Those MP3 player adapter thingies that you plug into your car's cigarette lighter, then stick a USB drive into it with MP3 files loaded onto it, then the adapter plays the music to your radio via FM. I bought one at the flea market. Now when I plug this in, it goes on, and there's no off button. So even when my ignition is off this thing will run unless you plug it out, and when you plug it out the whole thing resets and starts playing from the 1st song on the default FM frequency, and I find this extremely annoying. When I pause a song, the device ceases to communicate with the USB drive plugged into it, seeing that the USB drive's light stops flashing. So basically, when it's paused, only the LED display (like a calculator's display), the backlight, and the FM transmitter operates. So what I'd like to know is whether leaving this thing plugged in when the ignition is off will kill the car battery. My car radio also has a small light on the power button that stays on when the ignition is off, and of coarse the radio's settings are all preserved thanks to the fact that the radio is always powered.