Dissapointed in the 4xe Max Regeneration mode

Demonic

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That's not really how it would work under most driving scenarios.
You are reducing the inertia of the entire vehicle through your drivetrain, caused by friction of your tires and the road surface.
Unless the amount of braking overcomes the friction of your rear tires and it begins to slide, which I doubt would happen from regen.

The only scenario I could think of where AWD would aid this would be if the road surface was super slippery, and your rear tires are slipping with even the slightest resistance.
You're correct but I think also missing a bit of what he's saying. When a car stops, the majority of the breaking is done by the front wheels. This is intentional since the weight shifts forward, putting more weight on the front wheels, and allowing more braking power in the front before you reach the point where the tires would break loose and trigger the ABS. This is why the disc brakes are bigger on the front of the car. What Jahysea is saying, is that when the front drivetrain is not engaged - and therefore has no physical connection to the regen, the front wheels still need to do more than half the braking, and you'd therefore still have to be using the front brake pads. On a hybrid or electric car that is front wheel drive however, the front wheels will always be engaged and therefore you can achieve your increased front brake bias using the regen. If your regen is only able to take place through the rear wheels, then in order to maintain your increased front brake bias you have to rely more on the brake pads.





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Arterius2

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You're correct but I think also missing a bit of what he's saying. When a car stops, the majority of the breaking is done by the front wheels. This is intentional since the weight shifts forward, putting more weight on the front wheels, and allowing more braking power in the front before you reach the point where the tires would break loose and trigger the ABS. This is why the disc brakes are bigger on the front of the car. What Jahysea is saying, is that when the front drivetrain is not engaged - and therefore has no physical connection to the regen, the front wheels still need to do more than half the braking, and you'd therefore still have to be using the front brake pads. On a hybrid or electric car that is front wheel drive however, the front wheels will always be engaged and therefore you can achieve your increased front brake bias using the regen. If your regen is only able to take place through the rear wheels, then in order to maintain your increased front brake bias you have to rely more on the brake pads.
Except in this scenario, we aren't using brake pads to brake.
We are using a singular electric motor through the transmission to brake. When on max regen, the maximum braking force or resistance of this electric motor is constant regardless of how many wheels are driving it. Same amount of power is sent through the front wheels or rear, they both have go through a single point of entry, which is the transmission.

Again, the only time AWD would aid regen braking would be if the rear wheels are losing traction, and thus not sending maximum power through the drive-train, that's where the front wheels can help provide additional friction.

Under normal driving conditions, I do not believe the braking force of the electric motor would cause the rear wheels to lose traction.
 

Demonic

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Except in this scenario, we aren't using brake pads to brake.
We are using a singular electric motor through the transmission to brake. When on max regen, the maximum braking force or resistance of this electric motor is constant regardless of how many wheels are driving it. Same amount of power is sent through the front wheels or rear, they both have go through a single point of entry, which is the transmission.

Again, the only time AWD would aid regen braking would be if the rear wheels are losing traction, and thus not sending maximum power through the drive-train, that's where the front wheels can help provide additional friction.

Under normal driving conditions, I do not believe the braking force of the electric motor would cause the rear wheels to lose traction.
Brake bias is carefully calculated and engineered for the stability of the car while turning. You can’t just give a car 100% rear bias as long as you aren’t braking hard enough to break the rear tires loose or else going into a turn the weight transfer of the vehicle would be completely off and you’d spin out. You always need a significant amount of forward brake bias just to maintain stability in a turn.
 

tk23

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(Disclaimer: I had a BMW i3 that only had heavy regenerative braking, and now have a Chevy Bolt, which not only has a good max regeneration mode, but also has a paddle behind the steering wheel that when pulled gives you extra heavy regenerative braking which is great for when you're coming to a stop light and need that little extra breaking to stop without having to use the physical brake)

After a week with the 4xe I can't help but say that I am disappointed with the max regenerative braking mode. Besides the fact that it doesn't stay enabled when the car is turned off (unlike what the manual states) the actual regenerative braking itself is just way too wimpy. And this of course means I'm not getting as much charging back into the batteries as I could, and that I am using up my brake pads more than I should. (Now it is better than my friends RAV4 Prime which has no max regen mode - a dealbreaker for me)

In max regen the 4xe seems to operate differently depending on your speed. When cruising at highway speed when you lift off the pedal it barely slows the car. Compared to my Bolt I am finding situations where traffic on the interstate slows a little in front of me where on the Bolt I would just lift the gas pedal and I would slow down enough no problem, but with the 4xe it just doesn't slow enough and I find myself having to apply a little physical braking.

When going slower the 4xe does apply the regen more powerfully, but still not as much is my Bolt, even without using the paddle. I am finding that just coming to stops at traffic lights I am using my brake pedal more on the 4xe than the Bolt. Especially if you're coming in at a good clip like 50mpg, the fact that it barely slows you in the beginning and then still is not as powerful at the end means you're really using the brake pedal a lot more.

It's a shame because with such a small battery range I want as much regen braking as possible to get juice back into that battery. Plus it's awfully nice essentially not having to ever worry about changing your brake pads!

I hope this can be fixed with a software upgrade. Maybe giving us the option in the display of selecting how strong we want the max regen to be, and if we wanted to be of variable amount of regen or the same strength regardless of speed. I am sure it's all computer controlled, so should be something that can be easily implemented with a software upgrade.
does anyone know if pressing the brake pedal automatically engages the actual brakes? On my Taycan pressing the brake engages regen unless the amount of brake pedal pressure exceeds the amount of slowing the regen can provide. Only then are the actual brakes applied. The system is great and far more natural than an aggressive regen every time you lift off the gas. I haven’t driven a 4xe yet. Is there a regen gauge that you could monitor to see if hitting the brake pedal increases the energy return?
 

Arterius2

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Brake bias is carefully calculated and engineered for the stability of the car while turning. You can’t just give a car 100% rear bias as long as you aren’t braking hard enough to break the rear tires loose or else going into a turn the weight transfer of the vehicle would be completely off and you’d spin out. You always need a significant amount of forward brake bias just to maintain stability in a turn.
Sigh.. you are still thinking of braking with rotors and brake pads.
I already explained it plenty clear already. Here we go, one last time?:

Regardless of brake bias, the maximum braking potential of the electric motor is constant.
This isn't like brake pads where you can apply more force to it by squeezing it tighter.
In the case of regen braking, it's a very gradual and soft braking, think of it like engine braking. (Just imagine down-shifting using engine braking when you roll to a stop light, it works the same regardless of you are in 2wd or 4wd)

And I also mentioned that if the braking force exceeds that of the tire traction, you are losing braking potential. Sure, 4 rubbers on the ground will offer more braking potential than 2 rubbers, but like I said, I do not believe the regen braking force will exceed the rear tire's traction for braking potential on normal driving surfaces.

Brake biasing work on rotors and pads because you can apply more force on the brakes and maximize the braking potential. Because rotors and pads are designed to STOP your car and apply a much higher braking force than the potential traction of the tires.



If what I said went over your head, let's just leave it at that and call it a day.
 
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eLECTRICON

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(Disclaimer: I had a BMW i3 that only had heavy regenerative braking, and now have a Chevy Bolt, which not only has a good max regeneration mode, but also has a paddle behind the steering wheel that when pulled gives you extra heavy regenerative braking which is great for when you're coming to a stop light and need that little extra breaking to stop without having to use the physical brake)

After a week with the 4xe I can't help but say that I am disappointed with the max regenerative braking mode. Besides the fact that it doesn't stay enabled when the car is turned off (unlike what the manual states) the actual regenerative braking itself is just way too wimpy. And this of course means I'm not getting as much charging back into the batteries as I could, and that I am using up my brake pads more than I should. (Now it is better than my friends RAV4 Prime which has no max regen mode - a dealbreaker for me)

In max regen the 4xe seems to operate differently depending on your speed. When cruising at highway speed when you lift off the pedal it barely slows the car. Compared to my Bolt I am finding situations where traffic on the interstate slows a little in front of me where on the Bolt I would just lift the gas pedal and I would slow down enough no problem, but with the 4xe it just doesn't slow enough and I find myself having to apply a little physical braking.

When going slower the 4xe does apply the regen more powerfully, but still not as much is my Bolt, even without using the paddle. I am finding that just coming to stops at traffic lights I am using my brake pedal more on the 4xe than the Bolt. Especially if you're coming in at a good clip like 50mpg, the fact that it barely slows you in the beginning and then still is not as powerful at the end means you're really using the brake pedal a lot more.

It's a shame because with such a small battery range I want as much regen braking as possible to get juice back into that battery. Plus it's awfully nice essentially not having to ever worry about changing your brake pads!

I hope this can be fixed with a software upgrade. Maybe giving us the option in the display of selecting how strong we want the max regen to be, and if we wanted to be of variable amount of regen or the same strength regardless of speed. I am sure it's all computer controlled, so should be something that can be easily implemented with a software upgrade.
I agree. I am also disappointed with the regen. This is my first hybrid with nothing to compare to however it didn't Impress me. I don't get any charge back. I thought it was a malfunction at first.
 

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There is a noticeable difference to me between max regen and normal. It depends on the situation how much braking I needed but I've had plenty of situations in town with my couple hours of driving where I didn't use the brake except to complete the actual stop. I think the expectations of people are too high for a PHEV WRANGLER. This isn't even close to anything like a EV car. The wrangler, just like in several other situations, isn't a great vehicle compared to others. I personally think they have done a pretty darn good job with delivering a vehicle which is still very much a wrangler with all the faults (seems people love them) of a wrangler. The PHEV isn't for everyone. You need to drive a certain amount of miles with electric to get a certain gas mileage. Luckily, I'm one of the group who only cared about HP/Torque numbers and I'm happy so far. I also happen to do a lot of driving within its electric only range.
 

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For reference, Power Flow Chart under the hybrid page when decelerating in 2H and 4HAuto. Note that is distinctly changes the image to include the front wheels helping to charge when in 4HAuto.

1618486256815.png

1618486277925.png
 

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During regen, the electric motor becomes a generator driven by the vehicle’s momentum turning the driveshaft. So it makes sense that with the front axle engaged the front tires would be contributing.

However the electric motor only has so much magnetic resistance. That limits the rate at which the Jeep’s momentum can be captured. In 4WD, momentum would be getting contributed by all 4 wheels turning the driveshaft vs just the rears. So yes it would be 50/50 balanced. The thing is that the overall rate of momentum capture is low and steady. So traction issues don’t come into play.

I think thats the point others are trying to make regarding 4WD vs 2WD being borderline irrelevant to regen performance. It’s a very different situation from traditional brakes.
 

beaups

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Sigh.. you are still thinking of braking with rotors and brake pads.
I already explained it plenty clear already. Here we go, one last time?:

Regardless of brake bias, the maximum braking potential of the electric motor is constant.
This isn't like brake pads where you can apply more force to it by squeezing it tighter.
In the case of regen braking, it's a very gradual and soft braking, think of it like engine braking. (Just imagine down-shifting using engine braking when you roll to a stop light, it works the same regardless of you are in 2wd or 4wd)

And I also mentioned that if the braking force exceeds that of the tire traction, you are losing braking potential. Sure, 4 rubbers on the ground will offer more braking potential than 2 rubbers, but like I said, I do not believe the regen braking force will exceed the rear tire's traction for braking potential on normal driving surfaces.

Brake biasing work on rotors and pads because you can apply more force on the brakes and maximize the braking potential. Because rotors and pads are designed to STOP your car and apply a much higher braking force than the potential traction of the tires.



If what I said went over your head, let's just leave it at that and call it a day.
I think you are missing the point. Braking a vehicle by the rear wheels greatly reduces braking ability and potentially poses a threat to lose control as the traction decreases proportionate to the braking force, which is the opposite of what happens when braking with the front wheels.

Regardless of if you are using the drivetrain/regen or traditional pads and rotors the weight will always shift forward to the front of the vehicle when braking. The harder you brake (again, regardless of the braking method), the more transfer occurs. And when the load is transferred forward, the load (and thus, available traction) is removed from the rear.

Go out on a wet day and pull the parking brake handle hard enough to cause the vehicle to slow down slightly aggressively and I think you’ll see why the regen braking is dialed down. Rear tire traction and weight transfer doesn’t care if you are using the drivetrain or rotors.
 

blueweb

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Stupid question: Does the ICE in the 4Xe have an alternator, BSG, or use the transmission's electric motor for all charging & warm starts? Is there still a 12V lead acid battery & traditional starter for cold-climate starting?
This video should answer some of your questions

 

Arterius2

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I think you are missing the point. Braking a vehicle by the rear wheels greatly reduces braking ability and potentially poses a threat to lose control as the traction decreases proportionate to the braking force, which is the opposite of what happens when braking with the front wheels.

Regardless of if you are using the drivetrain/regen or traditional pads and rotors the weight will always shift forward to the front of the vehicle when braking. The harder you brake (again, regardless of the braking method), the more transfer occurs. And when the load is transferred forward, the load (and thus, available traction) is removed from the rear.

Go out on a wet day and pull the parking brake handle hard enough to cause the vehicle to slow down slightly aggressively and I think you’ll see why the regen braking is dialed down. Rear tire traction and weight transfer doesn’t care if you are using the drivetrain or rotors.
I think you are missing the point that nobody is talking about hard braking to the point of locking up the wheels till you lose traction of your tires. (And if you ACTUALLY read what I said, I made a specific comment about wet traction, so I assume you have not)

We are talking about a gentle coasting and rolling to a stop which is what the max regen really does.

If you have ever down shifted by using engine braking to stop you would know what I'm talking about. (If you have not, try it yourself, if you got an automatic, put your shifter into M and give it a go.)

Engine braking is EXACTLY like regen braking except you convert all that kinetic energy into heat instead of electricity.

There is no discernable difference between engine braking with 2wd and 4wd. Plenty of 2wd cars on the road using engine braking for a long time now. In fact, the cruise control inside these Jeeps use engine braking to slow down when you cruise on the highway in 2wd.
 
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Dusty

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does anyone know if pressing the brake pedal automatically engages the actual brakes? On my Taycan pressing the brake engages regen unless the amount of brake pedal pressure exceeds the amount of slowing the regen can provide. Only then are the actual brakes applied. The system is great and far more natural than an aggressive regen every time you lift off the gas. I haven’t driven a 4xe yet. Is there a regen gauge that you could monitor to see if hitting the brake pedal increases the energy return?
Oh, don't compare what Jeep engineers came up with to what Porsche engineers created. That's like asking a High School baseball team to play a MLB team. It's just not the same game. Porsche 919s won Le Mans with hybrid LMP1 cars thee years in a row. They know something about EV. Jeep hasn't done anything like that. There just isn't enough engineering depth.
 

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