Join Date: Aug 2007
Location: New Hampshire
Thanked 10 Times in 6 Posts
Rep Power: 10
Re: solar recommendations
It is not so much the size of your batteries... it is your pattern of using the boat. How many amp-hours are you consuming between charges?
First, I am assuming you stow the panels while underway in a smaller boat... they'd be in the way underfoot.
If you're on a 5-day cruise, sailing hard every day with instruments, VHF, TP22, etc., then spending the evenings at anchor listening to tunes and using lights... then you'll have lots of amp-hours to recoup once you do place the panels in sunlight service.
If your use is more of weekend use, maybe two daysails surrounding one overnight evening at anchor, you have much less to recoup.
Last, when you do charge via panel, how long before you're using the boat again? If the boat will be idle and charging for days, a smaller panel should suffice. If you'll be right back out in a day, a larger panel is called for.
For what it is worth, on my 28-footer with similar equipment to yours, my weekend-use pattern is easily-supported by one Group 27 90AH deep cycle battery recharged during the work week with a 30 watt panel ($65 on eBay). My battery very rarely gets below 12.55 volts... and after a charge typically reads in the low 12.7s.