Regenerative braking and range

[coma24]

Regarding how 'hard' to employ regen to maximize efficiency, something Borski said to me many months ago has been living rent-free in my head ever since. Losses increase disproportionately to an increase in current.

As such, given the choice between BRIEFLY accelerating HARD (big needle deflection) vs LIGHT acceleration for a LONGER period of time, there will be more efficiency in the latter approach, and that ignores aerodynamic considerations, which only work further in our favor.

Similarly, on the regen side, I believe the same is true....when approaching a light where you're coming to a full stop, you have discretion as to when to start the speed reduction (since you don't have to take your foot completely off the accelerator). This means you can regen HARD (relatively speaking) for a SHORT period of time (big needle deflection to the left), or you can regen softly, for a longer period of time (small deflection). Based on the premise that higher charge or discharge rates have higher losses associated with them, you can achieve greater efficiency using more gradual speed reductions (ie, lighter regen for longer).

All of this to say, if you're looking to maximize your efficiency on any given drive, keep the needle as close as you can to the middle during acceleration and deceleration. For cruise, it is what it is for a given cruise speed, headwind component, temperature and incline.

 

[hmp10]

To me, one of the great advantages of driving a Lucid is that I can drive it pretty much like I have all the ICE cars I've had over the years: stomping on the accelerator when I'm feeling frisky, enjoying accelerating out of a bend, punching out of traffic clusters, keeping up a crisp pace on a long road trip. I never, ever get anywhere near the range limit in daily driving. And on road trips it might take longer to charge than to fill a gas tank, but I don't have to stop any more often.

This is not a 2011 Nissan Leaf we're talking about folks, where hypermiling and trying to squeeze every ounce of efficiency out of the powertrain is an imperative. It's a powerful sport sedan that can be gleefully driven like one.

 

[levsha]

Some cars have adaptive one pedal option now, MEB platform from VW group for example: they use radar, camera and maps data to figure out what to do: to coast or to do regenerative breaking (and how much). That should be the most efficient option if works properly.
I tried it in Škoda Enyaq a year ago. It worked, but still not always exactly how I wanted it to work.

 

[levsha]

First, from my 40+ years of ICE driving experience, I have always been a fan of utilizing neutral for improved gas mileage and (theoretically) reduced wear on parts of the ICE drivetrain.

It is less efficient in modern ICE vehicles to switch to neutral when coasting: when you are coasting on a gear then electronics stops injecting the fuel into cylinders completely for economy, but when you switch the gearbox to neutral then it has to inject some fuel to keep the engine running.

So . . . I have yet to use neutral (regularly) on my Air Touring . . .

Neutral on electric vehicles has almost nothing similar to neutral on ICE: the main motor is always connected to wheels in BEV. Some cars have a clutch to disconnect a secondary motor for efficiency, but in those vehicles it is usually enough to just keep the vehicle in "non-sport" mode and electronics will do that automatically.

 

[coma24]

To me, one of the great advantages of driving a Lucid is that I can drive it pretty much like I have all the ICE cars I've had over the years: stomping on the accelerator when I'm feeling frisky, enjoying accelerating out of a bend, punching out of traffic clusters, keeping up a crisp pace on a long road trip. I never, ever get anywhere near the range limit in daily driving. And on road trips it might take longer to charge than to fill a gas tank, but I don't have to stop any more often.

This is not a 2011 Nissan Leaf we're talking about folks, where hypermiling and trying to squeeze every ounce of efficiency out of the powertrain is an imperative. It's a powerful sport sedan that can be gleefully driven like one.

I agree 100% however I find it interesting to understand the nuances and how to get the most out of it if circumstances warrant. To be sure, the car is incredible when you let it rip, or more realistically, push it here and there to get off the line, get out of a gnarly freeway situation, etc.

Trust me, I'm not getting EPA over here!

 

[hmp10]

I agree 100% however I find it interesting to understand the nuances and how to get the most out of it if circumstances warrant.

I didn't mean to imply that such a discussion isn't warranted or even that trying to wring the most range out of the car might not be an interesting and even fun exercise. In fact, I've reined myself in on occasion just to see how many miles/kWh I can get if I'm really trying.

However, in case any forum newcomers encounter this discussion, I just didn't want them to think it arose from concerns about the car's range.

 

[Daniel2022AT]

Every vehicle can coast in which there are friction losses in the powertrain and driveline and tires on the road. These friction losses are not insignificant. When a EV is in regen mode it is coasting too, but in addition (and instead of friction braking which is 100% energy loss to heat), a significant portion of the energy is converted into recharging the battery. It really is pretty simple. Regen is a good thing, people.

The Kia EV6 I’m driving is pretty stupid because regen is enhanced only by pressing the brake pedal. I hope my Lucid is repaired soon.

 

[levsha]

Every vehicle can coast in which there are friction losses in the powertrain and driveline and tires on the road. These friction losses are not insignificant. When a EV is in regen mode it is coasting too, but in addition (and instead of friction braking which is 100% energy loss to heat), a significant portion of the energy is converted into recharging the battery. It really is pretty simple. Regen is a good thing, people.

Yes, it is simple. And regen is definitely good thing for case where you'd engage friction breaks instead - when you need to slow down significantly.
It's not so simple when increased the speed and now just want to come down to your cruising speed and continue: your goal is not just to slow down in this case, your goal is also to continue moving (and reach your destination at the end). And in this case you'll have to spend the energy on this friction anyway to move your vehicle. So you have two options then: slow down to your cruise speed slower by coasting without regenerative breaking and spend the kinetic energy directly on moving your vehicle, or slow down faster by recuperating and then spend the energy from your battery to move your vehicle. It's not so obvious which option will be more efficient: recuperation cycle has significant loses, mechanical friction loses are just linear function of distance (so you'll have to spend the same energy on them), but the air resistance goes up faster with the speed, so by slowing down faster you'll spend less energy on the air resistance.

 

[Daniel2022AT]

A key part of maximizing EV efficiency is driving technique. Using active cruise control, for example, obliviates the above example. Of course if you accelerate only to have to slow down there are significant efficiency losses. Not smart. That’s why a real time mi/kwh meter is extremely helpful to train drivers on the nuances to improve efficiency. If you don’t care about such things, that’s fine, just drive as you want.

Regen is always a positive contributor in combination with with a well designed braking and inverter controls system and a well educated driver.

Lucid has the best regen and inverter controls system I have experienced. Use it, don’t complain about it.

 

[illopp00]

I believe it does. It is more efficient to coast from 75 to 55 than to regen from 75 to 55 continuing at 55. Even if I'm wrong it's still tedious to drive smoothly with multiple passing situations on secondary roads. After every pass I would have to hold partial accelerator (throttle) to keep from constant hard accelerating/decelerating. Much nicer to have the option of coasting. At least there wouldn't be a decel head bob after each pass.
I realize this is a specific, low frequency, driving scenario, but I am driving 120 miles on secondary roads (each direction) every weekend during ski season.

Use Swift Mode with Standard Regen Much gentler when you take foot off accelerator pedal.

 

[DOBrien]

Does being in high versus standard regenerative breaking impact range at all? My guess is not much.

I've made some informal measurements in regen range recovery. I live at 9,000 ft and frequently drive to Rocky Mountain Airport down in Broomfield, CO at 5,700ft. It's a 28 mile trip. When I arrive at the airport the car has 7 more miles on the clock than what I departed with. I also have a frequent short 8-mile round trip that drops me from 9,000 to 7,400 (yea it's a steep descent). When I get back up to the house with that 8-mile trip, the car loses 10 miles of the range. Recovery is a little less than 80%. All of my driving is hilly, and many steep ones (Coal Creek Canyon area). I don't drive aggressively, use high regen. My overall efficiency for the last year (leaving a trip odometer un-touched) shows an overall 4.0miles per kwh which included winter driving in temps down to 20 below zero. I've had as much as 4.8 kwh with summer temps in the flatlands over a 40-mile course.

 

[Grewsome]

I do alot of driving on secondary roads. When passing a truck I'll accelerate from 45 to 80 during the pass. I'd like let the car slowly return to 60 (fastest I'll go on rural road posted at 50). Right now I get regeneration, which I don't need and its hurting efficiency. I'd rather have the option of turning it off.

Man, if someone passed me and then immediately throws up the brake lights, I'd be pissed.

 

[scal_air]

Man, if someone passed me and then immediately throws up the brake lights, I'd be pissed.

Lol, Welcome to Southern California Freeways

 

[blanchardmark]

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.

Same experience here. It’s a little disconcerting when you let up on the accelerator expecting to slow significantly but get the feeling of free-falling.

The mobile tech checked with engineering and they said it’s intentionally reduced on steep slopes to protect the power inverter from overheating. You can see how much it’s limiting regen by looking at the charging gauge - it only charges in the portion with a solid line.

 

[hmp10]

The mobile tech checked with engineering and they said it’s intentionally reduced on steep slopes to protect the power inverter from overheating.

That's an interesting new tidbit. I love how much you can still learn about how Lucids work on this forum.

 

[DOBrien]

I don’t know the physics, so I’m not going to pretend to be an expert. All I know is when I drive downhill from Nederland (8200 ft) to Boulder (5600 ft) on high regen, I end up with a few kWh MORE in my battery pack than when I started. That would not happen with coasting. I might end up using almost no energy that whole way down, but I wouldn’t be gaining energy.

I can't imagine not having good regen capability on this car. When I leave my home in Coal Creek Canyon (9,030 ft) heading for Colorado Springs I'm almost to Castle Rock before the miles remaining on the car equal what they were when I left. I get a good 30+ miles of driving out of that 3,500 feet of elevation loss.

 

[xponents]

Lol, Welcome to Southern California Freeways

Wait, what do you mean my daily office commute isn’t a Formula 1 race?