If the tape deck in your car won't play tapes. (Yes we had a tape deck, a CD player too, though, I'm not that out of the tech-loop).
If the clock keeps resetting itself, even when the car is turned off.
If a 1-year-old battery dies.
If an 8-day-old battery dies.
Chances Are you have $.11 in your tape deck.
Resulting in no more tape deck, but a big gapping hole that is waiting for a new radio to be installed when our neighbor recovers from back surgery he just had....