Desktop Battery Supply

[DSwain]

I'm not so sure this actually exists, but does a desktop battery exist? I know there are UPS and those types of things, but they're very large and expensive. A notebook battery (if it could even be attached) would be drained far too quickly. does anyone know of anything else that could work like a battery for a desktop? I'm asking for a project I'm researching that I thought of, just to see if it's possible, and this is my last limitation that I can't seem to think of an idea for.

[duncanbojangles]

Current battery technology sucks. What you're asking is for a battery to supply 350-500 watts for who knows how long. That's quite a bit. It might, just might be possible if you're using a very lean processor, like VIA or mobile AMD processors, no huge graphics cards, and very few motorized peripherals (DVD drive, hard drives, etc.). You'd have to switch to laptop hard drives, laptop optical drives, an extremely power friendly display device (a GameBoy screen?) and you're kickass speaker system would have to go.

Odds are, no. You may have better luck with a small windmill, solar panels (if you live in California) or geothermal energy connected to a modified UPS.

[DSwain]

Well yeah the idea is to go as minimal as possible in this case. I would buy a fully intergrated motherboard with nothing additional, some type of lower end CPU/memory, so on and so forth, and probably a 250w power supply. I know though that's still a huge amount to ask for from a battery, so I guess it couldn't work. Well in that case any other ideas? Cluster laptop batteries? Who knows, just an idea.

[duncanbojangles]

What do you know? A few minutes ago a story was posted on slashdot about the $100 PC. The cool thing is it uses about 10 watts of energy and runs off of 12 volts DC! A laptop battery could handle that, and a UPS would be plenty, even if you used the monitor. Check it out here: Solarlite and LinuxPR press release

[DSwain]

Haha wow that's very nice. Minimum quanitity order is 100,000 lol. In any case, very nice. I'll have to take a look at some VIA products for this case (even though it's still doubtful that it'd work.) Very cool though.

[EnigmaOne]

Ok, you're talking about a standard desktop machine.

Take a look at the spec's for the motherboard current requirements. Prolly along the lines of:
+3.3V@30A
+5V@32A
+12V@14A
-12V@0.8A
+5VSB@2.5A

The -12V@0.8A is, realistically speaking, not a problem.
The +12V, +5V, and +3.3V--in aggregate--will require 78.5A of output current from any battery you decide to use. (You'd derive the lower voltages from the same DC source.)

You're talking about something larger than your average car battery to be able to operate the system for any reasonable length of time; most likely several 13.8V batteries in parallel.

If space isn't an issue, you can do what you want, but make sure you don't live upstairs, and that the floors will take the weight.

Check at Kragen Auto Supply for their current prices on deep-cycle auto/boat/truck batteries.

[DSwain]

Haha okay, okay I get your point, I just wanted to see if anyone had any ideas that were realistic. Other than battery power, this project could easily work. In fact, battery operation would be more optional than anything. Oh well though, it was worth a check.

[bwkaz]

Well... UPSes use a battery.

They only give you enough charge to run a system for about half an hour (obviously this depends on which battery they use in the UPS, and which power supply you use in your machine), but it's still a battery.

[DSwain]

Yeah but the problem with a UPS is that it's far too large for what I wanted to do. I never used one personally but from what I know they're pretty large things.

[EnigmaOne]

Sounds like you were hoping for a few C-cells to power the unit from.

I think it was BEST Power Systems that had a decent UPS--something on the order of a 1.5KW unit--that had enough room inside to install a couple extra batteries (yes, sealed auto types) in it, and was only a little larger than an HP NetServer chassis.

With the additional batteries in it, you could get over an hour run time out of the sucker, running your system, CRT, router and DSL modem. Going with LCDs only extended the run time.

Hey, the thing isn't *that* large, and a castered pallet would definitely make it >cough< portable!

How's your back?

[bsm2001]

4 of these might get you through. It's the highlited one in the list at the bottom.

[DrChuck]

Take a look at the spec's for the motherboard current requirements. Prolly along the lines of:
+3.3V@30A
+5V@32A
+12V@14A
-12V@0.8A
+5VSB@2.5A

As a sanity check, this comes to a grand total of 450W - most systems won't handle this peak power, let alone average. These numbers are probably the rated supply output, not the actual system requirement.
This power supply wattage calculator has been posted here before, but it's a cool widget. With an Athlon 2800+ and an average graphics card, I can barely break 250W peak. I've always wondered what the real-time power draw is, but I guess there is no way to tell without measuring.