In my M3 I keep a small flashlight which is charged by way of a USB cable.
I charge the light at home, place it in the glove compartment where it lays in case of an emergency. But every 6 months or so, it has to be recharged.
Because I am not that wise on batteries, energy, etc...
If I were to keep it always plugged into the car and I do not drive the that car that much, could that create a battery drain or would it be so small as not to worry about it?