Because of the intelligent key, last night I accidently left my G coupe power on and CD player running overnight (8-9 hours), I found out this morning when I got in the car. I was able to start up the engine with no problem. While warming up the car, I hear this ticking noise near the front side of the engine bay. After the car is warmed up, I drove for about 35min to work, and when I got to work that noise seem to disappeared.

What was that noise?

 

Could the ticking noise this morning come from the charging system? Since the battery could be extremely low from the CD playing all night? But then if the battery is extremely low then I would've had problem starting up the engine.

Another guess could be that the ticking noise is coming from the engine fan, it may not be spinning at the right speed because of low battery?