I had the same problems with keeping my batteries charged during long camping trips. I didn't like having to start my generator to charge my boat batteries when ever I returned to camp. So, I built a solar panel and installed it on top of my camp trailer. It produces +- 7amps during peak performance. I then installed a switch and plug outside my camp trailer which is tapped into my charging/battery system in the trailer that is dedicated to my boat battery charging tasks. I just plug into the camp trailer outlet and run the 12v power to my batteries in my boat. It will charge and float charge as needed. It works great and doesn't cost nothing to operate, I can camp for weeks and use my batteries heavy with confidence knowing they will be charged the next day.
I recommend solar over generator. Although there is nothing wrong with a good generator, (Honda) to charge batteries, it just cost more to operate/maintenance.