HAS ANYONE DETERMINED THE NUMBER OF TIMES YOU CAN CHARGE OFF THE 4 AA'S BEFORE THE RUN TIME OF THE CAR IS AFFECTED? wE ARE USING GOOD MAXELL BATTERIES. WE HAVE CHARGED OURS 10 TO 15 TIMES AND NOW THE RUN TIMES HAVE DROPPED FROM A RESPECTIVE 7 TO 8 MINUTES DOWN TO 5 AND 6 MINUTES. THE CHARGE TIME HAS STAYED ABOUT THE SAME AT 2 MINUTES AND 30 SECONDS. I HAVE A FEELING THAT IT IS THE BATTERIES, BUT JUST WONDERED IF ANYONE HAS HAD ANY EXPERIENCE WITH THIS.