xantrex sw2012 low voltage fault problem

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Notsirw
Notsirw Registered Users Posts: 7 ✭✭
I got a used sw2012 that was supposed to have come out a functioning system.  after trying to turn it on 3 times the mosfetts nearest the scorched part of the circuitboard blew up. I tried to replace them and those blew up some more.  i got a new whole board with the mosfetts and capacitors, which did not blow up. But i was still getting a fault and no turn on, so I bought the two hundred dollar screen that tells you what the fault is.

Now the problem shows as low voltage fault and the 200 dollar screen says i have 6.3 V, while the terminals at my leads read 12.7 V. ive tried on 2 seperate strings of 10 1.2v edisons and set of 2 6v golfs, same readings on each.  i tried disconnecting shutting down and restarting, and tried resetting defaults.

Any ideas what could be messt up and how i can fix without sending this box a couple hundred miles to a qualified shopp? Thx.

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  • Notsirw
    Notsirw Registered Users Posts: 7 ✭✭
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    Additionally there is no load, i have not hooked up a 110 outlet to it yet. Just trying to turn it on.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Generally, most electronics companies keep their hardware schematics pretty tightly held. Tracing through the DC input to the inverter you may find an A2D converter, possibly with a resistor divider circuit (bad resistors, cracked solder joint, etc.)...

    But it does sound like you have done the basics and figured out your DC battery bus voltage is OK.

    I would try a voltmeter and verify the battery bus voltage (and check the meter on your car/truck battery to confirm the meter is OK too... Have seen digital meters give some pretty strange readings with low internal batteries and/or other problems).

    And regarding failed FETs... Many times there are other issues that cause the FETs to fail (connecting to a 24 VDC battery bank, problem in FET drive circuitry, lightning nearby, etc.) and replacing FETs or even the FET driver board may not fix other issues...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Notsirw
    Notsirw Registered Users Posts: 7 ✭✭
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    Thanks Bill, will definitely check for this a2d.  meter's good, and perhaps the jerks before me hooked up 24v or backwards, but i was careful as i could be in my hookups. The scorching that was on the heatsinked capacitor mosfett board was in a long line acrossit in the direction of fanblow, showing that it was fully operating at the time.

    If nearby lightening is a problem, would a faraday caging help prevent those kinds of issues? Id never heard of that but i intend to put this near the top of a hill if i can get it working
  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Since you have solar panels, wiring, DC and AC power wiring, AC inverter and DC charge controllers--A simple Fariday cage is not going to be the answer. In general, grounding and surge suppressors. And properly wired lightning rods are not bad either.

    Some light reading:
    Re: Working Thread for Solar Beginner Post/FAQ

    A couple threads about Lightning:

    Off Grid Grounding Technique?
    Another Question, this time about Lightning

    Note, the above are discussions, not a do A, B, and C--and you will be "safe". There probably is no such thing with lightning. Several different techniques are discussed--and a few of those posters even have experience with lightning. :cool:

    And our host's FAQ:

    Lightning Protection for PV Systems

    From other past posts here, Windsun (admin/owner of NAWS), he said that most of lighting induced failures he saw were in the Inverters' AC output section.

    Towards the end of this thread is a very nice discussion of proper generator grounding.

    -Bill
    And some nice information from MIdnite about their Surge Arrestors:

    http://www.midnitesolar.com/documents.php?productCat_ID=23&productCatName=Surge+Protection+Devices&model=MNSPD-115&product_ID=283&act=

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Notsirw
    Notsirw Registered Users Posts: 7 ✭✭
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    Awesome, will read!
  • Notsirw
    Notsirw Registered Users Posts: 7 ✭✭
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    The new board is registering about 6v at each of the two tabs that bolt onto the transformer.  I put the old board back in (with the busted mosfetts) and the 200 dollar display no longer shows a low voltage fault. Shows 12.3 at the tranformer tabs. The boards are the same model number, but have a few slight diffs, the mosfetts on the new one have one leg wrapped in insulation, the heatsink plastic mount shield is slightly different in shape with a new mounting tab, abd theres a handfull of chips in the upper left that are on the old one but not the new one. Looks like a small triad w the middle leg cut, and surface mounted, with about 6 resistors around it. 

    If the new one is cutting my voltage in half, did i maybe get an sw 2024 board? 24v might chop the signal in half to run it through the same transformer? 

    I cant find something that is obviously an A2D, and the hot looks like it goes diectly through the heatsinks passes throught the board to the back tabs that go to the transformer, so im having a hard time figuring out where the voltage could be getting halved.

    Thanks for any input'
  • Notsirw
    Notsirw Registered Users Posts: 7 ✭✭
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    Just an update, what i got is a board out of a contex 2524, so it's halving my voltage on purpose.  anyone have a dire warning for me before i hook up a 24v bank to it and see if my non working 12v inverter will work as a 24?
  • Notsirw
    Notsirw Registered Users Posts: 7 ✭✭
    edited August 2019 #9
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    Update, it worksish!  a cotex sw 2524 mosfett/capacitor board  will effectivly make a xanthrax  sw2012 into a 24v system.  I hooked up a 24v bank and the 200 dollar screen reads 12.8 v for the battery input.
    I'm currently running a standard fridge, laptop, and the household HVAC inside airblower unit with the 200 dollar screen showing 120vAC at 6 amps.  The 200 dollar screen does not like this setup and will turn all black after a few minutes until you unplug it, but starts properly after being plugged in, again. 
    I do not believe it would be safe to use the ac in to charge batteries, but I dont know, im not attempting grid tie with this so its not a problem im trying to tackle  just now.