Right. But I don't think that was @sneakypete 's point. I don't think he was saying there is free power there - In fact he denied that he was looking for perpetual motion.
I don't want to put words in his mouth or mis-state his position, but I believe
@sneakypete theorized that we can extend the range of an electric vehicle by using its turning wheels, or the wheels of an attached trailer, to power a generator and produce more electricity to power the vehicle. We cannot, it's impossible. We would draw more additional energy from the vehicle's battery to turn the wheels with the additional load of the wheel-powered generator than we would put back into the battery from that wheel-powered generator, consequently reducing the vehicle's range.
While no one intends to suggest perpetual motion in this thread, if we could extend the range of the vehicle this way, then we would extend it even further while driving through that additional range, and further still while driving through that next additional range, etc. We'd be getting more energy out of the system than had been put into the system, which is a definition of perpetual motion.
There are any number of ways we can draw power off a running engine or electric motor to re-charge batteries, run heaters, etc; no one is arguing that can't be done or that it's a bad idea. What we are saying is that all of those approaches, including re-charging the batteries that drive the vehicle, will reduce a vehicle's range between re-charging or fill-ups.