There is many solutions for what you ask but I only use one : Bear Grylls method.
First you nee to find the tallest tree of the area where you are. Once you found him, do the following things :
Always bring a ribbon of electrical wire with you. Cut at least one meter of electrical wire, shave of the plastic around the copper then wrap you batteries in the wire, about 20 cm are necessary. Then cut a straight rod of nut tree, fresh (not dry, very important). The rod should be solid, elastic and around 2 meter tall. Fix the warped battery at the top and then wrap the rod with the rest of the copper to make it solidly attached.
Prepare yourself for the climbing. Cut your pants off to make a belt, like baby diaper, use whatever rope you can have around you and start the climbing. Once you reached the top of the tree, if you still alive, fix the branch at the top of the tree and go back.
Now, its time to make a fire because, in survival situations, a fire is always welcome to warm your little heart. Wait patiently a large storm and, with luck, a lightning should hit your installation. If yes, you will know it, be sure of that. Once the storm is gone, go up the tree to take off the rod.
You batteries is now full charged and ready to ignite you camera for at least one hundred years burst.