It is simple to create a homemade solar battery charger, just a build a solar panel and connect it with wires to the battery. Toe enhance your battery that its charging work more better you will need to install a blocking diode on your solar panel to prevent it from discharging power at night, also install a charge controller between the panel so that the battery can prevent the over or under charging.
Building your solar battery charger is not so expensive and complicated. The most difficult step is to get the photovoltaic solar cells, which are needed to build your solar panel. Damaged or rejected solar cells are much less expensive and works almost same like brand new cells. So it will be better for you to get the factory rejected or damaged solar cells.
When you the damaged solar cells then buy all cells of same size so that you will get matching current output; but extras in case some are damaged during shipping or while you are building your solar panels for that buy tabbed cells because it will be easier for you then to assemble them.
After having your solar cells you will need to solder the wires together in order for them to generate electricity to charge your battery. As the cells are so thin and extremely fragile, to protect them from any damage build a shallow wooden frame as a container for their protection; this finished assembly is your solar panel. The frame size for your solar cells depends on that how many solar cells you plan to put in it and how much power you’d like to generate. A solar panel frame basically is made of plywood backing, wood boards or slats to create the sides, pegboard to mount the solar cells to and a Plexiglas cover to protect it from the elements.
Fit together the back and sides of your solar panel frame then lay on the solar cells on the pegboard backing so they can be soldered together by the attached tabs. It’s easy to lay the solar cells upside down on the pegboard while soldering.
When all cells are connected together then turn them right side up on the pegboard and secure them in place. After that place the pegboard into the shallow frame box and attach your diode. Put positive and negative wires through a hole in the frame to the outside of the panel so you that you can plug in the controller or battery.
After checking that the every thing is working properly, then attach the Plexiglas cover now your solar panel is complete. For using your solar panel for battery charging simply put it on a sunny place facing southwards, then connect the positive solar panel wire to your positive battery post and similarly negative wire to your negative post.