I believe he is using the car charger to power his Lipo charger because he has no battery, which will work. Ever had a dead battery in a car, hook up a battery charger and turn the radio on? May not be the best method, but will suffice in a pinch. It may take a little longer to charge the 640 battery at 500 mah. The initial charge on my batteries were 50 min at 640 mah but subsequent charges took about 1 hr. 15. min at the same rate, and batteries didn't get warm, which is a good thing. Maybe 10 degrees above room temp.