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Thread: Online UPS as off-grid inverter?

  1. #1

    Default Online UPS as off-grid inverter?

    I have an APC 1400VA UPS that runs a 24V battery bank and is capable of 1000W output (not sure what its surge and continuous are at the moment, but its for computer servers, and it's a good one - Ive used it for some time as a backup for my servers) It's an APC SU1400RMXL3U with an add-on battery pack SU24R2XLBP.

    I know the onboard charger can't handle a huge battery bank, but that could be augmented with an external 24v charger if connected to a larger bank.

    Could this be used as an inverter for a small off-grid setup?

    This could be a good way for me to get into a smallish 24v system that I can grow later.
    We're documenting our move to the west Texas desert at http://theratracelosers.blogspot.com/

  2. #2

    Default Re: Online UPS as off-grid inverter?

    Here's a link to APC's product information:

    http://www.apc.com/resource/include/...U&tab=features

    It doesn't list all the info that you'd want for an off grid application, but I'm sure that the info exists somewhere. I can't be the first guy who has thought of this.
    We're documenting our move to the west Texas desert at http://theratracelosers.blogspot.com/

  3. #3
    Join Date
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    Default Re: Online UPS as off-grid inverter?

    I was given a "defective" computer UPS that was on it's way to the landfill/dump, from our local High School.
    Checked it out - - yes, the batteries (2X12 Volt) were shot. Other than that, the inverter part works perfectly. Has a roughly 400 VA 60 Hz output xformer. But beyond testing, I haven't used it as my system is 12 volts, not 24.
    1900 watts PV, (1000 watts PV feeding MidNite Classic 150; 900 watts PV + 160 watts micro hydro both feeding into a single shared Morningstar TS-MPPT-60) ; Xantrex Pure Sine 1800/12 for heavy loads; Xantrex Pure Sine 1000/12 on 24/7 for everything else; six Rolls Surrette 2 volt L16 @ 12 volts.
    Domestic hot water totally provided by the sun 8 months out of every year via thermal panel.

  4. #4

    Default Re: Online UPS as off-grid inverter?

    One of the nice things is that you could tie a super-efficient netbook to the serial port that is used for monitoring and get information about SOC, etc. There's lots of info available in the interface. NOt as much as the popular inverters for off-grid, but I am certain that there is enough information to trigger a genset to start, etc. I'll google it some more and maybe contact APC to see what I can glean.
    We're documenting our move to the west Texas desert at http://theratracelosers.blogspot.com/

  5. #5
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    Default Re: Online UPS as off-grid inverter?

    one potential problem may be that it syncs its frequency to the mains and without the mains how would it know what to settle on? other than that it looks as if it could work, but be wary of putting it to its max power, especially for long time periods.
    NIEL

  6. #6
    Join Date
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    Default Re: Online UPS as off-grid inverter?

    Quote Originally Posted by niel View Post
    one potential problem may be that it syncs its frequency to the mains and without the mains how would it know what to settle on? other than that it looks as if it could work, but be wary of putting it to its max power, especially for long time periods.
    Since it is an online/inline UPS, it will have to include a way to set its output frequency when the mains input goes away. That may be very accurate (crystal clock controlled) or it may be approximate (analog circuitry) but it will do its job.
    Good point about max power, since it may be specified based on not having to deliver max power from batteries beyond the expected run time of the batteries it came equipped with.
    However, it should be able to deliver max power indefinitely while inline with mains input.
    Sunny Boy 3000US, 18 x BP Solar 175b panels, installed 2009.

  7. #7

    Default Re: Online UPS as off-grid inverter?

    hi im using a sua1000xl and sua1500 since 2009 as inverters 24x7 my comments...

    good
    - They work fine producing a sinewave output even in high load
    - You can have information about battery and usage using apc software
    - You have an transfer switch between batts and grid or gen just by on off the ac input ...
    - They start without AC circuit

    Bad
    - They don't accept more than their rate i mean (my studer xpc2200 will take peak load of 3x time for seconds with no problems) the ups at 100% load will disconnect immediately ...
    - They consume a bit even with no load sua1000 no fan 20W sua1500 with fan 30W
    - Their charger sucks i have on both a big diode so that they don't charge my batts (but this will have 0.7 drop on the voltage)
    - sua1000 a bit noisier when on batteries
    - as they don't accept load peaks you can't connect them inductive loads engines that need a peak for starting....


    But they are up running from

    http://www.apc.com/resource/include/...sku=sua1000xli
    http://www.apc.com/products/resource...total_watts=50

  8. #8

    Default Re: Online UPS as off-grid inverter?

    My experience with using a UPS as an inverter is similar to fca1.

    I have an old APC Matrix 5000 UPS. I experimented with it running off grid for part of a day once in a while. I used the Matrix 5000 before I got my XW6048 inverter. The Maxtrix worked very well as long as loads were kept under the 5000 VA limit. Even a small surge above the rating, and the UPS would shut down immediately. It's not that the hardware of the UPS probably couldn't handle some surge, but the software/firmware of the UPS is programmed to shut down when the limit is exceeded.

    Also, as mentioned by fca1, the power consumption of the UPS was higher than a good inverter under idle and low load conditions. At high loads, the Matrix 5000 was quite efficient (in the 90's %) when I calculated the efficiency. At low loads, efficiency was much worse. I still have the Matrix 5000 and it is my backup in case the XW6048 is out of commission for some reason.

    Finally, I would think it would be hard to live off grid with only 1400 VA of power (with no surge capability). It might be possible, but you would need to keep your loads very minimal and stay away from any large motor appliances.
    On-grid with RE backup power. HY-2000 2kW wind turbine charging 48V 600Ah Concorde Lifeline battery bank. Wind power diversion heats water in an auxilliary 80 gal hot water heater. 2.1kW Evergreen solar panels & TS-MPPT-45. XW6048 inverter, Onan 6kW 6DJE diesel generator, and Yanmar YDG3700 diesel gen as backup.

  9. #9

    Default Re: Online UPS as off-grid inverter?

    I have no problems using mine off-grid (in my case only during utility outages), but it is a larger "double conversion / online" unit so no problems with surges up to 150%. APC claims 92% efficiency.
    12 kw Generac, Honda EU3000is, 4.2 kw APC UPS powered either by battery or a Prius. Really.

  10. #10

    Default Re: Online UPS as off-grid inverter?

    Quote Originally Posted by techntrek View Post
    I have no problems using mine off-grid (in my case only during utility outages), but it is a larger "double conversion / online" unit so no problems with surges up to 150%. APC claims 92% efficiency.
    150% thats great I will now swap my system for 48v
    Putting my 2x 24v bank to 1 48v.
    Mainly because my xpc died and for now I will use a apc sua3000xl as inverter.
    And I'm tempted to put the apc 5000 firmware on the 3000 to see if the shutdown at 100% loaf is only a sw limitation...
    Or if I don't brick it on firmware I would Brick it later in smoke

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