Klayfish wrote:Interesting discussion...though as a newbie I have to read each thing 5 times to really understand it. Only had my LEAF less than a week and 110 miles, so it's all still very new. I have noticed the huge difference in how the car drives in ECO vs. non-ECO mode. I've also been trying to figure out the regen braking and how it all works. Like others have said, I notice that I'll get more regen circles at higher speeds...such as if I let off the gas at 50mph. But at lower speeds, coasting doesn't create much (if any) regen. Also noticed that with touching the brakes. At low speed, no regen circles light. I haven't dabbled too much in B mode yet.
Yes, if you back all the way off the accelerator you will get more regen at 50 mph than, say, 20 mph. The reason is that your kinetic energy is greater so there is more regen available; another way to think of it is that the motor is spinning faster so the magnetic fields generate more energy to put back into the battery.
However, when the battery is nearly full you may see that you get a bit more regen at slower speeds than higher ones. I presume that this is done to protect the battery or that it is a quirk in the regen algorithm. (Abasile
first mentioned it I think, but I see it all the time also. Maybe it is the sort of thing one notices in the mountains.)
So if I'm reading right, where possible the best way to get regen is to coast where possible? Learn to use the B mode to help slow the car?
Not quite. Coasting, in most cases except at high speeds (high drag), is more efficient than regen braking followed by accelerating. Why? Regen is fairly inefficient because there are losses in generating the electricity, putting it back in the battery, pulling it out of the battery, then using it again to power the car. How inefficient
has been the subject of much debate here and I don't want to revisit it. That said, it is obvious that regen is a lot more efficient than plain old friction braking: at least some of the kinetic energy of motion is recaptured rather than being lost to heat in the brakes.
In general, it is better to keep the momentum of the car unchanged than to slow and then accelerate it again, even if you recover a bit of the kinetic energy from regen
during slowing. I learned it during the gas shortages of the '70s as "pretend you have an egg under the gas pedal and are trying not to break it", i.e. try to accelerate and decelerate gently for the most efficient driving (highest gas mileage). The most gentle deceleration is to just let the car coast and slow through aerodynamic drag and drivetrain friction.
B mode helps with "single pedal" driving: controlling the speed by just modulating the position of the accelerator. Many EV fans consider single pedal driving one of the advantages of driving electric. Others can't be bothered. B mode also helps with hill descents. The regen without B mode
is too little to keep the LEAF at a safe speed on steep hills. To me that's a big deal and a frustration with my 2012 model LEAF, which lacks B mode. For flatlanders it is irrelevant.
Finally, you need to display and learn to use the energy screen on the center console (push the "zero emissions" button, then the energy button). The pie chart on the left will show energy going out of or into the battery at any given accelerator position. It is much more detailed information than the dots on the dash. And, before someone else says it yet again, you should keep your eyes on the road in heavy traffic but, when conditions permit, using the energy screen will teach you a lot about driving efficiently. Including how to hold the accelerator at zero power, which is coasting without shifting to neutral.