What ever you are doing, if you are using solar or wind power, or planning to do so, you are going to need a way to store your energy. You need batteries, and a new battery is rather expensive, second hand they are of course cheaper, depending on their condition.
There is a way to recondition old batteries, in such a way that they are as good as new, and you can do this easily by yourself, if you have the right tools, and the know-how.
There is a guide available that will show you exactly what tools you need and how to recondition almost any old battery. The guide explains clearly how to test an old battery to see if it can be reconditioned.
The guide deals with the following battery types:
Lead acid (car battery)
Li-Ion (Laptop battery)
Ni-Cd (Rechargable battery)
Ni-MH (Long life battery)
DIY Solar Panels and Windmills Building Guides
Earth 4 Energy - Make your own solar panels or wind turbine. More info here
Home Made Power Plant - There are some other guides for DIY wind and solar generators, but all of those that I've read don't get into the same details. More info here