Getting 21 volts out of two 24 volt panels...

softdown
softdown Solar Expert Posts: 3,925 ✭✭✭✭
in Solar Beginners Corner #1
They put out about 39 volts individually. Was trying to replace MC3 connections with MC4 connections and doing a parallel connection for a 24 volt system. Things got a little perplexing for me....

Should be getting 39 volts with double the amps.

It was replacing the MC3 connections that I found a bit confusing. Lots of little pieces...
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #2
    If they put out 39V before, I would suspect a poor crimp in the MC4 connection or a poor mating if the male & female pieces... they are finicky  unless you have a good , proper  crimper for the M &F parts
     
    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
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  • softdown
    softdown Solar Expert Posts: 3,925 ✭✭✭✭
    edited August 2016 #3
    Made a couple little mistakes. Must be ~40 pieces to assemble with four panels. Got it working right. Very simple with a little practice. Just buy a couple more MC4 connectors than you will need. Replacing MC3s with MC4s may require a sober mind form some.

    Now....to wire six panels into a combiner box with four inlets and two outlets (of course).
    EDIT: Thinking that I need two combiner boxes....which I have. I don't like doing four unfused panels in parallel.Pretty sure that is a no-no.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • Photowhit
    Photowhit Solar Expert Posts: 6,011 ✭✭✭✭✭
    #4
    I'm not sure why you would bother replacing MC3 connectors with MC4, I'm pretty sure you can still get MC3 connectors or wires with MC3 connectors. They make "clam shells" to retro fit over the connectors to make them compliant to newer laws on making disconnecting more difficult. I think I still have 40 of those clams shells around somewhere if you need them.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • softdown
    softdown Solar Expert Posts: 3,925 ✭✭✭✭
    #5
    My combiner boxes are MC4. My goats would de-couple exposed MC3 connections....they mess with everything.

    Yesterday I did found some affordable MC3 connectors. The clam shells are something that I am unfamiliar with.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • Photowhit
    Photowhit Solar Expert Posts: 6,011 ✭✭✭✭✭
    #6
    It requires a tool to disconnect them, like MC4, and of course it can be done with out;

    http://shoals.com/products/mc3-locking-clamshells/


    Here's a photo;


    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • softdown
    softdown Solar Expert Posts: 3,925 ✭✭✭✭
    #7
    How much will you take for the clamshells? Looks like it works just fine.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • Photowhit
    Photowhit Solar Expert Posts: 6,011 ✭✭✭✭✭
    #8
    I'd just like to see them used. Send me your address and I'll send what I have, I'm not sure what I have 20-30 I think, I think. Just pay my postage or donate a couple bucks to a charity. Send me your address via message. My box might be full if it bounces, I'll clean some stuff out. (I'm house sitting but will go by the house a few times in the next couple days)
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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