Can Limited Regenerative Braking Be A Sign Of Anything Bad?

[therealjimbob]

Hello and sorry if this is a dumb question as I am still pretty new to owning my Tesla and this is just one area that I have not researched in depth.

So for the last two days my car has been showing limited regenerative braking. The weather here in Maryland has not been bad, today it was around 50F when I was driving and yesterday it was 60F. I thought that because I didn’t precondition my car yesterday that may have been the reason why it was showing limited regenerative braking but even after charging last night until the morning, preconditioning my car today and driving it for about 5 miles to take my son to school and come home, it still shows that the regenerative braking is limited.

What’s even weirder to me is that this has just started happening even though there were days that I went out and it was colder (last week I remember it was like 39F) and I didn’t experience this after preconditioning my battery.

So my question is, is this normal? Can this be due to any other underlying issues? Again, sorry if my question is newbish, but this is just something that I am not very familiar with.

 

[cleverscreenam]

Yes, but at low SOC why would the supercharging rate be lower than the regen rate in certain SOC/Temp combinations?

And the next question is: will frequent regen age and degrade the battery similar to how we think supercharging will degrade it? Should we all drive with "low" regen instead of "standard"?
And why is regen limited to 85kw when Teslas can supercharge at 150-250kw, and accelerate at 431kw?

 

[AAKEE]

And the next question is: will frequent regen age and degrade the battery similar to how we think supercharging will degrade it? Should we all drive with "low" regen instead of "standard"?
And why is regen limited to 85kw when Teslas that can supercharge at 150-250kw, and accelerate at 431kw?

Tesla did reduce the regen in the M3 compared to before recently in some cases, lika higher SOC and cold battery. Probably a finding that it caused more degradation than Tesla liked. Most probably the maximum regen is already thinked on twice by tesla so you do not need to reduce it.

Batteries can deliver more power than they can be charged with.
For supercharging, the batteries is preheated to quite high temperatures (like 48-50 degre celcius). This reduce the issues with high charging currents. When driving normally, the battery is not even near that temperature, this means that the charging need to be reduced by much to not cause lithium plating etc.

If you look at the maxmimum charging curve for a preheated battery above 50-60% or so doing supercharging the charging power will be less the regen power at the same SOC, despite not having the battery very warm. This is moist probabler because that the battery can handle higher regen power for a shorter time.

The 85kW regen is most probably selected as a reasonable regen power limit, to get reasonable deceleration.

 

[archae86]

I've got a 2023 model 3 RWD I picked up in early November. I see alerts of limited regeneration A LOT. Sometimes it is the dots, and sometimes it is the popup text message. Oddly enough those two forms of notification don't seem to accord well with each other. In particular, while I nearly always see quite a few dots at the beginning of a drive, often they dwindle or even go away. Then I'll get the popup at a moment when there are no dots at all--sometimes.

As my RWD has the LFP battery which Tesla advises us to charge up to 100% routinely, I've driven it at much higher states of charge than I see on our 2022 model Y LR, for which my standard home practice is to charge it to 80%.

But even when the 3 RWD is below 80% I'm seeing regen limitation notifications a lot more than I am used to on the Y. Possibly the colder weather is a major factor disrupting my comparison. Our garage now soaks the cars to 55F, while in the summer it was more like 80F.

My current guess is that for some reason Tesla may enforce tougher regen restrictions on the LFP battery than on their other main type, but that is just a guess.

 

[jcanoe]

I've got a 2023 model 3 RWD I picked up in early November. I see alerts of limited regeneration A LOT. Sometimes it is the dots, and sometimes it is the popup text message. Oddly enough those two forms of notification don't seem to accord well with each other. In particular, while I nearly always see quite a few dots at the beginning of a drive, often they dwindle or even go away. Then I'll get the popup at a moment when there are no dots at all--sometimes.

As my RWD has the LFP battery which Tesla advises us to charge up to 100% routinely, I've driven it at much higher states of charge than I see on our 2022 model Y LR, for which my standard home practice is to charge it to 80%.

But even when the 3 RWD is below 80% I'm seeing regen limitation notifications a lot more than I am used to on the Y. Possibly the colder weather is a major factor disrupting my comparison. Our garage now soaks the cars to 55F, while in the summer it was more like 80F.

My current guess is that for some reason Tesla may enforce tougher regen restrictions on the LFP battery than on their other main type, but that is just a guess.

Turn on the option under Pedals and Driving to have the Tesla Model Y automatically blend in the friction brakes whenever regenerative braking is limited or unavailable. You won't see the dots displayed on the power bar or the notification any more. Works seamlessly.

 

[archae86]

Turn on the option under Pedals and Driving to have the Tesla Model Y automatically blend in the friction brakes whenever regenerative braking is limited or unavailable. You won't see the dots displayed on the power bar or the notification any more. Works seamlessly.

Thanks. The Y is on FSDb, and only quite recently got a software version that includes that function. I had neglected to turn it on--and thanks to you--now I have. I hope the 3 will move on from the factory build to one that includes that function soon.

 

[derotam]

For supercharging, the batteries is preheated to quite high temperatures (like 48-50 degre celcius). This reduce the issues with high charging currents. When driving normally, the battery is not even near that temperature, this means that the charging need to be reduced by much to not cause lithium plating etc.

Yeah but that 48-50C is not a mandatory requirement for the supercharger to be able to push even 250kW. You can get 250kW with a battery at ~20-25C.. If there is such a big problem with high charge rates causing degradation sub 40C then they would be severely reducing charge rate while they heated up the battery...which would take longer than most charging sessions.

 

[AAKEE]

Yeah but that 48-50C is not a mandatory requirement for the supercharger to be able to push even 250kW. You can get 250kW with a battery at ~20-25C.. If there is such a big problem with high charge rates causing degradation sub 40C then they would be severely reducing charge rate while they heated up the battery...which would take longer than most charging sessions.

I do not know the max charging limit by heart but I know high current charging tends to cause lithium plating.
The trick to reduce lithium plating is to heat the battery. Common number is 40C in researchs anout this.
I also se a lot of posts about not at all reaching full charging speed from people that did not give the preheat enough time.

I have data from teslalogger about the max charging power vs cell temp at home but i am currently at work.
I would guess that you need at least 40C to reach 250kW.

I have never really cheated with the preheat so all my supercharging sessions have been with sufficient preheating.

 

[archae86]

I have never really cheated with the preheat so all my supercharging sessions have been with sufficient preheating.

How do you tell?
Also, about how long an approach with preconditioning active does it take for you? And with what starting condition of temperature or recent usage?

 

[AAKEE]

How do you tell?
Also, about how long an approach with preconditioning active does it take for you? And with what starting condition of temperature or recent usage?

I use scan my tesla with a tablet mounted in front of the steering wheel. All data in front of my eyes. This data is also sent home via teslalogger. So it can be viewed at home in detail.
Besides that own composition of values There is a lot of data. Like ”BMS MAX charge” which is the calculated limit that depends on batt temp and SOC.

This is at 23% SOC, the charging has only run for a few seconds.

If you navigate from enough distance it will start prechsrging about one hour before, at least when the ambient calls for need to heat the cabin, the heat is taken from the battery so after a long drive the cell temp is between 12 and 17C.
The preheat will increase the cell temp with about 1C per minute but when reaching 40C the ramping will go slower to hit 48-50C at the SuC.
During hot summer drives the batt can be 35-40C or so, almost no need for preheat and not that long time before.

 

[KenC]

I use scan my tesla with a tablet mounted in front of the steering wheel. All data in front of my eyes. This data is also sent home via teslalogger. So it can be viewed at home in detail.
Besides that own composition of values There is a lot of data. Like ”BMS MAX charge” which is the calculated limit that depends on batt temp and SOC. View attachment 879094
This is at 23% SOC, the charging has only run for a few seconds.

If you navigate from enough distance it will start prechsrging about one hour before, at least when the ambient calls for need to heat the cabin, the heat is taken from the battery so after a long drive the cell temp is between 12 and 17C.
The preheat will increase the cell temp with about 1C per minute but when reaching 40C the ramping will go slower to hit 48-50C at the SuC.
During hot summer drives the batt can be 35-40C or so, almost no need for preheat and not that long time before.

Is that a custom screen you made of the apis you are particularly interested in when driving?

 

[AAKEE]

Is that a custom screen you made of the apis you are particularly interested in when driving?

Well, yes

Its a bit re-arenged. I added the Amphs as i did some tests for @eivissa.

Normally six values seen
Actual speed in the upper middle, battery power to the left (delivered kW) instant consumption to the right.
Lower row, NFP + calculated full range and 0-100 km/h (the later must normally not show above 3.99s

Any other value is only a 1 second away, and I look at other things wuite often.
But that one is the default one.

 

[Davethebrave]

With recent software updates all of a sudden my Feb 2022 M3LR has started showing that 'reduced regenerative braking' symbol.

I keep the car charged at 77% (and park it outside in L.A.), so it's a bit of a concern.

I tend to agree with your observation with software updates. I have noticed after updates several things have changed/ happening. Regen is less while driving at a warmer temperature. 6 degrees C. . It strange, as I have a model 3 as well, and regen is still full strength while at 1 degree C.
Also, my Y reduces speed with message of reduced visibility.???? This a recent event after an update on my Y.
My Model 3 does not experience this.
I drive everyday the same route, road, lanes, time and almost the same raining weather. Its most annoying now, to having your model Y car operating differently after having it for two years(80000 kms)
I compare both the model 3 and Y , they both driven same route, time of the day, weather,...., but the Model 3 operates normal with no performance changes, compared to my Y. ??
Its strange, as I was going to contact Tesla about it, and this week I get another error message saying my power train needs a service. Again with forced reduced speed of 95 KM/hr.
Is this all a coincidence.
I am beginning to think Tesla maybe altering the operating system to suit their warranties.??
I love my Tesla's and considering on buying the cybertruck when it eventually available.

 

[MikeRadio]

Hi all. I found this thread after looking for info on the limited regen indicator.

I’ve had it in when it’s cold and the car is fully charged. I get that it was at 100z and couldn’t regen

today the indicator came on when it was not cold. Was about 75 or 80 degrees… I just finished going down a strep mountain (called the grapevine in I5 if you’re in socal) which made the car do a lot of regen breaking although the SoC was at about 80% and all if the sudden I got the limited regen light for a few mins. It then went away.

was just wondering why. It wasn’t the temp or the SoC of the car as there was plenty space…. The only thing is, it was regen very strongly for awhile Before.

do you think there may be an issue or should I just forget it“. I never seen this before and have been over this stretch in the past.

thanks for the help.

 

[jcanoe]

Hi all. I found this thread after looking for info on the limited regen indicator.

I’ve had it in when it’s cold and the car is fully charged. I get that it was at 100z and couldn’t regen

today the indicator came on when it was not cold. Was about 75 or 80 degrees… I just finished going down a strep mountain (called the grapevine in I5 if you’re in socal) which made the car do a lot of regen breaking although the SoC was at about 80% and all if the sudden I got the limited regen light for a few mins. It then went away.

was just wondering why. It wasn’t the temp or the SoC of the car as there was plenty space…. The only thing is, it was regen very strongly for awhile Before.

do you think there may be an issue or should I just forget it“. I never seen this before and have been over this stretch in the past.

thanks for the help.

Regenerative braking will be reduced or eliminated under specific battery conditions:

A) Low battery temperature (the battery is too cold to accept maximum power (kW) charging from regenerative braking). Solution: Precondition battery before starting to drive. When on route to a Supercharger and using Navigation the Tesla Model Y will Precondition the battery for the most efficient Supercharging charging session.

B) Battery state of charge (SOC); battery SOC is too high and cannot accept maximum power (kW) charging from regenerative braking. The Tesla Model Y's battery management system (BMS) will reduce the amount of regenerative braking that is being used to limit the maximum power going into the battery. If you will be driving on a prolonged downhill grade don't fully charge the battery before starting on the downhill drive. Leave a buffer of ~25% for the Tesla Model Y to make maximum use of regenerative braking, i.e. don't charge above ~75% before starting to drive.

 

[archae86]

Hi all. I found this thread after looking for info on the limited regen indicator.

I’ve had it in when it’s cold and the car is fully charged. I get that it was at 100z and couldn’t regen

today the indicator came on when it was not cold. Was about 75 or 80 degrees… I just finished going down a strep mountain (called the grapevine in I5 if you’re in socal) which made the car do a lot of regen breaking although the SoC was at about 80% and all if the sudden I got the limited regen light for a few mins. It then went away.

was just wondering why. It wasn’t the temp or the SoC of the car as there was plenty space…. The only thing is, it was regen very strongly for awhile Before.

do you think there may be an issue or should I just forget it“. I never seen this before and have been over this stretch in the past.

thanks for the help.

Your experience is perfectly normal. People here prattle on about battery temp and SOC being the only things, but in truth recent power flow (considering both directions) is also an extremely strong short-term determiner.

I happen to live in a place where going down a thousand feet of elevation over 5 miles is a routine start to a drive. That is not a very steep hill at all, but the steady modest (average about 10 kW regeneration power flow is enough greatly to reduce my available max regen on most days. Power flow in the opposite directly, for example, acceleration from a stoplight to 55 mph gives a big boost to available max regen.

I seriously doubt your car has a fixable problem.

But the flatlanders may need to drive some hills while running Scan My Tesla with the Max Regen parameter on display to begin to notice this additional factor.

 

[MikeRadio]

Your experience is perfectly normal. People here prattle on about battery temp and SOC being the only things, but in truth recent power flow (considering both directions) is also an extremely strong short-term determiner.

I happen to live in a place where going down a thousand feet of elevation over 5 miles is a routine start to a drive. That is not a very steep hill at all, but the steady modest (average about 10 kW regeneration power flow is enough greatly to reduce my available max regen on most days. Power flow in the opposite directly, for example, acceleration from a stoplight to 55 mph gives a big boost to available max regen.

I seriously doubt your car has a fixable problem.

But the flatlanders may need to drive some hills while running Scan My Tesla with the Max Regen parameter on display to begin to notice this additional factor.

So othe problem is not fixable?? I hope it is.... Or its a non ssue.

It hasn't happened since... Only after coming off the grapevine with a LOT of regen going on for awhile.... although I still was at a normal SoC and temp was hot.... Thats why I found it weird that went on... But it hasnt gone on since with other long drives.

 

[Rocky_H]

So othe problem is not fixable?? I hope it is....

There isn't any problem. There is nothing to be fixed.