The problem with coals, is that short of drowning them, they can relight. I would consider storing them in a tightly sealed steel container. And I would think having that steel container outside of your vehicle is a good idea. To be honest, I have never done a vend or cook, there I had to take the coals with me.
me: I don't drink anymore
Yelonutz: me either, but, then again, I don't drink any less