Imagine this, it's two weeks after the SHTF and you running low on AAs and there isn't a D cell around for 200 miles without a paranoid trigger finger between you and it. Your Maglite is dead, your comms radios are about to be done, and smoke signals draw too much attention. If you haven't thought about this before, then how about now?
If you have gadgets in your BOB or cache supply, like lights, radios, electric knives and that 2.4kw air conditioner compressor for the whiny pants in your group, how are you going to keep them humming; provided J.J. Abrams has not had his way with the SHTF event a la Revolution. The general assumption here is that electricity still flows through conductive material.
So simple recharges can be done a myriad of ways. Solar recharge pods like those from Goal Zero and Sunforce, cyclical recharging like turbines, alternators, and treadmill motors, friction like that of a shakelight, and chemical reactivity like alkaline and lead acid batteries.
In the end, you need to look at what you will be relying on and what it takes to maintain it. Oils, batteries, other manufactured goods. How are you going to make 3in1 oil to lube your rifle's parts? Do you need a jig to balance your bow? How are you going to make Paraffin Wax?
Take the things you are going to depend on, investigate how to make or manage them yourself. If you can't stock up. Just remember, it is not likely that the Mad Max Apocalypse is going to happen, but something like or worse than Katrina, Sandy and the Thailand Tsunami will. Can you and your gear get you past that hump before the rest of the world shows up to help?
Look to our DIY section for articles on improvising electrical systems from paddle wheel hydro rechargers and windmills to chemical batteries made from most anything with an odd number of electrons in its outer ring.