I have a Fm transmitter in my truck so I can just get Bluetooth calling and music. But I always unplug it when I'm done driving because how the truck charging ports still work after truck is completely off. The transmitter shows like around 10.7(I'm guessing battery draw) when the vehicle is completely off so I just unplug it to not drain the battery. Will it actually drain the battery or is it something I should not worry about unplugging every time?