Regenerative braking reduced warning

[spokey]

Hey @jcanoe I'd look for another electrician. You've been waiting forever.

 

[rjpjnk]

What I find most disconcerting is that braking is inconsistent. If you're used to 1-pedal driving it might work normally... it might be reduced... or on an exit ramp the car doesn't slow on its own at all and you need to hit the brakes.

This is my concern as well. Consistency in braking is critical for safe driving. At least for humans.

 

[jcanoe]

Hey @jcanoe I'd look for another electrician. You've been waiting forever.

They're late!

 

[rjpjnk]

It's been well-documented in the Model 3 community and I've tested it myself with the Scan My Tesla app. I've posted screenshots in another thread showing the Stator motors warming up and the battery pack temp increases over 30 minutes. Here's a cut and paste:


In the attached image, I've circled in red the relevant info. This is an image, after about 1 minute, when I woke the car up and turned on the heat. Ambient temp in my garage, 58F. Battery temp 66F. Take note of the battery flow (this is the coolant running through the battery) and the Stator motor temperatures, along with the Battery inlet temp. I'll explain all this shortly in my second reply with a second image showing pre-conditioning after 30 minutes.
View attachment 607944



Here is the car after 30 minutes of pre-conditioning.

Note the battery temps are now 82F. How does all this work by turning on your heat? This is how the car pre-conditions:

By turning on the heat, the Battery Management System (aka BMS) activates a non-motive power waveform to the Stator motors. This is to generate heat. This heat is carried away by the coolant via conduction, the same way gamers use liquid cooling on their CPU and GPU, or in gas vehicles with the radiator coolant passing through the engine block. This hot coolant eventually flows through the battery packs and then back through the Stator motors and the process is repeated. You can see the Battery Flow and Powertrain flow indicated in LPM (Liters per minute). You can also see what the temperature of the coolant is before it enters the battery packs, listed as Battery Inlet.

It also works in reverse in the summer when it's hotter outside and the batteries need to be cooler. Instead of heat conduction from the Stator motors, the Radiator Bypass is closed and the coolant is routed through the radiator fans. This speed can be found with the Radiator Fan Target. Fresh air is pushed over the coolant lines to lower the temperatures.

There you have it. Battery pre-conditioning 101.
View attachment 607945

Really great info PT. Thanks!

From your description it sounds like you took these screenshots on your Model 3, correct? I am wondering, as jcanoe asked, if this same battery heating process occurs on the 2021 Model Y. Can you confirm this?

If I understand correctly, the stators are being used as resistive heaters (by applying a waveform that causes current to flow but causes no movement), and then this heat is carried by the coolant to warm the battery. Given that the Model Y has a heat pump, I am wondering why that would not be used to heat the coolant (perhaps in addition to the stator non-motive waveform). Do you know if this is the case?

Lastly, what action(s) by the operator causes the BMS to preheat the battery? On the app I see at least three contenders: Defrost Car, Precondition, and Climate Control On. Do all of these cause battery preheat? The Precondition option seems to only be available as a scheduled event, which is great if I know when I want to leave, but not as convenient for spontaneous trips. A one-touch button would be preferable.

My goal is to understand the best practice to preheat my battery while plugged in outdoors on cold Winter mornings (typically 10-20F).

 

[pt19713]

Really great info PT. Thanks!

From your description it sounds like you took these screenshots on your Model 3, correct? I am wondering, as jcanoe asked, if this same battery heating process occurs on the 2021 Model Y. Can you confirm this?

If I understand correctly, the stators are being used as resistive heaters (by applying a waveform that causes current to flow but causes no movement), and then this heat is carried by the coolant to warm the battery. Given that the Model Y has a heat pump, I am wondering why that would not be used to heat the coolant (perhaps in addition to the stator non-motive waveform). Do you know if this is the case?

Lastly, what action(s) by the operator causes the BMS to preheat the battery? On the app I see at least three contenders: Defrost Car, Precondition, and Climate Control On. Do all of these cause battery preheat? The Precondition option seems to only be available as a scheduled event, which is great if I know when I want to leave, but not as convenient for spontaneous trips. A one-touch button would be preferable.

My goal is to understand the best practice to preheat my battery while plugged in outdoors on cold Winter mornings (typically 10-20F).

Screens are from a 2020 Model Y LR.

When I did the datalog, the software did a poor job of integrating the heat pump in cold weather. By March 2021, software 2021.4.11 was released and the heat pump was integrated better with the Octovalve system. I'll be doing more logs this winter, I just need colder weather to test.

All three will heat the pack. I don't use defrost unless it's parked outside and I need to warm up the front and rear glass. I typically use the cabin heat function, both in my garage and when the vehicle is parked outdoors at work. Pre-2021.4.11 when I tested both functions, both heated up the battery at the same rate, but defrost used more energy. I don't use the precondition function in the car. I tend to do everything manually.

One note, I've been testing how much the battery warms up from just charging before leaving work. If I charge for 2 hours, the pack hovers around 70-75F (normally 55F in my garage). This is more effective and efficient than charging late evening, and then preconditioning before leaving work. It would take about 20-25 minutes of preconditioning to get the pack up to that temp, so charging before leaving works quite well .

 

[jcanoe]

I have been preconditioning each morning, 2020 LRMY parked inside my garage (not plugged in because I usually charge away from home.) For the past month the battery warming indicator has displayed on the Tesla app while preconditioning if the garage temperature is 45F or colder.

My Model Y was just updated to 2021.40.6, this A.M. the temperature was 40F yet the battery warming indicator did not illuminate while preconditioning. The release notes for 2021.40.6 state Cold Weather Improvements, "when using climate controls on the Tesla App, automatic battery pre-conditioning has been optimized to consume less energy." Right now I don't know at what temperature the battery will be warmed. (In winter my garage usually stays above 30F, occasionally gets down to ~20F.)

 

[rjpjnk]

Screens are from a 2020 Model Y LR.

When I did the datalog, the software did a poor job of integrating the heat pump in cold weather. By March 2021, software 2021.4.11 was released and the heat pump was integrated better with the Octovalve system. I'll be doing more logs this winter, I just need colder weather to test.

All three will heat the pack. I don't use defrost unless it's parked outside and I need to warm up the front and rear glass. I typically use the cabin heat function, both in my garage and when the vehicle is parked outdoors at work. Pre-2021.4.11 when I tested both functions, both heated up the battery at the same rate, but defrost used more energy. I don't use the precondition function in the car. I tend to do everything manually.

One note, I've been testing how much the battery warms up from just charging before leaving work. If I charge for 2 hours, the pack hovers around 70-75F (normally 55F in my garage). This is more effective and efficient than charging late evening, and then preconditioning before leaving work. It would take about 20-25 minutes of preconditioning to get the pack up to that temp, so charging before leaving works quite well .

Thanks for the clarifications. Maybe I will install my OBD2 adapter soon and take a look at those temps myself. Is there a parameter that indicates if the heat pump is contributing to battery warming when preconditioning? I sure hear it running in my driveway just now. All I did was turn on climate on the app. It is 30 F.

 

[rjpjnk]

I have been preconditioning each morning, 2020 LRMY parked inside my garage (not plugged in because I usually charge away from home.) For the past month the battery warming indicator has displayed on the Tesla app while preconditioning if the garage temperature is 45F or colder.

Thanks. Very helpful. I didn’t know there was a battery warming indicator on the app. Where is it?

 

[jcanoe]

Thanks. Very helpful. I didn’t know there was a battery warming indicator on the app. Where is it?

In the latest version of the app it is at the upper left corner just to the right of the battery status. The icon is three short red horizontal wavy lines.

 

[rjpjnk]

In the latest version of the app it is at the upper left corner just to the right of the battery status. The icon is three short red horizontal wavy lines.

I have the latest (4.3.0) and have never seen this. Could it be because my car is still on 36.5.5?

 

[jcanoe]

I have the latest (4.3.0) and have never seen this. Could it be because my car is still on 36.5.5?

I have version 4.3.0 of the Tesla app for iPhone. The battery warming indicator comes on during Preconditioning (or at least it did before I installed 2021.40.6.)

This A.M., following perhaps a 10 minute period of preconditioning, a blue snow flake appeared on the main Tesla screen that was not displayed in the A.M. prior to installing 40.6 (at least not since last winter.) I have to investigate what it means.

 

[rjpjnk]

Interesting. Keep us posted.

 

[Big Earl]

Blue snowflake means range is reduced due to cold battery. The snowflake will go away and range will be restored once the battery warms up. The blue snowflake is usually accompanied by a portion of the battery meter being blue, indicating how much capacity is unavailable due to temperature.

 

[jcanoe]

Blue snowflake means range is reduced due to cold battery. The snowflake will go away and range will be restored once the battery warms up. The blue snowflake is usually accompanied by a portion of the battery meter being blue, indicating how much capacity is unavailable due to temperature.

This was following 10 minutes of Preconditioning at 40F with no indication that battery warming was taking place.

 

[Big Earl]

This was following 10 minutes of Preconditioning at 40F with no indication that battery warming was taking place.

Seems like the need to further tweak the recent tweaks to cold weather behavior.

 

[pt19713]

Thanks for the clarifications. Maybe I will install my OBD2 adapter soon and take a look at those temps myself. Is there a parameter that indicates if the heat pump is contributing to battery warming when preconditioning? I sure hear it running in my driveway just now. All I did was turn on climate on the app. It is 30 F.

The only field I could find is this one, but I've never really watched it, so I'm not sure what it's referencing.

 

[IMFletcher]

I have been complaining to my friends, who also own Tesla’s, about the reduction of regen braking. I live in Colorado and it has been getting down to low 20’s at night or cooler. Setting the car to precondition prior to me leaving for work at 7am has helped tremendously, still not like driving in the summer and totally one pedal driving but much better.

 

[spokey]

Might agree. We've been down in the 20s but I've probably only been out in the 30s and my regen seems a bit weaker. I've only got 3 or 4 dots typically but a couple times now I've had to actually brake coming to a light chaning (the horror) when I think I normally would not.

 

[torifile]

Might agree. We've been down in the 20s but I've probably only been out in the 30s and my regen seems a bit weaker. I've only got 3 or 4 dots typically but a couple times now I've had to actually brake coming to a light chaning (the horror) when I think I normally would not.

Wait. This is associated with reduced stopping power when lifting your foot off the go-pedal? I thought it just meant the batteries won’t be recharged from said stop. I didn’t realize the driving dynamics also change as a result of this.

 

[rjpjnk]

If they could find a way to activate the friction brakes automatically in situations where the regenerative braking is reduced, we could still drive with one pedal. This would keep the response consistent.