Connecting 3 140w panels in parallel

New to this forum, relatively new to solar. I've been trickle-charging a 6 battery bank of 12v 150ah deep-cycle batteries with a 90w 7a array, and have recently purchased 3 140w ~10a panels. These panels have MC4 connectors, and my question is this: Are there connectors available to connect these 3 panels in parallel to my controller? I'd like to come off the roof with only the 2-wire lead to the controller. I've looked on eBay, and I see the 1M2F and 1F2M connectors, but that gives me a series connection in the end, which is not what I'm looking for. Also, will the 90w array connect as just another panel in my system, or will I need to do something different? Thanks for anybody's help on this.

I live in Western Montana, pretty sunny here in the Mission Valley.

Comments

  • kenputer
    kenputer Solar Expert Posts: 27
    Re: Connecting 3 140w panels in parallel

    I think you are looking for 4 MC4 parlarl connectors. One set to join 2 panels and then another to join third panel and then to your charge controller.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Connecting 3 140w panels in parallel

    Usually, the warranty becomes a bit of a sticky issue if you cut the connectors...

    So, the easiest one off solution is to purchase a short length of male/female and cut it in half. Plug the connectors into the solar panel(s), and wire the cut ends into the balance of your system.

    8 Foot MC4 Extender Cable Male/Female $17.80
    wind-sun_2180_210626 8 ft. Latching MC4 Extender Cable 8 Foot MC4 (Solarline 2), Extender Cable with one male and one female connector ... 10 gauge (AWG) stranded copper wire Outdoor rated insulation UL listed MC4-08-MF...


    And some other MC4 stuff:

    Disconnect Tool for MC4 Connectors (set of 2) $9.00
    wind-sun_2180_1301613 Unlocking Tool For MC4 Cable Connectors The new MC4 connectors are a real bear to unplug from each other (one of the new ... we recommend this tool (set of 2) if you will need to unplug any of the MC4 latching connectors or extension cables. Meant mainly for an assembly ...

    Multibranch MC4 Connectors, Latching $26.00
    wind-sun_2181_2954746 SolarLine 2 Multibranch MC4 Connectors, Latching These are used to parallel and/or to series-parallel multiple MC4 connections, such as cables from solar panels. For most panels you

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Connecting 3 140w panels in parallel

    Thanks for the response, I had to reverse my thinking on that. Sometimes all it takes is another perspective. Like the norvegian said, "Den I vasn't tankin' agin!"
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Connecting 3 140w panels in parallel

    we advise people to fuse each pv (or each series string of pvs) when paralleling more than 2 and is required by the nec. this is why they don't make a multibranch adapter for more than 2 to be combined. most will use a combiner box for fusing/circuit breaking each pv and then combine their outputs. this could be inconvenient if it is inaccessible on a roof should the fuse or cb open, but that would be the case if only 2 wires are coming down. don't forget that 3rd wire for ground.

    if you intend to replenish your batteries by solar we generally advise going with a charge rate of 5%-13% and what those 4 pvs would yield is under 5% making some other charge source still necessary to bring up your batteries.
  • Fullpower
    Fullpower Solar Expert Posts: 69 ✭✭
    Connecting 3 140w panels in parallel

    I have 26 solar panels , in use.
    I did NOT pay 17 dollars for each positive and 17 dollars for EACH negative solar module interconnect.
    You can buy a LOT of heat shrink tubing, solder-seal butt connectors, and 10 Gauge THHN wire for the price of 2 or 3 MC-whatever jumper leads.
    All of my series and parallel connections are crimped, soldered and heat-shrunk., the whole lot did NOT cost a hundred dollars.
    Buythe tools, do a good job, and those PV modules will be making power for your grandchildren.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Connecting 3 140w panels in parallel
    Fullpower wrote: »
    I have 26 solar panels , in use.
    I did NOT pay 17 dollars for each positive and 17 dollars for EACH negative solar module interconnect.
    You can buy a LOT of heat shrink tubing, solder-seal butt connectors, and 10 Gauge THHN wire for the price of 2 or 3 MC-whatever jumper leads.

    That's fine as long as you don't mind having no warranty on your panels. Your choice, your panels, your decision. Just as long as you're aware of the warranty issue and assuming you don't need an inspection.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Connecting 3 140w panels in parallel
    wedunit wrote: »
    New to this forum, relatively new to solar. I've been trickle-charging a 6 battery bank of 12v 150ah deep-cycle batteries with a 90w 7a array, and have recently purchased 3 140w ~10a panels.

    Six 12 Volt 150 Amp hour batteries in parallel? There's two things wrong with that. One is the difficulty in coming up with and handling enough charge current for a 900 Amp hour battery bank. The other is getting that current distributed evenly between the six batteries.

    If this is a 24 Volt bank that's 450 Amp hours and eases the current concerns, but there's still no way 420 Watts is going to properly charge it, even with the 90 Watts thrown in. You have about half the array needed.
  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    Re: Connecting 3 140w panels in parallel

    I wasn't aware of the NEC reg. about fuses required for three or more panels in series or parallel strings connected to a breaker/fused combiner box. I found this 4-way adapter rated at 30 amps, so I'm not sure how one would use it and meet the NEC fuse requirement.

    http://www.ebay.com/itm/MC4-BRANCH-ADAPTORS-T-BRANCH-CONNECTORS-30A-TUV-SOLAR-PANEL-PV-DIY-US-/280963977521?pt=LH_DefaultDomain_0&var=&hash=item416ac21131

    Bill
    Bill
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Connecting 3 140w panels in parallel
    I wasn't aware of the NEC reg. about fuses required for three or more panels in series or parallel. I found this 4-way adapter rated at 30 amps, so I'm not sure how one would use it and meet the NEC fuse requirement.

    http://www.ebay.com/itm/MC4-BRANCH-ADAPTORS-T-BRANCH-CONNECTORS-30A-TUV-SOLAR-PANEL-PV-DIY-US-/280963977521?pt=LH_DefaultDomain_0&var=&hash=item416ac21131

    Bill

    I'm not sure there is a regulation about it, but it has nothing to do with the conductors' ability to carry current. It has to do with what happens if one of those parallel panels should short, causing the others to dump their full Isc to that short. If the combined Isc exceeds the current capacity of the single panel it can start a fire. The only way to prevent that is with over-current protection that will blow first and safely. Using connections capable of handling more current will not solve the potential problem at all.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Connecting 3 140w panels in parallel
    I wasn't aware of the NEC reg. about fuses required for three or more panels in series or parallel.

    NEC does NOT necessarily require fuses on three parallel panels... it depends on the specifications of the panels. For example, suppose you have 3 panels in parallel and each panel has an Isc of 5 amps. If the panels have a series fuse rating of 12 amps, then you do not need fuses for the three panels. If one panel shorts out, the maximum current that the other two can provide is 10 amps, which is within the range (12 amps) that the shorted panel can handle without burning up.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    Re: Connecting 3 140w panels in parallel
    I'm not sure there is a regulation about it, but it has nothing to do with the conductors' ability to carry current. It has to do with what happens if one of those parallel panels should short, causing the others to dump their full Isc to that short. If the combined Isc exceeds the current capacity of the single panel it can start a fire. The only way to prevent that is with over-current protection that will blow first and safely. Using connections capable of handling more current will not solve the potential problem at all.

    I can see where a dead short would mean trouble. It would seem that as thin as the connection ribbons are that go from solar cell to solar cell, they would act like a fuse and would open stopping the electrical short. I remember seeing here on this forum where a member had a fellow install homemade solar panels that caught the owner's roof on fire, so I can see how a short can start a fire. Just seems the thin cell ribbons would rather burn open quickly rather than continue to stay connected and heat up.

    I can see using a pair of MC4 connectors with an automotive style moisture resistant fuse holder in between on the three positive side connections of this style of connector. What size automobile style fuse would one use on the OP's three new panels?

    I'm looking at something of the same type of issue on my "phase two" array where I have three strings of four Kyocera 130w panels. Each string is series wired for 48v going to DC breaker in the combiner box and then to an Outback FM 80 controller and 24v battery bank. If, by some twist of fate I'd grid tie my system using two of Outback's GVFX3524, I rather wire it/fuse it correctly now than rewire the arrays later on...
    Bill
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Connecting 3 140w panels in parallel

    Really recommend not using automotive fuse holders... They really are not safe (can overheat/catch fire even if operated at less than rated power). They are just not designed to operate a near rated capacity for hours on end.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Connecting 3 140w panels in parallel
    I can see where a dead short would mean trouble. It would seem that as thin as the connection ribbons are that go from solar cell to solar cell, they would act like a fuse and would open stopping the electrical short. I remember seeing here on this forum where a member had a fellow install homemade solar panels that caught the owner's roof on fire, so I can see how a short can start a fire. Just seems the thin cell ribbons would rather burn open quickly rather than continue to stay connected and heat up.

    No, they will not act like a fuse. The reason being a fuse is a controlled point of failure, specifically designed to open under the correct amount of current and be able to interrupt the rated Voltage. The connections within a panel would open partially or completely at one or more points and allow arcing between because there is no guarantee of just where and how much failure there would be. This is why you do not use a short piece of thin wire as a fuse.
    I can see using a pair of MC4 connectors with an automotive style moisture resistant fuse holder in between on the three positive side connections of this style of connector. What size automobile style fuse would one use on the OP's three new panels?

    You shouldn't count on automotive fuses for this. They may/may not have sufficient Voltage rating to protect against arcing. Quite often they are of rather poor quality because they aren't expected to handle more than 1/2 their rated current and all at Voltage <15 (arc point).

    The OP's panels were/are apparently 10 Amps. No telling what the series fuse rating would be. If we extend vtMaps' example you'd have the shorted panel with a maximum series fuse rating of 15 Amps being fed <12 Amps Isc from the other two panels. For the most part it would work, unless something upped the insolation on the panels causing them to produce higher than expected current. That is why we err on the side of caution and recommend fusing three or more parallel connections regardless of ratings.
    I'm looking at something of the same type of issue on my "phase two" array where I have three strings of four Kyocera 130w panels. Each string is series wired for 48v going to DC breaker in the combiner box and then to an Outback FM 80 controller and 24v battery bank. If, by some twist of fate I'd grid tie my system using two of Outback's GVFX3524, I rather wire it/fuse it correctly now than rewire the arrays later on...

    Good idea to put the breakers in now rather than later. And in this case with the strings wired for nominal 48 Volts the Voc (which is what must be interrupted to prevent arcing) would be near 90 Volts. As such you must use something like MidNite's DC breakers with the 150 Volt rating.
  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    Re: Connecting 3 140w panels in parallel

    What type of fuse and fuse holder is suitable for solar power systems?

    Thanks,
    Bill
    Bill
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Connecting 3 140w panels in parallel
    What type of fuse and fuse holder is suitable for solar power systems?

    Thanks,
    Bill

    Depends on which part of the system and what Voltage & current are involved.

    Array combiners, fuses/breakers: http://www.solar-electric.com/sopawiinco.html

    Inverter fuses/breakers: http://www.solar-electric.com/infubr.html
  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    Re: Connecting 3 140w panels in parallel
    Depends on which part of the system and what Voltage & current are involved.

    Array combiners, fuses/breakers: http://www.solar-electric.com/sopawiinco.html

    Inverter fuses/breakers: http://www.solar-electric.com/infubr.html

    Thanks for the help with the disconnect and breaker specs, Cariboocoot. But, are you saying that fuses like the MNTS are to be used between each panel in the string of 4? http://www.solar-electric.com/mnts.html
    Bill
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Connecting 3 140w panels in parallel

    Bill, those fuses/Circuit breakers are needed when you have 4 panels in parallel (not series) combining into one wire. If one panels shorts there is a possibility of backfeeding the 3 other panels into that one panel that shorts, and causing a fire when the other 3 panels over Amp the shorted panel. Make sense?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    Re: Connecting 3 140w panels in parallel
    westbranch wrote: »
    Bill, those fuses/Circuit breakers are needed when you have 4 panels in parallel (not series) combining into one wire. If one panels shorts there is a possibility of backfeeding the 3 other panels into that one panel that shorts, and causing a fire when the other 3 panels over Amp the shorted panel. Make sense?

    Parallel strings and higher amperages....I can see how that can be dangerous for fire. Series panels of 3 or more don't need a fuse between each panel?

    So, I'm still trying to picture putting a fuse on each hot wire of each of the 4 panels to understand what type of fuse/holder is used under the panels.

    Thanks
    Bill
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Connecting 3 140w panels in parallel

    Three or more strings (typically) of parallel connected panels need one series fuse per string. We typically draw them in the + output of the last panel, and common ground all three (or more) - outputs to a common bus bar (not grounded to earth/green wire).

    Basically an "on/off" switch per parallel connected string. Too much current in any one string, and that fuse/breaker "turns off".

    You can get more complex and put a fuse in the - and + leads--And technically, that is "required" for floating outputs. But if your battery bank - Bus is earth/green wire/ground rod/cold water pipe grounded properly--Then you only need one fuse per panel string.

    Again, the fuse in the case of solar panels is not to protect against the panel outputting too much current (like the fuse/breaker on the output of a lead acid battery), but instead is there to prevent a shorted panel (hail stone, rock, etc.) that shatters the panel or a chafing wire that short to ground, that the other 2+ parallel strings do not feed enough current to light the panel/wiring on fire before the fuse/breaker pops.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Connecting 3 140w panels in parallel
    Thanks for the help with the disconnect and breaker specs, Cariboocoot. But, are you saying that fuses like the MNTS are to be used between each panel in the string of 4? http://www.solar-electric.com/mnts.html

    Those particular fuses are designed for strings used in GT systems where each string may produce Voltages up to 600. The breakers are more suited to off-grid applications. Many panels will have a maximum series fuse rating of 15 Amps, and you do not want to exceed that maximum.

    Again you only need them on multiple parallel connections; a string is one or more panels in series.
  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    Re: Connecting 3 140w panels in parallel
    BB. wrote: »
    Three or more strings (typically) of parallel connected panels need one series fuse per string. We typically draw them in the + output of the last panel, and common ground all three (or more) - outputs to a common bus bar (not grounded to earth/green wire).

    Basically an "on/off" switch per parallel connected string. Too much current in any one string, and that fuse/breaker "turns off".

    You can get more complex and put a fuse in the - and + leads--And technically, that is "required" for floating outputs. But if your battery bank - Bus is earth/green wire/ground rod/cold water pipe grounded properly--Then you only need one fuse per panel string.

    Again, the fuse in the case of solar panels is not to protect against the panel outputting too much current (like the fuse/breaker on the output of a lead acid battery), but instead is there to prevent a shorted panel (hail stone, rock, etc.) that shatters the panel or a chafing wire that short to ground, that the other 2+ parallel strings do not feed enough current to light the panel/wiring on fire before the fuse/breaker pops.

    -Bill

    Thanks for taking the time to help, Bill. You did a great job of clarifying that! On a related note, I ran across a U-tube video where the fellow used a bare #6 multi-stran ground wire running from his battery box to a heavy-duty copper-clad ground rod. I thought that any grounding wire had to be a solid wire.
    Bill
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Connecting 3 140w panels in parallel

    Basically, you have to refer back to the NEC code and see what is acceptable for grounding (I don't have a code book).

    In our area, external ground wires have to be run in an armored cable (conduit, or that "spiral wound" galvanized steel stuff) for better protection against breakage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Connecting 3 140w panels in parallel
    the fellow used a bare #6 multi-stran ground wire running from his battery box to a heavy-duty copper-clad ground rod. I thought that any grounding wire had to be a solid wire.

    I'm no code expert, but around here #6 stranded is what is used for safety ground. I believe that code is about the safety ground, not grounding for lightning. For lightning rods the best ground wire is braided.... I would imagine that solid wire would be the worst.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Connecting 3 140w panels in parallel
    BB. wrote: »
    In our area, external ground wires have to be run in an armored cable (conduit, or that "spiral wound" galvanized steel stuff) for better protection against breakage.

    How does the ground wire get out of the conduit and attach to the ground rod? Usually conduit terminates in an electrical box. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Connecting 3 140w panels in parallel

    They just cut back the steel (or a conduit bushing) next the ground rod.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Wannabesolar
    Wannabesolar Registered Users Posts: 5
    Re: Connecting 3 140w panels in parallel
    wedunit wrote: »
    New to this forum, relatively new to solar. I've been trickle-charging a 6 battery bank of 12v 150ah deep-cycle batteries with a 90w 7a array, and have recently purchased 3 140w ~10a panels. These panels have MC4 connectors, and my question is this: Are there connectors available to connect these 3 panels in parallel to my controller? I'd like to come off the roof with only the 2-wire lead to the controller. I've looked on eBay, and I see the 1M2F and 1F2M connectors, but that gives me a series connection in the end, which is not what I'm looking for. Also, will the 90w array connect as just another panel in my system, or will I need to do something different? Thanks for anybody's help on this.

    I live in Western Montana, pretty sunny here in the Mission Valley.

    Howdi , I posed a similar question on this same topic, three solar panels in parallel . I had to just break down, spend more money , buy a midnight solar combiner box, used 15 amp midnight breakers , wired it up to charge controller and be done with it . I just dont need or want a fire .I lived in anaconda montana for a few years when i was younger, spent summers there as well .I know those hugh green pine cones had left many hugh dents on our vehicles .I can just imagine one of those green pine cones weighing 5 pounds crashing on one of your solar panels causing a short . Im on the west coast now but still dont have solar panels on my roof and useing ground mounts on concrete . I prefer parallel over series just because shadeing does have a big effect in charging of my batteries and i found for my little system it fits my needs best . Cleaning my solar panels at ground level is a bonus and takes me less than 10 minutes and thast rolling the hose back up and putting the scrubber in the garage back ,lol .