Regenerative Braking Improvement At Low Temperatures Means What Exactly?

[gavine]

Does this only apply to the 90 and 70 batteries? Perhaps Tesla realized that the newer battery composition is more tolerant to higher kw charging at cold temps so they allow more sooner. Does this improvement show-up on 60 and 85's?

EDIT: Maybe that's what the ESP2 vehicles means?

 

[llavalle]

[...]Does this improvement show-up on 60 and 85's?[...]

Yup. It' in the release notes for my 85D.

 

[scaesare]

I had hoped that it would also improve the IC display of regen limiting.

The yellow dashed limiting-line always appears to be at a power level greater than what the car can achieve when temp limited (i.e. limit line at 30KW, and can only max regen to 20-25 or so).

Other times, the limit-line disappears completely, as if the limit has been removed, yet I'm still capped at 45KW or so.

From Ingineer's comments in wk057's hacking/teardown thread it's clear that the drive inverter dictates the limit based on BMS temp info and informs the IC what that limit is... so somebody is either not reporting or displaying correctly...

 

[Andyw2100]

Regenerative braking at low temperature has been improved for the way you drive.

Really? What if I drive and always have a foot on either the accelerator or the brake pedal, never giving the car the chance to utilize regenerative braking? Is it improved? What if I'm using the car only to drag race, putting the car on a trailer to take it to and from the track, and never doing anything else with it other than drag racing? How is the regenerative braking improved for me then?

Yes, those are ridiculous examples, but I'm using them to make my point that without knowing how the feature has been improved we can't make complete use of the improvement, and that the blanket statement is simply not sufficient.

My experience has been that more re-gen is allowed sooner than before. Although I wouldn't expect this to happen with range mode on.

Why wouldn't you expect this to happen with range mode on? With range mode on the pack is not heated. So are you actually suggesting that what is happening is that more power is being used to heat the pack sooner with range mode off, and that is the reason for more regen braking sooner?

This points to another example I didn't make in my response to mspohr above. If the only improvements exist with range mode off, then that would be a very realistic example of how the improvements do not apply to the way I drive because I always drive with range mode on.

As a Tesla enthusiast I am happy with any improvements to the car. Just make sure it is really an improvement.

Not being an engineer, I don't care about the specifics. Unless I need to do something, which here clearly is not the case.

So I am just happy and enjoy. For me it yould have been ok not even to mention it. Do you guys and gals really think they are informing you about each and every update to the car? Elon said they change 10 to 20 things a week. They won't tell you and they don't need to.

Maybe Tesla could offer info to the technically inclined. Got to find a proper platform for that (a TMC talk?). I can understand some users craving for more details and more technicals. But equally I understand the company not handing those out - for a thousand reasons.

But please don't bug me with more information than I need.

No one is suggesting that Tesla inundate people who don't want it with information that they don't need. But when a core feature of the car like regenerative braking is improved I think it is a fair request to want to know how it was improved so that we can take advantage of that improvement.

You say that in this case it is clear you don't need to do anything to take advantage of the change, but I don't know that. I may have to drive with range mode off. You may have to charge with range mode off. Or I may have to charge with range mode on. We just don't know, and there is no reason for us not to know.

I didn't even bother to read through the entire release notes, and didn't realize there is a blurb about this.

Improved regen at low temps? Great, now let me just drive.

No one is stopping you from "just driving." But I'm sure you'll understand why I don't give a lot of credence to your lack of interest in getting additional information about an undocumented feature if you readily admit that you didn't even read the release notes Tesla actually wanted you to read before using the new firmware.

why not drive the car and see if you can work out what is different?

Did you read the letter I sent to Tesla, included in the opening post? I have driven the car and have not noticed any change. That was one of the reasons I wrote and one of the reasons I started this thread.

 

[Lex]

Does this only apply to the 90 and 70 batteries? Perhaps Tesla realized that the newer battery composition is more tolerant to higher kw charging at cold temps so they allow more sooner. Does this improvement show-up on 60 and 85's?

EDIT: Maybe that's what the ESP2 vehicles means?

So ya, what exactly are ESP2 vehicles ? Perhaps it means dual motor models ? (ESP = Electronic Stability Program but I am guessing that's not it). Google is boggled too.

As for the idea that the newer packs are more durable, ahem well mine is at the factory for diagnosis, and when it threw the codes it was early morning on a cold day, so I was actually concerned that my datapoints might make future cold regen worse for everyone else.

As for demanding to know what Tesla meant, this one was just a suggestion of a minor improvement so I'd suggest not pressing the matter or else they may in the future just decide to not tell us as much to avoid commotion.

Not knowing how much weight you're adding with an accessory, on the other hand, as vdiv reported above is something I'd certainly expect them to supply, and not "explain away". That worries me.

 

[Andyw2100]

As for demanding to know what Tesla meant, this one was just a suggestion of a minor improvement so I'd suggest not pressing the matter or else they may in the future just decide to not tell us as much to avoid commotion.

I don't think there is anything in my correspondence with Tesla, or even in this thread that would indicate that I am "demanding" to know anything.

Tesla included a vague statement in the release notes about improving one function of the car, and I'm simply asking how it has been improved.

I realized that an answer was not likely to come from Tesla, so I thought it would be useful to discuss things here, to see if we could come up with the answer ourselves. I honestly did not expect to have to defend my position of having asked what I thought was a very reasonable question of Tesla.

 

[AnOutsider]

I honestly did not expect to have to defend my position of having asked what I thought was a very reasonable question

Silly Andy.

 

[Andyw2100]

Silly Andy.

Heh!

 

[scottm]

I have a lot of cold temperature where I live.

What I have noticed with this minor update is that regen seems to pull down the speed more firmly and will actually hit a yellow bar limiter, whereas regen wasn't previously hitting the yellow limiter. I would find myself hoping that it could hit the end of its limited scale. Began wondering just how fast would I have to be traveling to make it so?

Before this update, if I had a yellow bar on regen due to cold temps... driving from high speed (lots of inertia) and letting off the go pedal never made regen green sweep hit the yellow limit. It would stop short. The visual effect appeared to be proportionally scaling back the whole regen potential. e.g. if regen was showing capped at 60% (yellow line) then the car would also only seem to be using about 60% of that remaining limited sweep space... and never hit the yellow limit. It was like a double limitation: seeing you upper limit capped, and then seeing your actual use of that capped space was never fully exploited.

Being Tesla, the "improvement" could be they adjusted the yellow line lower bringing it into visual alignment with where the green sweeper ends. A UI fix only. And there's not any energy gain or algorithm tweak or such... just looks more correct. If it's something like that, then it would be a big let-down going all the way to engineering to get an answer back with no meat to it like that. "We fixed a UI bug."

Now it hits the yellow limit. I say it "seems" to be pulling the car down more firmly. But this could be only psychological, because I'm seeing the regen use up all the available space, whereas before I was seeing that it wasn't.. and therefore thought it could do regen more firmly but wasn't. If that makes any sense?

 

[AWDtsla]

I have a lot of cold temperature where I live.

What I have noticed with this minor update is that regen pulls down speed more firmly. (Applies more braking power.)

It seemed that before this update, if I had a yellow bar on regen due to cold temps... and even from high speeds of travel (lots of inertia)... letting off the go pedal never made regen green sweep hit the yellow limit. It seemed to be proportionally scaling the sweep. Like if regen was capped at 60% (by virtue of showing the yellow line there) then the car would also only use about 60% of the remaining limited sweep space... and never hit the yellow limit.

Now it hits the yellow limit.

Being Tesla, the "improvement" could also mean they adjusted the yellow line to a lower limit, bringing it into visual alignment with where the green sweeper ended. A UI fix only. And there's not any energy gain or algorithm tweak or such... just looks more correct.

There is definitely more regen available even when regen limit is displayed. I'd have to get on the brakes quite often in the prior release around the city.

 

[Andyw2100]

I have a lot of cold temperature where I live.

What I have noticed with this minor update is that regen seems to pull down the speed more firmly and will actually hit a yellow bar limiter, whereas regen wasn't previously hitting the yellow limiter. I would find myself hoping that it could hit the end of its limited scale. Began wondering just how fast would I have to be traveling to make it so?

Before this update, if I had a yellow bar on regen due to cold temps... driving from high speed (lots of inertia) and letting off the go pedal never made regen green sweep hit the yellow limit. It would stop short. The visual effect appeared to be proportionally scaling the whole regen potential back. Like if regen was capped at 60% (by virtue of showing the yellow line there) then the car would also only use about 60% of the remaining limited sweep space... and never hit the yellow limit.


Being Tesla, the "improvement" could be they adjusted the yellow line lower bringing it into visual alignment with where the green sweeper ends. A UI fix only. And there's not any energy gain or algorithm tweak or such... just looks more correct. If it's something like that, then it would be a big let-down going all the way to engineering to get an answer back with no meat to it like that. "We fixed a UI bug."

Now it hits the yellow limit. I say it "seems" to be pulling the car down more firmly. But this could be only psychological, because I'm seeing the regen use up all the available space, whereas before I was seeing that it wasn't.. and therefore thought it could do regen more firmly but wasn't. If that makes any sense?

That's an interesting answer, scottm, and I definitely understand what you are saying. I'll have to try to pay attention to that, and see if I notice the actual regen green bar reaching the limitation indication or not. I don't know that I've noticed it not reaching the limitation indication much in the past, but I did notice it a bit, and thought it was odd.

Do you normally drive with range mode on or off? I'm wondering if you have seen this behavior in both modes, or only in one?

Thanks!

 

[mknox]

Recent versions of the 7.1 firmware update, including the widely distributed version 7.1.2.12.126 have included a note under "Additional Improvements" that reads:

--
Regenerative braking at low temperatures has been improved.

This is my 4th winter with the car and I had my first ever loss of control due to re-gen situation. I have Nokian Hakka R2 winter tires in good condition on the car and lots of experience in slippery conditions (Canada, and all).

I was on the freeway decelerating due to traffic and as I came to a short underpass, there was a patch of black ice maybe 30' long. I was going about 50MPH and as the rear wheels hit the ice, the car's rear end swayed way out. The car corrected itself but I'm not sure if it was the car's stability control or whether it was simply the fact that I was on dry pavement again fairly quickly. All other traffic was slowing at the same rate and no one else I saw had this happen. I was lucky there was no one in the lane beside me.

- - - Updated - - -

not scientific here either, but i want to say since having this update a while; 1) full regen comes faster now (main notice), and 2) more regen is still enabled at very cold temps - e.g. where used to be like 20% avail, more like 40% to start.

That is likely the "problem". I was used to somewhat reduced re-gen in the cold for the past 4 winters.

 

[Andyw2100]

This is my 4th winter with the car and I had my first ever loss of control due to re-gen situation. I have Nokian Hakka R2 winter tires in good condition on the car and lots of experience in slippery conditions (Canada, and all).

I was on the freeway decelerating due to traffic and as I came to a short underpass, there was a patch of black ice maybe 30' long. I was going about 50MPH and as the rear wheels hit the ice, the car's rear end swayed way out. The car corrected itself but I'm not sure if it was the car's stability control or whether it was simply the fact that I was on dry pavement again fairly quickly. All other traffic was slowing at the same rate and no one else I saw had this happen. I was lucky there was no one in the lane beside me.

- - - Updated - - -



That is likely the "problem". I was used to somewhat reduced re-gen in the cold for the past 4 winters.

If the change was the cause for your loss of control, it's yet another argument for why Tesla should not keep us in the dark with respect to what has changed. If you had known regen was ramping up faster you could have either accounted for it, or, if you so desired and the conditions called for it, switched your setting to low regen instead of normal regen. But without additional information you were flying blind.

 

[AWDtsla]

This is my 4th winter with the car and I had my first ever loss of control due to re-gen situation. I have Nokian Hakka R2 winter tires in good condition on the car and lots of experience in slippery conditions (Canada, and all).

I was on the freeway decelerating due to traffic and as I came to a short underpass, there was a patch of black ice maybe 30' long. I was going about 50MPH and as the rear wheels hit the ice, the car's rear end swayed way out. The car corrected itself but I'm not sure if it was the car's stability control or whether it was simply the fact that I was on dry pavement again fairly quickly. All other traffic was slowing at the same rate and no one else I saw had this happen. I was lucky there was no one in the lane beside me.

- - - Updated - - -



That is likely the "problem". I was used to somewhat reduced re-gen in the cold for the past 4 winters.

I tried pretty hard, but I could never get the car to take corrective action after inducing slip via regen. Unfortunately I never found conditions for a real high-speed test. So it sounds like luck.

The only thing I have confirmed is if you hit a bump hard enough, regen will disable momentarily. Which BTW is a semi panic inducing situation.

 

[Andyw2100]

Below is the response I received to my request to forward my question to engineering.

--
I have forwarded a request to the proper channels requesting to provide more general information on the specifics of regenerative braking improvements in colder temperatures. Currently we do not have any customer facing information as to these specifics in regards to the temperatures and inner workings of the regenerative braking system and its latest improvements other that the general statement that is has been improved.

Please let us know if you have any further questions, comments or concerns and thank you contacting Tesla Motors Technical Support.

Sincerely,
--


I'm hoping they will provide some "customer facing information."

 

[scottm]

That's an interesting answer, scottm, and I definitely understand what you are saying. I'll have to try to pay attention to that, and see if I notice the actual regen green bar reaching the limitation indication or not. I don't know that I've noticed it not reaching the limitation indication much in the past, but I did notice it a bit, and thought it was odd.

Do you normally drive with range mode on or off? I'm wondering if you have seen this behavior in both modes, or only in one?

Thanks!

Normally range mode = OFF.

Which tends to heat the battery and raise or eliminate the yellow limiter faster. Because I don't need the range, and I want to keep up the temperature of that thermal mass below my feet. In floor heating you know :tongue:

I still have a dream and a wish that the car could direct the excess regen (above the yellow limiter) toward generating heat for the battery, instead of just not going there. In other words, when the car is cold and you have a yellow bar, the full regen sweep is possible and juice generated below the bar is directed to battery recharge, and juice generated above the bar got load dumped into a heater element... so the battery would heat faster.

- - - Updated - - -

This is my 4th winter with the car and I had my first ever loss of control due to re-gen situation. I have Nokian Hakka R2 winter tires in good condition on the car and lots of experience in slippery conditions (Canada, and all).

I was on the freeway decelerating due to traffic and as I came to a short underpass, there was a patch of black ice maybe 30' long. I was going about 50MPH and as the rear wheels hit the ice, the car's rear end swayed way out. The car corrected itself but I'm not sure if it was the car's stability control or whether it was simply the fact that I was on dry pavement again fairly quickly. All other traffic was slowing at the same rate and no one else I saw had this happen. I was lucky there was no one in the lane beside me.

Ditto that.

Michelin Xice3, top condition.

Lift off the pedal because it looks like black ice ahead, and yup! Regen is happening and hit a patch of black ice, and I'm doing an ass wiggle. Car recomposes itself far faster than I could with manual inputs... "road slippery" symbol flashing on the dash, chunk chunk brrrrrrr noise from the back... and I'm on my way, practically before I realized what had just happened. It sounded and felt like I had just run over an animal with the bumps and noises coming from the back end. But this was a clear and bright day... just black ice in the shadows of a mountain.

This was on a big sweeper corner, I was lead car of a pack taking this bend on a mountain pass highway. People (I thought) were all riding a little close on my ass for the conditions... When I got fully around the corner and onto the straight away again I looked back AND NOT ONE CAR was following me anymore. I could only imagine what kind of mayhem had happened and I just swore under my breath and broke out into a cold sweat... everyone was at highway speed following me 10 seconds ago... and now it was like an alien abduction had sucked up all those cars behind me. Gone off the face of the earth! Or at least, into the ditch.

IRONICALLY, a snow plow in sanding mode is the first oncoming vehicle I see 10 seconds later, and is laying down sand and salt going into that corner I left behind from the other direction and he would be the first responder onto the scene. If only he'd been there 2 minutes earlier I'm sure all cars would have come out on their own.

Black ice is nobody's friend.

 

[MP3Mike]

I still have a dream and a wish that the car could direct the excess regen (above the yellow limiter) toward generating heat for the battery, instead of just not going there. In other words, when the car is cold and you have a yellow bar, the full regen sweep is possible and juice generated below the bar is directed to battery recharge, and juice generated above the bar got load dumped into a heater element... so the battery would heat faster.

Probably the same reason that they won't use the shore power to heat the battery when it is too cold.

In the case of regen isn't the pack heater only ~5kWh? So they really can't dump much regen into that. And I don't think it would make sense to add ~55kWh of restive heating to the car, along with the required upsizing of the heat exchanger, tubing, pumps, etc. to handle that additional load for the rare usage. (At least in most climates it would be a lot of extra weight to carry around all year for the rare usage.)

 

[Lex]

I honestly did not expect to have to defend my position of having asked what I thought was a very reasonable question of Tesla.

You should not have, my apologies for the poor choice of words as you demanded nothing and simply requested something.

My failed idea was to suggest in a general sense that causing too many "escalations" can shut doors due to costs that we may need later (I posted during a quick work break with a lot of corporate navigation and cost overruns and escalated client concerns on my mind).

 

[Andyw2100]

You should not have, my apologies for the poor choice of words as you demanded nothing and simply requested something.

My failed idea was to suggest in a general sense that causing too many "escalations" can shut doors due to costs that we may need later (I posted during a quick work break with a lot of corporate navigation and cost overruns and escalated client concerns on my mind).

No problem at all, Lex, and I appreciate the note. My comment was a general comment, not directed towards any one poster in particular, as there have been several posts that really questioned my desire for additional information.

Thanks!

 

[AWDtsla]

Probably the same reason that they won't use the shore power to heat the battery when it is too cold.

In the case of regen isn't the pack heater only ~5kWh? So they really can't dump much regen into that. And I don't think it would make sense to add ~55kWh of restive heating to the car, along with the required upsizing of the heat exchanger, tubing, pumps, etc. to handle that additional load for the rare usage. (At least in most climates it would be a lot of extra weight to carry around all year for the rare usage.)

Wrong on many counts. Direct to water resistive heaters are light and cheap. 55kW might be excessive but 15-20kW would be great. It would add dozens of dollars to the car.