Regenerative Braking and Charge Limit

[mraschko]

It seems that regenerative braking capability is tied to the charging limit. I have my charging limit set to ~80%. I often drive down a long downhill within a few miles of my house. I've noticed that at the bottom, I have no regenerative braking capability and have to use the brake pedal. This seems odd to me as the battery should have capacity available.

I don't remember my Tesla behaving this way. The only time I remember not having regenerative braking when going down that downhill was once when I charged to 100% in advance of road trip.

I assume this a bug as the car could get better range if the regenerative braking didn't cut out once the battery charge limit has been hit rather than battery capacity.

 

[mraschko]

Crap. Meant to post this in Driving Dynamics, but can't figure out how to move / delete it.

 

[hydbob]

It seems that regenerative braking capability is tied to the charging limit. I have my charging limit set to ~80%. I often drive down a long downhill within a few miles of my house. I've noticed that at the bottom, I have no regenerative braking capability and have to use the brake pedal. This seems odd to me as the battery should have capacity available.

I don't remember my Tesla behaving this way. The only time I remember not having regenerative braking when going down that downhill was once when I charged to 100% in advance of road trip.

I assume this a bug as the car could get better range if the regenerative braking didn't cut out once the battery charge limit has been hit rather than battery capacity.

Seems to be working as intended no? You want to limit the charge to 80, so it won't let the batteries go above that limit regardless of how the energy is getting put in?

 

[mraschko]

Seems to be working as intended no? You want to limit the charge to 80, so it won't let the batteries go above that limit regardless of how the energy is getting put in?

Thanks for moving the thread.

Maybe it's intended, but as I mentioned I don't think my Tesla had behaved this way and I think it's a miss in terms of range. It's one thing to limit the charage, but (IMO) it's another to limit the reg braking capabilities. Also, it's a bit of a safety issue - if regenerative braking should always match the preferences set (aka driver expectations) when possible.

 

[Adnillien]

I don't think it is intended. The charge limit should not apply to regenerative braking. I would report it to customer care and get their comment.

 

[Halodde]

I don't think it is intended. The charge limit should not apply to regenerative braking. I would report it to customer care and get their comment.

The regen braking is definitely tied to charge level. I've had to charge to 100% the last couple of days for long trips. And as I'm looking at 99% charge, the regen braking is relatively non-existent. I agree the braking should not vary based on the charge level. It should brake the same whether or not it's able to charge the battery as it does it. But I believe in the owner's manual it says that the regen braking will vary at higher states of charge

 

[Adnillien]

The regen braking is definitely tied to charge level. I've had to charge to 100% the last couple of days for long trips. And as I'm looking at 99% charge, the regen braking is relatively non-existent. I agree the braking should not vary based on the charge level. It should brake the same whether or not it's able to charge the battery as it does it. But I believe in the owner's manual it says that the regen braking will vary at higher states of charge

Your case is different. When you are at 100%, the battery cannot take more charge so the car should and does limit regenerative braking. When you are at 80% like the OP, it should not limit regenerative braking.

 

[Halodde]

Your case is different. When you are at 100%, the battery cannot take more charge so the car should and does limit regenerative braking. When you are at 80% like the OP, it should not limit regenerative braking.

I guess I misunderstood the original post. But I still think that the braking should be consistent regardless of the state of charge. To change the regen braking or breaking in general just based off of the state of charge could definitely lead to issues. The car should break the same all the time for consistency and to avoid safety issues. Yes I understand that it cannot put the regen braking power back into the battery at a higher state of charge. But it should still break the same and then just dissipate the energy somehow

 

[MHDave]

I accidentally charged to 87% the other day when I usually have the charge limit set at 80. As I left the charging station I found no difference in regenerative braking, which is in line with others stating that the reduction in regenerative braking isn't apparent until you reach an SoC of mid 90's or so. I might be surprised if I were to drive down a steep hill and find a difference in regen speed reduction with SoC in the high 80's as opposed to 70's, but I would always automatically move to the brake pedal if my speed was still higher than I wanted. Use of the brake pedal should be consistent, but I don't need that to carry forward to conflate regen speed reduction.

 

[Halodde]

I accidentally charged to 87% the other day when I usually have the charge limit set at 80. As I left the charging station I found no difference in regenerative braking, which is in line with others stating that the reduction in regenerative braking isn't apparent until you reach an SoC of mid 90's or so. I might be surprised if I were to drive down a steep hill and find a difference in regen speed reduction with SoC in the high 80's as opposed to 70's, but I would always automatically move to the brake pedal if my speed was still higher than I wanted. Use of the brake pedal should be consistent, but I don't need that to carry forward to conflate regen speed reduction.

Agreed. It's not *necessary*. I cover the brake instinctively when slowing so I'm ready to brake if needed. But having the regen/automatic braking consistent throughout the SOC curve is also not a bad idea.

 

[xponents]

Where would it deposit the energy though? Or maybe the car can just force itself to be more inefficient and burn enough energy to offset the regen braking.

 

[Bunnylebowski]

I guess I misunderstood the original post. But I still think that the braking should be consistent regardless of the state of charge. To change the regen braking or breaking in general just based off of the state of charge could definitely lead to issues. The car should break the same all the time for consistency and to avoid safety issues. Yes I understand that it cannot put the regen braking power back into the battery at a higher state of charge. But it should still break the same and then just dissipate the energy somehow

The answer to your question is brake blending where the car uses friction brakes to offset when the SOC% is too high to take regen. BMW does this well, meanwhile Lucid, Jaguar and Tesla not at all. I think Lucid should be able to do this though as when you’re in brake hold mode when you stop you’ll feel the friction brakes engage at the end and feel the brake pedal depress some, so they definitely can use brake blending. In your situation though it should definitely behave as normal at 80% SOC, are you sure roll/creep are off and brake hold is on? Sometimes those accidentally get switched off? If my car is at 98% SOC it does regen the same it would as if it were 20%. If however it’s 100% it doesn’t regen at all (I’ve only charged that high twice).

 

[Bunnylebowski]

One-Pedal Driving– Please Don't Creep Me Out

EVs allow for a different driving technique known as “one-pedal driving.” But new drivers shouldn’t discover it on the way out of the dealer’s parking lot.

evchargingstations.com

This article helps explain some of the regen/brake blending problems. It’s manufacturer specific. This is written by Lucid owner John Higham, not sure if he’s a member here.

 

[Halodde]

One-Pedal Driving– Please Don't Creep Me Out

EVs allow for a different driving technique known as “one-pedal driving.” But new drivers shouldn’t discover it on the way out of the dealer’s parking lot.

evchargingstations.com

This article helps explain some of the regen/brake blending problems. It’s manufacturer specific. This is written by Lucid owner John Higham, not sure if he’s a member here.

Thank you for all the information. And yes all the settings are still appropriate

 

[Volund]

I've been 85% and have still had a fair bit of regen. So call customer care

 

[Trey]

Came to the forums just to make sure this was noted somewhere. I talked to customer care and:
If your car is 100% charged, it will not do "High" regenerative braking.

This is a huge miss and really dangerous. I ran 15 feet through a stop sign today and slammed on my brakes. BARE MINIMUM should be a notification that regen is not available. Best case would be regen or faked regen via software controlled brake by wire or something. I am rarely at 100% but am heading on a long road trip for the first time and experienced this today.

 

[joec]

Came to the forums just to make sure this was noted somewhere. I talked to customer care and:
If your car is 100% charged, it will not do "High" regenerative braking.

This is a huge miss and really dangerous. I ran 15 feet through a stop sign today and slammed on my brakes. BARE MINIMUM should be a notification that regen is not available. Best case would be regen or faked regen via software controlled brake by wire or something. I am rarely at 100% but am heading on a long road trip for the first time and experienced this today.

This has been covered many times on this forum. And it is typical of many EVs. Lucid should absolutely put up an alert when you are in this state. But the brake pedal is there for a reason.

Regen can lull you into a state of complacency. Have to work at staying alert for these things.

 

[Volund]

Isn't it in the user manual as well?

 

[Lucken]

Isn't it in the user manual as well?

I’m almost sure it is. I’m on my 5th EV and this behavior has been the same with all of them.

 

[kpbhat]

Agreed. It's not *necessary*. I cover the brake instinctively when slowing so I'm ready to brake if needed. But having the regen/automatic braking consistent throughout the SOC curve is also not a bad idea.

i think ther could be some complication related to discharging /storing power which cannot be transferred back to battery pack when in higher charge state. Tesla does the same when car is at full charge capacity when regen braking is completely switched off or non existent. I personally prefer car not reverting to braking system in manual driving mode and let me decide on braking. Otherwise I won’t know how frequently system is using brakes than regen braking.