>>3 Battery PONTOON BOAT - Trickle / maintenance ‘SOLAR charging kit’ setup help!!!

[Leonvilj]

10 is probably better if the runs are over 10' and under 40. Count wire length both ways.

from the first solar panel outside the storage unit to the first solar charge controller in the boat under the backseat in the storage unit will be about 35 feet… From the second solar panel again outside the storage unit to the second charge controller the same it will be about 35 feet for both wires from the solar panel to the controller
The wires from the charge controller to the batteries is going to be about 2 feet at most

 

[Partimewages]

Here's a link for a voltage drop calculator.

Voltage Drop Calculator | Southwire

www.southwire.com

It will help you determine what size exactly you need for all your wire runs. This will be easier to change.

 

[SparkyGage]

10 or 8 to reduce loss. If you ever touch the wire and it's warmer than ambient, you have a problem.

I would run each panel to one of these mounted inside the shed: https://www.amazon.com/Miniature-Circuit-Isolator-Magnetic-Disconnect/dp/B09BQR289J then run the cable to your boat charger. That way you could disconnect without even touching the boat (shock).

This https://www.amazon.com/Extension-Silicone-Battery-Portable-Generator/dp/B0BX5ZXK8J could give you the quick disconnect you need. It has a male and female, so cut it about 1-2 feet from the Female end and attach the cut to the switch. Attach the cut with the male to the charger controller. Now you have a manufactured quick connection that should be secure. Whether you put the long cord on the switch or boat side is up to you, but for my own use, I would rather have the long one on the boat and stow it.

Also: GET 24V NOT 12V PANELS. It's easy to be thinking "I'm using 12v batteries, I need a 12v panel". Remember the charge controller, converts greater than 12 volts down to a regulated 12v (actually just over, but it should be the "ideal"). I think the Victron you were looking at can take up to 75v? Greater voltage, mean fewer amps, which means less loss which, means less heat and less shock risk. (I'm a safety nut with boats: I enjoy sailing, enjoy the water, hate fire other than camping on an island, and I'm really not a fan of drowning.)