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Regenerative braking reduced warning

pt19713

Member
Feb 5, 2020
997
1,306
Delaware
My car is usually plugged in so I haven't done a lot of tests. I've tried it twice not plugged in and turning on the climate control via the app does not warm up the Stator motors and thus does not warm up the battery.
 

Rshephorse

Member
Aug 2, 2020
168
121
Plattsburg
My car is usually plugged in so I haven't done a lot of tests. I've tried it twice not plugged in and turning on the climate control via the app does not warm up the Stator motors and thus does not warm up the battery.
Parked, not plugged in to charging, turn on climate control in the app, and the battery does heat up- battery inlet temp quickly rises above cell temps, and then battery heats up. This would be worth it if you were driving down from a ski area- to catch all that regen at the start of the trip? It does use around 7.5 to 10.5 kw of juice to do it tho! Obviously best to be plugged in if possible in cold weather; and better yet to capitalize on some of the warming that occurs when charging as well. I guess charge up to a bit before departure and then blitz climate control for the 10-15 minutes before I leave to get the battery temp up into the 70's.....
 

pt19713

Member
Feb 5, 2020
997
1,306
Delaware
Parked, not plugged in to charging, turn on climate control in the app, and the battery does heat up- battery inlet temp quickly rises above cell temps, and then battery heats up. This would be worth it if you were driving down from a ski area- to catch all that regen at the start of the trip? It does use around 7.5 to 10.5 kw of juice to do it tho! Obviously best to be plugged in if possible in cold weather; and better yet to capitalize on some of the warming that occurs when charging as well. I guess charge up to a bit before departure and then blitz climate control for the 10-15 minutes before I leave to get the battery temp up into the 70's.....
I'll try again but I'm not seeing the Stator motors heating up (Scan My Tesla app) unless I'm plugged in.
 

HeyEph

Member
Mar 22, 2020
370
157
Fairport, NY
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

Is 30mins of pre-conditioning required to get warm enough? I tried 10mins the other day when it was 40deg and this was not enough.
 

pt19713

Member
Feb 5, 2020
997
1,306
Delaware
Is 30mins of pre-conditioning required to get warm enough? I tried 10mins the other day when it was 40deg and this was not enough.
It was 45 degrees in my garage this morning and I pre-conditioned about 15 minutes. Battery temps were ~ 67F when I pulled out of my garage and only 4 dots on the screen. They were gone within 5 minutes.

If you have a few dots on the screen, it's nothing to worry about. The issue is when it's at the halfway, which is when the reduced braking is noticeable.
 

Rshephorse

Member
Aug 2, 2020
168
121
Plattsburg
I understand that turning climate control on to accomplish preconditioning does difft things at different ambient temperatures. If you are down around freezing it is full-on with battery heating but at moderate temperatures may only heat the cabin. Of course you can fool the system by navigating to a nearby supercharger though to get battery heating even then.

My stators got up to 190 degrees with preconditioning [outside temp 31]. There is a glitch in 'Scan My Tesla" which fooled me. I thought the stators stayed hot even when I turned off climate control - which worried me. Turns out the stators do cool down. You can see this by the immediate drop in power coming out of the battery. What happens through, when stator-heating stop, the car stops sending out the stator temp info in the packet- "Scan My Tesla" just keeps posting the 'last value' for the stator temp.

The whole cold weather management could be a lot more sophisticated. There could be choices for heat cabin, just defrost, heat cabin with defrost, heat the battery, just defrost charging port, and the option to schedule this to happen prior to a departure time with or without scheduled charging....
 
  • Informative
Reactions: Stach and srlawren

pt19713

Member
Feb 5, 2020
997
1,306
Delaware
Yeah, I don't see that issue. This morning my motors were around 170F peak and about 2 minutes after I started driving, I noticed they were dropping in temp every 15-30 seconds. I typically don't monitor the motor temps; I'm usually looking at the battery inlet temp. As long as that value is greater than the battery pack temp, I know it'll warm up.
 

pt19713

Member
Feb 5, 2020
997
1,306
Delaware
I'll try again but I'm not seeing the Stator motors heating up (Scan My Tesla app) unless I'm plugged in.
Ok, tried again at work (not plugged in) and the motors were ~ 165F and the batteries were 71F (ambient 46F). I don't have an explanation why the previous two times I did the same thing at work the motors were at ambient. Not the most efficient thing to do with each motor drawing 3.5 kW but oh well, it's better for the battery.
 
  • Informative
Reactions: Stach and Barrygold

Rshephorse

Member
Aug 2, 2020
168
121
Plattsburg
Ok, tried again at work (not plugged in) and the motors were ~ 165F and the batteries were 71F (ambient 46F). I don't have an explanation why the previous two times I did the same thing at work the motors were at ambient. Not the most efficient thing to do with each motor drawing 3.5 kW but oh well, it's better for the battery.
I think there is a temperature, either ambient or battery where the battery heating occurs below it, and does not occur above it.
 
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Reactions: Stach

csb123

New Member
Nov 3, 2020
4
0
Durham, NC
Back to the original post in this thread...I own a Model 3 and rarely get the reduced regen warning unless it is really cold. Our new Model Y shows this error message much more frequently and the braking is noticeably impacted. Why the difference? Has the battery management system taken a step backward or is it just more complicated now?
 

pt19713

Member
Feb 5, 2020
997
1,306
Delaware
In the Y, more heat is being directed into the cabin. In the 3, heated filaments to care of this, so more heat from the motors went to warming the batteries
 
  • Informative
Reactions: srlawren

Stach

Member
Mar 23, 2019
470
259
Madison, WI
I'm very disappointed with the lack of battery warming with the heat pump in the Model Y, compared to what I was used to in my Model 3.

I charged for 2+ hours in my 55 degree garage and left with No Regen Dots (finally). It was 40 degrees outside and I immediately drove for 20 minutes to the store and ended up with 4 dots. I did 2 more quick 5 minute errands at stores (a couple miles of driving in between), and then drove the 20 minutes back home with dots all the way up to the N (10-12 dots). My MY sat in 40 degree temps outside for a total of 10-15 minutes and gained dots while driving 50+ minutes! IMHO, if the regen dots reach the D or go beyond, then regen is basically useless, which is what I will be seeing for the next 3-4 months in Wisconsin.

In this same scenario with my old Model 3, I wouldn't have seen a regen dot the entire time and even if I had started out with dots, they would have gradually disappeared as I drove. With my Model Y, it is the exact opposite.
 
Last edited:

Barrygold

Member
Jun 20, 2019
442
507
Midwest
I'm very disappointed with the lack of battery warming with the heat pump in the Model Y, compared to what I was used to in my Model 3.

I charged for 2+ hours in my 55 degree garage and left with No Regen Dots (finally). It was 40 degrees outside and I immediately drove for 20 minutes to the store and ended up with 4 dots. I did 2 more quick 5 minute errands at stores (a couple miles of driving in between), and then drove the 20 minutes back home with dots all the way up to the N (10-12 dots). My MY sat in 40 degree temps outside for a total of 10-15 minutes and gained dots while driving 50+ minutes! IMHO, if the regen dots reach the D or go beyond, then regen is basically useless, which is what I will be seeing for the next 3-4 months in Wisconsin.

In this same scenario with my old Model 3, I wouldn't have seen a regen dot the entire time and even if I had started out with dots, they would have gradually disappeared as I drove. With my Model Y, it is the exact opposite.
Same experience in colder weather. The Y battery cools down rather quickly if it’s not heat soaked from supercharging or a longer level 2 charging session.

I supercharged 2x in a 6 hr period last week in low 40* temps and the battery had to pre condition for 28 minutes before each session. heat started blowing really hot afterwards. You could tell the battery was warm but it eventually cooled off after driving 2 hrs.
 

Stach

Member
Mar 23, 2019
470
259
Madison, WI
Price we pay for having a heat pump, since it's scavenging the heat for the cabin, which is cooling the battery.

I've seen the acceleration dots already too, which is a bummer as well, since instant, strong acceleration is what makes the car so fun to drive. I rarely saw them in my Model 3, and if I did, it was far colder than it is now...
 

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