I agree. In the end, Ohm's Law decides what happening. An alternator provides a max of ~35 volts AC, 3 phase. It gets rectified and controlled to maintain 14+ volts with engine running and loads drawing current. Stationary, there's only a slight draw by the body controller for monitoring and security. A tender will electronically sense what's required and supply only the current needed to maintain the correct voltage, (engine off, 12.5- 12.8v). Compared to a basic battery charger that will try to pump out 16-18 volts of 60 cycle pulsing DC. Which peaks at over 20 v.Look at it this way. When you are driving is your alternator not still providing current? Yes, it is. It doesn't shut off. Your car actually runs off the alternator and the battery is the middle man. If it's OK for the battery when the car is running, then it's OK when you are parked and on the charger.