Great Brakes
- Thread starter David Towle
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MNSteve
Well-Known Member
I wish we had this option for the Clarity. I understand the engineer's goal in making the car creep forward when put in D and apply regen braking when you release pressure on the accelerator, to make the car a comfortable driving experience for folks who are used to that behavior with traditional cars. But I'd rather control both aspects myself. Options are good.
Chevy went whole hog on the L mode.
If you take your foot off the accelerator in L mode, check for tailgaters first.
It's kind of cool, but over the top.
This is not for efficiency, just easier to drive in stop and go traffic.
For comparison to Honda paddles, you would need eight chevrons and it would work all the way to a stop.
If you take your foot off the accelerator in L mode, check for tailgaters first.
It's kind of cool, but over the top.
This is not for efficiency, just easier to drive in stop and go traffic.
For comparison to Honda paddles, you would need eight chevrons and it would work all the way to a stop.
I think Ken's document said 8% recovery.
Our old Prius was rated at 10% energy recovery from regen, so that's in the ballpark.
Yeah, approx 90% is still lost through all the transitions, but all I can say is the brakes don't wear out.
Is it worth it? Jury is still out.
If you don't have to change brakes for 8 or 10 years that's very useful.
If I remember correctly, in Volt the paddles were an alternative way to call for the same max regen.
In Bolt, the paddle adds still more (additional) regen. Bolt L + paddle can make for some really strong regen (with brake lights). Maybe 10 to 12 chevrons equivalent!
So, the only thing I can think of is that most of the supporting infrastructure is already there for an electric or hybrid drivetrain.
Otherwise, its a lot of complication for 8% recovery.
It would be interesting to have a hybrid that hyper-miled natively with no regen - just drive and float without coast (no decel loading).
That would take some driver attention stay off the brakes, but it should generate great MPG figures.
First 90 year old driver on a long down-hill stretch inadvertently coasting up to 130 MPH would be the end of that idea.
But give the me the option hidden deep in a custom menu and I will try it out.
KentuckyKen
Well-Known Member
I think the graph in that doc is stating it’s 8% increased regen over normal EV regen not 8% total regen. I also think it’s more than 8% total because I observe that regen adds EV miles way more than 1/10 of what it takes to go the same distance.
Honda seems to have tweaked it to come on sooner and ramp up faster and stay on longer. Kudos to Honda for giving us a little more regen efficiency and range while making the most seamless transition between regen and friction braking on the market today.
Based on the graphs posted and the feel of the car when braking to a stop, I surmise that Honda has implemented active control of the regen - so rather than a simple "provide this much resistance to motion regardless of speed" for a given amount of braking, it may be actively managing the regen to provide a constant rate of deceleration. Under simple controls like my old Prius, the amount of energy taken out is proportional to speed, meaning that regen resistance falls to zero as speed approaches zero. The Prius switched to full friction brakes at 7 mph I believe. If Honda has done this, they deserve some kudos as normally the variability in friction brake engagement with pad travel makes smooth transition difficult. But since there is fuzzy logic in other parts of the car, such as pedestrian detection, maybe there is some feedback from each braking event into the next (or rapid enough feedback to adjust in real time).
I test drove a Leaf with the one pedal driving, and in that mode it will bring the car to a stop and hold it, even on an incline, when the accelerator is released. Because of the relationship stated above, I believe this requires actually driving the motor to a stop rather than simply using electromotive resistance.
Personally I didn't like it - I've had enough of feathering the gas pedal to be engine-off but non-regen in my Prius for 10 years. I'd actually like a true "0 chevrons" in the Clarity for the option to coast with no resistance. Maybe keep 1 as the default, but allow a pull on the '+' paddle to go to 0?
I test drove a Leaf with the one pedal driving, and in that mode it will bring the car to a stop and hold it, even on an incline, when the accelerator is released. Because of the relationship stated above, I believe this requires actually driving the motor to a stop rather than simply using electromotive resistance.
Personally I didn't like it - I've had enough of feathering the gas pedal to be engine-off but non-regen in my Prius for 10 years. I'd actually like a true "0 chevrons" in the Clarity for the option to coast with no resistance. Maybe keep 1 as the default, but allow a pull on the '+' paddle to go to 0?
Oh, regarding the question of "how much energy are we recapturing", I've seen my EV mileage estimate go up by 1/4 mile when stopping gently from 60 mph. The kinetic energy of a Clarity at 60 mph is around the average energy use to go .6 mi (1 km) on flat land, so I think recovery is above 50%. Remember, when stopping you not only get the range increase, you also get the ground you covered while stopping for free. When coasting the last 1/2 mile up to the first light into town, I find I can cover that 1/2 mile and come to a stop, and still come out .2 mi ahead on EV range estimate.
The Gadgeteer
Active Member
While many find it joyful to maximize regen it can lead to reduced range and inefficient driving.
The amount of energy captured during regen is far less than the amount of energy needed to get back to that speed. For instance if you slow down 10 MPH from 50 MPH to 40 MPH to get back to 50 MPH it will take far more electricity than was captured.
So it is better when possible to simply not use more energy to accelerate to or maintain a speed in excess of what you need in the first place. For example accelerating towards a stop light then heavy regen slowing down is not as efficient as just gradually slowing down by coasting and mild regen to the stop light.
If you have to slow down anyway the more regeneration you can do (vs friction brakes) the better because a good amount, although not all, of the energy that got you to speed is recovered.
The amount of energy captured during regen is far less than the amount of energy needed to get back to that speed. For instance if you slow down 10 MPH from 50 MPH to 40 MPH to get back to 50 MPH it will take far more electricity than was captured.
So it is better when possible to simply not use more energy to accelerate to or maintain a speed in excess of what you need in the first place. For example accelerating towards a stop light then heavy regen slowing down is not as efficient as just gradually slowing down by coasting and mild regen to the stop light.
If you have to slow down anyway the more regeneration you can do (vs friction brakes) the better because a good amount, although not all, of the energy that got you to speed is recovered.
Where the driver is dissipating energy used that could have been avoided in the first place, I completely agree that use of regen, is less efficient than good coasting driving. Thus the many similar discussions at the Volt forum, where the consensus in recent years was moving from L to D for maximum efficiency.
OTOH, with good driving in any mode or style, the differences are probably de minimis.
So, unless about plus or minus a few dollars is crucial to one's well being, just drive the way you enjoy driving, and try to fit into the real world of other drivers on the road as best as possible
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