Actual Solar Panel Cable Size

[Trebor8]

Hello.
Due too the short distance from my solar panel to my 40a controller - less than 3ft, I was thinking of just snipping off the mc4 connectors to the cable that is already there at the back of the solar panel and wiring directly into the controller, instead of using any further length of cabling in order to minimize any voltage drop.

But this cable size is only 2.5mm 14awg - max 20a. 20a is enough for me for now anyway, so thats fine. However, lets say, my controller is further away and hypothetically - as my single solar panel is 200w, I wanted draw more amps over 20a, I would of course leave the mc4 connectors on the solar panel cable and step up to say a 10 or 12 awg cable by connecting the mc4s. This is the bit I don't understand, I'm assuming the solar panel cable 2.5mm 20a cant feed any higher Amps into the larger cable 20 -30a?
Every video installation guide I see, they just connect an extra length of whatever thickness to the solar panel cable and the other end to the controller, seemingly thinking they are using the correct thickness.

Even if i added an extra 100w solar panel to give me 300w, the standard 2.5mm cable coming out the back of the panel wouldn't allow me to draw more than 20a

Am I missing something? Do people remove the cable from the solar panel and fit thicker cables? because I've never seen it on any video

 

[Charleswgibbs]

If your panels are connected in series than your amperage doesn't change, just the voltage. So you could keep adding panels in series as long as you don't exceed the voltage input limit on your controller and the amps through the pv cables will remain the same as a single panel.

If you connect in parallel, then your amperage adds up, but only on the cable run from the combiner box (or wherever they are connected in parallel) to the controller, each panel and Its wiring to the combiner box will still only see the amps of that single panel.

 

[Mattb4]

You can not draw more amps than the panel is rated at. W=VA
200w at 12vDC = 16.67a However likely your panels are at a higher voltage for Vmp than 12vDC therefore the amps are lower.

Lets just guess panel Vmp as being 18vDC 200w at 18vDC = 11.11a max

 

[robstrom]

Thought standard MC4 was 10 gauge wire?
Shortening up wire runs seems like z gain.

 

[robstrom]

Remember: amps from panel to SCC vs amps produced from there to bzttery. High volts/ low amps. Those MC4 from panels see low current ( amps).
My 40 amp scc never has more than aboyut 7 amps from the panels.The whole point of high voltage/ low amperage.
Save on big wire.

 

[MichaelK]

These questions lead to more questions? First, which controller do you actually have? None of the controllers I've ever seen have MC-4 connections, so cutting off the MC-4 is mandatory.

Matching a random 200W panel to a random 100W panel is not likely to work well. The amperages of both panels need to match each other within a few percent for them to be wired in series together. Say your 200W panel puts out 10A at 20V, and a 100W panel puts out 5.5A at 18V. Wire them in series and the most you will get out of the string is 5.5A at 38V.

Lastly, if the controller is so close to the panels, is it outside exposed to the weather? Do you just plan to run the wires through an open window?

 

[MrThisIsME]

Thought standard MC4 was 10 gauge wire?

I thought so too. Just put in some 485 watt panels - 12awg to the MC4.
I think the almighty penny comes into play. Than again, the larger panels are running a higher voltage.