Solar light is not working?

they use any rechargeable battery they usually pack it in (the unit ) after about 2-3 years not sure why but they dont charge up properly

A cool idea. Theoretically, if you have a light connected to a solar panel, and you focus the light back onto the solar panel, the panel puts out more energy so the light should get brighter, putting more energy into the solar panel, producing more light. It probably would work, but due to various inefficiencies already discussed, and others too numerous to mention, there would be a limit to how bright the light would get. You might be able to measure the difference, but it would be small. Think of it this way. A solar panel absorbs light and converts it to electricity. If you focused all the light from the bulb back onto the solar panel, you would get some extra electricty out that you could use to light another light, but you have lost the light from the first bulb because it all went back into the solar panel. So you don't have any more light. In fact you would have a lot less because of the losses to heat described above. Besides that all the lights would go out when the sun went down or when it got cloudy. This is a big problem with solar power. Your brother has a creative mind, which is great, but he has a lot to learn about how the real world works. Encourage him to learn.

you need to use batteries designed for solar lights, and while you have it apart you might as well replace the bulb also.