I have seen video of a lipoly burst......TRUST ME....you dont want that to happen in your car......ESPECIALLY while you are driving.

This being said, If you do choose to do this, it would be in your VERY best interests to use a fireproof container to store the lipo in while charging. Not only while charging in the car, but also while charging at home.

Most of us use a simple metal ammo can, as these are cheap, and will effectively contain the flaming lithium if it does burst.