Online UPS as off-grid inverter?

2twisty2twisty Posts: 156Solar Expert ✭✭
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.

Comments

  • 2twisty2twisty Posts: 156Solar Expert ✭✭
    Re: Online UPS as off-grid inverter?

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

    http://www.apc.com/resource/include/techspec_index.cfm?base_sku=SU1400RMXL3U&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.
  • waynefromnscanadawaynefromnscanada Posts: 3,009Solar Expert ✭✭✭✭
    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.
  • 2twisty2twisty Posts: 156Solar Expert ✭✭
    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.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    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.
  • inetdoginetdog Posts: 3,112Solar Expert ✭✭✭✭
    Re: Online UPS as off-grid inverter?
    niel wrote: »
    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.
    SMA SB 3000, old BP panels.
  • fca1fca1 Posts: 124Solar Expert ✭✭
    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/techspec_index.cfm?base_sku=sua1000xli
    http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SUA1500I&total_watts=50
  • keyturbocarskeyturbocars Posts: 375Solar Expert ✭✭✭✭✭✭
    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.
  • techntrektechntrek Posts: 1,357Solar Expert ✭✭✭
    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.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • fca1fca1 Posts: 124Solar Expert ✭✭
    Re: Online UPS as off-grid inverter?
    techntrek wrote: »
    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 ;)
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Online UPS as off-grid inverter?

    from fca1,
    "- They start without AC circuit"

    that's good, but how does it know what frequency to use if there wasn't a grid reference, as he proposes off grid?
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Online UPS as off-grid inverter?
    niel wrote: »
    from fca1,
    "- They start without AC circuit"

    that's good, but how does it know what frequency to use if there wasn't a grid reference, as he proposes off grid?

    The same way they do if the power goes off when they're connected to the grid. Not all UPS units need to have AC In before they start, but yes some do.

    If these are continuous UPS units they run constantly; converting grid power to charge batteries and taking the DC and inverting it to supply uninterrupted power that is very clean for Voltage and frequency. They will have a surge capacity above the constant V*A rating.

    If they are back-up UPS units they are not intended to run continuously and will be a poor choice for off-grid use.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Online UPS as off-grid inverter?

    nobody sees the circumstances i am talking of here so i give up.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Online UPS as off-grid inverter?

    Well I have an 800 V*A APC unit that is 24 Volts (dead batteries now) that can be turned on without any AC power present and it just comes up with 120 VAC @ 60 Hz like a regular inverter would.

    I keep it as a spare in case the Outback should fail. Hahahahaha! :p :D
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Online UPS as off-grid inverter?

    coot,
    the inverter in question can change it's frequency to either 50hz or 60hz based on grid sampling. without a grid sampling what does it do? how would it know the stuff you wish to run is for 50hz or 60hz without that sampling as the inverter is not the amazing kreskin? or does it just sit there acting dumb and don't do anything? is there a default setting switch present for frequency in the absence of a grid sample?

    i don't know and hence my question.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Online UPS as off-grid inverter?
    niel wrote: »
    coot,
    the inverter in question can change it's frequency to either 50hz or 60hz based on grid sampling. without a grid sampling what does it do? how would it know the stuff you wish to run is for 50hz or 60hz without that sampling as the inverter is not the amazing kreskin? or does it just sit there acting dumb and don't do anything? is there a default setting switch present for frequency in the absence of a grid sample?

    i don't know and hence my question.

    Now that I understand.
    So I went reading through the manual.
    My best interpretation is that a 230 VAC model runs 50 Hz and a 120 VAC model runs 60 Hz; the sync to utility power is within the ranges for frequency & Voltage given for each model. In other words one model will not auto detect either 230/50 or 120/60 but only the power within the range the particular model can handle so that when the grid goes down the output from the UPS continues without a noticeable 'blip'.

    Or else it works by magic. :p

    I did not see where it said it could start without AC IN. I did see where it said it will beep every four seconds when running on battery. That could get annoying in about eight seconds.
  • fca1fca1 Posts: 124Solar Expert ✭✭
    Re: Online UPS as off-grid inverter?

    Double conversion units normally need acin to start, line interactive as mine don't need ac in to start.
    You can disable the beep by software or by taking out the buzzer from the board..
    I know that they aren't for 24x7 but till now they keep ongoing...

    A old apc doc (2004) explain online vs ineteractive
    http://www.apcdistributors.com/white-papers/Power/WP-79%20Technical%20Comparison%20of%20On-line%20vs.%20Line-interactive%20UPS%20designs.pdf
  • techntrektechntrek Posts: 1,357Solar Expert ✭✭✭
    Re: Online UPS as off-grid inverter?

    I don't know about the SU line, but the SURT line gets voltage and frequency set in software so if it is cold/black started (no AC in) it knows what output it should use. SURT is the online (double conversion) type.

    fca1, take a look at the link in my sig if you want to see what I do with mine when it isn't attached to my battery bank.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • fca1fca1 Posts: 124Solar Expert ✭✭
    Re: Online UPS as off-grid inverter?
    techntrek wrote: »
    I don't know about the SU line, but the SURT line gets voltage and frequency set in software so if it is cold/black started (no AC in) it knows what output it should use. SURT is the online (double conversion) type.

    fca1, take a look at the link in my sig if you want to see what I do with mine when it isn't attached to my battery bank.

    That double conversion must add some adtitional losses how much does it consume without loads ?
    I already read your posts on Prius usage
    Nice..
  • techntrektechntrek Posts: 1,357Solar Expert ✭✭✭
    Re: Online UPS as off-grid inverter?

    Not sure, a clamp-on meter is on my "must buy" list but I haven't gotten around to it.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • MarkPMarkP Posts: 26Registered Users ✭✭
    Re: Online UPS as off-grid inverter?

    I have a SmartUPS 3000 running continuously poweriing a small fridge. The yellow tag on the fridge said 256 kwh/yr. I have 720 watts of panels charging eight 6-volt golf cart batteries (series, 48 volts nominal) through a Morningstar 45 amp mppt charge controller. The system is running 24/7 while I am not there. Seems to keep up with the reefer plus a few lights, although I run the generator if I am doing laundry. I had to dial back the sensitivity of the UPS to keep it from taking over from the generator when the heavier loads start. As it is when the heater in the washer comes on the genny stumbles and the lights dim but the UPS usually doesn't step in. Running straight off battery power the unit is rock solid so far, no dimming of lights or tripping at the loads I have hit it with so far.

    Basically the solar keeps the reefer running and babysits the batteries while I am not there. When I am there I supplement heavily with the genny. When passing through power from the genny it is pretty much silent. When idling on battery power there is an annoying hum. Add a little load and this hum gets less. Part of the problem may be that I have the UPS screwed vertically to the opposite side of one of the wood walls of my living space and this acts somewhat like a guitar. You can hear the sound more when you lean your head against that wall. I am going to try isolating from the wall by attaching with rubber well nuts instead of screwing the steel brackets directly to the plywood. I also found that I can reduce the noise by jamming a block of wood between the wall and the bottom of the UPS. This tells me that part of the noise is coming from individual parts or layers of the UPS that are rattling against each other. With the block in place they are held against each other and can't rattle. I am considering opening up the UPS and trying to see what parts there are and if I can pop-rivet them together.

    Part of the rational for the vertical mounting is that there is some chimney effect to help with cooling. This is a rack mount unit that is 17" wide, 26" front to back, and 4" to 5" tall when installed normally. Air is sucked in the front and expelled through holes in the back and sides (near the back). As I have it installed it is 17" wide, 26" high, and stands proud from the wall about 6".

    I pulled the top off the piezo beeper before I discovered the option to turn it off through software.

    There is a model that will accept external battery packs up to about 20 times the original capacity. Unfortunately mine is not that model, but nevertheless I can't say I have had any problems with mine. It so far has not gotten noticeably hot although I haven't really pushed it yet. The state of charge LEDs on the front are useless of course. The main thing I have gleaned from the internet is that it draws about 50 watts at idle, which sucks compared to purpose-built off-grid inverters.
  • BB.BB. Posts: 25,246Super Moderators admin
    Re: Online UPS as off-grid inverter?

    Is this a MSW UPS? The modified square waveform can cause the UPS and their loads to vibrate more than a pure sine wave unit would... I cannot think of anything else to do other than to look at the UPS and see if you can stop the chassis from vibrating so much and sound proof the room with the UPS from the rest of the place--But I am know you are already going down that road where you can.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MarkPMarkP Posts: 26Registered Users ✭✭
    Re: Online UPS as off-grid inverter?

    The SmartUPSs are true sine wave. It was designed to be mounted flat. Maybe that is part of the problem. I really like it mounted against the wall though so I am going to try to work with that.
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