In some cars you have to have the key in the ignition and set to ACC (accessory) to get power to the 12V DC outlets. This means more stuff is on in the vehicle while the phone is charging and the key is in the car, a security hazard. My cars are like this so charging the phone when off is a rare, emergency, occurance. However it doesn’t run down the battery.
If your DC power outlets are on all the time in the Explorer then no problem.