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.

 

[jdcollins5]

If your battery is Lithium-Ion and you are charging to 100%, it will have limited regen down to about 90-95%. There is no room for adding more charge.

 

[GtiMart]

Regen is charging... and on a dual motor, max regen is around 85kW. That is significant power. There are a few reasons why the battery will not accept full power, similar to when fast charging. Battery temperature is one of those things. For supercharging at 85kW the battery would probably need to be at +100F, which your battery clearly isn't. I think regen lowers those requirements to a point and adjusts dytnamically if you use it for too long, but it's still part of the requirements.
The other aspect is how full your battery is. As with supercharging, you won't get 85kW at the top. If you're over 90% SOC, don't expect full regen. Yes, it might be 95% but for good measure, let's start with 90%. Here too the BMS will let higher power go in the battery from regen than supercharging (because it's for a short period) but might limit if you go down a big hill.

As for detecting if something's wrong with regen... If you never get good regen after those two conditions are met then yes, maybe that is cause for concern. There are other aspects then however, like the car detecting tire slippage and thus reducing regen temporarily, that sort of thing...

 

[derotam]

So lots of variables here but everything sounds normal to me. 50F...even 60F can be "cold" for the car and cause limited regen dots on the left of the power bar to show up. My thought is that your preconditioning in the 39F day vs your preconditioning on the 50/60F day were done differently as far as how long your preconditioned...and/or the time and length of charging was different... For example...if it took longer to charge on the 39F day, then it held heat in the pack for longer and may have kept the pack warmer closer to your departure time, vs if it didn't take as long on the 50/60F day then it had more time to cool down... There are a lot of variables here. The other one is if you have sentry mode on, then you are discharging more and the time that the car goes to top off the pack can vary...if the pack is "cold" when it starts to charge then the car is going to use a good portion of the available charging power to heat the pack.

All seems normal... your pre-departure "pre-conditioning" isn't really programmed to appropriately heat up the battery pack, and if it did it really would be a waste of energy. I think the biggest issue for people is that they braking/regen operation has to change from what they are used too. There is a relatively new setting to allow for friction brakes to be used to supplement for lack of or reduced regen but I have not really played with it yet...maybe as it gets cooler here in the Northern VA area.

 

[KenC]

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.

Normal. Anything below 60F, the car might show limited regen dots on the display. It may disappear after 10mins of driving. If you precondition, your interior and your battery both get some heat, so you may not get limited regen, depending upon how long you preconditioned.

 

[jjrandorin]

I will chime in and also agree with everyone else who has responded to say "normal".

I only pre condition my car for the cabin, so I turn on the HVAC 5-6 minutes before I am leaving, using the app. I have limited regen most mornings, even though I live in southern california, and park in a fully enclosed, drywalled garage with insulated garage doors.

Since this sounds like your first winter with the car, the limited regen is not going to be the most surprising thing, its going to be how much more energy your car uses when its actually cold outside, and what things like "rain" do to efficiency (lol).

 

[therealjimbob]

Normal. Anything below 60F, the car might show limited regen dots on the display. It may disappear after 10mins of driving. If you precondition, your interior and your battery both get some heat, so you may not get limited regen, depending upon how long you preconditioned.

I will chime in and also agree with everyone else who has responded to say "normal".

I only pre condition my car for the cabin, so I turn on the HVAC 5-6 minutes before I am leaving, using the app. I have limited regen most mornings, even though I live in southern california, and park in a fully enclosed, drywalled garage with insulated garage doors.

Since this sounds like your first winter with the car, the limited regen is not going to be the most surprising thing, its going to be how much more energy your car uses when its actually cold outside, and what things like "rain" do to efficiency (lol).

Thank you both. So yeah maybe I’m just not used to it. Crazy enough I switched it over to use the brake when regenerative isn’t available because I’m so used to one foot driving and even after driving for a while it still shows the dots. However I am gonna take both of your advice and just treat it as if it’s normal.

As for the drop in range, yeah I’m waiting for that LoL.

 

[jjrandorin]

even after driving for a while it still shows the dots.

There is no "waste heat" from the engine (or, very little anyway) to warm the battery so it takes "a while" for a battery to warm up. My commute to work is 40 miles one way, and in southern california, where it only snows in the mountains, my "parked in my fully enclosed, drywalled garage that never goes below 45 degrees at any point" car can have regen dots for 25-30 miles of my drive to work.

TL ; DR -- yeah regen dots can be there a while, even someplace that doesnt get cold enough to snow, so its definitely normal for you to see them take a while to go away too.

 

[CheapBastid]

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.

 

[jjrandorin]

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.

It shouldnt be, because you probably havent been through a winter with your car yet. To answer the usual next question, yes, the battery gets cold, even in southern california, even if you are parking in a garage, so yes it will be cold parking outside (even in LA).

 

[AAKEE]

There was a clear change in regen power recently. There is some threads about it, I know because I did find put about that here. Having Scan My Tesla in view when driving show the obvious lower rehen until the batt is up in temp or SOC is low enough.

Tesla has limited the regen power with cold battery. I woul guess they did see that this caused increased degradation and because of this they reduced the regen with lower battery temps.

Last winter a set time for departure with preheat and conditioned battery redulted in about 6.5C or so on the battery. Im quite sure the 6.5C batt temp did not show the blue snowflake for cold battery. (I have data about this.)
This fall I recently set precondition for departure and saw 10C on the battery. No snowflake at 10C.
I also took the car for a drive + charging from cold (batt temp about +2C) and did see the snowflake until the batt temp was 10C.

I guess the same for the warming of battery. Tesla probably found that the battery should be a little warmer.

 

[CheapBastid]

it will be cold parking outside (even in LA).

While you are correct (conceptually) my datapoint is more specific:
It was 70ᵒF and sunny today, the cabin was warm enough that the AC kicked on when I got in at lunchtime to run to the store. The regenerative braking was reduced in a way it never has before the software updates.

Tesla probably found that the battery should be a little warmer.

That's my guess.

 

[jjrandorin]

While you are correct (conceptually) my datapoint is more specific:
It was 70ᵒF and sunny today, the cabin was warm enough that the AC kicked on when I got in at lunchtime to run to the store. The regenerative braking was reduced in a way it never has before the software updates.

That's my guess.

Regen feels less strong this year (2022) that I will agree to, but I have also been experiencing reduced regen from cool (but not snowflake) battery in southern california since 2018. I had more typed here but no matter how much I re wrote it, it sounded argumentative when it wasnt ment to be, it was ment to be informative from someone who lives in the same state.

So I will skip on any further feedback on this topic in this thread, and just say I am positive its nothing to be concerned about as far as something being wrong with the car.

 

[CheapBastid]

Regen feels less strong this year (2022) that I will agree to ... I am positive its nothing to be concerned about as far as something being wrong with the car.

We're in full agreement. =)
Again: My take is that recent software updates have made my M3 more 'protective' of the battery than ever before, as I have never encountered reduced regen (and it's been colder at my house). I didn't realized how much I'd miss one-pedal-driving.

 

[BigNick]

We're in full agreement. =)
Again: My take is that recent software updates have made my M3 more 'protective' of the battery than ever before, as I have never encountered reduced regen (and it's been colder at my house). I didn't realized how much I'd miss one-pedal-driving.

Some of the oldest Model 3 battery packs are 5 years old and they have fleet-wide data on all the packs. If they see a disturbing trend that would result in a ton of warranty claims for >30% degradation, they're going to be quick to change things.

With the number of 3s out there, a premature failure rate of even 10% would be catastrophic.

 

[AAKEE]

Some of the oldest Model 3 battery packs are 5 years old and they have fleet-wide data on all the packs. If they see a disturbing trend that would result in a ton of warranty claims for >30% degradation, they're going to be quick to change things.

With the number of 3s out there, a premature failure rate of even 10% would be catastrophic.

Its quite interresting that a Supercharge session maxed ~ 40-50kW at 85-90% but any regen at the same SOC could be st 85kW. I know it is short bursts, but still…

 

[derotam]

Its quite interresting that a Supercharge session maxed ~ 40-50kW at 85-90% but any regen at the same SOC could be st 85kW. I know it is short bursts, but still…

Yeah it is interesting that the supercharging vs regen rates don't align in like battery temp/SOC scenarios. Your scenario I think is more acceptable though because I would think the car is expecting to continue charging and therefor it needs to start balancing the cells. In regen, you are using regen and discharging so the BMS probably isn't as worried about balancing the cells in such a dynamic environment.

Now on the OTHER hand, when you have reduced regen because of cold, why can you have higher supercharging rates? THAT doesn't make sense. If you are going to limit my regen to say 30kW, then why can you supercharge at a higher rate than that at the same battery temperature? That does NOT make sense.

 

[GtiMart]

Supercharging is certainly limited by temperature. When you plug, the car starts heating up the battery while it charges.

 

[derotam]

Supercharging is certainly limited by temperature. When you plug, the car starts heating up the battery while it charges.

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

 

[GtiMart]

Because regen is for a short time whereas supercharger will last multiple minutes. It probably hurts the battery less.

Note that although good regen (50+kW) can be obtained in the 10-15C territory, the BMS will not keep it that high for long. I was looking at ScanMyTesla while going down a fairly long hill last winter with a battery around 10C and the max regen value was decreasing as I was going down the hill (e.g. regen was getting weaker). Once I stopped at the bottom and accelerated again, max regen started going up again. That value is not just based on battery temperature, it reacts dynamically to what you're doing.