How to connect panels to mppt

redunculousredunculous Registered Users Posts: 22 ✭✭
Hi all

Finally purchased myself 2 x 100 watt panels and a recommended mppt controller for basic use and before they arrive I wanted to get some information on installation...

My panels come with MC4 connectors, I would like to combine the output of my panels so I am assuming I purchase the mc4 y / branch connectors?

Next my big question is, how to connect MC4 to my MPPT? I have this MPPT 

https://www.amazon.com/dp/B01GMUPGX2/ref=twister_B01GMUPGW8?_encoding=UTF8&psc=1

Thank you for any help - its very much appreciated.

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 5,728 ✭✭✭✭✭
    Likely you should run 2 - 100 watt panels in series (+-+-) so you wouldn't need any connectors, in fact you likely would want voltage about 2x the system(battery) voltage.

    Most people figure out their distance from the panels to the charge controller and buy a single cable 2x as long, so if they will be 50 feet away, they would buy a single 100 foot cable with MC4 connectors, then cut the cable in half using one connector for + and one for -.
    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.
  • LumisolLumisol Registered Users Posts: 374 ✭✭✭
    Just pick up a package of MC4 connectors and a crimper and buy the length of 8AWG you need and put a connector on each of 2 wires, one male and one female. I did it that way and it worked fine.

    Strip the ends about 1/4 inch and put it in the appropriate input and tighten the screw.
  • redunculousredunculous Registered Users Posts: 22 ✭✭
    Thank you for the responses - I didn't realise it was just simply 8awg crimped in there, I wasn't sure if it was some proprietary cable, going to make life a lot easier.

    Can I ask why you would wire them in series? I thought Parallel to get the amps up. 

    I am using these to keep topped up 4 x trojan 105 6v batteries that are wired in series and in parallel. They are going on my sailboat - we don't use a great deal of power (we have replaced all bulbs with LED's and only have items that run occasionally such as fridge and freezer) so I figure if we can manage 8amps during the day from both panels combined we should be in great shape and be able to sufficiently charge the batteries daily after the night draw down.
  • redunculousredunculous Registered Users Posts: 22 ✭✭
    So you wired yours in parallel and just had 2 x + and 2 x - crimped into single MC4's? Trying to find where I would purchase the connectors.

    Lumisol said:
    Just pick up a package of MC4 connectors and a crimper and buy the length of 8AWG you need and put a connector on each of 2 wires, one male and one female. I did it that way and it worked fine.

    Strip the ends about 1/4 inch and put it in the appropriate input and tighten the screw.

  • redunculousredunculous Registered Users Posts: 22 ✭✭
    Forgot to ask, can I not just cut off the MC4 connectors that are on my wiring now and just use butt connectors to connect to a length of 8awg? I have asked the seller if this will void my warranty - if it doesn't then this should be the way to go right?
  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭
    With an mppt controller you would normally wire panels in series so voltage is increased but current is kept low. The advantage to this is minimizing wire losses to the controller. The controller takes the wattage available and charges batteries at appropriate voltage (eg. 145 watts charging at 14.5v =10a). A pwm controller can only pass current through, so wiring in series wouldn't work well.

    On a sailboat you likely don't have much distance from panels to controller, so wire losses will be less of an issue. What may be an issue though is shading. Even a shadow from the backstay, for example, can reduce output a lot. In parallel the unshaded panel will produce normally. In series, the shaded panel will reduce power for the whole string.

    When solar panels get hot, their voltage is lower. This could be a problem for your mppt controller. They generally like an input voltage well above battery charging voltage. ~35v in series should work well. ~17ish may or may not.

    As for the MC4 connectors, the advantage is they're designed to make a weatherproof connection which can be disconnected and reconnected easily.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • redunculousredunculous Registered Users Posts: 22 ✭✭
    Great info, thank you - I will wire them in series, I had it in my brain that I would be pushing 24v to my 12v battery setup. The distance to my mppt is roughly 9ft so not too far. If I was to extend to 25ft would that be an issue as I would like to wire my mppt down to my nav desk rather then at the back of the boat in the cabin where it will be difficult to get to.

    Mc4 makes sense, will make up a set.
  • EstragonEstragon Registered Users Posts: 4,496 ✭✭✭✭✭
    edited June 2017 #9
    The effect of distance on voltage is a function of wire size. There's a voltage drop chart in our host's learning center that you can use to look up various combinations of distance and wire size.

    I think using 8ga for 25' is probably ok, but best to check.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • redunculousredunculous Registered Users Posts: 22 ✭✭
    Thank you - I've decided to wire it to the rear cabin and run the remote to the nav desk. Saves me running cables there then back for the battery bank
  • littleharbor2littleharbor2 Solar Expert Posts: 1,653 ✭✭✭✭
    Thank you - I've decided to wire it to the rear cabin and run the remote to the nav desk. Saves me running cables there then back for the battery bank

    You really want to keep the distance between your controller and batteries as short as possible. Excessive voltage drop there will cause problems in what your charger "thinks" your batteries are at, and what they are actually at.

    As to another's suggestion to get wire, MC-4 ends and a crimping tool, unless you plan to be doing more "in the field" solar wiring, I would avoid spending the money on all this stuff. Buy a pre made length of PV wire w/ connectors and cut it in half, as Photowitt suggested.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • LumisolLumisol Registered Users Posts: 374 ✭✭✭
    The extra money you'll pay for premade wires will pay you for the crimpers and still save money as well as giving you more flexibility in the future. Crimpers are cheap and if you decide to you can sell them again when you are done.
  • redunculousredunculous Registered Users Posts: 22 ✭✭
    edited June 2017 #13
    Thanks for all the replies

    I have now installed the panels in series and wired up my mppt and remote. I ended up buying 8guage wire and crimping as I own the crimp tools anyway :)
  • LumisolLumisol Registered Users Posts: 374 ✭✭✭
    That's your best bet.
  • PhotowhitPhotowhit Solar Expert Posts: 5,728 ✭✭✭✭✭
    Thank you for the responses - I didn't realise it was just simply 8awg crimped in there, I wasn't sure if it was some proprietary cable, going to make life a lot easier.
    Sorry I didn't get back to the thread. You did use wire designed for sun exposure? "Use 2" or solar wire? Other will quickly become brittle in the sun.
    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.
  • SolraySolray Registered Users Posts: 246 ✭✭✭
    edited June 2017 #16
    You may also use conduit to route the wires and protect them from the UV light. Conduit is a good idea even for wire rated for sun exposure as it offers protection from abrasion and cuts as well.
  • redunculousredunculous Registered Users Posts: 22 ✭✭
    Thanks guys, sorry for the late response - we are now into our sailing trip

    We have the wires covered from the sun in conduit :)


  • SolraySolray Registered Users Posts: 246 ✭✭✭
     :) 
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