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Thread: UPS power backup as inverter?

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    Constant Bitrate CA 3000GT's Avatar
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    UPS power backup as inverter?

    So, there are these "ups battery backup" systems that basically are like power strips, except they have a 12V battery in them, and an inverter, and if the power goes out, they supply your comptuter with power for a little whill till the power comes back on...

    1) These things are designed to take 12v, and make it 110v
    2) These things are designed to produce a clean sine-wave power output..
    3) These things are fairly quiet.

    Im thinking one could take the battery out of one of these systems, and attach it to ones car battery, and then run a system like that. What do you guys think? anyone tried it?
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  2. #2
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    Probably cheaper to buy an inverter. A UPS is also normally only designed to run for a short time, so you may get problems there.

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    Matthew

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    Variable Bitrate
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    I have a Smart-UPS 1000 here on my desk with which Im planning to do a similar thing. The battery is dead, and we bought a new UPS as this was cheaper
    The only worry I have is that with the engine running, the UPS would be getting 14V rather than 12V, I plan to test this out at a distance
    With minimal load, it's quoted run time with battery is around 30 minutes. I dont really think it would have a problem with running for longer period as long as cooling is provided for it.
    It wont be going in my car till it's been tested for quite a while however.

    Dave

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    FLAC MP3DUB's Avatar
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    How the inverters deal with 14-14.5vdc from a cars electrical system would be the first concern, the second is that the standby (cheaper) ups are actually quite loud when running off of battery power.
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    Constant Bitrate CA 3000GT's Avatar
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    Thanks for the replys guys.

    -Probably cheaper to buy an inverter.
    Well... if you can find a ups cheap with a busted battery... lot of dead startups in this area selling that sort of thing for very little...
    Ive seen these for like $10-$20 (used, dead battery, posted on www.craigslist.org a massive community "online garage sale"

    - A UPS is also normally only designed to run for a short time, so you may get problems there

    Very true, I dont know if that might cause some sort of problem

    -How the inverters deal with 14-14.5vdc from a cars electrical system would be the first concern

    Isnt there a cheap system for cutting off voltage at a given point... say 12v? I think I remember this from a casetronics thread... I agree, this is a valid issue.

    I agree the noise is also something to keep in mind

    The nice thing about it... is that one might find a very affordable one.. or like thenominous, already have one.. and it would provide clean power, a good sine wave.. none of those chopped up waves that I hear sometimes cause systems on inverters to be buggy.
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    Retired Admin Aaron Cake's Avatar
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    There is one major problem: most UPSs will not come on without first seeing 120V (240V) "at the wall". So while there is no problem connecting the UPS to the car battery, getting it to turn on might be an issue.

    As far as runtime, don't worry about it. I have an APC280 at home connected to a 51AH deep cycle battery. This UPS will run for hours (about 10) off that monster battery, but then again it will take weeks to charge it back up.
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    FLAC MP3DUB's Avatar
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    Originally posted by CA 3000GT
    Thanks for the replys guys.

    -Probably cheaper to buy an inverter.
    Well... if you can find a ups cheap with a busted battery... lot of dead startups in this area selling that sort of thing for very little...
    Ive seen these for like $10-$20 (used, dead battery, posted on www.craigslist.org a massive community "online garage sale"

    - A UPS is also normally only designed to run for a short time, so you may get problems there

    Very true, I dont know if that might cause some sort of problem

    -How the inverters deal with 14-14.5vdc from a cars electrical system would be the first concern

    Isnt there a cheap system for cutting off voltage at a given point... say 12v? I think I remember this from a casetronics thread... I agree, this is a valid issue.

    I agree the noise is also something to keep in mind

    The nice thing about it... is that one might find a very affordable one.. or like thenominous, already have one.. and it would provide clean power, a good sine wave.. none of those chopped up waves that I hear sometimes cause systems on inverters to be buggy.
    Also, depending on the quality of the ups, the sine wave isnt necessicarily any better than the psuedo sine wave a inverter generates.
    -Nick

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  8. #8
    Variable Bitrate
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    Originally posted by Aaron Cake
    There is one major problem: most UPSs will not come on without first seeing 120V (240V) "at the wall".
    YMMV but Ive never come across one which behaves like this. I have a cheapo IBM one at home I use a bit like a portable mains socket, and Im sure the APC one's Ive played with seemed ok doing this.
    Im intending to run a fridge from mine for 24 hours (small fridge), got to figure out the battery requirement for that.

    Dave

  9. #9
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    I tried using an APC 420 UPS when I first set up my mp3car. It appeared to work just fine in the house off a car battery. You could force it to power on without AC power by holding the power button down for a specific few seconds.

    Of course after hooking it up to the car I quickly discovered it was hopeless. The UPS refused to operate on the higher voltage when the engine was running. And the noise that it generated was atrocious, both thru speakers and on the car radio am,fm stations.

    I ran out to Canadian Tire and picked up a 600 watt inverter. It's designed for running on car power and doesn't spew RF interference all over. For the measley $100 it cost me it was a bargain. It also survives starter cranking so I can leave the computer on while starting the car. The UPS wouldn't handle that.

    I also have an extra battery and isolator that I was planning to hook up so I can safely run the computer with the engine off. I found it a lot easier to just leave the car running on the few occasions it would matter. Half the time it's winter and I need the car running for heat anyway. I'll install it on my next car.
    -Seanster

  10. #10
    I'm sorry, and you are....? frodobaggins's Avatar
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    Cheapo UPS do not put out pure sine wave, it's a modified square wave usually.

    Expensive UPS will put out pure sine wave.


    And they don't like 14+ volts, you would need a 12v regulator before it, and where you gonna get 12v regulators that take that much amps

    as for noise, grounding solves it

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