I have a Sunbeam Tough Black rated at 114W above the companionway of my sailboat. The image below shows the PV voltage & current, Battery input current and yield in watts for two normal sunny days in Norway. It's hovering around 10% of the nominal yield rather than the 50% I would have expected.
The controller is a Victron MPPT 75/15. I see that the recommendation for optimal effect is to connect 2 panels in series to that controller - but struggle to understand how much of a difference that would do?
Would a 75/10 yield more?
Data for the panel can be found here:
EDIT: Page with actual data: