Troubleshooting 101.

hillsidehillside Registered Users Posts: 54 ✭✭
Image result for Solar panels in series and parallelHere's my setup (thanks to all who helped). This worked perfectly with the new batteries for about 2 weeks and then I noticed that batteries weren't charging as they should. I used my voltmeter to measure voltage from the panels at the controller.
Voltage had dropped from 54 to 39, about 25%.
I checked the oldest panel, a 5 yr. old Trina (all are 24 volt) and it showed 27volts...about right?
I can check for no voltage from a hot line but how to check these connections with 2 branch connectors?
How do I check if a negative to a positive is not functioning? These are all new MC4 's with electrical tape over them to keep rain out.
Appreciate any help, thanks

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,508 admin
    What, specifically, is the Vmp/Imp/Voc of the panels?

    What is the battery bus voltage (charging/discharging/resting)?

    Do you have the ability to measure current from your solar array (via the charge controller) or have a DC current clamp DMM?

    If flooded cell batteries, do you have a hydrometer and specific gravity readings?

    A hydrometer and a DC Current Clamp meter (really an AC/DC current clamp DMM--Digital Multimeter). Here is a nice midrange price/quality meter (you can find DC Current Clamp DMMs for less than $50 if you look around):

    https://www.amazon.com/gp/product/B019CY4FB4

    Note that DC Current Clamp meters need to be zeroed before you get accurate measurements.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • hillsidehillside Registered Users Posts: 54 ✭✭
    Mixed panels, One Boviet 255W, Vmp 30.5, Voc 37.8
                          One Trina 230W, Vmp 30., Voc 37.
                          Two Hanwha 235W, Vmp 30.1 Voc 36.8
    I'm not sure what you mean by battery bus voltage. I have readings on the controller showing as much as 27.5 and have not seen it go below 24.0.
    Measuring current from solar array I do at the controller, 54volts, now 38-39V
    I use a multimeter and s specicif gravity tester.
    Specific gravity went down to 1.225 on all 4 new Deka L16 6volt, 370AH FLA's.---so I shut it all down, and first covered the panels with tarps. Am in the process of using a 6amp battery charger on each battery separately (cables disconnected)and have brought two (so far) up to 1.275, almost 1.300
    One more thing. I took the cover off the Trina and noticed that something had gotten hot enough to melt one the the 4 plastic/nylon connectors, (not sure what they are) that are close to the outgoing positive. But it is still showing 27 volts in the sun. Could that be it ?
    Maybe I could post a picture of it..
  • icarusicarus Solar Expert Posts: 5,241 ✭✭✭✭
    If something got hot enough to “almost melt” one of the MC cable connectors (I’m assuming that is what it is, youhave a problem, and you need to figure out what it is...could be something as simple as an improperly plugged in MC cable connector, or a bad connector.  If i had to guess, you high resistance connection at that connector, and it is trying to push the current of the entire string (the two panels) through that bad connection, dropping the production of that string significantly.  I don’t know how big your battery bank is, but it sounds like you may be under paneled as well.  Assuming your battery bank is 48 vdc, you are, on a good day pushing ~15 amps into the battery.  That battery bank (assuming 48 vdc would like ~36-48 amps of bulk charge.  

    If you have them wired for 24 volts, they would like to see close to 90 amps or so.  You are probably seeing no more than about 40 amps I would guess, probably somewhat less.

    The only thing that kills batteries faster than over drawing, is undercharge current over time.  If they don’t see enough current, they will stratify, and begin to sulphate.  After you solve your current problem, look to double your PV if you want good service out of the batteries.  

    BTW, a 6 amp 6 vdc charger is barely enough for a float charge on those L-16,  each one would like ~40 amps EACH.

    Tony
  • hillsidehillside Registered Users Posts: 54 ✭✭
    It is wired for 24 volts and I know the system is under paneled by the past comments. But the system is only used part time; a couple of washer/dryer (propane dryer) loads a week, TV use 4-5 hrs. at night and often the system goes 2-4 days with no use and the inverter is turned off every time it's not in use.
    So I'll need to upgrade but having just bought the SRNE 40A controller (good for 1100Watts at 24V) and bought wiring, connectors, etc. I'm told here I will need a bigger charge controller, larger size wiring and somewhere in the area of 1300-1400watts. (Currently at 920watts)
    Is it worth it for part-time use? And with the frequent lightning strikes here in summer I'm reluctant to lose it all in one strike.
    Everyone we know has lost electronics here even with the best of surge protection. It's because of multiple pulses of lightning strikes (the best I can describe what people say). First pulse wipes out the surge protection and the next the electronics.
    Could the Trina be problematic?
  • BB.BB. Super Moderators, Administrators Posts: 29,508 admin
    If the J-box cover is melting, it is either bad/corroded/loose/etc. wiring terminals or a bad bypass diode.

    Many panels have sealed J-Boxes--So you are left figuring out if you want to try for warranty repair/replacement or cutting the box open and sealing it back up after your repairs.

    You need to get the batteries to ~29.0 to 29.6 volts, and hold it there for 2-6 hours (longer if batteries are deeply discharged).

    If you do not see over 28.something volts during the day when charging--Either you are not supplying enough current (5% minimum, 10%-20% for full time off grid recommended) or it will take a few days to get your battery bank recharged (especially if 5% rate of charge).

    Just to estimate your array output:
    • 4x235 Watts (average) * 0.77 panel+controller derating * 1/28.0 volts charging = 25.85 Amps (average "best case harvest" on cool/clear day around noon--panels pointing at sun)
    If you see no more than 50% of 25.85 amps ever (discharged battery bank, cool clear day, around noon) or ~13.0 amps or less peak into a 28.0 Battery bus--You probably have something wrong (like the Trina panel or other issues).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,241 ✭✭✭✭
    If your loads are so small, consider reducing the battery bank size to better match the loads and the PV.  It is a classic error to over battery small off grid systems as it gives one the false sense of security.  What it usually turns into is an expensive lesson in battery failure.  All three elements ought to be well balanced for good performance...Loads first, determine the battery bank, which in turn determines the PV/shore power charge regimen.  

    When I built my (current) system, I was drawn to using 4 L16’s wired for 12vdc, at todays cost of ~$1000. I decided to go with 4 t-105s at a cost of ~$600.  It turns out that I use about 10-15% of ah capacity per day, and charge at ~ 30 amps, getting fully charged in about 2-4 hours of good sun.  The financial equation was if the t-105s lasted 5 years and the l-16s lasted 8 I was money ahead with the t-105s.  I am in year 12 with the t-105s and they seem to be going strong.  They are used full time now about 4 months a year, used to be used 12 months.

    My guess (once you get your current problem sorted) you will not see anywhere near the expected life from those batteries sorry to say.

    YMMV.

    Tony
  • hillsidehillside Registered Users Posts: 54 ✭✭
    ok, thanks. Lots to think about. Here in the Caribbean there are limited sources and vendors of batteries. They're out there, but having just spent the $ on these I'm better off adding more panels. Buying from vendors stateside and paying for shipping almost doubles the cost. So buying from a supplier here that imports by the pallet load is the way to go, but you're limited by what they have in stock.
  • icarusicarus Solar Expert Posts: 5,241 ✭✭✭✭
    As you know, the batteries are the expensive part of the equation now...keep them happy and they will last a long time with your loading.  Budget more PV and figure out how to get it there.  Even considering shipping doubling the cost, PV is way cheaper than it used to be, and way cheaper to ship than L16s.

    good luck, find your problem and keep in touch,

    T
  • mcgivormcgivor Solar Expert Posts: 3,072 ✭✭✭✭✭
    hillside said:

    Measuring current from solar array I do at the controller, 54volts, now 38-39V

    Divide and conquer is the best method of finding a fault, split the parrallel strings by removing the Trina panels since one appears to have issues anyway, see how the other two perform. Then divide the series Trina string and perform a short circuit test on each to measure the current.

    Current is not the same as voltage, voltage is inversely proportional to current, when the batteries are demanding maximum current it will drag the input voltage down, this is normal. A short circuit test will reveal maximum current at zero volts, an ammeter is required to measure current, see post 3.

    The evidence of hest damage in the junction box could be caused by a loose connection, screw or dry solder, this may allow voltage reading to appear normal but cannot pass current, hense the short circuit test. Having the correct tools make trouble shooting so much easier.


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • hillsidehillside Registered Users Posts: 54 ✭✭
    Thanks again. So, let's say I remove the Trina 230watt panel and replace it with a new 235W and add two more panels which gives me 6 total, for about 1410watts.
    I'll need to replace the 40Amp SRNE controller with a 60 Amp size?
    Do I need bigger wire than the current 10AWG between panels? If so, what size?

    (24volt, 3000W Cotek pure sine inverter, 4- 6V L16 370AH batteries, currently with 920watts in panels)

  • mcgivormcgivor Solar Expert Posts: 3,072 ✭✭✭✭✭
    edited September 11 #12
    hillside said:
    Thanks again. So, let's say I remove the Trina 230watt panel and replace it with a new 235W and add two more panels which gives me 6 total, for about 1410watts.
    I'll need to replace the 40Amp SRNE controller with a 60 Amp size?
    Do I need bigger wire than the current 10AWG between panels? If so, what size?

    (24volt, 3000W Cotek pure sine inverter, 4- 6V L16 370AH batteries, currently with 920watts in panels)

    Rather than getting a larger charge controller you could get another 40A unit, use each on its own array, 3 series then parallel the controller  outputs to charge the battery, input voltage allowing of course, the maximum input voltage would need to be ~150V, in order to do this.

    Wiring wise, when increases in capacity are made its prudent to review the size of the conductors, but first there needs to be a plan, including current, voltage and distance, one step at a time is the best way to proceed.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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