AB3NA

I learned, the hard way, that you must always, always connect the battery to the charge controller before connecting the solar panel to the charge controller, and disconnect the solar panel from the charge controller before disconnecting the battery from the charge controller. (I'm sure that I could have said that it fewer words, but I want to be absolutely clear.) The battery needs to power-up the charge controller before the charge controller can switch the solar current. Does this mean that the battery must already be charged? I'm not sure. It may be that even a "really dead" battery would supply a low-resistance load to the panel to prevent it from going full open-circuit voltage and damaging the charge controller. As you configure your system, I suggest a label: "connect panel last, disconnect panel first", because there will come a time when you want to take it apart, and the panel is "hot" whenever the sun shines on it. I like the charge controller that charges two batteries, independently, so I can put my load on one battery, run until it's depleted, then switch to the other, and the charge controller will direct charge to the weaker battery as needed. When you found the "20A, 12V" rating on the panel, I suspect that someone meant to write "20W, 10V". Maybe it's just a typo, or maybe it's like the ingredient list at the restaurant that said the soup contained "crap". "Ha!", I thought, they meant "crab"". But, no, it was imitation crab meat. If I had complained about that, the chef's defense was ready: "I never said that there was crab in the soup". In your case, you might complain "20A? It's only 20W!" "Oops. Sorry about that; just a typo."

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