Regen Brakes Auto Disable on steep road?

[Rivan]

During our snow ski trip to the big bear mountain, I was happy that I am going to get a lot of charge back. I noticed a Regen Brake notification that got Disabled automatically? then the small screen showed the regen symbol, I think it looked like it was reduced. I never seen this before, even with my other EVs, BMW i3 or the Chevy Bolt.. If I had full charge I understand, not sure why it would be disabled if not fully charged? (however, i did get some charge back I think car went from 144 miles -> 158 for around 24 miles ) ..Any idea why it would be reduced?

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[atebit]

Cold battery?

 

[Milermore]

During our snow ski trip to the big bear mountain, I was happy that I am going to get a lot of charge back. I noticed a Regen Brake notification that got Disabled automatically? then the small screen showed the regen symbol, I think it looked like it was reduced. I never seen this before, even with my other EVs, BMW i3 or the Chevy Bolt.. If I had full charge I understand, not sure why it would be disabled if not fully charged? (however, i did get some charge back I think car went from 144 miles -> 158 for around 24 miles ) ..Any idea why it would be reduced?

This happens to me often. I live in a hilly area and going downhill I'll get the regen reduced notice and will need to use the brake.
I don't what's happening behind the scenes, but my assumption (pure speculation) is that regen dumps power into a holding area that gets fed into the main battery. When that holding area fills faster than it can dump into the main battery it stops regen.
Would like to know if someone with more facts has info.

 

[3l3c7r1c]

This happens to me often. I live in a hilly area and going downhill I'll get the regen reduced notice and will need to use the brake.
I don't what's happening behind the scenes, but my assumption (pure speculation) is that regen dumps power into a holding area that gets fed into the main battery. When that holding area fills faster than it can dump into the main battery it stops regen.
Would like to know if someone with more facts has info.

I live in a hilly area and happened to me a lot. I have the similar assumption and pretty sure it has nothing to do with cold battery, outside temp etc. From my house freeway is 1.5 miles away and steep downhill for about 1 mile. If I go all the way down, the car always reduce the regen towards the end of the hill.

 

[Rivdog]

It’s because the battery is too cold, according to the warning that pops up on my Rivian on a near daily basis in the mornings.

 

[s12dxer]

I have also noticed this coming over the Cascades, and it typically is on the very steep downgrades on roads like OR-58. Doesn't seem to matter if battery is cold or warm. Regen is always still available for me, its just "restricted". Albeit, I still end up gaining 2-3% going down the pass while in All-Purpose mode.

My guess had been that the warning was due to either brake temp, or just literally too much regen that the battery couldn't accept at once.

 

[Tahoe Man]

This happens to me often. I live in a hilly area and going downhill I'll get the regen reduced notice and will need to use the brake.
I don't what's happening behind the scenes, but my assumption (pure speculation) is that regen dumps power into a holding area that gets fed into the main battery. When that holding area fills faster than it can dump into the main battery it stops regen.
Would like to know if someone with more facts has info.

What would be considered a holding area?

I not sure what the regen power is going back into the pack depending on downhill grade, but my guess is maybe Rivian throttles it for safety reasons...or battery longevity while the rest of the regen is shunted.

 

[Milermore]

What would be considered a holding area?

Good question. I'm probably making stuff up from watching too much Star Trek as a kid or something.
I definitely don't have a good understanding of what goes on "under the hood" in an EV.

 

[Deleted member 11292]

What would be considered a holding area?

Capacitors.

 

[Insight75]

This happens to me often. Anyone know the specs in regard to how much power the regen puts back in? I like how strong it is....vs my Model 3.

 

[Tahoe Man]

Capacitors.

Perhaps but I'm not sure if there's any EVs that utilize capacitors... Why would it? The large battery packs can handle a good amount is incoming and outgoing power.

 

[DTown3011]

This happens to me in the mountains, both warm and cold temperatures. If I regen for too long, it's almost like it needs to relax or cool down a bit before I get full regen back. It always comes back in a few minutes. I get some, just not full. The regen gauge on the righthand side will actually show a portion of the top end of the range as "crossed out" and thats how you can tell your regen is limited.

 

[Deleted member 11292]

Perhaps but I'm not sure if there's any EVs that utilize capacitors... Why would it? The large battery packs can handle a good amount is incoming and outgoing power.

I'm not sure Rivian is actually using them, but they charge and discharge way faster than batteries and can do more cycles.

https://www.electronicdesign.com/ma...rative-braking-is-redefining-vehicle-dynamics

 

[Tahoe Man]

I'm not sure Rivian is actually using them, but they charge and discharge way faster than batteries and can do more cycles.

https://www.electronicdesign.com/ma...rative-braking-is-redefining-vehicle-dynamics

Yes they have that advantage, I'm not sure if it will ever come to fruition though. Similar to (without looking it up,) I think high pressure hydraulics were considered as an intermediate energy buffer system.

 

[jakef801]

Cold battery?

This. You can see the small snowflake icon next to the accel/regen indicator on the dash. Has happened to me a lot with the extremely cold and snowy winter in Utah. Definitely caught me off guard the first time it happened. It has even happened to me on days where it has been in the 50F temp range.

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