Snowflake symbol vs Regenerative Braking Reduced

[sleepydoc]

I accidentally posted this in the Model X forum (oops!) so I’m reposting it here. It’s probably the same for both models, though.

The weather has gotten a bit colder here in MN and I’ve gotten the expected “regenerative braking reduced” notice as well as the snowflake at the top of the screen. The other day I had something I haven’t seen before - the snowflake symbol showed up at the top of the screen but the regenerative braking bar had no dots, indicating I had full acceleration and regenerative braking. Has anyone seen this before? I didn’t find much in the manual. Supposedly the snowflake means a cold battery and reduced current capacity for charging and braking so it seems like they should go hand in hand.

Ke

 

[AlexHung]

Looks like this in the manual?

 

[GtiMart]

I would have thought so too but Tesla does things their own way. What I can tell you is that the bar that indicates regen and acceleration power is not "precise". I've seen my max power vary quite a bit without the right side showing dots. The dots only appear when I'm significantly reduced. In a similar way I've seen cases where I had no regen dots but regen was under the max of 85kW. regen might only be at 35 or 50kW and you would only have a handful of dots. It's a fuzzy display, not a precise display.
The other aspect is that regen's relation to battery temperature has changed over time. Other people on the web have documented this with graphics. Now we get significant regen on the single digits Celcius temperatures, and max regen might be a 10-11C. There might be a temperature where regen is high enough not to show dots while energy available being low enough to show the snowflake...

 

[Benito1283]

I've had overnight temps down to -10C / 14F and have never had a snowflake even driving the car cold in the morning, but I do have significant regen dots / reduced regen in those scenarios. It's weird that the battery would be cold enough for a snowflake but still have regen. I assume, despite your lack of regen dots, you didn't actually have much regen braking?

 

[Calliope]

Wow, I see the snowflake often with my car in the underground garage (unplugged), where it is about 5C, but don't often have reduced regen unless I'm parked outside somewhere (and then I try to precondition before leaving).

 

[GtiMart]

Thanks for the info. I can tell you that at 5C, the chance that you had access to the full 85kW of regen is virtually nil. My battery was at 8.5C (lowest temp) when I went out to grab lunch earlier and I had 55-60kW available. I did have ~4 dots on the regen side.
With the information you just posted, along with not being precise, it seems the indicators are not deterministic? There must be other variables than battery temperature that we don't quite have a grasp on...

 

[Benito1283]

I agree. I have a feeling it is dependent on software updates, possibly based on region. I and others I know have never once seen the snowflake despite overnight temps well below freezing and significant regen dots/reduction. I think all is fine with the cars, but some consistency in what is displayed would be helpful.

 

[sleepydoc]

I've had overnight temps down to -10C / 14F and have never had a snowflake even driving the car cold in the morning, but I do have significant regen dots / reduced regen in those scenarios. It's weird that the battery would be cold enough for a snowflake but still have regen. I assume, despite your lack of regen dots, you didn't actually have much regen braking?

Yeah, when I think about it, I often have reduced regenerative braking but no snowflake. When I've seen the snowflake It's generally been with reduced regenerative braking - to my knowledge, this is the first time I've seen the snowflake in isolation.

I can't say for certain, but I seemed to have normal, or at least close to normal regenerative braking when this occurred. That's what was so puzzling. I've also never seen dots on the power side, just the regenerative braking side. Of course I rarely accelerate that hard so I wouldn't necessarily notice them anyway.

Thanks for the info. I can tell you that at 5C, the chance that you had access to the full 85kW of regen is virtually nil. My battery was at 8.5C (lowest temp) when I went out to grab lunch earlier and I had 55-60kW available. I did have ~4 dots on the regen side.
With the information you just posted, along with not being precise, it seems the indicators are not deterministic? There must be other variables than battery temperature that we don't quite have a grasp on...

Question - do you know for sure what the battery temperature was or were you assuming it was the same as the ambient temp? The battery has a fair amount of thermal mass and active heating/cooling, so it's possible for the temperature to be different. Regardless, I think you're right - there's more than temperature at play here.

 

[sleepydoc]

Looks like this in the manual?

View attachment 743833

Yes - the manual also says:

The amount of energy fed back to the Battery using regenerative braking can depend on the current state of the Battery. For example, regenerative braking may be limited if the Battery is already fully charged or if the ambient temperature is too cold.

Which leads to why question - how can one be affected but not the other?

 

[GtiMart]

I use ScanMyTesla so I'm looking at actual battery temp, actual max regen value etc. I'm not just inferring.

 

[GtiMart]

I can add from this morning's drive that the max regen value is not just based on battery temperature. The car sat all night outside, -4C this morning but the battery itself was at 0C when I started preheating a few minutes before leaving. I started with ~30kW of regen with a battery close to 2C. That value quickly went up to 50kW as I accelerated a few times. I then did a hard acceleration to get on to the highway which saw the value go over 60kW, with a battery not quite reaching 3C. There's a big hill on that highway so regen was used significantly. I was looking at my max regen value during that time and it was constantly going down. I had lost 10kW of regen at the bottom. Accelerating normally made the value creep up slowly, and accelerating hard made it raise faster. Since the battery temperature doesn't fluctuate that fast, there's something else. It's possible that it's related to battery chemistry and what happens when you pull power out of it vs when you put power back in. I will stop at the "rough theory" level since I'm not battery specialist, but there is something at play.
I did have the snowflake with a significant slice of blue (a few percent).

 

[sleepydoc]

Ok - a week later in reasonably cold weather I’ve had multiple occasions where the snowflake was on and regenerative braking was not or only minimally affected, and multiple occasions where regenerative braking was significantly affected and the snowflake wasn’t on.

THere must be other factors besides temperature at play and I’m guessing something changed in a recent update.

 

[medphys3]

…There must be other factors besides temperature at play and I’m guessing something changed in a recent update.

I agree with this statement. My car (Model 3) is acting much different than it did last winter. I am seeing the blue snowflake all the time now, where I rarely ever saw it last winter (in similar conditions). I also have reduced battery pre-conditioning prior to departing work. Consumption is up to 350 Wh/mi on a cold (20f) day where last winter it would be around only 290 in similar conditions. It’s bugging the crap out of me because my range has gone down significantly. And my range on the guessometer is dropping 20+ miles while sitting in the parking lot over 8 hrs. It never did that last winter.