I have 2 of these
and the controller from northern tools
They are 15watts a piece. They are putting out together 19volts. They can't charge my optima deep cycle marine battery. They charge other batteries with no problem. When I bought the battery I had the same problem and took it back to the place I bought it from and they tested good. The way I have it to make it work is parallel to another battery and it charges them both.
Anyone else have about the same thing? I don't understand why it doesn't work. Only thing I can think of is that the deep cycle batteries take more to charge them.

and the controller from northern tools
They are 15watts a piece. They are putting out together 19volts. They can't charge my optima deep cycle marine battery. They charge other batteries with no problem. When I bought the battery I had the same problem and took it back to the place I bought it from and they tested good. The way I have it to make it work is parallel to another battery and it charges them both.
Anyone else have about the same thing? I don't understand why it doesn't work. Only thing I can think of is that the deep cycle batteries take more to charge them.