Regenerative Braking and RWD...

[Trace26]

Considering that some 80% of braking power comes from the front wheels and Slate is RWD, I can only assume that the regenerative braking capability will be rather minimal when compared to this. capability for AWD or FWD vehicles. Also, because of this, single pedal steering is unlikely. Is my understanding correct?

Most of my vehicles have been RWD manuals and used engine breaking far more than my brakes. So same basic concept, but instead of making heat and noise it's charging the battery.

 

[beatle]

You can still offer 1PD without blending in friction brakes. I had a 2015 Model S, and Tesla used induction motors all around, so regen tapered off to nothing as you get close to 5 mph. I always needed to manually "blend in" friction brakes to stop the car. Then my 2019 Model S had a permanent magnet motor up front, and regen continued all the way to zero for 1PD. Buuut, if it was cold out or your battery was full, Tesla limited regen and did not blend in friction brakes for a similar experience. Newer Teslas (and Rivian, and probably others) will blend in friction brakes for a similar deceleration experience regardless of the amount of regen available.

For Slate, I think they'll keep it simple and it'll be similar to the 2019 Model S since the Slate motor is permanent magnet. You'll be able to stop the truck with 1PD as long as you have sufficient regen available to do it, but that experience might change as it gets colder or your battery is full.

 

[AKrietzer]

Why does regen change if it's cold outside? I can understand if your battery is fully charged.

 

[ElectricShitbox]

Why does regen change if it's cold outside? I can understand if your battery is fully charged.

Charging is limited in the cold to protect the battery, so regen is too, since from the battery's perspective it's the same thing.

 

[AZFox]

When you jump off the throttle and onto the brakes because of drivers cutting you off, then you will feel the lurch and the repetition will make you nauseous.

I have a hard time believing this Barf Bag Lurching is an inescapable characteristic of 1PD.

 

[Tom Sawyer]

I know, my Tesla co workers have to do this and I end up getting nauseated.

So, you're a passenger for this and not the driver? I thought your experience was from the perspective of being the driver.

Edit: Maybe that's why you feel nauseated. Do you suppose the driver has any impact here?

There's probably a joke in there about a spouse's driving lol.

 

[Tom Sawyer]

Most of my vehicles have been RWD manuals and used engine breaking far more than my brakes. So same basic concept, but instead of making heat and noise it's charging the battery.

I'd hate to keep breaking engines far more than brakes! Sounds expensive.

 

[Trace26]

I'd hate to keep breaking engines far more than brakes! Sounds expensive.

That's what I get for using voice to text. Lol

 

[ElectricShitbox]

Engine breaking is why I bought my first EV

 

[metroshot]

So, you're a passenger for this and not the driver? I thought your experience was from the perspective of being the driver.

Edit: Maybe that's why you feel nauseated. Do you suppose the driver has any impact here?

There's probably a joke in there about a spouse's driving lol.

Both - as a driver and passenger - my cousin has a Tesla MY and I have also been in a X and S as well.

My coworkers have the 3 and Y and going to lunch in their cars have lurching effect that I am not used to.

I am just old and set in my ways so 2PD is the only way to drive....

 

[JoeBlow-Kokomo]

Considering that some 80% of braking power comes from the front wheels and Slate is RWD, I can only assume that the regenerative braking capability will be rather minimal when compared to this. capability for AWD or FWD vehicles. Also, because of this, single pedal steering is unlikely. Is my understanding correct?

No. And not sure why you think it would be that way? What does weight transfer under braking have to do with RWD or other? They ALL do that. So.........

 

[JoeBlow-Kokomo]

Hopefully the Slate has a slightly more rear-biased weight distribution. The RWD Model 3/Y is 48/52. This extra weight in the rear will allow for more regen strength.

Regen isn't like mashing the brakes hard. You aren't doing THAT kind of slowing that would transfer weight like that. You don't need to worry about weight in the rear for regen in normal conditions.

 

[beatle]

Yes, I'm aware of what regen feels like. It's not about worry, it's about being able to have more regen available when there is more weight over the wheels doing the regen.

And "normal conditions" can also be low traction scenarios where that additional weight is more apparent and needed to maintain a margin of safety.

 

[Shrink36s]

Yes, I'm aware of what regen feels like. It's not about worry, it's about being able to have more regen available when there is more weight over the wheels doing the regen.

And "normal conditions" can also be low traction scenarios where that additional weight is more apparent and needed to maintain a margin of safety.

I believe the Slate has a 50/50 weight distribution, so the weight is over the rear wheels equally as much as the front. I may be remembering that wrong, so don't quote me.

 

[Kopsis]

tl;dr - For the kind of braking you do in normal city driving, FWD/AWD/RWD has no significant effect on regen.

Time for some napkin math! Various studies put normal city driving braking (mostly stopping for intersections) right around 0.2 G average. It's reasonable to treat weight transfer as basically linear, peaking at around 80/20% with 1 G braking, so that means normal city stops will see an effective weight distribution around 56/44%.

Going back to that max 1 G braking, a 2300 kg Slate is going to have an overall traction budget of around 22.5 kN. Allocate 44% of that to the rear wheels (the weight ditribution in our 0.2 G stop) and you get almost 5 kN of available traction per rear wheel. But the 0.2 G stop only needs 2.3 kN per rear wheel, so you can generate all the 0.2 G stopping power from just rear wheel regen and still be using less than 1/2 of the available (good conditions) traction.

More aggressive stops need more force while at the same time reducing rear wheel traction by transferring more weight forward. So aggressive drivers may hit a point where they'd get more regen from a FWD/AWD EV. But if that's a high enough percentage of someone's stops to matter, I kind hope I never have to share the road with them (or be a passenger in their car).