Power packs

[squall9126]

I've been searching for a portable power pack that i can plug my PC into during a blackout. My town has had over a dozen blackouts this year so far and I can only read so much during them. I haven't had too much luck finding out a lot of info on them, i think it's my search terms, anyways can anyone recommend a unit or point me in the right direction. I want something that would last at least 6 hours, I've got a fairly basic PC with a 300W power supply and an 18" lcd monitor if that info helps. I'm not too knowledgeable about how power works so if you ask me for more info try and be as simple as possible. Thanks.

[MrIntruder]

Uninterruptable Power Supplies, simply put, are not cheap, the cheap ones typically last minutes at full load. The idea is with these is that if there is a powercut, you can safely power down your system without losing any data and/or have enough time to switch power over to a backup generator.

I'm not too familiar with the details myself but I believe this is along the lines of what to do.

[Slysoft]

I'd recommend getting a Tripp lite SU40K

[MarchHare]

With UPS units, you get what you pay for. As MrIntruder said, cheaper ones won't get you far if you want to keep going during a power outage. If you need to be able to work on the internet for longer than, say for instance, 30 minutes, you're better off getting a battery backup for your network equipment and have a laptop run on battery.

[kitamesume]

6hours sustained is absurdly long, if it were a 300watt load the UPS would need a battery-bank with 150AH/12V or 125AH/24V.
the battery alone at that size would cost you no less than $1500 - http://www.lithiumion-batteries.com/products/12v-150ah-lithium-ion-battery/


the best compromise, is a 3KVA generator and a fairly cheap but reputable UPS that could sustain a 2KVA load for at least 5minutes (this would mean an average of 35mins for a 300W load).

the power sizes are just an example, a good rule is having 2 times your entire circuit's maximum draw or you'd fry the UPS's inverter.
the generator must be at least 30% larger than your maximum load otherwise you could choke it, take note that a PC is an inductive load.


this is what a diesel generator's fuel efficiency chart would produce.

Code: [Select]

[30% efficiency conversion @ hour]
1L     diesel / hour = 2,988 Watts / hour
0.1L   diesel / hour =   299 Watts / hour
0.01L  diesel / hour =    30 Watts / hour
0.001L diesel / hour =     3 Watts / hour

i researched it comparing it to my local electricity cost, it barely breaks even, not accounting investment cost which means its impractical as an alternative to the grid.

PS: 30% efficiency is average efficiency of a typical diesel generator, only the ultra-long stroke special duty diesel engine can reach upwards of 60% efficiency.
a turbo-charged and fine-tuned middle-end diesel engine averages at 45%, the most efficient diesel car engine is still stuck at 50%.
i used diesel fuel's energy content as means to get the power output, gasoline is less efficient.


better yet grab a laptop with high battery life, macbook air i think lasts 7hours on light surfing.

[Pentium100]

I would suggest a fairly big UPS (I use a  APC Smart-UPS 2.2kVA and a 3kVA) to last trough he shorter blackouts (my two UPSs last 45-90 minutes total depending on whether the monitor and one optional PC is on or not, both UPSs have 4x12V/20Ah batteries each for a total of about 1kWh o energy). Then for the long periods get a gasoline or diesel generator. However, you either have to buy an on-line UPS (more expensive than line-interactive) or a generator with an inverter (more expensive than a regular one), otherwise, the UPS will most likely not work properly when powered by the generator.

[NaRu]

If you have the money I recommend http://www.newegg.com/Product/Product.aspx?Item=N82E16842102118

I get about 20 mins of power. If you only use 300 watts you will get about 40 mins on this thing.

[Pentium100]

I would advise against buying a rackmount UPS, unless you really need it. Due to the form factor, rackmount UPSs use lots of small batteries, which cost more than a few large ones with the same total energy capacity. Also, a more powerful UPS does not necessarily mean that it has bigger batteries.

For example, either of my big UPSs use 4x 12V 20Ah batteries for a total of 48V 20Ah capacity. The UPS in the link has 4x 12V 9Ah batteries for a total of 48V 9Ah capacity - half of what mine has. OTOH, my UPS would use up 4.5 rack units.

[kitamesume]

rackmount UPS are expensive and mostly aren't worth it unless you're in need of a really good UPS.

the common 800VA UPS you see from powercom or APC would work well enough, swap the battery for a larger one (50AH~100AH) and you could sustain a 300W load for hours at least.
the only problem with this is that these UPS aren't designed for sustained battery mode, none of the cheap UPS are, you may end up burning out the inverters.

will the OP be commenting back though? i doubt he'd be able to afford these suggestions of ours without compromises.

[Pentium100]

rackmount UPS are expensive and mostly aren't worth it unless you're in need of a really good UPS.

At least for APC, usually there is aversion of the UPS with a tower case - exact same UPS just in a case that allows for smaller number of bigger batteries.

Case in point - Smart-UPS 3000 and 3000RM use the same exact electronics - I have the main board from 3000RM in my UPS after the old one blew up.

[Freedom Kira]

Check out this Kickstarter project, which funded a little while ago.

[Tatsujin]

I've been searching for a portable power pack that i can plug my PC into during a blackout. My town has had over a dozen blackouts this year so far and I can only read so much during them. I haven't had too much luck finding out a lot of info on them, i think it's my search terms, anyways can anyone recommend a unit or point me in the right direction. I want something that would last at least 6 hours, I've got a fairly basic PC with a 300W power supply and an 18" lcd monitor if that info helps. I'm not too knowledgeable about how power works so if you ask me for more info try and be as simple as possible. Thanks.

Backup Batteries are awesome. I have two running and I'm thinking of getting me a third one with more juice inside. They save your equipment, surely.

This is what I have. Never tested it on full load. Though the beauty about this one and the older model (2008 model) is that they will instruct your computer to shut down (by force) if no power comes back after 5 minutes. The old model doesn't seem to put up very well so I have to switch my main computer to the new one. But man these things work wonder.

Doesn't matter which area your in and how much you brag about your buildings back up power and surge protectors. Having an extra insurance on your end is better than nothing.

[Freedom Kira]

this is what a diesel generator's fuel efficiency chart would produce.

Code: [Select]

[30% efficiency conversion @ hour]
1L     diesel / hour = 2,988 Watts / hour
0.1L   diesel / hour =   299 Watts / hour
0.01L  diesel / hour =    30 Watts / hour
0.001L diesel / hour =     3 Watts / hour

This chart makes no sense. A Watt is a unit of rate of energy consumption - a Joule per second. For the two sides to be equivalent, you'd have to say a volume of diesel can be translated into a rate of energy consumption.

[brunoais]

watt hour is energy.

Code: [Select]

watt = Jule / second
W = J/s
Wh = J/s * h
W*h = J * h/s
W*h = J * 3600/1 , 1h = 3600s
W*h = 3600J

See? Watt hour is energy .

Edit:
Oh wait... I think I get it... It's because he mentions as diesel / hour.
I think what he means is, for example,
If you are consuming such that, after 1h, you consume 1L of diesel, you have produced the amount of 2 988 Watt/hour of energy.

Edit2:
Fixed the formula above with something that I think is more correct...

[kitamesume]

this is what a diesel generator's fuel efficiency chart would produce.

Code: [Select]

[30% efficiency conversion @ hour]
1L     diesel / hour = 2,988 Watts / hour
0.1L   diesel / hour =   299 Watts / hour
0.01L  diesel / hour =    30 Watts / hour
0.001L diesel / hour =     3 Watts / hour

This chart makes no sense. A Watt is a unit of rate of energy consumption - a Joule per second. For the two sides to be equivalent, you'd have to say a volume of diesel can be translated into a rate of energy consumption.

deisel has 35.86MJ/L and thats exactly 2988Wh at 30% energy conversion efficiency.
35,860,000J / (60seconds * 60minutes) = 9,961.11 Wh
9,961.11 * 0.3 = 2988.33 Wh

i just simply converted 1L of diesel's megajoules into Wh, at 30% efficiency.
of course its in over-time, thats why its in "liters per hour".

ohh and - "The kilowatt hour, or kilowatt-hour, (symbol kWh, kW·h, or kW h) is a unit of energy equal to 1,000 watt-hours, or 3.6 megajoules."
http://en.wikipedia.org/wiki/Kilowatt_hour
doesn't it make perfect sense that 35.86MJ = 2988Wh @ 30% efficiency?

watt / hour is energy.

Code: [Select]

watt = Jule / second
W = J/s
W/h = J/s/h
W/h = J * h/s
W/h = J * 3600/1 , 1h = 3600s
W/h = 3600J

See? Watt hour is energy .

Edit:
Oh wait... I think I get it... It's because he mentions as diesel / hour.
I think what he means is, for example,
If you are consuming such that, after 1h, you consume 1L of diesel, you have produced the amount of 2 988 Watt/hour of energy.

exactly.

edit: so it simply meant that if your engine could burn 1L diesel per hour then you can expect it to produce 2988Wh @ 30% efficiency.

[Freedom Kira]

watt / hour is energy.

Code: [Select]

watt = Jule / second
W = J/s
W/h = J/s/h
W/h = J * h/s
W/h = J * 3600/1 , 1h = 3600s
W/h = 3600J

This algebra is incorrect going from the second step to the third because you are missing parentheses. 1 W/h = 1 (J/s)/h = 1 (J/s) * (1/h) = 1 J/sh.

Oh wait... I think I get it... It's because he mentions as diesel / hour.
I think what he means is, for example,
If you are consuming such that, after 1h, you consume 1L of diesel, you have produced the amount of 2 988 Watt/hour of energy.

Don't confuse Watt hour with Watt/hour. A Watt hour is the amount of energy consumed or produced of one watt in an hour; i.e. 3600 Joules. A watt per hour is a rate of change of a rate - like you're increasing by one Watt every hour, like acceleration is to velocity.

deisel has 35.86MJ/L and thats exactly 2988Wh at 30% energy conversion efficiency.
35,860,000J / (60seconds * 60minutes) = 9,961.11 Wh
9,961.11 * 0.3 = 2988.33 Wh

No, 35,860,000J / 3600s = 9,961.11 W.
9,961.11W * 30% = 2988.33 W.

i just simply converted 1L of diesel's megajoules into Wh, at 30% efficiency.
of course its in over-time, thats why its in "liters per hour".

ohh and - "The kilowatt hour, or kilowatt-hour, (symbol kWh, kW·h, or kW h) is a unit of energy equal to 1,000 watt-hours, or 3.6 megajoules."
http://en.wikipedia.org/wiki/Kilowatt_hour
doesn't it make perfect sense that 35.86MJ = 2988Wh @ 30% efficiency?

Yes, so why do you not see that your units and charts don't make any sense?

I don't really care about the background numbers - they're not really relevant. Diesel contains x J/L of energy. Burning y L/hr gives you z J/hr at E efficiency, which is a unit of energy over time, or Watts, not Watts per hour.

edit: so it simply meant that if your engine could burn 1L diesel per hour then you can expect it to produce 2988Wh @ 30% efficiency.

Still incorrect - If you burn some amount of diesel per hour, you are producing a certain amount of energy per hour. 2988Wh is an amount of energy. You can't burn 1L/hour until the end of time and still produce only 2988Wh of energy.

Point is, stop putting in per hour. 1L produces 2988Wh. That's it.

Let me put it this way. You're trying to say that if your car is moving at 30 m/s per hour, you should move 108km per hour. What the hell is 30 m/s per hour? What the hell is 2988 J/s per hour?

[brunoais]

Failed at algebra again...
I have to stop that...

[kitamesume]

edit: so it simply meant that if your engine could burn 1L diesel per hour then you can expect it to produce 2988Wh @ 30% efficiency.

Still incorrect - If you burn some amount of diesel per hour, you are producing a certain amount of energy per hour. 2988Wh is an amount of energy. You can't burn 1L/hour until the end of time and still produce only 2988Wh of energy.

Point is, stop putting in per hour. 1L produces 2988Wh. That's it.

Let me put it this way. You're trying to say that if your car is moving at 30 m/s per hour, you should move 108km per hour. What the hell is 30 m/s per hour? What the hell is 2988 J/s per hour?

no because liter is NOT a unit of energy. point is, burn a 1L of diesel in a span of 1second and you get 2988watts * 3600 of energy in watthour at 30% efficiency.
edit: because? burning a 1L diesel in a span of 1second means you're burning 3600liters per hour, which is 10.76megawatthour.
its a redundant thing, AND is the formula, if you hadn't notice it.

deisel has 35.86MJ/L and thats exactly 2988Wh at 30% energy conversion efficiency.
35,860,000J / (60seconds * 60minutes) = 9,961.11 Wh
9,961.11 * 0.3 = 2988.33 Wh

No, 35,860,000J / 3600s = 9,961.11 W.
9,961.11W * 30% = 2988.33 W.

3600s = 1hr
35.86MJ = 1L diesel
substitute values?
1L diesel / 1hr = 35.86MJ / 3600s

hence:

Code: [Select]

[30% efficiency conversion @ hour]
1L     diesel / hour = 2,988 Watts / hour
0.1L   diesel / hour =   299 Watts / hour
0.01L  diesel / hour =    30 Watts / hour
0.001L diesel / hour =     3 Watts / hour

edit: this made me wonder of what converting W to Wh is.
although the notion of "/" is interchangable with "per", math "/" means division so if it was as what the formulas say is true though then.
rather than 2988 watts / hour = 2988watthour, 35.86MJ = 10.76megawatt / hour which meant 10.76megawatt / hour = 2988watthour, which is incorrect or is it?

so it might be that part thats wrong, watts per hour would be correct and watts/hour wouldn't, or simply watthour then shrug.
which means this would be a better way to put it.

Code: [Select]

[30% efficiency conversion @ hour]
1L     diesel / hour = 2,988 Watthour
0.1L   diesel / hour =   299 Watthour
0.01L  diesel / hour =    30 Watthour
0.001L diesel / hour =     3 Watthour

[kureshii]

Watt-hour is "Wh", commonly also given in other metric forms like kilowatt-hours ("kWh"). "W/h" is not watt-hour, at least it wouldn't be, unless someone could show screenshots of watt-hours being represented as "W/h" in industry.

Pardon the interruption, please carry on.

[kitamesume]

then the latter chart is more accurate.


this talk about generators made me wonder of what UPS types that are best used with a generator and why.

googling gave me this.
http://www.upssystems.co.uk/knowledge-base/the-it-professionals-guide-to-standby-power/part-6-matching-a-generator-to-your-ups/