Power Invertor's and Desktop PC's

Sluggs on 17/5/2010 at 09:15

Been thinking of buying a new car battery and a power invertor to run my PC during power cuts. I can't afford a laptop, so this would be the next best thing.

Would a cheap power invertor run a desktop PC with a CRT monitor?

Muzman on 17/5/2010 at 12:04

Never tried it myself, but this article suggests a cheap one might have trouble these days:

(http://www.dansdata.com/diyups.htm)

(old article, Australian prices)

Namdrol on 17/5/2010 at 12:50

I live off grid, we have a 40 kw diesel generator but we only run it 6.30 - 8 and then 4.50 till 11 to save on juice.
So I run loads of stuff on an inverter.
Ok, there are a few things. Using a cheap inverter(iv) and a CRT will mean that you will get a line passing up your screen every few seconds. A cheap iv has a modified sine wave, (basically a square wave) and this interferes with the cathode ray as it fires.
Depending on the psu in your computer, it might or might not like the modified sine wave.
My laptop transformer is happy with a modified wave but my mates isn't and he had to get a new psu.
So you're really looking to get a pure sine wave inverter if you want guaranteed reliability.
There's also the matter of cost, most cheap iv's are either 150w or 300w and I don't know what psu your desktop is, but then you've got your CRT as well. A monitor won't draw much when running but they've got a big start up load.
(One of the considerations for me when I got my new monitor was that it had an eco mode and draws bugger all).
So, you'll need a minimum 600w iv.
We now come to batteries and chargers.
Car batteries are not ideal, they don't like being discharged below 90%, they normally are kept full in the motor and their life will be very short if you constantly cycle them.
What you need is a leisure/deep cycle battery.
Size matters here. Depending on how long you want to run your stuff for you should look at least around 105ah - 110 ah (and if your running 500w you'll only get a couple of hrs at the very most out of that.)
With a charger, if you want a set and forget, you'll need an intelligent one that will switch to trickle once the battery is fully charged, otherwise over time you'll just boil your battery dry.
A decent one will condition your battery and greatly extend its life.
I spent about £240 on my set up, with 70 on the charger, 140 on the battery and 30 on the inverter.
But you can get a reasonable battery for around £80/90.
(http://www.donrowe.com/inverters/inverter_faq.html) Here's a good site on this whole topic.
Hope all this helps. :cool:
I see your here in the UK, drop me a note if you want pointed in the right direction for sourcing things.

edit; Muzman's article is spot on, except I know from experience that it is pot luck if an modified sine wave will power computer equipment. My satellite modems psu wouldn't work, but luckily I had one with the same voltage and polarity that did, so I could use it in its place.

TBE on 17/5/2010 at 17:56

If your car is running, then yes, you should be able to run a PC with a monitor off the inverter. You'll probably want a nice inverter that supplies about 750 peak watts.

You'll be able to power the computer with the car off for a while, but you're going to drain the car's battery pretty fast. Expect no more than 45 minutes of use with the car turned off.

That ghetto UPS solution is kind of cool, but very pricey. I bought a nice UPS for $99, and it typically runs my PC about 30 minutes after power goes out. I've got a 500 watt power supply, so this is a long time for a UPS to run my PC.

A good power inverter for a vehicle is a good idea to have on-hand any how. Makes those times when you're not prepared for a power outage a little better. Like during the winter, my wife wanted to watch something on tv. We had a power outage. I ran extension cord from vehicle to inside and plugged in the tv and a lamp. Power came on about 4 hours later, but we got to watch the episode of whatever reality show she wanted to watch for an hour.

Namdrol on 18/5/2010 at 12:08

Actually, TBE's post has made me realise that I've overly complicated things. :D
I've got a setup that runs things for a few hrs everyday, day in, day out, which from your post doesn't seem to be what you're looking for.
So the charger isn't important for you, any cheapo thing would do and you don't need a fuck off battery.
I would still say get a leisure battery though of around 100 ah. These hold their charge and don't mind being deep discharged.
And yeah, as TBE said an inverter of around 750w peak.

(http://www.tayna.co.uk/catalog/284/0/Leisure-Batteries-Numax-Leisure-Batteries-page1.html) Here's a good battery site with some batteries from £50 to £90 that would suit. (I've bought from them)
(http://www.maplin.co.uk/module.aspx?TabID=1&criteria=usb&ModuleNo=48724&C=SO&U=Strat15) And here's a 600w inverter from Maplins for £55

ZylonBane on 18/5/2010 at 14:55

Quote Posted by Sluggs

Power Invertor's and Desktop PC's

Power invertor's what?

(I know, I know, I shouldn't poke fun at people who don't speak English as their native language)

Sluggs on 19/5/2010 at 04:20

Namdrol, you've been a great help. That Invertor from Maplins looks like it will do the job. Shame the batteries are so expensive, but I guess you get what you pay for.

Thanks again for the help.