How to I set up storing solar energy in a spare car battery?

My girlfriend and I have just bought a camper van, and we would like to hook up some roll up solar panels to a spare car battery so we can store energy in it to use with small electrical appliances.

I have no idea about how this could be done, if it is even possible. I would be very grateful for any help on how I might achieve this.

Thanks for all your replies! 🙂

The plan is to use the other battery to run small electrical appliances, phone charger, music etc, not to charge the actual car battery. I should have made that clearer to start with, I apologise. But your replies are still all helpful! 🙂

I was thinking of using the roll up solar panels that are available, does anyone know where I could buy a kit online that would contain the right battery and other components that are necessary?

Thanks for all your help! 🙂