The car has been running and starting fine. My wife went out to put up the windows and noticed the interior lights were real dim and the car wouldn't start. I put a meter on the battery and got only 8 volts. I figured the car been sitting for 2 days, something must have been left on. When I tried to charge the battery with the charger set to 12 volts / 2 amps the charge meter jumped right up to the "start" range and the green full charge light went on. Whats up with the battery?