There was a solar calculator I found back in the day when we were looking at caravans. It was a spreadsheet a guy called Richard Graylin had made up. I personally found it quite useful.
You can find Richards website at http://www.campertrailers.org/solar_spreadsheet.htm or you can simply download it directly by clicking here
What does the spreadsheet do ?
- You enter a couple of required values into the spreadsheet (the coloured fields) such as your expected or actual battery amp hours
- The current or expected state of charge
- and some other various details
and the spreadsheet will display the calculated results of how long that particular setup will last based on sun events etc, From that you can determine if you need more or less solar or more or less battery supply.
It’s free so give it a go 🙂