Kyocera KC130 output issue...diodes?

Hello folks, I could use some advice.
Yesterday I did a routine system check out at the combiner boxes (2) (2 arrays) and found low voltage output on two different strings on one array.

Arrays are configured as 24 volt strings of 2 Kyocrea KC130's in series.

I found one low output panel in each of the two subject strings. Voltage readings are almost exactly half of the normal readings of the rest of all the system panels.
10.6 vdc on one and 11.2 vdc on the other.
I got readings of 22.1 or so on all other panels in the arrays.

No recent lightning or storms.
Inspection of the cell areas and back of panel areas show no signs of heat. Interior junction box inspects shows no sign of heat damage or damaged diodes.

My guess here is that some diodes went bad in the two panels.

It appears that to check the diodes, I need to actual remove them to isolate them in order to check them...

Is that correct?
If not, what is the correct proceedure to check them, and if bad, what are the spec's for and equvalent diode?

I'm guessing someone here has ran into this and can lead me in the right direction.

I'm also hoping of course, that the panels are ok, just bad diodes.

Thanks in advance for your assistance.
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Comments

  • BB.BB. Super Moderators Posts: 26,872 admin
    Re: Kyocera KC130 output issue...diodes?

    Before I take them apart, I would call the retailer or Kyocera directly for warranty service.

    If this is just the open circuit voltage reading, and the connections are otherwise ok, the panels should probably be replaced.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    Hello again, I just tested the output amps (connected to the battery load) and I was suprised to find the output was just slightly (.4 amp) less than the other strings.
    I used a clamp on meter.
    Same amp reading when the rest of the strings where connected to the battery load or not.

    Does that indicate the panel is good and it is in fact bad diodes?
  • BB.BB. Super Moderators Posts: 26,872 admin
    Re: Kyocera KC130 output issue...diodes?

    It is strange. If this is a 24 volt array on a 24 volt battery bank with a pwm controller, I would have guessed a much larger current shortfall in current.

    This would lead me to wonder if there is an intermittent or poor connection somewhere.

    The panels need to generate more than 25-29 volts to push current to the battery bank. It should not be possible if one panel is at 1/2 output voltage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    Just pull the diode and see if the voltage recovers

    Either the diode is shorted or its doing its job and bypassing half of a bad panel. Takes only a few minutes to test

    Current test isn't good for this check as you can short the string but the diode just bypasses the open string within the panel
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    hi, i just got back home again with some time for testing.

    i pulled the diodes from a spare "emergency replacement"
    panel i have here...KC120, but the diodes are the same rm3c diodes. Replaced the subject panel with the diodes from the good panel.

    I'm happy to report open circuit voltage is back to normal, and the output current (with battery load connected) is now matching other panels at about 5.66 amps (current light conditions)

    So, it would appear at this point that it is just the diodes...at least on the panel i checked. That leaves me with trying to locate replacement diodes.

    I have found a supplier for Kyocera diode packs of 25pcs. for $60...no way. I should be able to find equivalents for about 80 cents each.

    Anyone have the specs i need to find the diodes?
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    Solar Guppy,
    I went ahead and just pulled the diodes from both low voltage panels...voltage jumps back to normal voltage of about 21.7 vdc. (I also get normal amp output this way)

    Does that mean the panels are good, but just bad diodes?
  • BB.BB. Super Moderators Posts: 26,872 admin
    Re: Kyocera KC130 output issue...diodes?

    Sounds like it... Diodes frequently do fail shorted.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    The story continues....I pulled all the subject diodes.
    Tested all. Found three bad ones; 2 totally shorted, 1 not conducting either direction. Replaced with spares borrowed from my spare KC120.
    ALL PANELS UP AND RUNNING! :) (GOOD FEELING)
    So my final question seems to remain....where to find specs for replacement...Thanks all.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    Would this be of any help: http://www.solar-electric.com/8ampbypdiod.html ?
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    hi, thanks, i did look at those. what i am looking for are 2 lead axial type to fit the kyocera kc130 junction box.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    james,
    when you pulled the diodes did they have markings of both numbers and letters? this would give a reference to the exact part used in the pvs.

    i also in my research found this from kyocera,
    Replacement bypass diodes for Kyocera J-Box equipped modules
    are sold in packs of 25; part number 705070
    do not confuse the part number from kyocera as being the actual part number on the diodes. an example diode might look like 1n4002, but can be other numbers and letters that can vary even by the country of origin.

    if you go with a different part than the original parts i would suggest replacing all of them in that pv with the newer part as older parts are questionable due to stress brought on by adjacent diode failures and that mismatches could force a failure on otherwise good parts.
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    Thanks Neil, my web search came up with the same kyocera number. I only found one distributor on the web showing them...$60 for 25pcs. No good.

    The number on the diode is RM3C....thats it other than "41***",which is not very helpfull

    I found several mfg. of the RM3C diodes, but no cross reference listed that i can find yet. I'm probably going to try to match the specifications listed on the RM3C data sheets to a equivalent silicon or Shottkey diode.

    These types of diodes are commom, should only cost about 80 cents each. I just need to match the specs.

    i'm going to call around today to check with some of my electronic componet suppliers to see if the have a cross reference.

    Honestly, I was just hoping someone had run into this before and already knew of a source.

    Thank you
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    interesting as i wonder what that 41*** is?

    anyway i researched what you gave me and it comes up a 1000v piv 2.5a diode with a vf of .95v max. btw, vf is forward voltage drop and piv is peak inverse voltage or its breakdown point for the reverse polarity.

    interesting that in searching rad shack i found this diode,
    http://www.radioshack.com/product/index.jsp?productId=2062577
    and i noticed a 41 in both the model and catalog numbers. coincidence?

    i can't say for sure as the rad shack diodes aren't showing the standard diodes numbers to check specifications, but i would bet that these diodes would work. on closer look at fine print the piv is 50v. too low.

    they do have this 3a diode at 200piv,
    http://www.radioshack.com/product/index.jsp?productId=2062578

    unless you are doing a gt install these smaller piv ratings around 200v will work fine for nearly all off grid type pv arrays.

    edit to add:
    if you go to rad shack, make sure the physical size of the new ones are the same or larger than the old ones. generally a part that handles more amps is larger in size than one that is lower in amps so this would just give a rough verification you are going in the right direction.

    we also just missed each other as you must've signed off while i was posting to you before.:roll: ahh there you are again.
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    Hi Neil, Yes I saw that one also.
    I would have thought this would be an easy find...Not so.
    I did find a US distributor of the RM3C but they have a $50 min order. My searches to cross reference have been fruitless.

    I'm trying to match the specs from the Sanken spec sheet i found on the web.

    To match the exact (or even real close) has been difficult as well...I'm going the contact Kyocrea today and ask that they send me some as a courtesy! Of course, they are not up yet this morning...(california?)
    thanks
  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    The 3 amp Radio Shack is fine, 50V is more than enough for a 21V OC panel

    Glad is was just the diodes, seems like a common point of failure for the KC120/130's
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    Solar Guppy, I'm guessing the forward current rating is more important than the max reverese voltage rating? thanks
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    james,
    being you will not have the possibility of having more than 50v on your pv system you can get away with the 50v piv rating. if you were to utilize a higher pv voltage you could pop the diodes. your choice and i believe about 5 cents difference in cost per diode at rad shack.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    Niel,

    The reverse voltage rating doesn't have to be the total string voltage as the diodes are in series with the other panels diodes. All that is required is the the voltage is greater than the cells being bypassed when shaded, in the KC120/130, that's about 10 volts

    For the KC120/130, its all about the current when forward biased, and you want the lower vdrop to minimize overheating of the diodes

    SG
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    Thanks to Neil, solar guppy, and all for your help.
  • mike95490mike95490 Solar Expert Posts: 7,307 ✭✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    I prefer to purchase semiconductors (diodes and such) from Digikey or Mouser, I've not had quality troubles from them, but I have had lots of problems from a chain store (brand not mentioned) with part quality.

    If the panel is 5 amps, I'd use AT LEAST, a 10 amp diode, or even larger, as there is no heat sink on it, or if you are able to leave the leads long, they will radiate heat from the part too.

    5A @ 1V, Vf = 5 watts disipated by the diode, while the panel is in hot sun. Toasty!

    I did a quick search and found this
    http://search.digikey.com/us/en/products/SB5100-T/SB5100DICT-ND/278750
    but, I could not find any diodes over 5A, with wire leads.
    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 ,

  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    Mike, The KC-120/130 has quantity 3, 3A Didoes in Parallel. No need beef up to a 5 amp.

    The Vf of the diode actually decreases with heat to about 0.5V so the losses are well within the spec of the parts
  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    Yes, the RM3C diodes in the kc130 are 2.5 amps foward current max and the max reverse current rating is 10 amp. The panel actually take six (6) diodes each. 3 for each half of panel.
    i also buy from digikey, mouser, jameco, newark, etc.
    i was just having trouble trying to find an exact match.
    i also just found that a NAWS competitor sells the replacement diodes for about $2.50 each. Since I need a minimum of 6 for the old kc120 i borrowed from, as well as at least 6 or 12 more for potential future issues, i'll try to find a reasonally priced subsitute from digikey, etc. Unless, of course, Kyocera is nice enough to give me a bag for my troubles :)
  • mike95490mike95490 Solar Expert Posts: 7,307 ✭✭✭✭
    Re: Kyocera KC130 output issue...diodes?
    Mike, The KC-120/130 has quantity 3, 3A Diodes in Parallel. ...

    Yow !! Zipper diodes. The weak one frys, then then next, then the next.

    No ballast/current sharing resistors ?

    ( and you don't want to know what the spell checker came up with for correcting didoes )
    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 ,

  • JamesJames Solar Expert Posts: 245 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    wasn't that some female singer/songwriter from england? :)
  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    Diodes are excellent on sharing as the loss goes down as they heat up so its not an issue and very common in designs. Transistors are the same way and that's why there safe to parallel in designs.

    SG
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    even if the originals failed from sharing inequalities, the new ones would have an extra 1/2a capability making this a very remote thing to happen.8)
  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    Using axle lead diodes don't provide much heat dissipation and is probably why they are going bad.

    5 amps is going to give you about 4 watts of dissipation on the diode. It will get blistering hot without at least some heat sinking on the leads.

    If you have the room it is better to use the TO220 packaged diodes with some metal heat sinking. Use TO220 heat sink insulator with heat sink grease to isolate diode from metal heat sink.

    The bypass diodes only come into conduction when there is some partial shading on panel. A leaf or bird dropping can trigger bypassing and is likely worse then morning or afternoon panel shading since the sun can be at full illumination producing the most bypassing current through the diode.
  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: Kyocera KC130 output issue...diodes?
    Diodes are excellent on sharing as the loss goes down as they heat up so its not an issue and very common in designs. Transistors are the same way and that's why there safe to parallel in designs.

    SG

    Yes for MOSFET's, definately no for bipolars and diodes.

    Thermal runaway occurs as one takes more current, it heats up more, driving down its forward conduction voltage relative to other parallel diodes making it take more current away from other parallel diodes making it even hotter.

    The reduction in forward voltage is relatively small (<200 mV). The forward voltage drop doesn't come close to making up for the added heating power caused by the additional current it hogs away from other parallel diodes. You end up with about 20% forward voltage reduction and 90+% hogging of the total current which nets out to more heating on the single diode.

    The KC130 panel has 36 cells, arranged in 4 rows of 9 cells. Usually each bypass diode in a junction box at the top end of the panel bypasses a down and back row pair making it easier to bring the connections to the junction box. With two down and back row pairs I would expect KC130 to have two bypassing diodes each bypassing 18 cells which is reasonable and keeps the maximum reverse bias on any single shaded cell to about 10 vdc.

    The third diode could be a series blocking diode or there are 12 cells per bypass diode although this would be an ackward conduction strip dressing within the panel. You don't want to run conductors tracks over the back of the cells to get up to the junction box and with side by side spacing between the cell's placement the only option to get a 3 X 12 cell bypassing arrangement in a 4 x 36 cell placement is to run long conductor tracks along the perimeter edge of the panel. A bit messy but not impossible.

    Because the KC130 is only a 20 vdc panel it is possible to only put a single bypass diode across all 36 cell if the cells are carefully graded for shunt resistance. It would be a stupid design to have a single 36 cell bypass with three diodes in parallel however. Functionally that would effectively be one diode in parallel with two inert diodes that provide some small amount of additional heat sinking for the one diode that is carrying most of any bypass current.
  • marsofoldmarsofold Solar Expert Posts: 42 ✭✭
    Re: Kyocera KC130 output issue...diodes?

    Gosh, my new solar system uses six Kyocera KD210GX-LPU panels. I hope this isn't a Kyocera-wide problem with all of their panels. Some of mine get shaded in the winter months. Are there reports of others having similar problems with Kyocera panels? Should I be concerned?
  • DapdanDapdan Solar Expert Posts: 313 ✭✭✭✭✭✭
    Re: Kyocera KC130 output issue...diodes?

    I read this thread with great interest as I am having a similar problem with my KC130TM as indicated in this thread I started:

    http://forum.solar-electric.com/showthread.php?t=12113&page=2

    I never got to follow through on my warranty enquires as I had to travel and kyocera was asking for me to do some testing and report to them. I could not fully understand why they need the info (since my pic show an obvious panel defect/problem) but I was being a good boy and following their orders. I now need to follow through on there request

    Cheers...
    Damani
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