Store said batteries carefully. I think I remember this topic from past thread. Several folks mentioned a specific type of battery that should not off-gas Hydrogen. (Hindenburg Syndrome: very tough on the system, right?)

I use a small solar system to charge if dry camping in an area that forbids generators.

Try researching with some solar websites, or search this site's forums as I seem to remember much to do about this very subject from the past.

Also, see the Storing Propane thread that was going earlier today. It serves to show why one must be very careful with gasses that go bang inside the home. (very sad story)