UPS run from inverter?

FyreDaug · 01-06-2005, 01:40 PM

I have a XS800 by APC running my home computer. I was playing around when I first initially set up my carputer and the (EDIT2:ups NOT inverter) would keep switching from online (ac source) to battery mode, every 5 seconds, even when the car was running. Is that because of the sine wave caused by the inverter? Or SHOULD the battery backup work? I don't see a reason why not if its getting it from an AC source and everything else is running off that AC fine.

Has anyone hooked up a UPS off an inverter?

I dont understand why it wouldnt work, and it would be a HUGE help because this current setup (my athlon) draws alot of power so I cant turn the car off and back on, or have it off for 5mins (while I pump gas or something) because when I crank it restarts. My old setup with an 800mhz duron and 250w psu would be fine after 20mins of having it run off the battery, voltage would go to 11.0V and it would still crank and allow it to run. Now when I turn the car off it goes to 12.2V and if it goes below 12.0V it will restart the computer. I've done it twice to try to find the sweet spot, but it barely exists.

Stupid power hungry PC

EDIT: And while I'm here is it true inverters are only 50% efficient? I know its not very efficient, but I wasnt sure if it was as low as 50%. So my 800w inverter on full load would really need 1600w to run, or can the 800w inverter only supply 400W?

With my system cranked, with 4 speakers at max 90w + computer+monitor +charging my phone + USB Hub I dont go above 180W (according to the inverter).

EDIT 2: Oops at the top I said the ivnerter kept switching from online to battery, I meant the UPS.

n8scstm · 01-06-2005, 01:52 PM

Its more efficient than that. I think somewhere around 85%. It could be that your using a modified sine wave inverter. Contact the manufacturer of the UPS and see if it requires a pure sine wave. You could buy a capacitor and place it before the inverter. 1/2 farad should work for that. And just forget about the UPS.

FyreDaug · 01-06-2005, 01:55 PM

I was considering using a capacitor instead aswell which actually might be even better and cheaper, maybe I should go with a larger cap? 1/2 farad should be good, but I havent really dealt with caps before.

Inverters are really 85% efficient? Wow, I thought it was lower, then why dont more people use inverters instead of dc-dc psus? I paid 100 bucks for the inverter and 55 for my 420 TT PSU, all tax in. I've seen some 250w dcdc psus for like 200 bucks. Whats the deal?

Scouse Monkey · 01-06-2005, 01:56 PM

I did hear on here that UPs don't like inveters. i am sure someone has done a post about this before.

n8scstm · 01-06-2005, 06:57 PM

Well for one thing inverters take alot of room compared to an OPUS. I went with the inverter so I can plug other stuff in. All said and done, I spent way more on the inverter setup than I would have on an OPUS.(aux batt, isolator, cables, inverter, fuses, volt meter, junction block) It all came to about $500.

FyreDaug · 01-06-2005, 08:20 PM

My inverter has a digital read out of input voltage, wattage and output voltage on it. Right now (until I mod it) it sits under the dash totally out of the way, the fan is loud in it, so it needs to be modded for setup #4

KyferEz · 01-06-2005, 10:11 PM

Inverters do NOT work off of modified sine wave inverters. They May work with a sine wave inverter, but it depends.

One possible method to use a UPS is to connect the battery terminals from the UPS to the car battery, don't connect it to AC at all. Some inverters will work this way; they allow you to turn them on without AC power. Some won't. This would be fairly efficient, but not very small.

And when using an inverter, don't forget to use a startup shutdown power controller. They make life so much easier.

KyferEz

n8scstm · 01-07-2005, 09:51 AM

What ups has a battery terminals? Ive never seen that before. And then it would only be 12 volts. How would you plug anything into it? You really lost me!

bosskong · 01-07-2005, 08:07 PM

Open up a UPS. Batteries are inside... How do you think it keeps running after you unplug it?

FyreDaug · 01-07-2005, 10:51 PM

Hmm, is it 12V really? Either way I wont be doing this. I dont have a start up shutdown controller, but the button is right next to my ignition to hibernate (which im having troubles with grr) and sometimes I want to leave it on when the car is off (pumping gas) but Im having problems with cranking with this system, it doesnt like the low voltages like the old psu did.

KyferEz · 01-07-2005, 11:51 PM

Yes. Every single UPS that I have ever opened (which is a great many) use a sealed lead acid 12V battery

If you are having trouble cranking the system, you need a "tank circuit". Search these forums for that phrase, there are a great many solutions.

KyferEz

choyak · 01-08-2005, 01:06 AM

Most UPSs have multiple 12v batteries in them, unless it is very small. I have 400VA MGE UPS and it has 2 12v like 6AH batteries in there. Also this is just like using the UPS as an inverter because basically that is what an UPS is (it has synchronization circuitry also). The UPS's charging circuitry would also be confused unless it is disconnected completely.

frodobaggins · 01-08-2005, 02:40 AM

Most UPS will not work off a modified sine wave invertor. Which is likely what you have.
The UPS thinks the invertor is "dirty power" and it is.

You're UPS will eventually go flat or die if you continue to use it off a MSW Invertor.

n8scstm · 01-08-2005, 12:08 PM

If your only problem is during cranking, just use a capacitor. You can get one at best buy even, although it may not be the best buy. That will slove your problems. And its a lot easier than hacking up a ups, and it will look correct. Wont look like a hacked up solution.

n8scstm · 01-08-2005, 12:14 PM

Quote: Originally Posted by bosskong

Open up a UPS. Batteries are inside... How do you think it keeps running after you unplug it?

So it steps down to 12v, charges the batteries, then inverts it back to 120v? How do you calculate the watts it will power using it as an inverter?