What solution do you suggest for a small 12V/40AH solar installation?

The solar panel (fig. 1) needs to be the 18V model (not the 36V - 60 cells or 40V - 72 cell model), for example the 150Wp model will work fine, providing some up 8 Amp charging current.

The fuses (fig. 2.) should be always connected to protect against short circuit. In this type of installations you can use the automotive 12V/24V fuses with 10 Amp rating (here for AWG)

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