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Regenerative braking reduced warning

jmatero

Member
Feb 5, 2020
554
462
San Jose, CA, USA
This was brought up in another thread but got way off track. I'm coming from a Model 3 to Model Y and since the temps here started dropping (in San Jose area, daily temps under 65) I've been seeing a constant "Regenerative braking reduced" warning. Rarely if ever saw that in the M3 unless battery was fully charged or temps went below, say 50F.

I discovered these things (and a reset didn't change any of them):
  1. No matter how long I drive, the warning is always present and the car constantly shifts from coasting to 1-pedal and back again even on shorter drives.
  2. The temp is almost 70 today and I'm still seeing this behavior despite a 20 mile drive.
  3. If you go to driving settings and change braking from normal to low... then back to normal... the warning goes away and 1-pedal driving returns.
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 started with a recent SW update that (unfortunately) coincided with lower daily temps. Is anyone else experiencing this? If so, is it fixed for the current drive by performing number 3 above?
 

LNL_HUTZ

Member
Aug 3, 2020
300
237
San Francisco
Sounds like something fishy is going on. Since it started getting colder, I've been getting a few bubbles on the left side of the green bar, but no warnings. Granted, I don't leave the car outside overnight, so it probably never gets much colder than 60 degrees.

Do you get the warning regardless of the SoC?
 

pho35

Member
Aug 20, 2020
45
26
Texas
I have noticed the same experience on colder day in TX where regen warning came on and as the day gets warmer it works as expected. I'm wondering if this is per design because to prevent the vehicle from skidding in ice condition? Just a thought. All in all, I react to the vehicle just to be on the safe side.
 
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pt19713

Member
Feb 5, 2020
999
1,307
Delaware
I have noticed the same experience on colder day in TX where regen warning came on and as the day gets warmer it works as expected. I'm wondering if this is per design because to prevent the vehicle from skidding in ice condition? Just a thought. All in all, I react to the vehicle just to be on the safe side.
Cool/cold batteries don't like to be charged, so the BMS limits brake regen until the battery packs are warmer. The batteries seem to want to be around 77-83F.
 

WADan

Member
Sep 28, 2020
318
269
Bellevue WA
I did notice that yesterday. I’ve only driven my Y 100 miles totally, and I didn’t know what’s causing it. The temperature was in the 40’s yesterday!
 

PedramGh

Member
Jan 20, 2020
191
271
Berkeley
I had that yesterday but I drove for 15 mins and after battery warmed up it disappeared. It was relatively colder but not a very cold day. 60-65 ish
 

Puma2020

Member
Jun 16, 2020
423
453
New Hampshire, USA
Cool/cold batteries don't like to be charged, so the BMS limits brake regen until the battery packs are warmer. The batteries seem to want to be around 77-83F.
I had to re-read this to fully understand the implication. As I am in, the much cooler north, I have seen the re-gen warning for several weeks. I've started trying to re-train myself to turn on climate control before I want to leave. That helps to warm things up (battery and cabin). The # of dots on the screen diminishes if I wait a few more minutes before leaving. I wonder if I should just set a scheduled departure time like 7 AM. I wonder if repeatedly warming and cooling the battery (if I don't drive it) every day is a bad or good thing.

Regen_braking_cold (1).JPG
 

pt19713

Member
Feb 5, 2020
999
1,307
Delaware
I had to re-read this to fully understand the implication. As I am in, the much cooler north, I have seen the re-gen warning for several weeks. I've started trying to re-train myself to turn on climate control before I want to leave. That helps to warm things up (battery and cabin). The # of dots on the screen diminishes if I wait a few more minutes before leaving. I wonder if I should just set a scheduled departure time like 7 AM. I wonder if repeatedly warming and cooling the battery (if I don't drive it) every day is a bad or good thing.

View attachment 607896
Don't worry about durability. The batteries can handle it.

Scheduled departure can be a bit buggy at times and I don't like using it, especially if you're taking a trip and wake up to find that the car didn't charge. For a tech/software company, the person that was in charge of this project failed miserably and Tesla hasn't bothered to put resources towards making it better.

10 minutes of pre-conditioning will warm up the batteries faster than 30 minutes of driving. The ~ $0.05-0.08 it costs to pre-condition pays for itself because of the higher efficiency of the battery while it's warm, plus having a higher threshold of brake regen.
 
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MacZ

Member
Jun 14, 2020
113
40
Toronto
I am at Toronto, and starts getting warnings in the cold days, but the warnings go away automatically after battery gets warmed up after about 20min driving, but regen is still at very low condition until battery get well warmed.

However, I have a problem with displayed range is getting lower and lower (MYP). 3 weeks back was 450+km, 2 weeks ago was 441km, the update did not change anything, and now keeps showing 430km, and looks like it will keep going down this way. Is any one have the same issue?
 

FormationLap

Member
Jul 29, 2020
35
6
Toronto
10 minutes of pre-conditioning will warm up the batteries faster than 30 minutes of driving. The ~ $0.05-0.08 it costs to pre-condition pays for itself because of the higher efficiency of the battery while it's warm, plus having a higher threshold of brake regen.

New to Teslas - are we sure that turning on the climate control, does indeed warm up the battery? (And not just the cabin). I mean it makes sense that it would...

I'm located in Toronto, and have also noticed quite a few bubbles showing up as it's getting colder. Scheduled departure hasn't helped much.

Might give this a try:
If you go to driving settings and change braking from normal to low... then back to normal... the warning goes away and 1-pedal driving returns.
 

pt19713

Member
Feb 5, 2020
999
1,307
Delaware
New to Teslas - are we sure that turning on the climate control, does indeed warm up the battery? (And not just the cabin). I mean it makes sense that it would...

I'm located in Toronto, and have also noticed quite a few bubbles showing up as it's getting colder. Scheduled departure hasn't helped much.

Might give this a try:
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.
upload_2020-11-13_9-34-17.png




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.
upload_2020-11-13_9-34-35.png
 

FormationLap

Member
Jul 29, 2020
35
6
Toronto
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

This was beautiful. Thank you. Will definitely start up the climate control before going anywhere moving forward.
 

MacZ

Member
Jun 14, 2020
113
40
Toronto
@pt19713

Please help here, do you have loosing displayed range on your Tesla?

Does scan my tesla APP can check Battery Health or it just reads data from BMS?

As I mentioned above, my MYP was displayed 458km 3 weeks ago, and right now 423km at 100% SOC.
 

pt19713

Member
Feb 5, 2020
999
1,307
Delaware
@pt19713

Please help here, do you have loosing displayed range on your Tesla?

Does scan my tesla APP can check Battery Health or it just reads data from BMS?

As I mentioned above, my MYP was displayed 458km 3 weeks ago, and right now 423km at 100% SOC.
I use percentage, so I can't answer your question on range reduction. What you're seeing is probably due to a colder battery and the system is adjusting it downward, but I can't validate that since I was under the impression the displayed range on the main UI is based upon the EPA rating and not current conditions.

The app does show the nominal full pack size (75.3 kWh), cell voltage max and min (cell imbalance) but nothing that would answer your question. I'd suggest switching to percentage and only use the Energy /trip graph to show mileage estimates.
 
Last edited:

MacZ

Member
Jun 14, 2020
113
40
Toronto
I use percentage, so I can't answer your question on range reduction. What you're seeing is probably due to a colder battery and the system is adjusting in downward, but I can't validate that since I was under the impression the displayed range on the main UI is based upon the EPA rating and not current conditions.

The app does show the nominal full pack size (75.3 kWh), cell voltage max and min (cell imbalance) but nothing that would answer your question. I'd suggest switching to percentage and only use the Energy /trip graph to show mileage estimates.
Thanks!
 

jcanoe

Active Member
Oct 2, 2020
3,499
3,540
Maryland
Does the Model Y also use the electric motors to warm the battery pack or is this handled by the heat pump?

I noticed when my Model Y is displaying the message that regenerative braking is reduced that if I access the driving settings and set regenerative braking to Low instead of Standard (my Model Y has this capability) that the message disappears.
 

pt19713

Member
Feb 5, 2020
999
1,307
Delaware
Does the Model Y also use the electric motors to warm the battery pack or is this handled by the heat pump?

I noticed when my Model Y is displaying the message that regenerative braking is reduced that if I access the driving settings and set regenerative braking to Low instead of Standard (my Model Y has this capability) that the message disappears.
Motors. Scroll up for tech info or click here Regenerative braking reduced warning
 

jcanoe

Active Member
Oct 2, 2020
3,499
3,540
Maryland
Motors. Scroll up for tech info or click here Regenerative braking reduced warning
Thank you for your reply. When I use the Tesla built-in navigation and set a nearby SuperCharger as the destination the Tesla Model Y appears to perform additional warming of the battery pack beyond the previously noted Power Wave within the motors in preparation for SuperCharging. If so, how is this additional battery pack warming accomplished?
 

pt19713

Member
Feb 5, 2020
999
1,307
Delaware
Thank you for your reply. When I use the Tesla built-in navigation and set a nearby SuperCharger as the destination the Tesla Model Y appears to perform additional warming of the battery pack beyond the previously noted Power Wave within the motors in preparation for SuperCharging. If so, how is this additional battery pack warming accomplished?
It's exactly the same process. The Stator motors are warming up and that heat is what's warming the batteries to prepare for supercharging.

The only difference is pre-conditioning while plugged in at home will heat up the front Stator more than the rear. While pre-conditioning for a supercharger and driving, the rear Stator heats up more than the front. This is most likely due to the car being mostly RWD in most driving conditions so the rear motors are generating more heat than the front.
 

jcanoe

Active Member
Oct 2, 2020
3,499
3,540
Maryland
Thank you for your explanation. If I precondition my Model Y while not plugged in does this affect the battery warming process that you noted when the vehicle is plugged in?
 

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