Those batteries are definitely going to die pretty quickly. I don't think those solar panels are going to recharge them in an efficient way. Also, a motor that size is going to draw hundreds of amps, so it's going to kill the batteries right away. I wouldn't be surprised if they even start overheating and spew acid everywhere, like Scead mentioned.
For the fact that they made it from junk they found lying around, though, it is fairly impressive. I just don't think it's going to work as well as they think it will.