If you're phone is plugged into the charger there will be some battery drain on your vehicle. For practical purposes the charger alone will not drain your battery.
Assuming that the car is turned off and he charger is plugged into the phone and the car, then yes, your charger will drain the battery of the car. If the car is on there is no problem.
Not any more than any of the other devicee that draw power from your car battery, because the battery in the car is always being recharged as the car runs.
If your phone is plugged in to the car charger, and the car is off, it will slowly drain the battery. However, if the car is running, the alternator will keep the battery charged.
Depends on the car AND how long you leave charger. I own iPhone and charger. white charger with a LED light indicator. I had the charger left for 2 days and it did not charge the car, but in theory, it will drain since a trickle charge.
