DaveinOlyWA
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Re: Max regen - at what point do mechanical brakes engage?

Sat Jun 15, 2013 7:47 am

TickTock wrote:Here is a very short video illustrating how friction braking is feathered in with regen. Bar graph on the top center display (to the right of the graph on the left CANary display) shows the total amount of braking force applied with the green portions indicating the amount of regen and the red indicating the amount of friction. Starting from 55mph, I modulate the break pedal slowly harder then softer and so forth. You can see how regen is diminished as friction is brought in. As I ease up, friction is reduced and regen is increased.



(There is a 1080p version available under Settings if you view in YouTube)
nice illustration and all the more reason why the B mode is such a valuable addition to the LEAF. A lot of people dont believe in one pedal driving but i consider it essential if you really want to get the full benefit of the LEAFs limited range. Its clear that touching the brakes will introduce some friction braking no matter what. Even on my 2011, i dont use brakes that much. With B mode, i should be able to reduce the usage just a little bit more.

i think Nissan was using this fact when boasting a big range and also the reason why it did not show up in Tony's Range tests
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 7059.6 mi, 95.35% SOH
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cwerdna
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Re: Max regen - at what point do mechanical brakes engage?

Sun Aug 04, 2013 11:34 pm

Interesting... sorry, I haven't had time to read all the regen discussion as I finally got my Leaf a week ago...

So, short of having a tool like TickTock's, what can we do to maximize regen? I don't really like driving in B mode (yet?).

To avoid using friction brakes as much as possible, should I just basically try to almost be at the max regen of the energy info screen? If I'm not on that screen, should I just try to be at the edge of engaging the leftmost regen bubble?

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JPWhite
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Re: Max regen - at what point do mechanical brakes engage?

Mon Aug 05, 2013 5:19 am

cwerdna wrote:Interesting... sorry, I haven't had time to read all the regen discussion as I finally got my Leaf a week ago...

So, short of having a tool like TickTock's, what can we do to maximize regen? I don't really like driving in B mode (yet?).

To avoid using friction brakes as much as possible, should I just basically try to almost be at the max regen of the energy info screen? If I'm not on that screen, should I just try to be at the edge of engaging the leftmost regen bubble?
Using the energy screen helps with training your braking technique, but can be very distracting, so be careful where you use it.

Simply coasting in any drive mode will create regen without any danger of using physical brakes. So working on your hypermiling 'red light' techniques will help. If you don't like driving in B mode, why not use it decelerating to a red light, then switch back to D or eco once you come to a stop? Once you get over the thrill of the instant torque, you will find B mode more than adequate for everyday driving.
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DaveinOlyWA
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Re: Max regen - at what point do mechanical brakes engage?

Mon Aug 05, 2013 7:30 am

cwerdna wrote:Interesting... sorry, I haven't had time to read all the regen discussion as I finally got my Leaf a week ago...

So, short of having a tool like TickTock's, what can we do to maximize regen? I don't really like driving in B mode (yet?).

To avoid using friction brakes as much as possible, should I just basically try to almost be at the max regen of the energy info screen? If I'm not on that screen, should I just try to be at the edge of engaging the leftmost regen bubble?
congrats on finally getting one! any details (or link) to share?
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 7059.6 mi, 95.35% SOH
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dgpcolorado
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Re: Max regen - at what point do mechanical brakes engage?

Mon Aug 05, 2013 9:34 am

cwerdna wrote:Interesting... sorry, I haven't had time to read all the regen discussion as I finally got my Leaf a week ago...

So, short of having a tool like TickTock's, what can we do to maximize regen? I don't really like driving in B mode (yet?).

To avoid using friction brakes as much as possible, should I just basically try to almost be at the max regen of the energy info screen? If I'm not on that screen, should I just try to be at the edge of engaging the leftmost regen bubble?
Seems strange to be making suggestions to someone who has been "here" so long but here goes:

Use regen only when slowing is needed. Coasting is usually more efficient so max regen is to be avoided unless significant slowing is required.

Example: the light up ahead turns red, coast until you either need to slow to a stop or the light changes and you can then speed up again. (I presume that it is obvious that this may not be practical in heavy traffic.)

Example: when descending steep hills where speed control is a safety or speed limit issue, use regen as needed to keep an appropriate speed. If it is safe, you can begin to coast near the bottom of the hill to keep momentum up. (If you can do this without the brake pedal, say in B mode, that is preferred because it eliminates any use of friction brakes.)


It is easier to drive this way in Eco, because the accelerator pedal is mapped to specific power levels: hold the pedal steady and it will keep the power level constant, whether it is 12 kW, zero (coasting), -7 kW (regen), or whatever level is needed to maintain the speed you desire (use the energy screen pie chart to verify this). With practice, you can control your speed with minimal use of the brake pedal or unnecessary regen. With use of B mode it ought to be possible to use single pedal driving much of the time, with use of the brake pedal only to hold the car still at a stop. But that would take some practice to get used to.

D mode is mapped differently from Eco. D seems to be constant acceleration, as opposed to constant power, and I find it harder to hold a constant speed in D, especially on undulating terrain. I also find that I tend to speed more in D, because the acceleration keeps going unless one backs off before reaching the desired speed, although one can learn to do that with practice. My impression is that most hypermilers, and many others, prefer Eco because constant power mapping makes it easier to modulate speed (and regen braking) precisely.
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DaveinOlyWA
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Re: Max regen - at what point do mechanical brakes engage?

Mon Aug 05, 2013 10:09 am

cwerdna wrote:Interesting... sorry, I haven't had time to read all the regen discussion as I finally got my Leaf a week ago...

So, short of having a tool like TickTock's, what can we do to maximize regen? I don't really like driving in B mode (yet?).

To avoid using friction brakes as much as possible, should I just basically try to almost be at the max regen of the energy info screen? If I'm not on that screen, should I just try to be at the edge of engaging the leftmost regen bubble?
only way to do that is be in B mode. if you touch the brake pedal, you will start charging the braking system and seems to me someone has already shown that friction braking applies (however lightly) at first then backs off based on braking need.

but other than that, the real key is to try to adjust speed to avoid the changes in velocity. Having lived in your area, i do know that is a much tougher challenge than the sleepy hamlet where I live but I do daily "freeway coasting" here due to the traffic issues around JBLM (Joint Base Lewis-Mcchord)

But you had a Z before so guessing it would be easy for you to get used to going from N to D to B, etc... ;)
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 7059.6 mi, 95.35% SOH
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Klayfish
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Re: Max regen - at what point do mechanical brakes engage?

Mon Aug 05, 2013 10:19 am

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.

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?
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DaveinOlyWA
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Re: Max regen - at what point do mechanical brakes engage?

Mon Aug 05, 2013 10:45 am

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.

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?
well the amount of regen surely has to do with the RPMs of the device (motor) creating the regen which would be higher at higher speeds so more regen at higher speeds is implied.
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 7059.6 mi, 95.35% SOH
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dgpcolorado
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Re: Max regen - at what point do mechanical brakes engage?

Mon Aug 05, 2013 11:25 am

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.
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JPWhite
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Re: Max regen - at what point do mechanical brakes engage?

Mon Aug 05, 2013 11:32 am

dgpcolorado wrote: To me that's a big deal and a frustration with my 2012 model LEAF, which lacks B mode. For flatlanders it is irrelevant.
I test drove a 2013 LEAF recently and was spectacularly unimpressed with the B mode in the LEAF. It is still quite insipid. Having experienced the B mode in the Misubishi I-Miev I do have a frame of reference. Shame Nissan couldn't come closer to how Mitsubishi implemented their 'B mode'. With the Mitsubishi single pedal driving is very easy, with the LEAF, you still need the brakes more than I'd like.
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