/31/2020 9:31 PM: I would like to calculate the approx runtime for my UPS. I did a search, but found conflicting formulas. 12 volt 18 Ah Total use of computer, monitor, and router is about 200 watts. The simplest and most efficient way is to plug two lamps with 100 watt bulbs into your UPS and unplug everything else. Next unplug the UPS and note the time. When the bulbs start to fade, the up time is calculated by again noting the time and subtracting. The use of engineering formulas isn't very accurate. There are a bunch of highly nonlinear factors at play especially near situations were the battery is almost used up. I think that even UPS manufactures supplement theory with pull-the-plug-under-known load tests. Of course there loads are more accurately known than the light bulbs I suggested but you'll get a reasonable estimate fairly quickly. -- Jeff Barnett That's one way. Would need to wear some ear plugs to avoid listening to all those beeps that occur every minute. :-) Andy |
#8
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UPS runtime
On Wednesday, April 1, 2020 at 3:54:32 AM UTC-5, Paul wrote:
Andy wrote: I would like to calculate the approx runtime for my UPS. I did a search, but found conflicting formulas. 12 volt 18 Ah Total use of computer, monitor, and router is about 200 watts. Thanks. To start with, you can characterize the load better, with a Kill-O-Watt power meter. They're cheap and reusable for all sorts of projects. (Model has "Watts" and "VA") http://www.p3international.com/products/p4400.html For example, my PC might range from 96W to 370W. The 370W would be with Furmark and Prime95 running. The UPS will not drain the battery flat. It has a cutoff threshold it uses. The battery spec of 18Ah, should be taken with a grain of salt. It does not take too many cycles of draining those batteries flat, to damage them. By keeping that in mind, I was able to get ten years out of my battery. Generally speaking, you should use the cabling interface provided with the UPS, to automatically shut down the PC cleanly when the power fails. It would take a pretty large rack of batteries, to make riding out all power outages possible. A Tesla powerwall (~$10K magnitude) is one pre-packaged way to do it. The longest conventional power failure I've had here, was 24 hours, for a relatively minor issue. The longest unconventional failure might have been three days (nuclear reactors all scrammed). During the ice storm more than ten years ago, some rural sites were without power for two weeks. Maybe a $100K worth of Powerwalls could handle that. At some point, it becomes absurd to prop up the PC :-) Paul I used a watt o meter to come up with the usage figures. Andy |
#9
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UPS runtime
On Wednesday, April 1, 2020 at 4:21:26 AM UTC-5, Paul wrote:
R.Wieser wrote: Andy, I did a search, but found conflicting formulas. 12 volt 18 Ah Neither is a formule, just some numbers. Just for the record, next time please include those formulas. They simply might include factors that are outside of a quick calculation (which we could than point out to you). But, onto the quick calculation: 12 volt times 18 Ah = 216 watt-hour. 216 watt-hour divided by 200 watts = a few minutes more than an hour Than again, that ignores any kind of conversion losses, the fact that when the battery goes near empty its voltage will drop (possibly causing the UPS to cut out early), and that VA's are not the same as watts. YMMV. Regards, Rudy Wieser With modern "Active PFC" ATX supplies, the power factor is around 0.99 or so. This means that roughly "VA equals Watts" on those. With the older supplies, the PF was around 0.7 or 0.65 or so, meaning a Kill-O-Watt meter might come in handy for characterizing the load. The Kill-O-Watt meter is good enough at what it does, to nail the "off" power (like when the PC sleeps). Many other measurement methods can be off by a factor of ten (when you believe them). For example, using the Kill-O-Watt, my machine with 8 DIMMs draws 7.5W at S3 sleep, and the machine with 4 DIMMs draws 5W at S3 sleep. If the 8 DIMM machine is in Soft Off state, power drops to 1.3W and some of that is USB devices on 5VSB. Some UPS do not behave well, when on battery and driving extremely light loads. Throwing a couple 3W lights onto the UPS, might keep it running with such a light load. (Preferably 3W incandescent, or even power resistors, if you have the skills to wire some of the correct value up.) If your UPS continues to run down to zero load, then... great :-) And some UPS, if you switch them off using the switch, then switch them on, they won't go back onto battery. They're refuse to do anything until the power comes back. If you were thinking "I'll just switch this off so in an hours time I can do X", they don't necessarily accept your request when asked. They can be temperamental. Paul I installed software for my UPS as well as connected a cable from my computer to my UPS. It said Time to Empty is 40 minutes. I have periodic power outages, but they usually only last a few seconds to a few minutes. Andy |
#10
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UPS runtime
On Wed, 1 Apr 2020 at 04:54:27, Paul wrote:
[] It would take a pretty large rack of batteries, to make riding out all power outages possible. A Tesla powerwall (~$10K magnitude) is one pre-packaged way to do it. The longest conventional power failure I've had here, was 24 hours, for a relatively minor issue. The longest unconventional failure might have been three days (nuclear reactors all scrammed). During the ice storm more than ten years ago, some rural sites were without power for two weeks. Maybe a $100K worth of Powerwalls could handle that. At some point, it becomes absurd to prop up the PC :-) Paul There comes a point where a generator becomes economic. OK, you've got to have fuel for it, but the energy density ... Though you've also (assuming you truly want the U of UPS) got to switch over while you've still got enough power to start it, and a way to instigate that. -- J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf After I'm dead I'd rather have people ask why I have no monument than why I have one. -Cato the Elder, statesman, soldier, and writer (234-149 BCE) |
#11
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UPS runtime
J. P. Gilliver (John) wrote:
On Wed, 1 Apr 2020 at 04:54:27, Paul wrote: [] It would take a pretty large rack of batteries, to make riding out all power outages possible. A Tesla powerwall (~$10K magnitude) is one pre-packaged way to do it. The longest conventional power failure I've had here, was 24 hours, for a relatively minor issue. The longest unconventional failure might have been three days (nuclear reactors all scrammed). During the ice storm more than ten years ago, some rural sites were without power for two weeks. Maybe a $100K worth of Powerwalls could handle that. At some point, it becomes absurd to prop up the PC :-) Paul There comes a point where a generator becomes economic. OK, you've got to have fuel for it, but the energy density ... Though you've also (assuming you truly want the U of UPS) got to switch over while you've still got enough power to start it, and a way to instigate that. This is true. I hate gas, which is why I don't think in those terms. It's keeping them starting, keeping them running that bothers me. You might convince me, if the device ran off natural gas, as then there'd be no fuel injection scheme, I'd just have to change the oil (I can do that), put in a new sparkplug at some point, and that would make a palatable solution. AFAIK, the natural gas network stays up during power failures. When I was a teenager, I pulled the starter cord so many times on our gas lawnmower, I snapped the cord on it :-) These are the experiences I remember. I would need a "significant incentive" to think that way :-) My multiple attempts to fix carbureted devices has left a bad taste in my mouth (probably the taste of gasoline). Needle valves and all that jazz. I probably need to take a "small engine" course. Paul |
#12
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UPS runtime
On Thu, 2 Apr 2020 at 05:24:26, Paul wrote:
J. P. Gilliver (John) wrote: On Wed, 1 Apr 2020 at 04:54:27, Paul wrote: [] It would take a pretty large rack of batteries, to make riding out all power outages possible. A Tesla powerwall (~$10K magnitude) is one pre-packaged way (Someone pointed me at a link yesterday to electric Tornados [the fighter aircraft]. I twigged more or less immediately - no way current technology could do a fighter, small passenger plane maybe - even before I got to them having to sometimes fly inverted to make sure the special USB charging cables ...) [] of Powerwalls could handle that. At some point, it becomes absurd to prop up the PC :-) Paul There comes a point where a generator becomes economic. OK, you've got to have fuel for it, but the energy density ... Though you've also (assuming you truly want the U of UPS) got to switch over while you've still got enough power to start it, and a way to instigate that. This is true. I hate gas, which is why I don't think in those terms. (We call it Petrol, of course.) It's keeping them starting, keeping them running that bothers me. You might convince me, if the device ran off natural gas, as then there'd be no fuel injection scheme, I'd just have to change the oil (I can do that), put in a new sparkplug at some point, and that would make a palatable solution. AFAIK, the natural gas network stays up during power failures. Never thought of that! Yes, it has some reserve capacity (tanks with heavy lids to keep the pressure up), and probably has non-electric pumps to do so too. When I was a teenager, I pulled the starter cord so many times on our gas lawnmower, I snapped the cord on it :-) These are the experiences I remember. I would need a "significant incentive" to think that way :-) My multiple attempts to fix carbureted devices has left a bad taste in my mouth (probably the taste of gasoline). Needle valves and all that jazz. I probably need to take a "small engine" course. Paul Diesels are a lot simpler, though I'm not sure there are very small ones. (I once had reason to see the backup generator at one of my employers: it wouldn't have been out of place in a small freighter!) -- J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf WANTED, Dead AND Alive: Schrodinger's Cat |
#13
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UPS runtime
J. P. Gilliver (John) wrote:
On Thu, 2 Apr 2020 at 05:24:26, Paul wrote: J. P. Gilliver (John) wrote: On Wed, 1 Apr 2020 at 04:54:27, Paul wrote: [] It would take a pretty large rack of batteries, to make riding out all power outages possible. A Tesla powerwall (~$10K magnitude) is one pre-packaged way (Someone pointed me at a link yesterday to electric Tornados [the fighter aircraft]. I twigged more or less immediately - no way current technology could do a fighter, small passenger plane maybe - even before I got to them having to sometimes fly inverted to make sure the special USB charging cables ...) [] of Powerwalls could handle that. At some point, it becomes absurd to prop up the PC :-) Paul There comes a point where a generator becomes economic. OK, you've got to have fuel for it, but the energy density ... Though you've also (assuming you truly want the U of UPS) got to switch over while you've still got enough power to start it, and a way to instigate that. This is true. I hate gas, which is why I don't think in those terms. (We call it Petrol, of course.) It's keeping them starting, keeping them running that bothers me. You might convince me, if the device ran off natural gas, as then there'd be no fuel injection scheme, I'd just have to change the oil (I can do that), put in a new sparkplug at some point, and that would make a palatable solution. AFAIK, the natural gas network stays up during power failures. Never thought of that! Yes, it has some reserve capacity (tanks with heavy lids to keep the pressure up), and probably has non-electric pumps to do so too. I can't honestly say I've seen any natural gas infrastructure in town here. I don't know where the reservoir is, if one is present. Never seem to have a problem with pressure. When they have natural gas pumping stations, there's usually a good deal of clearance around them. A buddy at work, used to work on stuff like that. And he said, sometimes he'd drive to a site in his pickup, and there'd be a crater in the ground, where the pumping station used to be :-) And that's why it's better not knowing where stuff like that is located. It would have been interesting, to know where he parked the pickup... how far away, and how fast he could run. Paul |
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