Are the temperature thresholds for regenerative braking overly conservative?

[PastyPilgrim]

With spring arriving now, I've been surprised by how conservative the regenerative-braking-lockout seems to be. I took delivery last July, before the R1s had any limiting of regenerative braking due to cold temperatures, so I'm not sure yet what Rivian is defining as cold, but with temperatures in the 50s, 60s, and 70s now (in New England), I've been surprised to find that regenerative braking is still usually limited when starting out. Do other EVs restrict regeneration as conservatively as the R1s do (or at all even)?

That sensation of having regenerative braking cut out from under you at a variable and unexpected threshold is such a triggering sensation. It reminds me of those effects that Inception used to wake people from dreams (the sensation of nearly falling, etc. that immediately trigger your mind).

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[sierraskier]

Following....

Probably my biggest gripe with the vehicle so far.

 

[srnyoung]

Yes!
Headed out to work last week and was surprised by minimal regen at 45+ deg temps. If the battery is not warm - 70+ maybe? - seems like minimal regen.
When that's the case I wish there was more warning than the teeny snowflake next to the speedo.

 

[VSG]

I don't think outside temperature is the primary factor. Regenerative braking charges the battery, so the amount of braking is limited by what the battery can accept at the time. State of charge can limit regenerative braking, and a battery that's too cold can limit regenerative braking, but this is more about the battery than the outside temperature. I imagine preconditioning the battery before driving would eliminate some of the variability.

 

[Sgt Beavis]

My perception is that regen has gotten more sensitive to temps over the last few months. I do a lot of mountain driving and it seems that everyday I get a reduced regen alert at some point. Originally that never happened..

It’s not a massive problem for me but I have noticed it.

 

[Rivdog]

With spring arriving now, I've been surprised by how conservative the regenerative-braking-lockout seems to be. I took delivery last July, before the R1s had any limiting of regenerative braking due to cold temperatures, so I'm not sure yet what Rivian is defining as cold, but with temperatures in the 50s, 60s, and 70s now (in New England), I've been surprised to find that regenerative braking is still usually limited when starting out. Do other EVs restrict regeneration as conservatively as the R1s do (or at all even)?

That sensation of having regenerative braking cut out from under you at a variable and unexpected threshold is such a triggering sensation. It reminds me of those effects that Inception used to wake people from dreams (the sensation of nearly falling, etc. that immediately trigger your mind).

Couldn’t agree with you more!

 

[Dark-Fx]

It takes a long time for the battery to heat up from outside influences, and it's still been significantly cold over night here, so plenty of opportunity for it to cool down.

 

[mikehmb]

They radically curtailed regen duration and strength in, I believe, 2022.47.x. That’s about when I was no longer able to go over the hill here from home and regen all the way at max strength down the other side.

 

[rhumbliner]

My perception is that regen has gotten more sensitive to temps over the last few months. I do a lot of mountain driving and it seems that everyday I get a reduced regen alert at some point. Originally that never happened..

Recently I was routinely driving a very curvy stretch of highway with a 7% or 8% grade. The downhill portion always gave me the “regenerative braking reduced“ message so I punched the emergency flasher to mark the log and then called service and asked them to diagnose the problem. They told me the BMS reported the battery was overheating due to the regen and they had to let it cool down.

 

[jjswan33]

They radically curtailed regen duration and strength in, I believe, 2022.47.x. That’s about when I was no longer able to go over the hill here from home and regen all the way at max strength down the other side.

Agreed. I had never saw a regen warning coming down from Mt Hood to home until that update now I see it every time regardless of temp.

So yes it is now more sensitive to temps it is just more sensitive overall, battery cold or not. Hope they improve this in an OTA.

 

[Trandall]

Recently I was routinely driving a very curvy stretch of highway with a 7% or 8% grade. The downhill portion always gave me the “regenerative braking reduced“ message so I punched the emergency flasher to mark the log and then called service and asked them to diagnose the problem. They told me the BMS reported the battery was overheating due to the regen and they had to let it cool down.

Could be a motor overheating situation as well.
My daily commute home takes me down a long, steep, windy descent where I have been needing to put the friction breaks through their paces more than I would like. Can really feel the inertia of a 7K# truck on a steep descent. I would certainly welcome increased regen.
Any engineers who could recommend a strategy to absorb or bleed off the regen power when it can be taken by the battery due to temperature or charge limits?

 

[cjones1130]

Recently I was routinely driving a very curvy stretch of highway with a 7% or 8% grade. The downhill portion always gave me the “regenerative braking reduced“ message so I punched the emergency flasher to mark the log and then called service and asked them to diagnose the problem. They told me the BMS reported the battery was overheating due to the regen and they had to let it cool down.

I wonder if swapping to standard regen in this type driving would be better.

 

[VSG]

They radically curtailed regen duration and strength in, I believe, 2022.47.x.

Did this coincide with the changes to fast charging where the charging rate used get limited and turned down shortly after hitting 200kW due to the battery heating too fast?

 

[mikehmb]

Did this coincide with the changes to fast charging where the charging rate used get limited and turned down shortly after hitting 200kW due to the battery heating too fast?

Ooh - really good question. I think it was prior to the changes in battery prep for the improvements in charging efficiency.

 

[jjswan33]

Did this coincide with the changes to fast charging where the charging rate used get limited and turned down shortly after hitting 200kW due to the battery heating too fast?

It started with 2022.47.0.

From the release notes:

• Improved battery longevity, battery durability, and regenerative braking performance. Also enhanced regen availability, and you can use regen for longer durations.
  

  NOTE
  Regen performance may be reduced at lower ambient temperatures.

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