You damaged the generator in your car? That's pretty odd for several reasons: There's a fuse between the generator and the socket in your car to prevent damage from shortcircuits The generator is able to charge a car battery which by far exceeds anything you n900 will ever draw There's a battery in your car being able to take load of your generator. This battery is able to provide several thousand amps. To summarize: Whatever you plug into your car will burn and smoke way before any harm to the generator is being caused.