Outback 2812 FX Inverters

Bruce Clark
Bruce Clark Registered Users Posts: 4
We have a cottage solar system with two Outback 2812 FX Inverters, 12 Volt batteries with 3250 Amp Hours of capacity, about 1,500 watts of solar panels, a 6000 watt backup generator that is set to start automatically at various set points and the customary ancillary boxes, transformer, switches, etc. The system is wired to a conventional 110/220 volt electrical panel and works incredibly well.

However, we have one small problem that someone else may have encountered. The system has simply shut down a few times for no apparent reason. It does not happen when there is a particularly large load and just starts working again after a couple of hours. If anyone has any thoughts on this, I'd appreciate them.

Thank you.


  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Outback 2812 FX Inverters

    welcome bruce,
    i think you may need to be a bit more descriptive of what you see there to have any of the guys narrow down some possibilities.

    for some examples,
    are the inverters in search mode due to low power consumption?
    is it at any particular time of day?
    is it with a particular load on it?
    how often has this happened and give an idea of how often?
    etc. etc.

    now i don't have a suspicion on the cause or even have any outback stuff to relate, but may.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,477 admin
    Re: Outback 2812 FX Inverters

    Are the inverters connected in "stacked" mode (120/240 VAC)?

    Also, I would suggest getting a DC Current Clamp Meter (Sears has an AC/DC Current Clamp meter that is good enough for $60) and start measuring current in the parallel battery strings.

    I am not a big fan of paralleled batteries (I prefer one string and recommend a maximum of 2-3 parallel strings). Also, pulling large loads (much over 1,200 watts) becomes problematic (1,200 watts at 12 volts is already > 100 amps--and system/fuses should be wired to >168 Amp minimum for a 1,200 watt inverter/load).

    Whether these have anything to do with your issues--I am not sure. But I always like to start with the basics first (wiring, parallel connections, battery health, is the solar/generator charging appropriately, etc.) first--Then start looking at the secondary issues (sync cable between inverters, flaky hardware, etc.).

    If you have a 3,250 AH @ 12 volt battery bank, I would suggest you don't have enough solar panels. Nominally, we recommend 5% to 13% rate of charge:
    • 3,250 AH * 14.5 volts charging * 1/0.77 panel+charger eff * 0.05 rate of charge = 3,060 Watt array minimum
    • 3,250 AH * 14.5 volts charging * 1/0.77 panel+charger eff * 0.10 rate of charge = 6,120 Watt array Nominal
    • 3,250 AH * 14.5 volts charging * 1/0.77 panel+charger eff * 0.13 rate of charge = 7,956 watt array "cost effective maximum"

    I would suggest at least 2x larger array than you currently have--But at those current and probably power levels--I would be suggesting going to a 48 volt battery bank--Unless you use the genset a fair amount, even during the summer.

    The current array is really only enough for maintenance charging and not enough for quickly charging a deep cycled battery bank without using the generator.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    Re: Outback 2812 FX Inverters

    In addition to the other questions, what is the battery voltage when they are off ??

    Maybe it's as simple as voltage going below the L battery cutout (LBCO) ?

    Are there any error LEDs blinking ? It just comes on by itself ??

    There is a remote On/Off jumper on those inverters on the AC board that sometimes can get
    loose and turn the inverter off. That was somewhat of an annoyance at times in the past.

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Outback 2812 FX Inverters

    Shall I mention that the system is so out of balance it's a wonder it works at all?
    3250 Amp hours? Are you sure? On a 12 Volt system that is crazy. That's 39 kW hours of stored power! If you need that kind of power you should be running a 48 Volt system. I don't know what your batteries are, but I bet parallel strings come into the formula. Right there you have a potential problem of some of them being "left out" and others doing all the work. Over time this means the ones doing all the work are being used up, resulting in the Voltage dropping quickly when loads are used. In all likelihood the problem is there: battery Voltage falling below minimum, turning off the inverters, followed by resurgence of Voltage and the inverters coming back on.
    Then there's that 1500 Watts array. It is not possible that it can properly recharge that much battery. It would have to be two arrays to begin with, each on a separate controller, as the current potential there exceeds what even a MidNite Classic can handle for 12 Volts. That said, it is only about 96 Amps, which would be a mere <3% charge rate for that enormous battery bank. That auto gen start must be functioning far too often.

    This is a very common problem: too much battery for the panels (or indeed system requirements). It will start out working (apparently) but over time the problems will occur. Not might occur; will.

    I suggest you start by re-evaluating your loads and seeing just how much battery bank you actually need. Second, check each and every battery (hopefully they are flooded cells) and see what state they are in: resting Voltage and specific gravity after full charge. Equalize if you find cells out of line. Pick the best of the bunch you can make a battery bank out of and reduce the over-all size. Inspect every bit of wiring for bad connections, corrosion, unequal wire lengths on parallel runs.

    The details of the battery bank will be very important for finding the problem. It will also help to know what charge controllers are being used.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Outback 2812 FX Inverters

    with points made by others here it could be a problem with the batteries themselves due to them not receiving sufficient charge. i am supposing that under heavy load the genny kicked on so you don't know what would happen if the genny safeguard wasn't in place. try it without the genny backup and see if the batteries can handle a large load and pay attention to the battery voltage before and during the high load. if it fails under a heavier load that it should deliver on, then suspect the battery bank needs replaced.

    i believe you should elaborate on the battery setup as to the age, type, capacity, make and model, how wired and with what gauge wires, etc.. i am supposing that your system was of the period where extra battery capacity was thrown in because of the high pv costs, but if you lack the ability to charge the batteries properly then that cushion will cost you in battery life. i also notice that there isn't any mention of charging the batteries from the generator so as to bring them up to snuff.
  • Bruce Clark
    Bruce Clark Registered Users Posts: 4
    Re: Outback 2812 FX Inverters

    Thanks very much for the replies. As someone who didn't grow up in the electronic age and have not participated before in a blog, I must say I find it very interesting to see how people can communicate throughout the world on matters of mutual interest.

    In any event, I appreciate the comments and will check the system with these in mind when I get back up to the cottage. Unfortunately, I have not had an outage while I am there and the system has come back on before I go there so I'm not sure if there are error lights on, but I can check. It has only happened twice last year and twice this year.

    For what it is worth, I have gradually built the system over 25 years or so and would do it far differently if I were to start again. For example, I now appreciate that I should have had a higher battery voltage (24, 36 or 48 volts), but the investment in the 12 volt system is too significant to change at this time (6-2 volt batteries and 2 2812 Outback inverters). I am also constrained by the south facing slanted roof and have two sets of panels (one at 17 volts and the other at 34 volts, going to 2 separate 80 amp Outback MPPT controllers). My thought in getting a disproportinately large set of batteries with a backup generator was that limiting the discharge cycles (they are usually above 80% charge and almost always above 50%) would increase the battery life. It also allows us to use the system on the weekend and have it charge up during the week.

    The batteries are about 4 years old and usually have a resting voltage of 12.0 to 13.0 volts. The Outback equipment is about 2 years old and the panels are varying ages up to 25 years but I can tell from the metering that they are delivering close to the maximum wattage.

    In any event, I appreciate the thoughts and will take the blog up to the cottage to check out the various suggestions.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Outback 2812 FX Inverters
    (6-2 volt batteries and 2 2812 Outback inverters).

    You did at least one thing absolutely right by getting 6 two-volt batteries, allowing you to get the AH you need with a series string instead of paralleling batteries!
    A separate voltage measurement of each of the cells and maybe a set of hydrometer readings would confirm their general health and rule them out as a factor in the strange behavior.

    I take it that both Outback inverters shut down at the same time? How are you using the two? Are they set up as two legs of a 220 supply? Are there any loads which are common to both inverters which might explain a simultaneous trip?

    As Neil suggested, one thing which could take them both out at the same time would be a (apparent) drop in the battery voltage below the cutoff point.
    SMA SB 3000, old BP panels.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Outback 2812 FX Inverters
    The batteries are about 4 years old and usually have a resting voltage of 12.0 to 13.0 volts.

    Resting voltage of 12 volts is way too low.