Solar combiner box questions
I'm looking for a solar panel combiner box for the RV's roof. I'm going to start with 2 panels with the option to add 2 more if needed. I've seen some that are stupid expensive and some that aren'...
Forum Discussion
johnm1 wrote:
Won't the loss be too big if I run the MC4 cables (10 gauge wire) all the way to a combiner box sitting next to the charge controller?
I also need to do the math on the cost of MC4 extension wire vs 2 or 4 gauge wire and lugs and heat shrink, etc.
You shouldn't need 2 AWG from the combiner box. I'd suggest to buy a length of 4 awg welding cable, red and black heatshrink, a crimper and the necessary lugs to connect up this project. If you have some 4 AWG left over, it may be incorporated in a different project.
A lot of the solar users on this and other Forums are absolutely terrified of using a wire that is bigger than barely adequate. Most guys are also squeamish about pulling wire through the roof. A marine bulkhead fitting removes that worry. MO is that wire is still cheap and I want to get ALL of the solar harvest through the controller and out to the batteries. I don't want a 3 percent voltage drop. YMMV.
If you do extend MC4 down through to the controller, at least you'll know how it is easily pulled. When you add a module or two, you'll either be repeating that or adding in more "Y" connectors.
Also suggest to use an online calculator for different wire sizes, length of run, and current involved. It's a lot easier when you know how all this works and are not having a load on your shoulders about missing a piece of the puzzle. Here's a calculator
It sounds like you are developing a good plan. What controller do you have in mind?
