Regen losses mean it is best to coast rather than regen with the brakes.

[plus 3 golfer]

.....

Edited July 10, 2013 by Plus 3 Golfer

[viajero]

You guys have got me thinking about coasting a bit.  It seems there are two cases - coming to a complete stop and pulse/gliding.

 

When gliding, you definitely don't want to regen due to the aforementioned inefficiences.  You want to keep your kinetic energy as long as possible with the engine cut off, rather than converting kinetic energy into battery energy and back to kinetic energy again.  Various hypermilers say they've verified this by experiment, but I don't pulse and glide myself.

 

When coming to a complete stop, all your kinetic energy has to be converted into some other form of energy.  When purely coasting to a stop, 100% of the kinetic energy converts to heat, through friction in the tires, drivetrain, and through air resistance.

 

When coming to a complete stop from the same speed using regen, some nonzero percentage of that kinetic energy becomes useful battery charge, which can be used to save fuel when you next accelerate.

 

So at first glance it would seem stopping with regen is more efficient, at least in terms of what percentage of kinetic energy is recovered.  But, since your stop would be more abrupt using regen than purely coasting, you would have been traveling at full speed for more time, thus losing more energy to air resistance before you started slowing down.

 

Which one uses more energy to get from point A to point B?  Hard to theorize without more data.  It may vary depending on how fast your initial speed is.  I'm not sure.  Maybe someone with more time and motivation than I have can do some experiments...

[plus 3 golfer]

"In neutral, the output shaft is disengaged from the wheels and no power flows through the transmission..The electric motor does not provide power to or hold the final drive and the final drive can spin freely." Those two sentences are directly from the shop manual.

 

You are correct. I was going to further explain but forgot. Yes, there is no physical disconnection. Disengage simply means MG1 and MG2 armatures are free to rotate with the wheels. MG1 or MG2 are neither generating nor using power and thus "disengaged" from the wheels.

Edited July 10, 2013 by Plus 3 Golfer

[BIG ROCCO]

Yeah - in some situations, I like to shift to Neutral and coast, rather than feather the gas pedal to maintain speed...I guess I have done that for 40 years and I think it's still better.  There is an area on the way to work - a gradual downgrade for about 2 miles.  If I leave it in D, I have to give it some gas to keep going 50 MPH.  If I shift to N, my speed will go up from 50 MPH (the speed limit), to almost 60 MPH (which most people are doing) and then start to drop before a known common speed trap as the hill flattens out, and then be around 50 MPH again as I approach a traffic light.  That works in conventional cars, too, and probably saves even more than in a hybrid.