How many solar panels are needed to keep the refrigerator on all day?
A 100 litres refrigerator has a power of 40 W. In 24 hours (assuming that the compressor runs for half of the time), it consumes about 480 Wh, which can be obtained, on a summer day, from 2 SP 50 panels or 1 SP 100 panel.
A small sailboat where the battery must be kept charged only for the radio and the navigation lights?
A SP 23 ALLinONE will do the job. Install it on your own, by simply connecting the cable already provided to your battery terminals.