Regenerative braking - why have the option to NOT have this?

I always have ECO on (for easier pedal modulation and lower heater power usage) and 90% of the time I use B.

The two times I want D mode (or less):

1. On the highway when I want the regen to not kick in so fast in cruise control.

2. When driving in snow, sleet. I really don't want regen to kick in and out as it senses the surface.

EVDRIVER said:

Nissan needs to really change their product to win in the new landscape or even survive

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http://cleantechnica.com/2015/03/28/ev-demand-growing-global-market-hits-740000-units/

dthwaite said:

I think it would be simpler to always have maximum regenerative braking and just have the "eco" mode to dampen acceleration/limit aircon as it does. With "b mode" you get two levels of regen which is extra superfluous.

I find it tedious always to select "b mode" (its not the default) and I also find it disconcerting that the regen is significantly lessened when the battery is full, so my driving experience is materially altered for no good reason (hey, why's the car not slowing down? oh, battery full).

You can always reduce/control the regen braking effect by keeping your foot lightly on the accelerator. I also think the regen slowing is more similar to engine braking in cylinder cars .

The only reason I can think of having no (or less) regen is perhaps there being some regulatory requirement that lifting your foot of the accelerator pedal should not induce too much braking? Or maybe the brake lights don't go on in max regen mode? But I should think they would go on triggered by the rate of deceleration rather than by what means was used to slow the car.

What do others think?

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While I agree, having a "no-regen" mode would be helpful in non-traffic/country driving to save energy, the current D mode only does 10kW of regen and unless you are rolling uphill or against a head-wind, takes a very long time to bring the vehicle to a near stop. My wife's automatic transmission car has twice the engine braking that the Leaf does in D mode so I've always thought that D mode regen was just very weak to begin with. In usual up or down hill driving or traffic, you find yourself using the brake a lot to control speed. I don't know if I would want the vehicle to truly coast all the time (no-regen) to save a very small percentage of energy in the long run. On the flip side, the B mode has a lot more stopping power than my wife's car, so I can almost drive with a single pedal around town, actually saves a lot of accelerator and brake swapping with the foot.

Driving the vehicle at 100% charge is basically no-regen mode for a couple of miles and it does take a little time to get the correct mind-set that if I let off the pedal, I will keep rolling pretty darn fast. But I've never had any problems with the brakes and my mind only takes a short amount of time to adjust my driving accordingly to the change until the battery is finally depleted enough to create a better braking effect.

With that said, I think what the Leaf has, currently, is about the best "one size fits all" that they could do for non-technical drivers. I live in an area where I pass a hundred other Leaf vehicles every day and most of the people that I talk to that own a Leaf just drive it like a car, never touch Eco mode or B mode on the vehicle and many don't even know what they do. So it is easy for us, the very technical and knowledgeable Leaf owners to criticize the choices for regen in the Leaf, but I think Nissan is probably trying to cater to the masses on this.

I much prefer the regen arrangement on the e-Golf: free wheel coasting in D, regen on the brake pedal, and 4 levels of regen available on the shifter D1, D2, D3 and B in increasing order.

Coasting is by far the most efficient way to move the car, and making this easy means that you accelerate less, and then you use regen less, too. Regen is only used when you have to slow down, instead of friction brakes.

To do this in the Leaf, I have to shift into neutral. Which is easy enough, but the e-Golf is easier still - and to go again, you don't need to put it back into D.

finman100 said:

Hmmm, excess regen generates heat you say? big ol resistor? i'd say we have another cold-weather package to sell! Take that heated resistor and force the hot air into the cab for all those in winter climates. Heck, even i'd like some of that for defog purposes up here in the PNW. Go fast, then brake to 'over-regenerate', thus creating defog/heat for the cab. win-win.

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For some reason this reminds me of The Martian. Have you read it?

Seen the movie.
I imagine the book has many different details than the movie did? I'll have to find a copy since I liked the movie.

Nubo said:

garsh said:

I've said before that I'd like to add a big-old resister. Whenever the battery is too full, shunt the regenerated power to the resistor. That way you always have full regenerative braking available, and the brake performance can always be the same, instead of having diminished regenerative braking when the battery is full.

But that's an extra expense, and you have to figure out how to safely dissipate the generated heat.

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These guys will hook you up. :lol:

http://www.mosebachresistors.com/resistors_rl.html

To OP, you can't just dump energy into the battery when it's full. That would result in disastrous overcharging of the cells. The alternative is as garsh suggested, a "big ol' resistor". That is what diesel-electric locomotives use. REALLY big ones. Converts the excess electricity into LOTS of heat.

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I think , at one time , subway cars used a bigmresistor bank , too ?

God bless
Wyr

dthwaite said:

I think it would be simpler to always have maximum regenerative braking and just have the "eco" mode to dampen acceleration/limit aircon as it does. With "b mode" you get two levels of regen which is extra superfluous.

I find it tedious always to select "b mode" (its not the default) and I also find it disconcerting that the regen is significantly lessened when the battery is full, so my driving experience is materially altered for no good reason (hey, why's the car not slowing down? oh, battery full).

You can always reduce/control the regen braking effect by keeping your foot lightly on the accelerator. I also think the regen slowing is more similar to engine braking in cylinder cars .

The only reason I can think of having no (or less) regen is perhaps there being some regulatory requirement that lifting your foot of the accelerator pedal should not induce too much braking? Or maybe the brake lights don't go on in max regen mode? But I should think they would go on triggered by the rate of deceleration rather than by what means was used to slow the car.

What do others think?

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Dear OP:
This is my very first post.
I brought LEAF (Chinese version Venucia e30) one year ago.
We don't have the ECO button on the steering wheel instead on the shifter we have "D" and "ECO" mode.
Our "ECO" mode = Your "ECO"+"B"
Our "D" mode = Your "Non ECO"+"D"
And yes the car remember your last choice.

I agree there are drives have no clue what "ECO","None ECO","D","B" means (I personally know people driving this car for month without knowing there is a "ECO" mode).

I personally love your "B" mode, but I hate "ECO" slow down the paddle response make the car feel less agile and nimble(And there is no cruise control option in China).

So I order the steering wheel button assembly from Japan and a cruise control module for Nissan ICE car.

Retrofitting on my car:


It's true for a experienced driver if you turn off or dail down break regen you have more mileage.
Especially on the high way if you drive downhill coasting change POTENTIAL energy to KINETIC (height -> speed) is much more efficient then charging your battery (efficiency < 40%).

According to the LEAF service manual:
Leaf is capable of 80kw of out put and 24kw of break regen.
On the power meter of the instrument panel:
Each dot on the right side(Power Output) represent 8kw of energy (10 dots in total).
Each dot on the left side(Power Regen) represent 6kw of energy (4 dots in total).


YES Nissan also change the logo front and back of rebranded leaf in china.



Which I changed back to the original outlook.

Also Chinese version of leaf have spare tire and rear fog light:


Maybe I'll create a dedicated thread for those who interested in Chinese leaf owner.

And yes there are thousand of us and we are having fun:

I love the regen brake but am annoyed that it does not work when the battery is 100% charged.
But the makes sense, because if the battery is charged there us no room for the regen.

My complaint is that I cannot program the car to stop charging at a certain percentage or battery level.
(2016 SL)

So our car charges to 100%. We live on a mountain and drive down hill for the first 5 miles. But we get no regen because the batt is at 100%. It sucks that we have wear down our brake pads rather than use regen.

I hope Nissan fixes the software so a stop charge % can be set by the user.

Xriva18707 said:

I love the regen brake but am annoyed that it does not work when the battery is 100% charged.
But the makes sense, because if the battery is charged there us no room for the regen.

My complaint is that I cannot program the car to stop charging at a certain percentage or battery level.
(2016 SL)

So our car charges to 100%. We live on a mountain and drive down hill for the first 5 miles. But we get no regen because the batt is at 100%. It sucks that we have wear down our brake pads rather than use regen.

I hope Nissan fixes the software so a stop charge % can be set by the user.

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Doesn't your '16 allow 80% when using the charging timer? My '13 has 80% as a menu option, if set for 80% it only charges to 80% unless one changes the menu option. My '12 lacks the 80% menu option but does allow 80% if charging using the timer. I've setup a timer on my '12 where if I plug it in, it starts charging immediately but only goes to 80%. If I push the timer override button I can get a 100% charge. Does your '16 not even have the 80% with the timer?
I agree, no regen at a high SOC isn't very nice, I love my regen. On my '13 I start gaining back regen very quickly, like one bar available at 98%, two at 96% and by low 90s full regen is available to me. Now my '12 is totally different, I don't get regen until the low 80s SOC and has to be darn near 50% before I get full regen, really bothers me and probably my biggest complaint about the '12. Even with full bars I find the regen(engine breaking) far less on the '12 than '13(I always use ECO and being a S model ECO also includes B mode) not sure why but I know it's the case. On the '13 with full bars I hardly have to use the breaks when exiting a freeway with a long ramp, this is not the case with the '12 where I always have to use at least some friction breaks to stop. I knew right ways when I purchased the '12 used as the wheels were covered in break dust whereas my '13 generally has no break dust on the wheels.

Note even if your '16 lacks the 80% feature you should still be able to simulate it by using the departure time timer. If you plan on leaving for work at 8am set the timer for say 6am and plug your car in the night before. Because your leaving early the car won't be fully charged. Play with the end time and eventually you should be able to figure out a time to set it to so you'll get your desired SOC when you leave. Note for setting the time it matters what the amperage of your EVSE is as well as the current SOC when you plug it in. Not nearly as easy as if they had the 80% option but better than nothing

Nissan removed the 80% charge option in 2014. It made the car look better on paper.

The EPA took the average of the range at 80% and 100%, and put that on the sticker. 11/12 Leafs are rated at 73 miles, 13 at 75 miles, and 14+ at 84 miles. The battery didn't change in 2014. Nissan just removed the option to charge to 80%. Voila! The sticker range jumped from 75 miles to 84 miles!

I really hope Nissan brings back the option for the Leaf 2

GetOffYourGas said:

Nissan removed the 80% charge option in 2014. It made the car look better on paper.

The EPA took the average of the range at 80% and 100%, and put that on the sticker. 11/12 Leafs are rated at 73 miles, 13 at 75 miles, and 14+ at 84 miles. The battery didn't change in 2014. Nissan just removed the option to charge to 80%. Voila! The sticker range jumped from 75 miles to 84 miles!

I really hope Nissan brings back the option for the Leaf 2

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Thanks for the info, I knew the newer Leafs didn't have the 80% always like the '13's but I thought they still had it using the timer like on the '11 and '12s.
I agree it would be nice to have it back on the next gen Leafs and hopefully like Tesla does it where you can select from more than just 80%. It would also be nice to have the ability to regulate the amount of regen you want, like I've read you can do on the Teslas. That would be the best, people that didn't like regen could turn it way down and those that like a lot could turn it up, give us the choice Nissan.

Tesla gets all of this correct because they approached EVs from a clean slate. They did what made sense given the nature of the battery / motor / regen / etc systems that they had.

Nissan et. al. got this wrong because they approached EVs as just another car. So they went out of their way to make it behave like any other car in their lineup. As a result, we lose access to a lot of the potential that an EV drivetrain offers. On the flip side, there is less of a learning curve to initiate drivers into an EV. It's a tradeoff.

I don't mind the "default" behavior of the car being that it acts like an ICEV. I just hope that more cars give us the option to change that if we desire. The eGolf is a good step in the right direction.

As a first EV, I love my Nissan Leaf, but things like this regen issue really baffle me. Let's take a look at 6 years down the track.
2010/11 Nissan create this car and it is the first one. there is a lot of consultation but in their wisdom they decide to build it "like" an ICE so that it does not alienate people, but then they do a futuristic (at the time) design, so that alienation happened anyway, so they should have either built it looking like an ICE or they should have built it working like an EV. Fast forward 6 years and the car does not look all that futuristic, so better acceptance (but it has not appreciably changed in style, either). But the car does not have all the EV features it could have, either. Very little development of the way the car drives or can be tweaked. Apart from B mode regen, what else has changed?

It's all software. In 6 years you could employee a programmer and let them run amok with the system, it is a really cheap investment and could pay big dividends. Just listen to the community and see what ideas work. So why does it feel that has not been done? Probably because the computer system is really small? not much storage, not much CPU power? no idea as I have never seen specs for that part. Maybe it is just an Android type tablet (probably not, but certainly possible).

So here's my input to the regen discussion. I have a 2012 model in Australia. Sounds very similar to the Chinese model but mine does not remember I was last in ECO mode, I have to double shift everytime to put it into ECO mode. I'll see if there is a firmware upgrade at my next service, doubtful, but maybe lucky and this is added. It's just software, so why not give me s settings option to ask what mode I want to be in? Too easy, probably don't understand what it is when I first drive the car, but two days later I would be going to that option and changing it to my preference.

Same with regen. Ok, so new car has "D', "B" and "ECO", where ECO can be combined with B or D. Again, it is just a software parameter I suspect, so why not give us s settings option? D mode regen - Off, Low, Medium, High. B mode regen - Off, Low, Medium, High. If the regen works on kw (0-24) and has a resolution of 6kw, then those options make good sense. My model has D and ECO, so I just set mine accordingly.

Let's look at Cruise Control. Plenty people tell us there is an energy penalty because of it. I agree, it works like an ICE cruise control and not like a low range EV where every kw counts. The cruise control aggressively tries to maintain the speed, mostly. So if it drops below speed it kicks in and gets up to speed again. In D mode that is great, just what I want D to do, be responsive and snappy. But it does the same thing in ECO mode, not what I want. In ECO it should increase power until there is acceleration and then hold it or back off. I don't care if it takes 1 minute to go from 50 back to 60 (ok, maybe a little bit faster), but I don't need to get from 50-60 in 1 second when I am in ECO mode.

Going downhill with Cruise Control is a disaster. Puttering along at the speed limit and hit a steep downhill, regen kicks in to slow the car down but it is only about 10kw, so the car just keeps on building up speed, almost double the limit by the time I decided to override it and use the brake pedal, guess what regen went to 20kw and slowed the car down. Surely the program should be "keep applying regen amont until we either slow the car down to the limit or we reach maximum regen"? If I use Cruise Control I want the car to maintain a set speed, within reason, not let it get out of control (faster down a hill or slower up a hill).

Now the issue of the 100% battery and regen. On my 2012 the regen starts to work at about 90% battery (as reported by LeafSpy SOC). My Leaf only charges to about 93% (82% SOH), so I get to 90% pretty quickly once I start driving. At 90% the regen is very small, maybe the 6kw mark (one bubble), certainly not over 10kw. When I get to 80% SOC the regen can go to 30kw as you see it reported on the energy screen. no matter what the SOC I rarely see it go about the 30kw marker, but it can do that (not sure of the exact conditions yet). Ok. so if the regen has nowhere to go, then dumping the excess into the heater element would be one option (that can take a bit of power). The SOC drops reasonably quickly and the regen can go into the battery fairly quickly. The other option is just a big ol' resistor or heat sink. Obviously these are good cold weather solutions, maybe not so useful in the Summer. Friction brakes dump heat everytime they are used, so maybe there is a method to dump the heat for excess regen in the same sort of way. It should be very transitory as the SOC gets to the point where the battery can be recharged will be reasonably quick.

For that poster who lives at the top of the hill, without the 80% charge cut-off option (2012 has this as part of timer option, manual override goes to 100%) your only option is to calculate the time to charge to x% and then unplug when you reach that time. I think one poster suggested using an end timer, but you need to set the end timer to a time after you actually would leave, eg: leave at 8:00am, set end timer to 8:30 or 9:00, then the charge is that much less than 100% when you actually leave because the charging is trying to get to 100% by 8:30 or 9:00 but has actually only gotten to 80% or 90% by 8:00 when you leave. Pretty simple but does not work if you don't know when you will leave or you are trying to maximise off-peak power (my off-peak finishes at 7:00am, but I leave at 8:00am, so no good for me to do it thks way).

Imagine if someone (listening Nissan?) made their software open source. Maybe restricting access to critical system parameters so you could not (for instance) disable the brakes, but allowing all the other parts of the system to be tweaked. Look at what reverse engineering LeafSpy has achieved, and I am sure if those people had access to the source of the system they would have made a program 10 times better than it is. Maybe they could inject codes onto the CAN or EV bus so I could set my own regen values. The possibilities would be interesting and potentially the Leaf would be a better car because of all the development this side of the system would get.

Now, if only I could make the heater work using ECO settings when I am in D mode...

garsh said:

I've said before that I'd like to add a big-old resister. Whenever the battery is too full, shunt the regenerated power to the resistor. That way you always have full regenerative braking available, and the brake performance can always be the same, instead of having diminished regenerative braking when the battery is full.

But that's an extra expense, and you have to figure out how to safely dissipate the generated heat.

Click to expand...

That's how trains do it... Massive braking resistors!

Nubo said:

The alternative That is what diesel-electric locomotives use. REALLY big ones. Converts the excess electricity into LOTS of heat.

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Light rail trains do it too. Much better braking than the friction brakes can do.

Tsiah said:

That's how trains do it... Massive braking resistors!

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Yeah, I worked at GE Transportation Systems for five years building locomotives.

The fact that most of these changes that we want could easily be configured via software, but Nissan doesn't seem very interested in adding any of these feature sets is rather bothersome. Annoying, I would even say. Nissan isn't too keen on "fixing" anything unless it is absolutely necessary. Their continuously variable transmissions are a good example, expanding the warranty on them in the 2000 era models, but not for the 2014 era. Ours went out at 45,000 miles, and they pretend like their CVTs don't have issues. It wasn't until ours was completely failing that they replaced it, even though it exhibited symptoms of failure long before then. :x

Durandal said:

The fact that most of these changes that we want could easily be configured via software, but Nissan doesn't seem very interested in adding any of these feature sets is rather bothersome. Annoying, I would even say. Nissan isn't too keen on "fixing" anything unless it is absolutely necessary. x

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This shows the contrast between Nissan and Tesla. Amazing to me is how much time Tesla spends following the Tesla forums. Many of the ideas forum members bring up on the Tesla forum end up being implemented by Tesla often in the form of over the air software updates.

Too bad there isn't a plug and play ultra capacitor pack solution. An ultra capacitor pack would take a lot of stress off of the traction battery. If set up right, the battery probably would never see any regen current and would never see any high acceleration current. It would basically just trickle feed the system, putting out around 15kW maximum. The ultra capacitor pack would usually soak all the regen current and then give most of the acceleration current. You'd never need to worry about your battery's temperature or state of charge. It would have full regen capability in nearly every situation except going down a long hill with a fully charged battery.

My challenge with regen is in living at the top of a 700' hill with a steep, twisty 2 mile gravel road. If I have room for regen, it only really works if I stay off the brake pedal. As soon as I start controlling speed with the brake pedal, the system fades regen out and goes entirely friction due to unequal wheel speeds on gravel (regen is front wheel only). That is the proper choice for safety, so I'm not complaining there. As well, it's better than the sudden ABS cutout of regen on hybrids I've experienced, where you feel an abrupt decrease in braking and must depress the brake pedal further to compensate. My LEAF blends it far better.

Descending that hill gives me at most a net 0% energy use due the the gravel. After a couple of small hills on the way down I start getting one bubble of regen at the bottom, but that's about it. Going back up, it uses about 3% SOC on my 30 kWh pack.

In the end, the massive disc brakes dump the kinetic energy into heat, and we need friction brakes anyway, so adding dynamic motor braking via a resistor bank and fans would seem to be extra complexity for minimal functional gain. I do happily run the climate control on the way down, though.

I'd still prefer the option to limit charging to a percentage I select so I can charge at the top of a hill and recover some energy heading back down. In the end, though, I realize it wouldn't be all that much of a net gain.