A petrol/gasol generator would probably be the quickest way to charge. The downside is noise, local pollution and complexity. I don’t like the idea of burning fuel in order to create electricity.
By using solar panels electricity can be harvest from the sunlight. No moving parts and no noice. The downside is the efficiency of the panels and the dependency of cloud free weather. To get a usable charge current I would have to use about 3-4 square meters of cells, given that there is no clouds.
Using the wind to harvest electricity is common in these areas. Modern wind generators are efficient with a moderate wind force demand. What you need is a generator, small tower and an extension cord.
And the winner is…. The wind generator! Given that we normally have a couple of days with winds around 8-10ms I should be able to get some energy into my batteries. Since I run a 48 volt system I need a 48 volt wind generator. Fortunately Southwest Windpower makes a small, 120cm diameter, generator with an integrated controller. The controller makes sure that the batteries receive the correct voltage while charging.
Have a nice vacation, I know I will.