How heavy is 35 kilograms?

Factual Questions
61

Then just have them running all the time! When at home, they can be plugged into the wall, and when moving around, they can be unplugged and carried around.

Well, maybe the UPS could be plugged in first, wait a night or a few hours to energize fully, and then after its fully charged, you could unplug it and carry it around like a portable.

But I wouldn’t want an inverter anyway, because it’s too heavy, too much hassle and I think they all emit toxic radiation waves and radio signals or they burn toxic plastic stuff inside of them.

Plus they are loud and they generate lots of heat. The one I have is made of plastic and it gets extremely hot, sometimes it is dangerously hot to touch, and it blocks out most/all car radio signals as well.

It also makes a static/vibration effect on the metal phone when I plug that into it. It makes the phone difficult and worrisome to hold, and I have dropped it dozens of times when trying to hold it while it’s plugged into the inverter.

That’s a terrible idea! If it’s outside the case, no one will let you into their buildings for probably sound reasons. If it’s hidden inside the case, all the monoxides will come out and murder everyone.

If the case is sealed, the monoxides will build up and up until it either explodes or you open the case, and trillions of monoxides will flood out, instantly burying the entire neighborhood and probably half the city with immediately fatal amounts of monoxides.

Plus there is also the chance that someone might not look first and assume you’re a terrorist on a motorbike trying to run people down and then they might pull out a gun and start shooting wildly at you or something.

Those are of course silly explanations, but the reasons behind them are actually somewhat sound, just in case you were making a serious suggestion.

62

I have never encountered the pound-mass. Does anyone actually use it?

63

Engineers and scientists do, sure. 1 pound-mass exerts 1 pound-force when accelerated at 1 G, so the most people don’t think about the distinction between pound-mass and pound-force during everyday discussion. 32.174 pounds-mass is equal to 1 slug.

Similarly, there is a unit called the kilogram-force; it’s the force exerted by 1 kilogram accelerated at 1 G. If you have a bathroom scale with springs or load cells, it’s reporting your weight in kilograms-force or pounds-force; if you have a balance like the classic one at the doctor’s office with sliding masses, it’s reporting your mass in kilograms or pounds-mass. If the two instruments are calibrated to read the same numerical values at sea level at the north pole, the bathroom scale will read differently at the summit of Mount Everest (but the balance will read the same as it did at the pole).

64

All that’ll be left is a wasteland with a burned-out Apple Store with a sign out front reading UNLESS.

65

That’s fair enough, though you should realize that a UPS has a built-in inverter. They’re basically a battery, inverter, and automatic switch in a single package.

…wat?

I’m having a hard time taking you seriously. But I’ll try…

If you really wanted to cart around a computer and 20 kg of batteries or whatever, you could use a hard plastic rolling case like one of these (to pick a random image from Google).

You could also skip the inefficient conversion from battery to AC to DC. Desktops these days run mostly off of 12 V, with minor use of 5 V and 3.3 V. You could just make a big 12 V battery pack, and use DC-to-DC converters to supply other voltages.

Here’s a guy that made a 2 kWh battery pack for an electric bike. If you picked out relatively low-power desktop components, you could conceivably run a computer all day with something like that. But you really need to know what you’re doing so you don’t set your house on fire, electrocute yourself, or blow yourself up…

Attempting the same with a UPS is going to be an expensive and sub-optimal compromise.

If you want something that works without a lot of serious tinkering, just buy a gaming laptop.

66

lazybratsche makes an excellent point. Using a UPS to convert DC to AC just so the computer can convert it back to DC (12 VDC and 5 VDC) is so inherently inefficient that it pretty much scuttles the whole project.

The OP would be much better off pulling the power supply out of the computer case and using 12 VDC direct from a battery pack. A simple voltage regulator module could provide 5 VDC. (Yes, I know there are some other control issues, but they’re not insurmountable.) Even a fairly large UPS would provide no more than 30 minutes of operating time.

Or, maybe everyone has created this thread as a big joke on me.

67

That’s the ticket.

A computer like the one in question calls for innovative transportation thinking. Moving it in the same way you’d haul quarter-sections of a moose you just shot and butchered seems exactly right.

68

Like this one?

69

The OP’s proposed rig is starting to remind me of The Homer.

70

Having not seen the episode in years, I think that is what post #31 was implying.

71

You could just get a ‘carputer’ PSU board like this one - to get a properly-levelled ITX power supply from a 12VDC source.

It looks a bit light though, so may need to be enclosed in a lead-lined iridium casing, to ensure this project doesn’t dip below the minimum weight requirement.

72

Surely injecting an unstable 12.8v from a car battery, especially a dodgey one, into fragile and extremely expensive (or reasonably expensive) computer components isn’t a good idea, even if it has a $5 walmart regulator attached to it?

73

You would be surprised at how stable and nice a lead acid battery is. Indeed it is hard to get a smoother and cleaner supply. A DC-DC converter for 12 to 5 volts is a very common device, and you can get very high quality ones. Very efficient, and with all the protection you might want. (It isn’t a $5 Walmart component.)

However the efficiency of a modern inverter is actually pretty good. So long as you get a good one. Semiconductor switching elements (MOSFETs or IGBTs) are now have ridiculously low forward drops that you lose very little power in them. Copper and iron losses will dominate.

But the question seems odd. There are made for purpose PC power supplies that are designed to connect to 12 volt batteries. For instance High reliability 12V Input PC ATX computer DC-DC Power Supplies, 12VDC Input, autonomous vehicle computer power. car computer power supply, 12 volt, 320W, 450W, 500W, 650W, 1000W, 1500W, 2200W, ATX DC-DC

74

The Google data center server motherboards are custom-designed to run only on 12V, and each motherboard has its own 12V backup battery. At least, that was the design used in 2009 when this article was written.