Regenerative braking and range

[Pittsburgher]

For what it’s worth, coasting in neutral on a downgrade is illegal in many states.

“The driver of a motor vehicle when traveling on down grade upon any highway shall not coast with the gears of such vehicle in neutral.”

the range gained by trying such tricks is minimal at best and not worth the bother.

Not unlike BMW making complex alternators and "smart" battery charging electronics that result in the aforementioned $700 battery replacement. Assuming a car battery last 7 years, what are the MPG gas savings and extended fuel savings for that 7 year period ? If I had to guess, probably "minimal at best, and not worth the bother" (unless you consider the $ made by BMW and their dealerships vs. a normal $150 battery replacement requiring 15 minutes labor). Obviously a pet peeve of mine ! !

That said, still curious if anyone knows the mechanics and/or electronics behind our Lucids "neutral" ? Is there a clutch that disengages motor(s) from drivelines/axles ? For dual motor cars (all but Pure) are there 2 clutches ? Maybe some means other than a clutch - like applying just enough energy into the motors to make them feel like they are in neutral (like an electronic version of feathering the accelerator to be in between accelerating and regen ?

IIRC, electric motors have a decent amount of internal resistance when not being driven (because of the magnets) . . . ie if one goes to manually turn an "unplugged" electric motor it takes significant effort to overcome the force of the magnets. . . no ?

 

[hmp10]

IIRC, electric motors have a decent amount of internal resistance when not being driven (because of the magnets) . . . ie if one goes to manually turn an "unplugged" electric motor it takes significant effort to overcome the force of the magnets. . . no ?

I don't know anything about your other questions, but motor "drag" from magnets is a characteristic of permanent magnet motors (which Lucid uses) but not of induction motors (which Tesla used to use but are now either replaced by permanent magnet motors or used on one axle with a permanent magnet motor on the other).

Each technology has its advantages and disadvantages, but permanent magnet motors are more efficient in most use cases for EV propulsion. However, they experience an effect called "cogging" which can make the car feel as if it's cycling through surges at low speeds. One of the reasons Tesla used a permanent magnet motor on one axle and an induction motor on the other was to gain some of the efficiencies of the permanent magnet motor but to enable low-speed propulsion of the car without cogging effects by disengaging the permanent magnet motor and using only the induction motor.

One of the motor breakthroughs Lucid made with the Air was to reduce significantly the cogging effect in permanent magnet motors, thus allowing them to be used on both axles for their greater efficiency.

 

[Buffalo Bob]

I don't know anything about your other questions, but motor "drag" from magnets is a characteristic of permanent magnet motors (which Lucid uses) but not of induction motors (which Tesla used to use but are now either replaced by permanent magnet motors or used on one axle with a permanent magnet motor on the other).

Each technology has its advantages and disadvantages, but permanent magnet motors are more efficient in most use cases for EV propulsion. However, they experience an effect called "cogging" which can make the car feel as if it's cycling through surges at low speeds. One of the reasons Tesla used a permanent magnet motor on one axle and an induction motor on the other was to gain some of the efficiencies of the permanent magnet motor but to enable low-speed propulsion of the car without cogging effects by disengaging the permanent magnet motor and using only the induction motor.

One of the motor breakthroughs Lucid made with the Air was to reduce significantly the cogging effect in permanent magnet motors, thus allowing them to be used on both axles for their greater efficiency.

Interesting! I do a lot of low speed slogging through my building's parking garage, and have never noticed the slightest bit of 'cogging'... while I'm 'slogging'.

 

[AlignTrex]

I like regen braking, but it is making my leg weak!

When I owned a manual BMW both of my legs were strong. Then when I went to automatic only my right leg was getting a workout shifting between accelerator and braking pedal.

Now, I barely have to move any of my legs! Soon, I won’t even have to move my arms. Eventually I’ll have chicken legs with Trex arms!

 

[dcase99]

I'm curious about regen and seeing what it takes to show an increase in the battery percentage. Has anyone seen the percentage go up? I live in TX, so there are not that many hills to coast down, and when there are, they aren't that long, so unless I go somewhere else, I imagine I won't see it but have others? If so, how long does it take before the increase shows up? I know many variables exist, so I'm not looking for anything exact; I'm just curious.

 

[xponents]

I'm curious about regen and seeing what it takes to show an increase in the battery percentage. Has anyone seen the percentage go up? I live in TX, so there are not that many hills to coast down, and when there are, they aren't that long, so unless I go somewhere else, I imagine I won't see it but have others? If so, how long does it take before the increase shows up? I know many variables exist, so I'm not looking for anything exact; I'm just curious.

I'm assuming @joec would be well placed to answer this question?

 

[Buffalo Bob]

I'm curious about regen and seeing what it takes to show an increase in the battery percentage. Has anyone seen the percentage go up? I live in TX, so there are not that many hills to coast down, and when there are, they aren't that long, so unless I go somewhere else, I imagine I won't see it but have others? If so, how long does it take before the increase shows up? I know many variables exist, so I'm not looking for anything exact; I'm just curious.

I was on a return trip through Payson, AZ on the way to metro Phoenix. I charged in Payson, and reset my trip computer wondering how the long downhill would affect my miles per kWh. Payson is about 3,900 feet higher than Phoenix. One interesting thing is that while the trip computer is continually computing the true miles/kWh, it will not show anything higher than 6.2 miles/kWh on the display. I'm not sure why, as it's not like there's no room to display a higher figure. That said, if you suddenly shift from a long downhill to a long uphill, the 6.2 miles/kWh figure will not change until the true figure drops below 6.2 miles/kWh. I ended the 81 mile trip at 5.6 miles/kWh.

 

[segbrk]

I'm curious about regen and seeing what it takes to show an increase in the battery percentage. Has anyone seen the percentage go up? I live in TX, so there are not that many hills to coast down, and when there are, they aren't that long, so unless I go somewhere else, I imagine I won't see it but have others? If so, how long does it take before the increase shows up? I know many variables exist, so I'm not looking for anything exact; I'm just curious.

I drive in the "mountains" of Virginia currently and even here I've seen the charge go up significantly on a descent. It's been a while, but I recall gaining as much as 10% coasting down one of our (not very tall) mountains. There is a limit to how much energy regen can put back into the battery which depends on temperature and state of charge, so it'll vary. I imagine you might even be over that limit riding down from a steep pass, so a longer more gradual descent is probably more efficient.

 

[joec]

I'm assuming @joec would be well placed to answer this question?

Yeah. It all depends on how much of a decline, how far you are declining, and how you feather the throttle to maximize your regen. But there are lots of places in the Colorado mountains where I’ve gained four or five percentage points by the time I get to the bottom.

 

[coma24]

I experienced 'partial regen' today with SOC 94% (breakfast at diner took longer than expected so I ended up with a higher charge than expected at the EA station).

There was no annunciation that regen was compromised (2.2.10), but it certainly got my attention at the bottom of a steep driveway leaving the shopping center. At the next traffic light, though, I experienced full regen breaking (I was paying close attention at that point as you might imagine).

I was under the impression that anything other than full regen would result in a message to the driver with the newer software as a result of recent changes...evidently not, at least not for 'partial regen'.

 

[xponents]

I experienced 'partial regen' today with SOC 94% (breakfast at diner took longer than expected so I ended up with a higher charge than expected at the EA station).

There was no annunciation that regen was compromised (2.2.10), but it certainly got my attention at the bottom of a steep driveway leaving the shopping center. At the next traffic light, though, I experienced full regen breaking (I was paying close attention at that point as you might imagine).

I was under the impression that anything other than full regen would result in a message to the driver with the newer software as a result of recent changes...evidently not, at least not for 'partial regen'.

@mcr16

 

[segbrk]

I experienced 'partial regen' today with SOC 94% (breakfast at diner took longer than expected so I ended up with a higher charge than expected at the EA station).

There was no annunciation that regen was compromised (2.2.10), but it certainly got my attention at the bottom of a steep driveway leaving the shopping center. At the next traffic light, though, I experienced full regen breaking (I was paying close attention at that point as you might imagine).

I was under the impression that anything other than full regen would result in a message to the driver with the newer software as a result of recent changes...evidently not, at least not for 'partial regen'.

It's a spectrum. It's not "regen off" or "regen on," it's "how much energy can the battery take right now?"
They have to draw the line somewhere, and it doesn't make sense for that line to be at 100% of what the battery could theoretically take. It fluctuates all the time depending on temperature, not just state of charge, and the difference is minimal enough that we don't notice.

That said, I do agree the threshold is still too high. I, too, have seen significantly reduced regen without getting the warning.

 

[Buffalo Bob]

So, here's an interesting math question for you... On a 100 mile downhill trip, how many miles per kWh would you have to generate in order to end your trip using none of the kWh you started with? Hint: I must be one hell of a hill!

 

[segbrk]

Also for what it's worth, the Home Assistant integration graphs regen as you drive. It only samples every 15 seconds, so it won't catch everything, but the highest regen charge rate I've seen is about 85kW. Not bad.

 

[coma24]

It's a spectrum. It's not "regen off" or "regen on," it's "how much energy can the battery take right now?"
They have to draw the line somewhere, and it doesn't make sense for that line to be at 100% of what the battery could theoretically take. It fluctuates all the time depending on temperature, not just state of charge, and the difference is minimal enough that we don't notice.

That said, I do agree the threshold is still too high. I, too, have seen significantly reduced regen without getting the warning.

That's fantastic info, thank you. The spectrum makes sense, however, from a safety standpoint, if the regen breaking is ANYTHING other than what would be expected when it's fully working, I would expect an annunciation, especially knowing that annunciations of that nature exist. Knowing this is the current state of affairs, though, I'll be on the lookout for it in the rare cases where I'm leaving a charger with such a high SOC. Honestly, I was a little surprised NOT seeing the annunciation the moment I left the station...I was proactively looking out for it. Not seeing it gave me the false sense that I'd 'definitely' have the expected regen, which made for an interesting circumstance at the 4-way stop at the bottom of said hill. I transitioned to the brake pedal soon enough and stopped normally, but I was caught off guard for about a second there.

 

[borski]

That's fantastic info, thank you. The spectrum makes sense, however, from a safety standpoint, if the regen breaking is ANYTHING other than what would be expected when it's fully working, I would expect an annunciation, especially knowing that annunciations of that nature exist. Knowing this is the current state of affairs, though, I'll be on the lookout for it in the rare cases where I'm leaving a charger with such a high SOC. Honestly, I was a little surprised NOT seeing the annunciation the moment I left the station...I was proactively looking out for it. Not seeing it gave me the false sense that I'd 'definitely' have the expected regen, which made for an interesting circumstance at the 4-way stop at the bottom of said hill. I transitioned to the brake pedal soon enough and stopped normally, but I was caught off guard for about a second there.

For what it’s worth, when I picked up my loaner at 100% (I do not know why they charge every car to 100% lol; nobody is driving 500 miles from a service center, but I guess it’s free energy) it displayed the “regenerative braking limited” message at the beginning of the drive, but then it went away a few seconds later. Is it possible you missed it?

Or maybe 94% is right on the cusp. Not sure.

 

[Pragmatic]

I have had a loss of regen at much less than 80%. Parking near the top of a hill plugged into a 120v outlet for two days and charged to close to 80%.
Leaving the Lodge I drive down a hill that varies between 5% and 14% grade down. It is a winding road where I accelerate to 40 (pressing accelerator but using little power) and slow quite quickly to 15 (using mostly regen). This is a steady down hill for approximately 10 miles with a total elevation loss of 1500 feet.
Not an alot of total elevation but fairly steep, steady and alot of drastic slowing events. Usually just before town I'll slow for the last switchback and have no regen.

 

[coma24]

For what it’s worth, when I picked up my loaner at 100% (I do not know why they charge every car to 100% lol; nobody is driving 500 miles from a service center, but I guess it’s free energy) it displayed the “regenerative braking limited” message at the beginning of the drive, but then it went away a few seconds later. Is it possible you missed it?

Or maybe 94% is right on the cusp. Not sure.

Good point, I'll try a test at home in similar weather conditions and see.

 

[borski]

I have had a loss of regen at much less than 80%. Parking near the top of a hill plugged into a 120v outlet for two days and charged to close to 80%.
Leaving the Lodge I drive down a hill that varies between 5% and 14% grade down. It is a winding road where I accelerate to 40 (pressing accelerator but using little power) and slow quite quickly to 15 (using mostly regen). This is a steady down hill for approximately 10 miles with a total elevation loss of 1500 feet.
Not an alot of total elevation but fairly steep, steady and alot of drastic slowing events. Usually just before town I'll slow for the last switchback and have no regen.

Wait, what? I'm not sure I understand what you mean by 'had a loss of regen'.

At 80% or below, it should have zero issue regenerating energy from the brakes. Of course, if you're going downhill, it's already going to be doing that, and so regen may feel lighter than it would if you were on a flat road, as you have gravity helping you regen, rather than fighting against it.

But the regen is definitely going to be at max at that SOC. Unless I'm misunderstanding something.

 

[Pragmatic]

It seems you are misunderstanding what I'm trying to convey.
After 5 or so miles of driving with many larger decreases in speed (45 mph to 15 mph ) combined with a fairly steady decent 5% to 10% with a peak 24% (according the a popular bicycling web site) negative grade, I've noticed a decrease in regen. This will occur at one of the less steep curves near the bottom where I will get significantly less braking effect.
This has never happened more than once on a trip down the hill, but it has happened on three separate trips down the hill.
The first two times I thought I was misjudging how the car was reacting. But after the third time I am sure there is less braking action. This never happened during winter ski season. It did happen during spring skiing when temperatures were in the 60s.
I will likely not be making this trip with the Lucid again until December (ski season). Most trips in the summer I need to transport equipment (cement mixer, scaffolding, etc) that require the pickup truck.
I drive this hill 12 to 20 times a year (and have for the last 25 years). So I'm very familiar with the curves and pitches and do not believe I am misreading the situation.