If using the B mode to slow the car instead of the brakes, it must be increasing some wear on the motor bearings and transmission components ( and perhaps even the battery?) but I imagine the extra wear is quite small compared to what is already taking place with "normal" driving ( e.g., D mode). It will also take closer attention with the accelerator to operate the car in B mode than D mode if smoothness is goal.

 

If using the B mode to slow the car instead of the brakes, —

B and D both use the exact same amount of regen. There is no difference between the two. Pressing the brakes in D engages regen (not friction brakes). Letting go of the power pedal engages regen.

Only after a treshold for decelaration is exceeded are friction brakes (discs and drums) utilized.

As has been discussed ad nauseam.

 

It has been reported here, extensively , that driving in D mode is more efficient and better overall for range, "ad nauseam".
I am quite sure it is better, long term, for wear as well

 

It has been reported here, extensively , that driving in D mode is more efficient and better overall for range, "ad nauseam".

Which has absolutely nothing to do with the topic, but I guess you needed to move to goal posts.

Also the drive mode chnages only what triggers regen braking. Nothing more, nothing less. One mode is not more efficient than the other. Whether a more economical style of driving is easier to achieve in one than in the other is not a function of the drive mode. Your consumption does not magically drop by selecting D. It drops, if it does, because it changes your driving style.

I am quite sure it is better, long term, for wear as well

Your feelings on the matter that are based on nothing are hardly a relevant argument.

 

There is so little gear lash in our drivetrains that I suspect any interplay between power on, coasting, and decelerating leads to no measurable mechanical wear when we're talking about steady-speed cruising, and at the power levels we're talking about in this condition seem like they would be trivial – though I'd be curious to know the effect on the solid state switch gear.

However here's something to chomp on: under B mode, foot-off-pedal regen is some percentage of maximum regen. It's very possible, maybe even likely, for a B mode driver to use less regen than a D mode driver who is maybe a little to heavy on the brake pedal.

 

There is so little gear lash in our drivetrains that I suspect any interplay between power on, coasting, and decelerating leads to no measurable mechanical wear when we're talking about steady-speed cruising, and at the power levels we're talking about in this condition seem like they would be trivial – though I'd be curious to know the effect on the solid state switch gear.

However here's something to chomp on: under B mode, foot-off-pedal regen is some percentage of maximum regen. It's very possible, maybe even likely, for a B mode driver to use less regen than a D mode driver who is maybe a little to heavy on the brake pedal.

Part of the reason not all of the energy can be recovered during regen is that the momentum of the car is being transferred as increased pressure on the gear teeth and bearings as well as other bearings in the drivetrain. Then, of course, there are the losses due to motor/generator efficiency as well as losses from converting the electrical energy to the chemical reaction in the battery.

Just like with an ICE maximum efficiency can be reached with more coasting and less braking, no matter how you brake. Driving without braking, either with friction brakes or regen should be more efficient overall.

 

Well, no matter what you do, if you completely remove your foot from the accelerator, you get into regen. I stay in B mode because that's what I have been doing from the start and whenever I switch to D mode (by error from park), «it feels wrong».

From personal experience, I try to be accelerating (ie: no regen) or staying at constant speed most of the time, so there is no difference. When I get out of the highway, I turn off the cruise control and it decelerates significantly. If I'd be on D, then I'd have to press the brake. So it should be about equal.

Of course you'll be causing more «usage» if you accelerate hard and then decelerate hard because you are doing high speed stop and go. Then it would be best for wear and tear, and for range, to accelerate slowly and decelerate slowly... which is the same as with a gas car!

jf

 

Driven the same way (same roads at the same time, same speed, same rate of acceleration and deceleration) it won’t matter if you’re in B or D mode. Both use the motors for regeneration as much as possible. Doesn’t matter to the motors whether you press the brake manually or the car simulates it. Just drive in the mode you prefer and enjoy.

If you want to reduce wear and tear, do the same things you would do to improve efficiency… drive as smoothly as possible with as little slowing down and speeding up as possible, which is done by leaving lots of stopping distance in front of you and not accelerating hard. Also, don’t drive excessively fast. Same things that would get you better mpg in a gas car

 

Driven the same way (same roads at the same time, same speed, same rate of acceleration and deceleration) it won’t matter if you’re in B or D mode. Both use the motors for regeneration as much as possible. Doesn’t matter to the motors whether you press the brake manually or the car simulates it. Just drive in the mode you prefer and enjoy.

If you want to reduce wear and tear, do the same things you would do to improve efficiency… drive as smoothly as possible with as little slowing down and speeding up as possible, which is done by leaving lots of stopping distance in front of you and not accelerating hard. Also, don’t drive excessively fast. Same things that would get you better mpg in a gas car

This is the way. And, it is much easier in D than B.

 

It’s almost like drive mode matters **** all in itself…

 

I really don’t understand why there is so much confusion around B mode. As others have said it’s just a different way to control the acceleration and brake. Does Tesla only offer regen in one pedal mode or something? I’ve never driven one. It seems weird that so many people think regen only happens in B, in spite of the amount of regen being reported on the dash.

 

Teslas don’t have blended braking so you can’t turn off regeneration…

 

The exact same amount of attention you need in D to maintain a steady speed without further acceleration.

Extremely difficult, I know.

I would disagree with that. It's the reason VW, Audi and Porsche do not use stronger regen.

 

You can drive around ine an ICE with the engine running at 5-6K rpm and carefully modulate the accelerator you might be able drive smoothly or run the car a higher gear with 2-3K rpm and it will be much easier to drive smoothly without really any attention to pedal movement. Oh, and it is also more efficient.
Edit: I forgot to mention less friction, less engine wear, less motor mount wear, etc.

 

I don't know, and I will likely never know the answer....I use B exclusively, and if I ever make the mistake of starting in D mode I will stop and immediately change it to B.

 

I drive in B 100%, city or highway and rarely use cruise control.

I can see the OP's point about the challenge of keeping a steady speed in B, but only if there is no traffic and the road is perfectly level and straight. In that scenario, I could see where there might be more wear.

In reality, there is usually traffic and roads are not perfectly level and straight where I drive in New England and the Northeast part of the country. As such, it has become second nature (with no extra effort) to anticipate subtle changes in traffic and road conditions and feather the acclerator to maintain a fairly steady speed or change it as needed.

To me, this would be more difficult to do in in D where I would have to switch pedals more often than when using B. The delay in switching of pedals might result in the need for slightly more agressive braking (regen) or acceleration, thus actually resulting in more wear?

 

To me, this would be more difficult to do in in D where I would have to switch pedals more often than when using B. The delay in switching of pedals might result in the need for slightly more agressive braking (regen) or acceleration, thus actually resulting in more wear?

Another difference is that if all of your routine deceleration (to accommodate varying road conditions) is done in B mode, you KNOW that it was all done by regeneration. If you're in D mode, you have to be pretty good at feathering the Brake pedal to ensure that you stay in regenerative braking and don't enter the region where friction braking starts to burn away the energy.

In other words, one must learn to feather the Accelerator OR the Brake; TANSTAAFL.

 

There's an article today on this topic at insideevs.com although it's not clear - especially reading the comments - that the author's experiment was particularly valid, but he did use a VW Buzz for the test which might be of interest here.

It does seem like a pretty complex situation to analyze given the effects of resistance (wind, rolling, etc) and various efficiencies of power conversion inside the vehicle as well as the type of driving.

Personally I love the B mode, especially around town. This is my first "automatic" transmission car ever but it seems really intuitive. Unlike the opinion of many reviewers I don't mind having to move over to the brake pedal to do the final stop. That seems intuitive too. On the road I have generally turned things over to one of the cruise-control modes where it seems the car is doing the trade-offs by itself.

 

It does seem like a pretty complex situation to analyze

My take is that article missed the point.

There's an undeniable rule that energy conversion is not free.

This means that any time the car is regenerating, some of the energy it is converting away from forward motion being lost.

If the driver is absolutely flawless and only lets off the accelerator enough to regen when they need to slow down at a defined rate, then there's no penalty.

However if the driver is a "normal" human driver who drifts faster and slower a bit and occasionally regens to bleed speed when coasting is sufficient, then there is energy being lost, unrecoverable.

That's not saying regen is bad, just that it is more efficient to drive at a steady speed and if there's room to do so, coast to slow down.

This is a "most efficient" scenario: steady state highway travel. Mix the inefficiencies of traffic and stoplights and stops and starts in to the equation, where regen is inevitable and coasting is impractical, and the whole discussion takes a turn.