1. The problem statement, all variables and given/known data Obviously I do not believe this to be the case, but when running a car the battery is I assume having current drawn in, reversing its normal means of depletion so that the potential chemical reaction can take place later on. My question is when you turn on the radio while you are driving (and the current generated by the magnets in your wheels is charging the battery) is this excess current from the induction? (I assume that is how it works)..It can't be that the battery is working and charging at the same time... Thanks for helping out, I will be back in a few hours so if I do not reply don't let that be a sign that I don't care or something. 2. Relevant equations electricity only flows one way 3. The attempt at a solution wiki page on car batteries leads me to believe that just the cranking (starting) mechanism is the only function of the battery and that the induction from the wheels provides all the DC power after conversion.