Fuel tanks are in the back for solid reasons. But they are placed before the second wheel axis. In case of crash that area will protect the tank. Pinto had it after the rear tires, so totally unprotected.

A big battery in the place of the motor will turn you into a BBQ in case of collision because fire will fall directly towards the driver. Lithium batteries start burning when hit with some force, and can't be stopped once they start burning.