Regen and brake lights

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garygid said:
At high speed, one suddenly takes one's foot OFF the "go-faster", and ... what? ... sudden maximum regen-braking until zero mph is reached?

No, I do not think that strong, abrupt braking action would be acceptable!

Which is why they're not going to do that! Give them a break - they're engineers, yes, but there are technicians there to keep them straight! :lol:

Other commercial EVs that add regen when the operator removes their foot from the accelerator pedal use about 6%. It's very small and designed to mimic engine braking when in a high gear.

I'm one of the sickos that prefers a manual transmission (sorry to let you down, evnow!) and I really like the accel and decel control one has with a stick. But none are likely to enjoy the abrupt nature of pulsing the accelerator pedal in second gear. :D

Andy
 
This sicko has never owned a vehicle with an automatic transmission as a matter of policy. I'm trying to skip straight from a stick shift to no shift. :D
 
AndyH said:
...I really like the accel and decel control one has with a stick...

When you use the transmission and engine to slow a car, aren't you just transferring wear and tear from cheap parts (brake pads) to expensive parts (gears, clutches, CV's etc)? Except for long downgrades I've never understood the benefit of downshifting.
 
LTFT...
You are correct.

Previously:
I was not suggesting that Nissan would do such an implementation, but rather trying to illustrate why "kballs" suggestion would not work well.

Braking tends to "throw" the driver forward, increasing pressure on the pedal being used. So, using the go-faster for braking is not really a great idea.
 
The 2010 Prius assumes that, with your foot (almost) OFF the go-faster pedal, that you want to be slowing down. So, it invokes some regen, zero with the foot slightly on the pedal, and gradually increasing to a larger amount (which depends upon vehicle speed) as the foot is gradually removed from the pedal. Nothing "abrupt", a very smooth emulation of typical automatic transmission "drag". Likewise, there is a further, smooth increase in the regen-braking as one applies pressure to the go-slower. Integration with the gradual application of mechanical brakes is also smooth and seamless. It does not give any clear indication (as far as I know) as to when the disc brakes are being used.

However, when driving for economy, that is a poor assumption, and drag-free, zero-power "coasting" is what one really needs.

I suspect the "coasting" will eventually appear, first as a user-controlled setting, as EVs evolve and people become more experienced e-drivers.

If the LEAF has "coasting", I will be surprised, but that would be a "plus" in my decision to actually buy one.
 
Every electric car I've ever driven handles regenerative braking in a different way. Some of them are good, some of them are very good, and some haven't quite worked it out just yet.

When I drove the Nissan LEAF mule last month, there was minimal regenerative braking from taking your foot off the accelerator, and the brake pedal activated the mechanical brakes. I'm told that the production LEAF will incorporate more regenerative braking, although nobody could tell me how that would be activated.

The G-Wiz activates regenerative braking through the brake pedal: the harder you press the brake pedal, the more regenerative braking you get. If you need lots of braking because you're stopping in a hurry, then the mechanical brakes get activated. Thanks to some really clever software on the later cars, most people won't feel the difference between regenerative braking and mechanical braking. When you are just driving along and take your foot of the pedal, there is a tiny amount of regenerative braking going on, but not a lot - the car happily coasts along quite nicely. The new REVA NXR is even better with regards to regenerative braking. Quite frankly, in this regard, REVA are the very best in the industry when it comes to incorporating regenerative braking. It really is very impressive indeed.

The Tesla Roadster handles regenerative braking in a very different way. You take your foot off the accelerator and the regenerative braking kicks in straight away. Leave your foot off the accelerator and the car will just come to a halt. If you use the brake pedal, that just activates the mechanical brakes. Basically, you don't need to use the brake pedal at all in most driving - just the accelerator. However, there is a fair amount of 'grab' in the regenerative braking system and it is up to the driver to feather the throttle to give a smooth drive. But then, you don't drive a Tesla for its smooth drive, right?

The Modec electric van incorporates regenerative braking when you take your foot of the accelerator, but its relatively minimal. There is no way to increase the regenerative braking and when you put your foot on the brake pedal, you're activating the mechanical brakes. The Aixam Mega City is similar.

The Mitsubishi i-MiEV has two modes for regenerative braking: relatively modest when you're in DRIVE or ECO mode, but significantly more in BOOST mode. I tend to drive the car in ECO mode for most of the time, shifting to BOOST when I want to slow down. The regenerative braking effect reduces as the speed reduces and shuts down at around 8mph and the car then just creeps forwards, which gives the car a similar feel to a gasoline automatic car. As soon as you press the brake pedal, the mechanical brakes kick in.

I had the chance to try the Mitsubishi i-MiEV with zero regenerative braking recently and I was impressed with how far the car would just roll. I personally think Mitsubishi should change the way regen works on their car to remove regen braking completely in ECO mode and max it out under BOOST so that it can completely stop the car.

With my G-Wiz, I hardly ever activate the mechanical brakes. In fact, I think I've probably only ever activated the mechanical brakes a dozen times in the past four years. With the i-MiEV, unless I have to come to a complete stop I rarely use the brakes. I drove about five miles this morning on a mixture of busy freeway, fast trunk road, and urban driving. Until I stopped outside my house I didn't use the brake pedal once.
 
MikeBoxwell said:
Every electric car I've ever driven handles regenerative braking in a different way. Some of them are good, some of them are very good, and some haven't quite worked it out just yet.

When I drove the Nissan LEAF mule last month, there was minimal regenerative braking from taking your foot off the accelerator, and the brake pedal activated the mechanical brakes. I'm told that the production LEAF will incorporate more regenerative braking, although nobody could tell me how that would be activated.

The G-Wiz activates regenerative braking through the brake pedal: the harder you press the brake pedal, the more regenerative braking you get. If you need lots of braking because you're stopping in a hurry, then the mechanical brakes get activated. Thanks to some really clever software on the later cars, most people won't feel the difference between regenerative braking and mechanical braking. When you are just driving along and take your foot of the pedal, there is a tiny amount of regenerative braking going on, but not a lot - the car happily coasts along quite nicely. The new REVA NXR is even better with regards to regenerative braking. Quite frankly, in this regard, REVA are the very best in the industry when it comes to incorporating regenerative braking. It really is very impressive indeed.

The Tesla Roadster handles regenerative braking in a very different way. You take your foot off the accelerator and the regenerative braking kicks in straight away. Leave your foot off the accelerator and the car will just come to a halt. If you use the brake pedal, that just activates the mechanical brakes. Basically, you don't need to use the brake pedal at all in most driving - just the accelerator. However, there is a fair amount of 'grab' in the regenerative braking system and it is up to the driver to feather the throttle to give a smooth drive. But then, you don't drive a Tesla for its smooth drive, right?

The Modec electric van incorporates regenerative braking when you take your foot of the accelerator, but its relatively minimal. There is no way to increase the regenerative braking and when you put your foot on the brake pedal, you're activating the mechanical brakes. The Aixam Mega City is similar.

The Mitsubishi i-MiEV has two modes for regenerative braking: relatively modest when you're in DRIVE or ECO mode, but significantly more in BOOST mode. I tend to drive the car in ECO mode for most of the time, shifting to BOOST when I want to slow down. The regenerative braking effect reduces as the speed reduces and shuts down at around 8mph and the car then just creeps forwards, which gives the car a similar feel to a gasoline automatic car. As soon as you press the brake pedal, the mechanical brakes kick in.

I had the chance to try the Mitsubishi i-MiEV with zero regenerative braking recently and I was impressed with how far the car would just roll. I personally think Mitsubishi should change the way regen works on their car to remove regen braking completely in ECO mode and max it out under BOOST so that it can completely stop the car.

With my G-Wiz, I hardly ever activate the mechanical brakes. In fact, I think I've probably only ever activated the mechanical brakes a dozen times in the past four years. With the i-MiEV, unless I have to come to a complete stop I rarely use the brakes. I drove about five miles this morning on a mixture of busy freeway, fast trunk road, and urban driving. Until I stopped outside my house I didn't use the brake pedal once.


There are ways to adjust the Tesla regen from 0-to full. This is such a silly debate because having it adjustable gives everyone the regen they prefer on pedal.
 
MikeBoxwell said:
The Tesla Roadster handles regenerative braking in a very different way. You take your foot off the accelerator and the regenerative braking kicks in straight away. Leave your foot off the accelerator and the car will just come to a halt. If you use the brake pedal, that just activates the mechanical brakes. Basically, you don't need to use the brake pedal at all in most driving - just the accelerator.
I like the Tesla principal -- I would not complain if that's how the LEAF ended up doing it. I have driven the Roadster. For anyone who hasn't ... look for a Tesla Store near you; they're pretty generous about test drives. And just so that the "... will just come to a halt." does not create false impressions ... as mentioned elsewhere, your right foot has full control of the deceleration (=regen=charging the battery), but even in the case of accidental (?unintended?) complete pedal-lift, the Roadster goes from 60-15 (mph) in about 700feet (without brake lining wear :) and just in time for you to take that turn you were planning ...). So, yes, it's strong, but not an emergency braking kind of maneuver. This also means (in reply to a comment somewhere) that the regen braking is not strong enough to propel your body forward and/or cause you to push back on the accelerator pedal. You definitely feel it, though. (The "Tesla regen-principal" might come in handy in an emergency ;) think medical emergency ... :cry: )

Another interesting result of the "Tesla way of doing it" (Mini-E does it that way too :p ): When on cruise control down a long hill .... the regen is strong enough that the car won't accelerate, yet you're getting the benefit of some very massive battery charging :D
 
Personally, I'd like zero pressure on gas pedal = 100% coast (no regen)
Pressure on brake pedal = regen (more pressure, more regen)

I live in some hilly terrain....I'd like to be able to completely coast down the hills at speed using virtually zero power. If there was regen involved, I'd constantly be switching back and forth.
 
Jimmydreams said:
Personally, I'd like zero pressure on gas pedal = 100% coast (no regen)
Pressure on brake pedal = regen (more pressure, more regen)

I live in some hilly terrain....I'd like to be able to completely coast down the hills at speed using virtually zero power. If there was regen involved, I'd constantly be switching back and forth.

I would think you'd like to collect regenerative power while maintaining speed down those hills, rather than coasting? Unless the hills are shallow enough that you never accumulate too much speed without braking now.
 
DeaneG said:
I would think you'd like to collect regenerative power while maintaining speed down those hills, rather than coasting? Unless the hills are shallow enough that you never accumulate too much speed without braking now.

maintaining speed = coasting. Atleast thats how I'm using it.
 
Jimmydreams said:
Personally, I'd like zero pressure on gas pedal = 100% coast (no regen)
Pressure on brake pedal = regen (more pressure, more regen)

I live in some hilly terrain....I'd like to be able to completely coast down the hills at speed using virtually zero power. If there was regen involved, I'd constantly be switching back and forth.
Well I certainly hope regen is involved driving up and down hills. Using minus energy is a lot better than no energy. And I, too, don't want to be switching back and forth between pedals while doing it. But I'm having trouble making sense of your position. Are you saying you want your foot on the go-pedal going uphill and on the stop-pedal going down? Isn't that switching back and forth? Me, I want my foot on the go-pedal going either up or down. And I want enough regen to keep the car from speeding up on steep hills unless I push the pedal to tell it to do so.

After 55 years of knowing I should never hit the brake going around a corner downhill, there is no way I could bring myself to do it, even if I was coasting way too fast.

OK, OK, I guess if you've got one o' them newfangled traction thingamabobs that rule don't apply no more. But it's deeply ingrained in my brain cells, and probably the brain cells of about fifty million other "seasoned" drivers.
 
There is NO fixed value of Regen that will work for all downslopes and speeds. So, to be useful in "holding back" the car, the Regen amount must be variable.

Typiccally, there are only two variable controls that are familiar, the go-faster and go-slower. One can split the Regen control between them, with zero to "light" on the go-faster, and "light" to "full" on the go-slower.

Then, "coasting" is not easily available, but might be accomplished by holding the go-faster down a little.

Or, the Regen (a going-slower function) can be entirely controlled with the go-slower. Then, low-drag coasting would be done with the foot off the pedals, or even "barely touching" either pedal. This is not a "keep the same speed forever" mode, the tire and wind drag would gradually slow the car.

On greater-than-gentle slopes, the "little" regen will be insufficient, so one will need to use the go-slower. Occasionally (perhaps not in "flat-land") there will be steeper grades that will require more than the "full" regen, so the mechanical brakes will be needed ... all the way down the "possibly-long" grade, perhaps 1 to 50 miles.

Note: This means a LOT of brake heating! Much MORE than a typical (down-shiftable) car would require. Hopefully, the EV brake designers realize this, and provide brakes that have ZERO heat-fade.

When anticipating stopping, it is best to have one's foot already on the go-slower.

Having the "light" level of Regen adjustable (or switchable) from "light" to "zero" would make the controls satisfy both camps.

This can be a simple Software setting, no extra physical buttons or controls are needed.

During every "anticipated" slowing or stopping sequence, there is the possibility to save energy by not using any, by coasting. Slowing with Regen might only be 50% energy effective. However, when judging when more braking is needed, I want my foot in the safest place, already on the go-slower. In traffic, the cars in front of me can decide to brake suddenly. Also, as soon as I decide that de-acceleration is necessary, I want my car's stop-lights to go on, to give warning to the guy behind me.

Rear-end accidents are the most common here in freeway traffic, and you can stop OK, but giving extra warning to the driver behind ... might save YOUR life, and at least save your LEAF.
 
kballs said:
... parallel hybrids have done it wrong (with their complicated jerky/uneven brake blending systems that are universally noted as an annoyance).
Universally noted as an annoyance??? I drive a 2004 Prius and you CANNOT tell where the regen braking ends and the friction braking begins. A few (VERY few) people have characterized the Prius brakes as "grabby," but they are a tiny minority. NOT "universal."

Toyota manages the combination of regen and friction braking on the brake pedal excellently. If they eliminated braking from the accelerator pedal entirely, and eliminated vehicle creep when the feet are off the pedals, it would be perfect.

"Coasting" to me does not mean steady speed. It means no power to the car, and no braking. The car rolls freely, subject only to rolling resistance and gravity.

Putting all the regen on the accelerator pedal (Tesla style) requires a lot more skill from the driver. Maybe that's okay for a high-performance roadster, but not for a family sedan.

But putting light or no regen on the accelerator, and none on the brake pedal, means you mostly use the brake pads, and this is wasteful, and for long steep downhills would be dangerous. So the brake pedal should use all regen until regen is no longer adequate and the brake pads become necessary. (Toyota style.)
 
garygid said:
On greater-than-gentle slopes, the "little" regen will be insufficient, so one will need to use the go-slower. Occasionally (perhaps not in "flat-land") there will be steeper grades that will require more than the "full" regen, so the mechanical brakes will be needed ... all the way down the "possibly-long" grade, perhaps 1 to 50 miles.

Note: This means a LOT of brake heating! Much MORE than a typical (down-shiftable) car would require. Hopefully, the EV brake designers realize this, and provide brakes that have ZERO heat-fade.
That's why the very strong regen on the Tesla is sufficient on (probably) all but the steepest hills to maintain a constant speed without touching either pedal ... the cruise-control controls the go-faster pedal (although I don't know if it actually "moves" the pedal, since all it needs to control is the current into or from the motor). For the LEAF it would be great while the driver is using cruise-control that it maximizes the regen on a down-hill to avoid use of the friction brakes. The fact that the driver is using cruise-control should be a "flag" to the software to allow maximum (more than normal) regen. Brake heating therefore would not be a concern.
(The maximum regen on the Tesla runs between 80-90A. At nominal 375V for the battery, this means 30-34kW ! (Think "charging the battery" !) Most of the time, that's for short durations, of course, but on a long steep hill (think Tahoe to Sacramento) it is for a significant benefit.)

Edit: before somebody jumps in ... ok, Tahoe to Sacramento is not one constant downhill, and it also has uphills, but you get the idea.
 
If the battery gets "full" (quite possible) and there is no place to "dump" 35 kW of power, the Regen is basically useless.

So, on the long trip home from Tahoe, the mechanical brakes will get ... VERY hot!

So, yes, brake heating is an important, even vital, safety issue.
 
Of course ... I guess the Tesla driver is expected to be smart enough to NOT leave Tahoe with a full battery ! :D But, good point, thanks for pointing that out.
 
DeaneG said:
Jimmydreams said:
Personally, I'd like zero pressure on gas pedal = 100% coast (no regen)
Pressure on brake pedal = regen (more pressure, more regen)

I live in some hilly terrain....I'd like to be able to completely coast down the hills at speed using virtually zero power. If there was regen involved, I'd constantly be switching back and forth.

I would think you'd like to collect regenerative power while maintaining speed down those hills, rather than coasting? Unless the hills are shallow enough that you never accumulate too much speed without braking now.

That's exactly what I'm saying. Most hills around here would cause ANY amount of regen to slow the vehicle, while 100% coast would be perfect. I agree on steeper hills you want some regen to keep the speed from increasing. If the regen is adjustable, I'm a happy camper. If it's preset and I have to work around it, I'll be slightly less so.
 
On any downhill grade a car will increase in speed if allowed to "coast."

They can program the regen to maintain speed. That would not be coasting.

I think Nissan's design goal is to have the car drive just like any car with an automatic transmission, minus the shifts. There is forward creep when the brake is released and the car is stationary, for example.

We'll find out how the regen works soon enough!
 
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