Read the following context and answer the question.
Context: He had been sitting in the car for a while waiting for us and listening to the radio . When he went to start his car the battery was dead . So we decided to take my car over there instead . I always hate having to park the car somewhere because then I have to worry is someone going to notice it or is it going to get towed or whatever .
Question: What caused the car battery to be dead ?
Answer:


Using auxiliary power while playing the radio in the car killed the battery .