Disconnect/breaker between solar panel and charge controller

jubilantjill · October 2019

Hi all! I'm in the process of building out a camper van with solar and have a question about a switch between the solar panel and the charge controller.
I have a single 200 watt panel, 30A mppt charge controller and 176Ah AGM battery. The panel is mounted but nothing is hooked up yet. From what I've read I can't find a reason to fuse between the single panel and charge controller, but I would like an on/off switch there to be able to easily disconnect the panel.
My question is what kind of switch can I use? I have a simple leftover 12V switch that's rated for 16amps, but I'm not sure that will work.
What do you guys recommend? And by all means let me know if I do need a fuse for my single panel. I've done a fair bit of home wiring, but this DC solar stuff is all new to me.
Oh, and is there a work around to buying a $25 MC4 crimp tool to do 2 measly crimps then never use it again?

Cheers!

Estragon · October 2019

You don't really need a fuse, but a DC rated breaker makes a handy shutoff switch. If using a switch, be sure to check that it has a DC load rating. Switching DC is different than AC, and many AC switches have much lower DC amp ratings (or none at all).

Not sure why you need to crimp mc4. Typically, you'd get an mc4 extention (with male and female mc4 ends) about 2x the distance from panel to breaker or controller, and cut it about in half. Connect the mc4 ends to the panel, and the bare ends to breaker/controller.

jubilantjill · October 2019

I'm in rural Spain and all I can find online are DC 16A single pole breakers for$45! That's pretty dang expensive if I don't actually need the fuse. I was hoping to find a more economical solution and thought maybe the little 16amp 12v switch I already have would work. It says 12V unipolar. Do you think that means DC? I bought it for light switches off an RV website.

jubilantjill · October 2019

Ah! I found another site with the 16A DC breaker for $10. That's reasonable.

Estragon · October 2019

Our host sells mnepv DC breakers in 1 to 63a sizes for $12.46. Not sure what $45 would be for, maybe a gfci (which can be spendy)? $10 sounds more like it.

The panel should have a spec for maximum series fuse, which is what really should be used, but in this case the OCP isn't really needed anyway.

If it's polarized (one terminal marked + or line), that's the pv side. They're sometimes designed with an arc chute (the arc is the main difference from AC breakers/switches), which needs to be on the right side for it to work properly disconnecting under load. It's best to turn off the controller first though.

jubilantjill · October 2019

Thanks for responding. The panel says use a 15amp fuse (11amp panel). I realized the breaker I wanted needs to go into a panel box attaching to a bus bar. I just want to mount a switch on the floor by the charge controller so I went with a different style that only comes as a 20amp. I'll try to post a pic of what I ordered.

jubilantjill · October 2019

Braveheart · October 2019

Hi Jubilantjill,

How did finally worked with the break? I do also have a campervan and would like to install a fuse or breaker between the panel and controller. Did you mounted on the positive wire coming to the controller?

Gracias y saludos!

Disconnect/breaker between solar panel and charge controller

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