Model S regen

[Lyon]

I'm not sure that the Roadster and the S are doing the same thing when you take your foot off the "Go-Pedal".
The Roadster automatically makes the brake lights come on but the comments on the Model S are that there is a gyro that turns the brake lights on when appropriate?

The comment from the Tesla employee on our drive about the gyro controlling the brake lights in Model S was that Tesla had been using that system since the Roadster. I took that to mean that they used the same gyro to measure deceleration on the Roadster and put on the brake lights if needed.

 

[J in MN]

I took that to mean that they used the same gyro to measure deceleration on the Roadster and put on the brake lights if needed.

Well, one uses an accelerometer to measure acceleration, not a gyro. They probably use one of the accelerometers from the stability control system.

 

[Zextraterrestrial]

the only thing about regen is that I could have used more! I would like one w/ 120 or 100 (Kw/hr?) not just the 30 and 60 . I'm not sure if this was due to my fatass passengers (except the Tesla Navigator) or just my excess speed when using it.

 

[markwj]

I'm not sure that the Roadster and the S are doing the same thing when you take your foot off the "Go-Pedal".
The Roadster automatically makes the brake lights come on but the comments on the Model S are that there is a gyro that turns the brake lights on when appropriate?

The roadster doesn't turn on the brake lights if you just reduce pressure on the accelerator slightly, so it is not a simple on/off switch. It only comes on if there is a significant deceleration - and that sounds exactly like the ModelS approach. Works pretty well, and I'm glad I have it.

 

[gg_got_a_tesla]

the only thing about regen is that I could have used more! I would like one w/ 120 or 100 (Kw/hr?) not just the 30 and 60 . I'm not sure if this was due to my fatass passengers (except the Tesla Navigator) or just my excess speed when using it.

+1. I found (Standard, not Low) Regen to be fairly mild; the weight of the car and the fact that it's aimed at the mainstream audience may have something to do with the strongest available regen setting being relatively weak.

If technically feasible, Tesla, please do provide a stronger setting or two but continue to default to Standard.

 

[vfx]

+1. I found (Standard, not Low) Regen to be fairly mild; the weight of the car and the fact that it's aimed at the mainstream audience may have something to do with the strongest available regen setting being relatively weak.

If technically feasible, Tesla, please do provide a stronger setting or two but continue to default to Standard.

Was told that the S regen is actually stronger than the Roadster but the extra weight makes it feel ike less. And that the regen is at battery acceptable input limit. (which I only kinda believe sine the ACP Ebox had adjustable hard stop regen.)

 

[VolkerP]

If I'm in the car behind and the regen kicks in brake lights would be appropriate. I plan to use regen quite a bit instead of using my brake pedal, but the result is the same and I do NOT want anyone plowing into me.

Exactly!
As long as it is set properly, I don't see anyone having trouble with it.
I was curious as to what the opposing point of view is?

Some dumb EU regulations call for brake lights only lighting up if the driver presses the brake pedal. Tesla had to adapt the EU Roadster version and decreased the regen power Deceleration in an ICE with manual transmission in a low gear is a comparable issue. BMW did some experimental brake lights where the light intensity correlates with the braking pedal pressure applied. Drivers following behind got the signal in an instant, yet existing regulations forbid that. I agree that a change to regulations would be good, to allow the brake lights being controlled by a deceleration sensor. Perhaps widodh will set up yet another mass mailing to flood the appropriate EU regulation authority? :biggrin:

 

[jerry33]

the only thing about regen is that I could have used more! I would like one w/ 120 or 100 (Kw/hr?) not just the 30 and 60 . I'm not sure if this was due to my fatass passengers (except the Tesla Navigator) or just my excess speed when using it.

Regeneration is always going to be limited by the maximum input current the battery can take and the state of charge of the battery.

 

[Zorba]

BMW did some experimental brake lights where the light intensity correlates with the braking pedal pressure applied. Drivers following behind got the signal in an instant, yet existing regulations forbid that. I agree that a change to regulations would be good, to allow the brake lights being controlled by a deceleration sensor.

That reminds me that the brake lights on BMWs do flash when making an emergency stop, which I find a very useful feature

 

[Zextraterrestrial]

Regeneration is always going to be limited by the maximum input current the battery can take and the state of charge of the battery.

So you could get at least 90Kw regen then based on super charging I think

 

[brianman]

Regeneration is always going to be limited by the maximum input current the battery can take and the state of charge of the battery.

In the full sense, yes -- you can only capture as fast as the battery can accept.

Buy as far as decelerating (and just burning off the excess energy) even faster than the battery recharge allows, that's a theoretical option -- isn't it? Whether Tesla plans to have a setting for this (in any model), I have no idea.

 

[Doug_G]

I'm not sure that the Roadster and the S are doing the same thing when you take your foot off the "Go-Pedal".

The Roadster actually has a slightly complex algorithm. It's not based on pedal position!

It turns on the brake lights when the deceleration reaches a certain level - from observation, approximately "half".

It also turns on the brake lights immediately if you lift off quickly.

The Roadster's brake lights go out again when it switches over to "creep" mode.

The system works very well, and I really doubt they changed it for Model S.

 

[Zextraterrestrial]

I didn't feel much regen that I would have wanted brake lights go on for during my test drive - I downshift my automatics also - to 3rd for highway slowing and 2nd in city slowing

 

[jerry33]

In the full sense, yes -- you can only capture as fast as the battery can accept.

Buy as far as decelerating (and just burning off the excess energy) even faster than the battery recharge allows, that's a theoretical option -- isn't it? Whether Tesla plans to have a setting for this (in any model), I have no idea.

Me neither, but in most cars-with-batteries, as you get closer to a full charge the charging rate from regeneration will go down (The Prius will repeatedly spin the engine to use electricity to keep the battery from going over the limit as well as stopping the regeneration). Now this will probably never be an issue with the 85 kWh pack except for a short distance after a range charge (unless they make it so that if you did a standard charge it uses that as a cap), but it could possibly be an issue with the 40 kWh pack--particularly if you drive in a mountainous area.

 

[JRP3]

In the full sense, yes -- you can only capture as fast as the battery can accept.

Buy as far as decelerating (and just burning off the excess energy) even faster than the battery recharge allows, that's a theoretical option -- isn't it? Whether Tesla plans to have a setting for this (in any model), I have no idea.

Burning off excess energy as heat, you mean like the brakes do? :wink: Which gives me an idea, they could incorporate a braking system that uses the brakes to compensate for lack of regen on a full pack, so it would feel the same.

 

[brianman]

What I was trying to get at is this...

One of the concerns raised was that regen is "unpredictable" because if your battery is "above some threshold", the (regen) braking characteristics of the vehicle are different than otherwise. For something as important as braking, this is a reasonable concern. My point was that if the battery's charge rate prevents having consistent braking regardless of battery fullness, then perhaps regular brakes (or a computer in the frunk computing PI?) could use up the excess so that the driving feel is the same.

 

[JRP3]

That's what I was suggesting, integrate the brakes to eliminate the feeling of no regen. Or a large bank of resistors that come into play when the pack is full.

 

[strider]

Now this will probably never be an issue with the 85 kWh pack except for a short distance after a range charge (unless they make it so that if you did a standard charge it uses that as a cap), but it could possibly be an issue with the 40 kWh pack--particularly if you drive in a mountainous area.

The Roadster allows full regen after a full Standard-mode charge so I'm sure Model S would similarly not "cap" the capacity after a standard-mode charge.

I drive a Roadster every day and I can tell you that regen does vary based on speed (it backs it down as you slow) but it is very intuitive and you get used to it in minutes. You quickly learn whether you need to use the friction brakes or not. All of these extra system to "simulate regen" or whatever is additional complexity that isn't necessary. Just drive it

 

[jerry33]

The Roadster allows full regen after a full Standard-mode charge so I'm sure Model S would similarly not "cap" the capacity after a standard-mode charge.

I didn't really think they would, but I mentioned it because it was a possibility. And you're right. There is no need to simulate regen. You either have it or you don't.

 

[cinergi]

What I was trying to get at is this...

One of the concerns raised was that regen is "unpredictable" because if your battery is "above some threshold", the (regen) braking characteristics of the vehicle are different than otherwise. For something as important as braking, this is a reasonable concern. My point was that if the battery's charge rate prevents having consistent braking regardless of battery fullness, then perhaps regular brakes (or a computer in the frunk computing PI?) could use up the excess so that the driving feel is the same.

Regen power doesn't vary until either the pack is *very* cold or you've charged in range mode. Generally speaking, it'll behave the same every time.

I did talk to Tesla engineers that during the times when regen is reduced or disabled for those reasons above, the behavior of the car is different and that isn't particularly safe (and it's alarming unless you're expecting it). I'm not sure what they've done to improve this in the Model S, if anything.