Regenerative Braking

SnBGC

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You may have better info than I do but 1-pd is total regen as the motor is doing all the work to slow and stop the car. When the brake is applied some of the energy in braking is lost to friction heat with the pads and rotors.
In my example above......I am describing what happens when you lift off the accelerator pedal and let the vehicle come to a stop without any additional intervention. Say for instance you are driving on an abandoned air field and have lots of room to play around. Get the vehicle to 60 mph and pull your foot off the accelerator pedal. The 1PD setting won't harvest as much energy as the pre-programmed regen setting native in Engage or Unbridled. (Whisper has zero regen so the vehicle will coast until it's kinetic energy runs out naturally due to rolling and wind resistance). Assuming level ground.

However, the theory applies even under the condition you describe. When you depress the physical brake pedal the regen level is increased. You have to really press down quite hard before the friction brakes are blended in. A driver with reasonable driving habits will almost always be able to maximize the recovered energy even when 1PD is turned off.

Conversely, with 1PD enabled......if the driver abruptly lifts off the accelerator pedal, the vehicle MAY blend in the friction brakes because it might interpret that as a panic stop. Not normal, but could happen. I believe the vehicle uses the on board ADAS features to assist 1PD with smooth operation so the car may in fact blend in the friction brakes even though the driver isn't aware of it. (not confirmed yet.....just a suspicion of mine at the moment......) Even then, it's a very slight difference and not significant enough to make a difference in overall range.

I am very curious to do some data capturing runs while descending a large mountain grade. I want to try it in 1PD and maintain a preset safe speed. Then do it again with 1PD off and holding speed with the brake pedal and then once more with L engaged and 1PD off. I am curious to see how much and how often the friction brakes are applied. I believe I can do that by data logging the ABS pressure but not sure yet. ?
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Blackbluff

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In my example above......I am describing what happens when you lift off the accelerator pedal and let the vehicle come to a stop without any additional intervention. Say for instance you are driving on an abandoned air field and have lots of room to play around. Get the vehicle to 60 mph and pull your foot off the accelerator pedal. The 1PD setting won't harvest as much energy as the pre-programmed regen setting native in Engage or Unbridled. (Whisper has zero regen so the vehicle will coast until it's kinetic energy runs out naturally due to rolling and wind resistance). Assuming level ground.

However, the theory applies even under the condition you describe. When you depress the physical brake pedal the regen level is increased. You have to really press down quite hard before the friction brakes are blended in. A driver with reasonable driving habits will almost always be able to maximize the recovered energy even when 1PD is turned off.

Conversely, with 1PD enabled......if the driver abruptly lifts off the accelerator pedal, the vehicle MAY blend in the friction brakes because it might interpret that as a panic stop. Not normal, but could happen. I believe the vehicle uses the on board ADAS features to assist 1PD with smooth operation so the car may in fact blend in the friction brakes even though the driver isn't aware of it. (not confirmed yet.....just a suspicion of mine at the moment......) Even then, it's a very slight difference and not significant enough to make a difference in overall range.

I am very curious to do some data capturing runs while descending a large mountain grade. I want to try it in 1PD and maintain a preset safe speed. Then do it again with 1PD off and holding speed with the brake pedal and then once more with L engaged and 1PD off. I am curious to see how much and how often the friction brakes are applied. I believe I can do that by data logging the ABS pressure but not sure yet. ?
I have driven a lot of city miles in Whisper mode and seen a good regen recovery displayed. Doing some research on your response led me to this
How Regenerative Braking Works in Electric Vehicles (circuitdigest.com). Good technical description of the way a motor can become a generator.
 

SnBGC

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I have driven a lot of city miles in Whisper mode and seen a good regen recovery displayed. Doing some research on your response led me to this
How Regenerative Braking Works in Electric Vehicles (circuitdigest.com). Good technical description of the way a motor can become a generator.
While in Whisper mode, lifting off the accelerator does not achieve any regen if in D (with 1PD turned off). The only way to get the car to regen in Whisper is to use/select any one or more of the following:
1. Brake pedal
2. 'L"
3. 1PD
 

nhdave

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I'm curious what data you have to support this. Logically I would think 1pd is either more efficient or the same.
 


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I'm curious what data you have to support this. Logically I would think 1pd is either more efficient or the same.
On 1pd but when brake coach shows the 100% power recoup. On way home some of the journey is at below 3kw/mile then on the last half of the journey there is more regen involved and then the efficiency goes to above 3.5lw/ mile. Just an observation.
 

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I'm curious what data you have to support this. Logically I would think 1pd is either more efficient or the same.
My information comes in large part from engineering studies performed by Magna International who is the firm that developed and wrote much of the software for the Focus Electric, Jaguar iPace and components for many other BEV manufacturers (including Tesla).

Without getting into the weeds too much....
It comes down to the maximum harvesting rate for the specific system. Smaller systems (motors, cables, inverters, battery pack etc) have a limited maximum sustained harvesting rate which is measured as a percentage of the output rating. Larger systems have a higher percentage, meaning they have the potential to harvest more energy compared to a smaller system.

There is a specific amount of energy required to bring a vehicle to a stop. That number is fixed. Most Electric Vehicles are capable of harvesting anywhere from 40% to 70% of that energy last time I looked (technology keeps improving so it's a moving target).

A vehicle with a smaller harvesting rate will require more time/distance to slow the vehicle without using the friction brakes. A vehicle with a larger EV drive system can do it in less time.....but it generates quite a bit of heat (more work always equals more heat....law of physics that always applies). So, while the total amount of recaptured energy is about the same.....the net amount that ends up in the battery is less because some of it is spent to deal with the heat generated (cooling the motor, electronics etc).

For the most part, 1PD systems were exclusive to EVs with larger motors, batteries etc. EVs with smaller systems did not have 1PD because it generates more heat and sometimes would blend in the friction brakes depending on driving style. An EV with a 19 kWh usable battery needs all the energy it can get so wasting a tiny bit of it on 1PD was undesirable. EVs with 88 kWh batteries can accept the small energy penalty since the driver will never notice any difference in range.

VW ID.4 doesn't use 1PD for this very reason.
Fleet vehicles don't use 1PD for a related reason but different concerns.

EDIT: One more bit of information to clarify. 1PD can yield exactly the same amount of energy returned to the battery compared to manually using the brake pedal assuming a reasonable driving style. My original example was for rapidly lifting off the accelerator and allowing the vehicle to go into max regen. Maximum regeneration equals maximum heat which equals waste. Responsible regeneration is less wasteful. I could have probably just led with this bit of information and saved us all a bunch of reading. :)
 
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I am very curious to do some data capturing runs while descending a large mountain grade. I want to try it in 1PD and maintain a preset safe speed. Then do it again with 1PD off and holding speed with the brake pedal and then once more with L engaged and 1PD off. I am curious to see how much and how often the friction brakes are applied. I believe I can do that by data logging the ABS pressure but not sure yet. ?
so, did you ever do these test runs? if so, what did you find out?
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