RobbW wrote:Thanks, all. That's explanation enough for me. I'm usually super sensitive to any type of vibration, bump, rattle, clicking, etc. in my cars. I'm always afraid something is going wrong or breaking down. I guess the "drag" I was feeling in Eco mode was just the reduced go pedal sensitivity.
I understand that regen braking AND acceleration occurring at the same time would be highly inefficient. However, that begs me to ask another question that I've wondered about every since I first heard about production EVs. I'm sure this is going to be an extremely naive question for most of you EV old-timers, but I'm a newb and curious. Take our MiEV, for example. It is rear-wheel drive. Since the front wheels are not drive wheels and are merely free-spinning, why not have some sort of mini-generators/turbines attached to them that would create energy as the front wheels spin while you are driving? Sure, that would create some resistance that would normally lower the efficiency of the vehicle, but would the energy generated be more than enough to make up for that and then some?
I'm not proposing some type of pie-in-the-sky perpetual motion/energy machine. But I imagine that with front-wheel generators constantly creating energy as you drive combined with the rapid energy created from regen braking, you would be able to recoup much more of the energy used to drive the car than with regen braking alone. Does any of this make sense, or is it obvious that I have absolutely no idea what I'm talking about? I suspect the latter!
Sorry RobbW, unfortunately the latter...
What you are actually proposing is 'pie in the sky perpetual motion' because you are implying that the energy you get out of the front 'mini-generators' is more than the energy you have to supply to spin these things. As soon as they are attached to the front wheels, they will put extra drag on that wheel, which will have to be overcome by the main motor using energy from the traction battery. Since no machine is 100% efficient, the energy your mini-generators will produce will be substantially less than the energy taken out of the traction battery to overcome the extra drag.
The generators at the front wheels would definitely be useful during braking, as all energy that is dissipated by the front friction brakes is completely lost to heat, while if we had regen brakes in the front, that would allow more energy to be recovered during the braking process, especially in cases where you're using more braking force than can be generated by the main motor regen mode. Most likely this would add too much cost and complexity to the car to be worthwhile, but I'm sure this is something that will be implemented in future EV's that would come with all wheel drive - that is, use a separate traction/regen motor for front wheels and a separate one for rear wheels, and use both for regen with the ability to properly set regen braking bias between front and rear axles. Seems to me like something that Tesla may be working on for the Model X.