If it is good/very good, then I would like to have a generator-motor VOLT with no batteries.

Koz, good point and this gets us back to the reason for lift-off regen — drivability. It makes an EV drive more like an ICE car and gives people some control over decel rate without having to move their foot over to the brake pedal. I’m all in favor of that as default behavior, I’d just like to be able to turn it off. Second best option is a clear indication (detent or visual display) of the pedal position which produces gliding.

You’re also right about auxilary loads. A better example is Car B lifts off 507/4 meters after Car A, decels for 507/2 meters and then drives 25 m/s for 507/4 meters. This equalizes the elapsed times, and thus the aux loads, for the two cars. It also better equalizes the aero loads. The numbers change a little but the conclusion stays the same.

My powers of interpretation had expired.

I doubt Nasaman will disagree with the accuracy of your analysis, other than you have negelected auxiliary loads which can be assumed to be equal but gliding will have them acting over a longer period of time. Thus, there will be more auxiliary losses for the glider but these will surely be less than the inefficiency losses of the regen/repower cycle.

BUT, gliding is not a practical way to drive for most people and even for the gliders it’s not practical in most driving situations. You could use the drag, the discharge characteristics of the battery, and other energy factors to determine the most optimal accerlation and speed and gliding point. This would maximize range but wouldn’t be very good for time. For that matter, you could walk or ride a bike and use less battery energy. How often will you be able to know or even be able to practically execute gliding at the optimal moment. Yes, any amount of gliding is better than none. I would prefer that they design lift-off to allow for gliding to be easily achieved before regen forces are applied, but not to do away with lift-off regen altogether. Lift-off regen will make driving in heavy traffic a lot easier and many drivers will end up with better range if they can more effectively utilize regen this way. Ultimately, I believe it is more important to avoid as much friction breaking across the entire Volt fleet than to try to increase gliding but they aren’t mutually exclusive.

If they want to allow disabling of lift-off regen for “gliders”, I don’t have a problem with that.

No way in hades.

Here’s another Car A/B example. Except for a few minor simplifications, these numbers are representative of Chevy Volt performance. Cars A and B both travel at 30 m/s (about 67 mph) toward a “Reduced speed” sign. Car A lifts off at point A and glides, hitting 25 m/s exactly when it reaches the sign. Car B lifts off halfway between point A and the sign, but decelerates more rapidly due to decel charging and also hits 25 m/s exactly as it reaches the sign.

Aero drag, rolling resistance and driveline drag exert 450 newtons of force on Cars A/B at 30 m/s (i.e. 13.5 kW). At 1500 kg, Car A thus decels at 0.3 m/sec2. At 25 m/s speed the force is down to 360 newtons and decel rate is only 0.24 m/sec2. Total decel time is thus 18.5 seconds and distance covered during decel is 507 meters.

Car B decelerates twice as fast, 0.60 m/sec2 initially falling to 0.48 m/sec2 at the signpost, because decel charging is set to exerts a decelerating force exactly equal to aero drag, rolling resistance and driveline drag. Decel charging thus bleeds off half the delta KE, or 103,125 J. If we generously assume a round-trip regen efficiency of 80%, that’s 82,500 J of recaptured energy available to drive the wheels. But how much extra energy did it take to push Car B that first 258.5 meters, while Car A was already gliding?

450 N * 258.5 m = 116,325 J

Car B thus burned 33,825 J of net energy (116,325 – 82,500) during the 507 meters while Car A burned zero. Since decel charging burns more energy, it REDUCES your range vs. gliding. This is logically consistent, since decel charging involves losses which gliding does not experience, and also matches Prius hypermiler results in which best MPG is achieved by taking great pains to avoid the built-in decel charging.

If you disagree with this conclusion, I’ll need to see your math.