We're building an autonomous boat which should be powered by solar panels. We want to put two 100W solar panels on it. Most panels I see are 18V and for redundancy we want to link them in parallel. That way when one solar panel breaks at sea, we still have the other one to finish the mission.
We're now looking into what kind of battery we are going to build for it. I read somewhere that the solar panel should have a 40% to 80% higher voltage than the battery. That means that a 12V battery pack should be logical. And in between the solar panels and the battery pack we'll put an MPPT charge controller.
My question is; does all this make sense? Is it true that the solar panel voltage should always be 40% to 80% higher than the battery pack? Or can I also use an 18V solar panel to power for example a 5S li-ion (nominal voltage of 18.5V and a max of 20.5V)?
All tips are welcome!