regen vs mechanical brakes

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Mx5racer

Well-known member
Joined
Oct 18, 2010
Messages
176
Location
Yorba Linda, ca
Is there any way to tell the max point of regen vs. mechanical braking
Do the mechanical brakes not start being applied until after all the brake dots are full?
I wish there was a light that showed the point that you were pushing too hard.
 
Feel how the car brakes when it is charged to 100%. That is almost all mechanical brakes. You'll notice there is a very light touch to not apply the mechanical brakes. When you are using regen (pack down to 80% or less), just barely push down on the pedal and the regen will go to maximum if you are going fast enough to regenerate. If you give any extra it will be applying the mechanical brakes as well.
 
Mx5racer said:
Is there any way to tell the max point of regen vs. mechanical braking
Is that a question

:D

Missing question mark notwithstanding, see Owner's Manual, page 2-7: "Instruments and controls"/"Meters and gauges"/"Power meter".
You get max regen when all four dots on the left light up.
When dots on the left have single-line circle around them instead of double-circle, it means that regen is being limited to prevent overcharging the battery. For example, when the battery is fully charged, all four dots on the left have single-circle border.

Mx5racer said:
Do the mechanical brakes not start being applied until after all the brake dots are full?
The brake control module controls the amount of hydraulic brake assist by operating a pump in the master cylinder, coordinating between the traction motor's regeneration and signal from the brake pedal travel sensor (LEAF Service Manual, page BR-12). The brake control module does a gradual transition between regenerative braking force and hydraulically assisted braking force.

That said, I can always feel the cut-over point when the regenerative braking cuts out completely and braking becomes 100% hydraulic, when slowing down from speed to a near crawl. As I slow to a walking/jogging speed, I can feel a sudden twitch in the brake pedal and the pedal sinks a tiny bit.

Mx5racer said:
I wish there was a light that showed the point that you were pushing too hard.
If all four dots on the left light up like a Christmas tree, there's probably regenerative energy being lost. (The "Energy Usage" screen of the "Energy Info" display in the center panel shows power used or regen'ed by the motor: navigation system owner's manual, page IT-3. Regen is at its max when the display shows -30kWh.) It's a bit of a game for me to gauge my braking distance/force/time to get max regen up until the moment I come to a stop.
 
While you are braking, put the car in neutral. This will "turn off" regen and you can get a feel for how much mechanical brakes are applied.
 
Mx5racer said:
Is there any way to tell the max point of regen vs. mechanical braking
Do the mechanical brakes not start being applied until after all the brake dots are full?
I wish there was a light that showed the point that you were pushing too hard.
The more you drive, the more you’ll want right pedal regen. Intuitive, accurate, responsive, efficient. Nothing to distract you from your driving task. Problem solved!
 
KeiJidosha said:
The more you drive, the more you’ll want right pedal regen. Intuitive, accurate, responsive, efficient. Nothing to distract you from your driving task. Problem solved!
Yes, I think of that as "stick shift" mode, which would make driving the car feel like you had a manual transmission stuck in first gear. I've driven the AC Propulsion eBox with adjustable regen set to "max" and that's exactly how it felt. It doesn't take long before you are driving with just the right pedal and not really using the brake much at all.

So what we really want is an auto vs manual "transmission" (feel) setting in the car. But if they add that, they should probably add per-keyfob settings, so my wife can leave her preference set to "auto". Sure would be nice if the different fobs also adjusted the seats and mirrors for each person, too...
 
townsat said:
Adjustable regenerative braking. That is what every electric car should have.
Well, thinking about it some more, I'm not entirely sure I agree. Before I got my LEAF, I was sure that I would have preferred it to have a "max regen" mode if not adjustable. I was also convinced that I would hate ECO mode. But since I've had my car (for just a few weeks now) I've actually grown to think that they did a pretty decent job selecting and tuning the two modes that we do have (D and ECO). I usually use ECO because I want the more aggressive regen, but I also like the more direct responsiveness in D.

Perhaps most importantly, I suspect that most people who are used to driving a car with an automatic transmission will find that the Leaf is very similar to what they're used to, and will therefore help confirm that this is "just like a normal car" rather than something strange.
 
I have had my Leaf for a couple of months now (#567), and have found drive mode is better for many everyday driving situations. I throw it into eco whenever I see a reason to slow down, since it is a gentler way to engage the regen than using the brake pedal. I also don't want to be the slow poke leaving the stop light - no reason to, I am already cleaner than any other vehicle near me, and the cost is negliglble since I can regain a portion of the energy by slowing after the quick start. I have gotten pretty good at feeling when the max regen point is hit, and the display mentioned above does help - I wish it was the default screen - the map is too distracting for me, and the radio too boring. I touch the blue menu button and then the energy info button on start up, it is a clearer guide than the in dash dots.
 
LEAFfan said:
townsat said:
Adjustable regenerative braking. That is what every electric car should have.
I believe the VW Golf e-Motion (2014) will have adj. regen.

Anytime you start messing with the brakes you open yourself up to suits and bad press.. not a good idea. Best way to conserve range is to drive like you had no brakes at all.
 
Herm said:
LEAFfan said:
townsat said:
Adjustable regenerative braking. That is what every electric car should have.
I believe the VW Golf e-Motion (2014) will have adj. regen.

Anytime you start messing with the brakes you open yourself up to suits and bad press.. not a good idea. Best way to conserve range is to drive like you had no brakes at all.
I respectfully disagree.

Maximum regen doesn't mess with the brakes at all.

If the Go pedal had maximum regen, I'd hardly ever need to use the brakes while driving.
But any driver who moves his foot to the brake would get all the friction brakes on top of the 'engine drag'.

I really like the comparison to driving a big-bore stick-shift car in first gear. If you let off the gas, it's going to come to a stop pretty quick. There's no reason an EV couldn't do the same.
 
Max regen on the go pedal would not be good for your range, you want to glide/coast on occasion and since you have no clutch then the analogy to a stick shift fails.. but then someone will suggest a button on the steering wheel that disables the regen so that you can coast.. thats where the suits to Nissan start to come in when people make a mistake. My idea: let go of the go stick and the car coasts, no regen (but people expect braking action from an auto transmission.. more suits) you step on the brakes and the car automatically blends regen and friction braking. I'm sorry lawyers that are forum members.. you need to die :)

Probably the best way is to let off the go stick a bit and the car glides, let go all the way and mild regen takes over (or strong if you prefer).. brakes still automatically blend the two types of braking. I think this is the way the Leaf works, smart people those Nissan engineers.
 
GroundLoop said:
I really like the comparison to driving a big-bore stick-shift car in first gear. If you let off the gas, it's going to come to a stop pretty quick. There's no reason an EV couldn't do the same.
I drove a Mini-E once and it was set up this way. It was quite a surprise, but it was also apparent what to do with it. I don't think anyone's been killed using it.
Herm said:
but then someone will suggest a button on the steering wheel that disables the regen so that you can coast..
And the EV-1 had a coast button on the stick. And people liked it. And no one died using that, either.
 
So, if I understand correctly - the LEAF's braking system is kind of like this?

So, you can get most of the available regen without applying the friction brakes, then there's a little bit more regen available with the friction brakes lightly applied, then the rest of the way the regen continues contributing at 100% and the friction brakes handle the remainder?

brakesgraph.png
 
I think the that let go of gas= coast, tap brake=light regen, apply brake =more regen would be a nice way to adjust regen without really distubing normal driving habits.
 
wgs1912 said:
I think the that let go of gas= coast, tap brake=light regen, apply brake =more regen would be a nice way to adjust regen without really disturbing normal driving habits.
Really? What other cars behave like that? Everything I've ever driven before, manual or automatic transmission, hybrid or non-hybrid, applies either engine braking or regen when you take your foot off the accelerator.

Ray
 
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