Electricity captured by regenerative braking per mile

[joewaters]

In my Carwings 'My Driving Style' page, there is a section on braking techniques and regen. In this section it appears that the scoring is counterintuitive, in that greater use of regenerative braking is rewarded. I posit that the logical concept would be coasting down to a stop / not accelerating excessively / leaving reasonable space in front of the car would benefit efficiency more than any type of braking. Regen is not 100 percent efficient, so not using power by aforementioned techniques should score higher than braking.
I'm a recent ex Prius convert, so maybe some of the hardcore EV guys can shed light on the folly of my thinking. I believe I am doing well at 4.5miles/kwh, but surely there is room to improve my technique. Should I be hitting the brakes more? Is not all braking above 8mph, except emergency, done with regen as is with the Prius?

 

[planet4ever]

There are lots of threads on this here, and no, there is no folly in your thinking, except for your final statement. Braking, with the brake pedal, is a blend of regen and disk braking. This is certainly true with the LEAF and I'm sure it must be true with the Prius as well. Heavy braking would generate huge power levels to the battery if it was all regen, much higher than the battery can accept without being damaged. As it is, the LEAF allows regen of up to about 40kW, which is very close to the 48kW maximum it allows for Quick Charge. Since the Prius has a much smaller battery, its maximum regen level must be much lower.

Go to the forum search page, and find the Google search box near the top. (I think you have to be signed in to see it.) Try typing something like "regen vs coasting" and plan to spend an hour or more browsing.

Ray

 

[mkjayakumar]

I posit that the logical concept would be coasting down to a stop / not accelerating excessively / leaving reasonable space in front of the car would benefit efficiency more than any type of braking

Absolutely. Or in other words, if you end up doing a lot of regen in your Leaf you are not driving efficiently.

 

[joewaters]

Guys,
I appreciate the responses, but somehow the original question went unanswered. In my subtlety, I gave dry humor the reins, and people focused on the re-use vs. reduce issue. I really already knew the answer to that. I simply questioned the logic of the Carwings rating for regen, i.e. is the rating using some 'bad science' to make drivers feel good about [not] not wasting energy?

 

[stjohnh]

Guys,
I appreciate the responses, but somehow the original question went unanswered. In my subtlety, I gave dry humor the reins, and people focused on the re-use vs. reduce issue. I really already knew the answer to that. I simply questioned the logic of the Carwings rating for regen, i.e. is the rating using some 'bad science' to make drivers feel good about [not] not wasting energy?

Well, you and the other replies are correct and carwings is wrong- for the educated/devoted driver. However, the bulk of Leaf drivers never log onto these forums, have only a slight interest is getting best efficiency, and have no idea of the recapture issues surrounding kinetic energy usage.

For the common Leaf driver, they drive using the GOM, charge their cars to 100 or 80% and leave them at a high SOC. They drive using the brake pedal a lot, and for them, the regeneration recapture to the battery pack on the Leaf is indeed more efficient than slowing using only friction brakes. So, for the majority of Leaf drivers, carwings is correct.

 

[joewaters]

For the Common Leaf driver

I don't think I am an uncommon Leaf driver, we are all bunched together as early adopters of a technology that requires a behavior shift in both driving technique and lifestyle. Maybe some drivers focus on performance, others on charging availability, still others on hypermiling, but we all need honest feedback from our equipment/software to make us better drivers.
Telling me that using the brakes more will give me a better score in Carwings is akin to telling me to keep driving like all the jackrabbits around me. Giving bad feedback will lead to more novice drivers thinking the 75 miles range is overrated and Nissan deceived them. If you train a driver to cooperate with the technology, 100 miles is achievable range under reasonable conditions.
Thank you Holland, though, for making me feel special.

 

[Larrycar]

I have a 2013 SV, 4.5 never see that, 4.1 maybe. I love to drive and out performing similar gas powered vehicles is fun. I love the feel of electric acceleration. I get my range by using the B mode whenever possible. It is as easy to use as selecting another gear. One word of caution, guard your rear, remember the brake lights are not on and your speed reduction might not be noticed.

 

[joewaters]

I have a 2013 SV, 4.5 never see that, 4.1 maybe. quote]
The efficiency is a result of driver input, vehicle output, and road conditions. I drove a gen II prius for 5+ years at 51+mpg lifetime avg. A coworker, who started with gen I, and moved to the gen II, drove roughly the same terrain and distance, but couldn't break 48 with his gen II, even though he was more experienced. Difference was that I valued efficiency over travel time, and made up the difference in less time at filling station. He was willing to pay the premium of money for the illusion of time.
With the Leaf, the tradeoff of miles/kwh is doubled in range and in charge times. It's a lot easier to ignore the charge times, as you are not tied to the car while it charges. But I have an 80 mile round trip without unattended charging at work. Hot rodding would cost me an hour sitting at the charger near my work(and miles off the route) before I could drive home. That's a pretty good incentive to baby it. Plus it'll also be easy on my tires and suspension, increasing their lifespans.

 

[Reddy]

...I have an 80 mile round trip without unattended charging at work....

Let us know how that goes as we approach winter. Could be a pretty cold drive. Sounds like it could get tough in NW Illinois. What are your contingency plans? Charging at work? Driving an ICE on the worst days? Having dinner at a midway station? Slowing down will certainly help (if you've got the right road for that), but adds significant time to your commute.

 

[joewaters]

Let us know how that goes as we approach winter. Could be a pretty cold drive. Sounds like it could get tough in NW Illinois. What are your contingency plans? Charging at work? Driving an ICE on the worst days? Having dinner at a midway station? Slowing down will certainly help (if you've got the right road for that), but adds significant time to your commute.

I have 2 ICE vehicles to choose from for winter: I can swap with my wife, who has a 2008 Yaris @ 42mpg for her 7 mile commute, or take the Jeep @ 21mpg but 4X4 capable.
My hope is that I can pre-heat with line power and drive conservatively to make the full commute. Maybe a little chilly on the ride home, but I can handle driving cold better than walking to keep warm.

 

[donald]

Joe, I agree with your logic for questioning what readings you get out of the system with lots of regen.

I don't see how the system can determine how much of the regen power is recovered and usefully held by the battery. So, I reckon the gauges simply integrate the total power in and out of the motor, rather than usable power from and back-to the battery. Do a lot of regen work and you gauges will lie to you and flatter your poor driving style with apparently good energy consumption readings.

I've even seen journalists writing about EVs say how they were unable to 'benefit from stop-start in cities' to regenerate energy. Doh! Sorry, but although the figures you get in town may look good, unless they're obtained by steady non-stop driving then I would not trust their veracity.

Of course, if the calculated regen energy has some built-in fudge factor to adjust for this, then maybe I am in error. But I can't see how they would really do this as it would still depend on other driving conditions, rate of regen and health of the battery. Maybe they already deal with all this in the gauge figures, but it doesn't look that way to me.