XW MPPT60 generating "Battery Over Current Fault"

twistedtreetwistedtree Solar Expert Posts: 126 ✭✭✭
I've got an off grid system consisting of:

Two 1.6kw solar arrays, each running through it's own XW MPPT60 charge controller
XW 6048 Inverter/charger
SCP
AGS
Whatever the wireless monitor thing is called.
1300ah of FLA batteries @48VDC

I'm occasionally getting "Battery Over Current Fault" from the MPPT60s. This is being reported to be via email from the monitor thingy. Both of the MPPT60s indicate the same error at the same time.

Even under the best of conditions I don't think my arrays are capable of anywhere near 60A each, so I find it hard to believe that I have an actual over current situation. The faults are transient in that they don't shut the system down, which is good. But sometimes I'll get two or three of them in a row back to back. The system has been in service since 2008 and had been trouble free other than two bad battery cells along the way. These faults typically (maybe always) happen in the AM, but I don't know if that's significant.

My suspicion is that this is some sort of firmware bug, but I see that Schneider doesn't post firmware updates, or anything for that matter, on their web site.

Anyone seen this before and/or have any suggestions?

Thanks,

Peter

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    I believe that Schneider responds better to phone calls for help. At least initially (in posts past), they did not respond well to initial email/web based questions.

    Only question I can think of--What are the various components (inverter/charge controllers/etc) programmed as to the size/type of battery bank.

    In general, the MPPT charge controllers should not have any issues with output curren. They are designed to self limit/regulate to their rated output (normal/safe function of controller) if the solar array can provide more than rated output current.

    This error sounds like some piece/software in the system "believes" there is a current limit to the battery bank that should not be exceeded. This is pretty strange in that the XW system does not have a common battery shunt (that I know of) and cannot really "see' the difference between current being supplied to the battery bank vs current supplied to loads+battery bank (unless the management software is adding information from the inverter and charge controllers and coming up with "net" battery current).

    Otherwise--Bumping your post so somebody with more XW experience can help--if they have further information.

    -Bill.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,665 ✭✭✭✭✭
    What does the scp say, not the combox? You could have programmed something in the combox that it is not liking. There have been no updates for these chargers for over 5 years. The SCP should record the individual charger that is causing the problem, if there were a problem which I doubt.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • twistedtreetwistedtree Solar Expert Posts: 126 ✭✭✭
    I'll check what the SCP says, but in all past cases it's the same as what's been emailed to me. By the way, I don't have the combox, but rather what I think it it's predecessor. It's called a "Gateway". From what I've seen is always sends the same info as whats logged in the SCP. I always get the same fault reported from both chargers at the same time.
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,665 ✭✭✭✭✭
    I'll check what the SCP says, but in all past cases it's the same as what's been emailed to me. By the way, I don't have the combox, but rather what I think it it's predecessor. It's called a "Gateway". From what I've seen is always sends the same info as whats logged in the SCP. I always get the same fault reported from both chargers at the same time.


    So you are the one, The last beta testing I did on the XW, the project engineer talked about there being someone who liked the gateway and that it was still working. Good to meet you!

    Yea, see if the faults and warnings on each charger are there on the SCP, you might check the inverter log also. Make sure you are not programming current limiting below the 60A setting on the -60's or the inverter is set different than the defaults. You can get 80 amps out of those chargers and they will be happy, as they warm up they will just start limiting the current out to whatever the heat sink/ambient air is..
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • twistedtreetwistedtree Solar Expert Posts: 126 ✭✭✭
    I have the Gateway, but I won't say I like it. It's a great example of a product that was abandoned have way through development. It does serve to report faults remotely, but that's about it. The biggest issue is that when it reports the amount of power harvested, it's actually reporting how much power you have consumed, i.e. how much AC output the inverter has produced. They basically designed it to work with a grid tie system where AC output = power harvested. But then they went and sold it for use with the Hybrid system. In the Hybrid system, it gives no indication of how much solar is harvested, just how much AC is consumed, which is pretty useless.
  • twistedtreetwistedtree Solar Expert Posts: 126 ✭✭✭
    Anyway, I think I found the problem. I decided to open up the wiring boxes and check for lose connections. What I found was quite alarming. Inside the XW wiring/breaker cabinet is a factory supplied DC negative bus bar. It has plastic standoffs, space for about four 3/8" cable lugs, plus a smaller bus bar for other wires. Well, the bus bar was running at 200F, the smaller bus bar arced when I wiggled one of the wires, and the main battery cable was lose and wiggling. Holy crap! The plastic standoffs were deformed and melted, which is what allowed the large and small bus bars to separate. They are sandwiched together with screws that anchor into the plastic standoffs. As the plastic softened, the screws pulled out and the two bus bars lost firm contact.

    It's not clear where the problem started, but once the overheating began the whole thing just fell apart. That's a pretty crappy design if you ask me. I got it all put back together with machine screws through bolted to hold the two bus bars together, and a new standoff arrangement. Ran it for a while and now there is no measurable temp increase at any of the joints. I'm guessing I won't see any of those errors anymore.

    So if anyone else has one of these XW wiring cabinets, check the negative bus bar carefully. If there is any heating, it's prone to coming apart completely as the plastic softens.
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Ouch!

    Thank you for letting everyone know.

    I have "blinking lights" syndrome in my own utility powered home... Oh well, thank you for reminding me to get off my but, take off the breaker panel covers, and see if I can find the cause(s).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,665 ✭✭✭✭✭
    Maybe on the day that we check smoke detector batteries we add on the list to check panels and electrical connections. Lucky that you got the e-mail warnings but strange that the breakers did not trip. I would test them. Good that the mppt-60's sent out the warnings, I never have seen that.

    As for the design, it is pretty much industry standard stuff in the XW panel. I have installed over 30 of them and never had any problems. I do tell my clients who install themselves to check wiring torque at 30 days and one year.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • twistedtreetwistedtree Solar Expert Posts: 126 ✭✭✭
    I don't think I ever had any over current situation, at least not enough of one to trip a breaker. I suspect the faults were all the result of a marginal/intermittent ground. The small bus bar - the one that was nearly detached from the main bus bar - is where the two solar CCs wire in. Time will tell for certain, but I'd wager a beer or two that the problem won't happen anymore.
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,665 ✭✭✭✭✭
    I don't think I ever had any over current situation, at least not enough of one to trip a breaker. I suspect the faults were all the result of a marginal/intermittent ground. The small bus bar - the one that was nearly detached from the main bus bar - is where the two solar CCs wire in. Time will tell for certain, but I'd wager a beer or two that the problem won't happen anymore.


    Loose wiring most likely. The 80 amp or less DC breaker on each of the controllers should have tripped. Something generated your e-mail? You do have these breakers correct? If there was any metal damage from the overheating it could happen again. Once this kind of thing happens, it is best to replace anything that is not shiney and electronics clean. I use the big buss bar for grounding high amp controllers because you do not have to worry about the contact between the small buss to the large. The small buss is rated OK but there is one more connection to ground. An inch pound torque wrench should be used unless you have the feel and do this enough. Good Luck!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • twistedtreetwistedtree Solar Expert Posts: 126 ✭✭✭
    Here's a quick update on this.  After repairing the ground bus, the problem is resolved.  No more errors, and the system is running well again.

    And yes, breakers galore.  Breakers at the pole for each string of panels as they enter the combiner, another breaker at the power panel before the solar goes into the CC, then another breaker on the output side of the CC.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    The loose connection might have caused one or the other -60 to try to send more current to the battery as the other one went temporarily offline. But more likely the combination of the high temperature and intermittent connection just caused an unusual situation that the firmware misinterpreted as overcurrent.
    SMA SB 3000, old BP panels.
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,665 ✭✭✭✭✭
    If you have fried wiring and contacts you would see the problem on the combox displays. You definitely will not on the old gateway.
    That thing should be given a decent burial.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • mike95490mike95490 Solar Expert Posts: 8,373 ✭✭✭✭✭
    I've got a gateway, and have abandoned it for the Combox.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • sridharTSsridharTS Registered Users Posts: 33
    One question If we using mppt charger controller to regulate and charge the battery. the inverter choosen is inverter/charge XW6048 is again recharge the battery so it get over charges the battery to cause failure also

  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    sridharTS said:
    One question If we using mppt charger controller to regulate and charge the battery. the inverter chosen is inverter/charge XW6048 is again recharge the battery so it get over charges the battery to cause failure also

    Sridhar, this getting a bit confusing--I think.

    MPPT is "Maximum Power Point Tracking"--It is used by both DC Solar Charge Controllers (MPPT types) and by GT Inverters (central and micro) to "track" the Vmp/Imp of the array to get the most energy possible out of a solar array. For DC solar charge controllers, MPPT also allows us to "match" the IV curve of the solar array to that of the battery bank. For example (remember the wiring calculation I just did in your other question), we can run a "high voltage" (100 Vmp) array into a "low voltage" battery bank (12 VDC).

    There are other issues with MPPT controllers, but that is the basic answer of why MPPT charge controllers are "nice".

    And, the XW6048 does have a "battery charger" capability (take power from the AC input--AC1 from mains, AC2 from Genset) and even "run backwards" with GT inverter connected to the AC Output. With a correctly configured XW6048, using AC1/AC2/AC-Output as sources to charge the battery bank, there should be no problem with over charging (although, with "most" AC Off Grid Inverters running "backwards" with GT inverters on AC-Output, the charging is less "ideal" (charging is not as accurate, and not as "gentile" as AC1/AC2 or using a Solar Charge Controller (MPPT or PWM).

    I am going to move your and mine posts to your other Wire AWG thread--Lets try to keep your questions in one spot--I think it will be less confusing.

    Also, I would suggest you ask "exactly" the question(s) you want to do for your installation. Generic questions tend to get confusing (for example, if you ask about GT Inverters and have no utility power, then talking about GT inverters sort of makes things more complex).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Hmm... I still am getting used to this new software--I don't see how to move these two comments into your other Wire Sizing thread...

    Sridhar, can you please just post all of your questions in that one thread:
    http://forum.solar-electric.com/discussion/350008/wire-sizing#latest
    It will be much less confusing.

    Thank you,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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