Why doesn't Tesla have a blended braking system? A blended braking system could feed in more regen and have a more consistent one pedal driving experience.
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Blended Braking System
- Thread starter Yoliber
- Start date
bobby g
Member
More Regen~
In EVs I've driven with a blended brake system + one pedal driving, you could brush the brakes to have more regen. Theoretically you could put your systems full regen potential in one pedal driving, but it will be not as smooth and very alarming if you take your foot off the pedal.
Consistent One-Pedal Driving~
With good blended braking algorithm, you'll be able to do one-pedal driving at 100% charge. As of right now, the car would coast in high SoC and require you to use the brake pedal. This is not one-pedal driving. In a blended system, the car will apply the physical brakes for you as you let off the go pedal. This could yield a more consistent performance regardless what SoC you're in.
In EVs I've driven with a blended brake system + one pedal driving, you could brush the brakes to have more regen. Theoretically you could put your systems full regen potential in one pedal driving, but it will be not as smooth and very alarming if you take your foot off the pedal.
Consistent One-Pedal Driving~
With good blended braking algorithm, you'll be able to do one-pedal driving at 100% charge. As of right now, the car would coast in high SoC and require you to use the brake pedal. This is not one-pedal driving. In a blended system, the car will apply the physical brakes for you as you let off the go pedal. This could yield a more consistent performance regardless what SoC you're in.
GM used blended braking on the Chevy Volt (both Gen1 and Gen2 Volt design.) When you applied the brake pedal the Volt would use regenerative braking before applying the friction brakes. This worked seamlessly. The Volt did not support one pedal driving. With one pedal driving the advantage of blended braking is OBE because you rarely touch the brake pedal. Even without one pedal driving the stronger regenerative braking on the Tesla means you don't have to use the brake pedal until you are almost at a full stop.
What's OBE? I still have to use the brake pedal when I'm at high SoC. There isn't enough regen. I think there are benefits in blended braking systems for both one and two pedal driving for reasons I listed above.
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angus[Y]oung
Active Member
I like regen as it is. It's very similar to downshifting a manual transmission, without all the work. You can easily apply all the regen available without causing any friction braking, ensuring no added efficiency losses. As far as I know, the battery and regen hardware limits the maximum regen, not excessive deceleration when letting off the accelerator. More regen may shorten battery life (implied by those temperature and SoC limitations).
The current regen is fine for gliding to a stop in a reasonable manner, very much like I used to do in my manually shifted cars. Then I just have to tap on the brakes at the very end to control my final stopping point, or if I'm coming in hot. It has always seemed very natural.
The current regen is fine for gliding to a stop in a reasonable manner, very much like I used to do in my manually shifted cars. Then I just have to tap on the brakes at the very end to control my final stopping point, or if I'm coming in hot. It has always seemed very natural.
ScoobyDoo82
Member
I personally think that the regen system we have in our Teslas is awesome just the way it is. I have a MY so I can’t select the regen strength like my buddy can I’m his M3.
But, the max setting that is set by default (can’t adjust it) is great after you get used to it. I agree that it’s akin to downshifting. The guy who said this must have a good idea of how to properly use the regen system. It’s all about foot control. I can get my MY to come to a complete stop from 80 mph on every freeway off-ramp without touching the brake pedal consistently.. It just works.
But, the max setting that is set by default (can’t adjust it) is great after you get used to it. I agree that it’s akin to downshifting. The guy who said this must have a good idea of how to properly use the regen system. It’s all about foot control. I can get my MY to come to a complete stop from 80 mph on every freeway off-ramp without touching the brake pedal consistently.. It just works.
Maybe I'm not being clear. I'm not complaining about the concept of OPD.
I'm saying blended braking could improve it by giving consistent deceleration regardless of weather conditions or SoC, whether it is from regen or friction brakes.
If I'm at 100% and it's freezing cold outside, I still want to experience the same deceleration/one pedal driving experience I get when I'm at 20% in sunny weather.
I'm saying blended braking could improve it by giving consistent deceleration regardless of weather conditions or SoC, whether it is from regen or friction brakes.
If I'm at 100% and it's freezing cold outside, I still want to experience the same deceleration/one pedal driving experience I get when I'm at 20% in sunny weather.
What @Yoliber is saying is that the driving experience should, or rather could, be the same regardless of conditions (within reason) and I agree.
My first mile every day is down hill and in the m3 when it's cold out letting off the accelerator does nothing. This versus the afternoon (and most warmer mornings) when I can one pedal the same intersection.
Sometimes I forget and get startled when I take my foot off and nothing happens.
My first mile every day is down hill and in the m3 when it's cold out letting off the accelerator does nothing. This versus the afternoon (and most warmer mornings) when I can one pedal the same intersection.
Sometimes I forget and get startled when I take my foot off and nothing happens.
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Gauss Guzzler
Safety Score = 42
It's really hard to tune blended braking well enough to provide the consistent pedal feel that people expect so Tesla decided it wasn't worth the trouble and potential PR & service hassles. They'd have to mess with the brake booster to vary the pedal stiffness according to the amount of regen available and there's only a miniscule amount of energy to be regained considering that the standard regen setting that most people prefer nearly eliminates all brake pedal use. And note that higher regen levels would be even more inconsistent across the temperature/SOC spectrum than what we already see with standard regen.
Most other car brands do blended braking but they pair it with fairly mild regen so any tuning roughness is not too disturbing. It makes sense for them because when you trade in your old gas Buick for a new electric version you're going to want a similar driving experience - mushy throttle on one pedal and mushy brakes on the other. But with no legacy customers Tesla had the freedom to reinvent anything they wanted, from door handles and air vents to dealerships and one-pedal driving. They chose to force one-pedal not just because most people prefer it, but also because it gives them a range advantage over legacy makers who have to make sacrifices for customer continuity.
Now for blended regen (adding brakes when the battery can't take full regen) I think it's likely that Tesla will add this soon. Surely most people would prefer a more predictable one-pedal behavior and it's easy enough to do this well. They already blend the brakes with regen when cruise control needs to slow down quickly so to fill in for a cold battery should be a relatively simple addition.
Most other car brands do blended braking but they pair it with fairly mild regen so any tuning roughness is not too disturbing. It makes sense for them because when you trade in your old gas Buick for a new electric version you're going to want a similar driving experience - mushy throttle on one pedal and mushy brakes on the other. But with no legacy customers Tesla had the freedom to reinvent anything they wanted, from door handles and air vents to dealerships and one-pedal driving. They chose to force one-pedal not just because most people prefer it, but also because it gives them a range advantage over legacy makers who have to make sacrifices for customer continuity.
Now for blended regen (adding brakes when the battery can't take full regen) I think it's likely that Tesla will add this soon. Surely most people would prefer a more predictable one-pedal behavior and it's easy enough to do this well. They already blend the brakes with regen when cruise control needs to slow down quickly so to fill in for a cold battery should be a relatively simple addition.
How it works is Tesla's battery management software limits the amount of regenerative braking energy that is allowed to flow into the battery. The battery cannot be charged or accept energy from regenerative braking when it is too cold. You start to see this effect when the temperature of the battery pack is lower than ~70F. The power display indicator on the center screen is a thin bar just below the speed indicator. When you see a series of dots on the power use indicator these are to inform that regenerative braking is limited. The reduction in regenerative braking becomes very noticeable when the temperature of the battery pack is lower than 50F.
When the temperature of the battery pack is above 70F the Tesla has full regenerative braking. Between 50F and 70F the Tesla vehicle has some regenerative braking. Below 50F there is very limited or no regenerative braking. Overnight, parked, the temperature of the battery pack in the Tesla will fall and be close to the ambient temperature in the garage or outside air temperature. You can minimize the reduction in regenerative braking by preconditioning the Tesla vehicle in colder weather. Preconditioning the Tesla vehicle will automatically warm the battery pack as well as warm the passenger cabin. In winter plan on preconditioning for at least 15 minutes or more before driving. The Tesla vehicle does not have to be plugged in to use the preconditioning feature however the battery must have at least a 20% state of charge. A typical preconditioning cycle in winter will use 2% of the battery charge (maybe a bit more) depending on how cold it is and long the preconditioning is left running before you drive.
When the battery pack is charged over 85% then regenerative braking is limited. When the battery fully charged or almost fully charged then no regenerative braking is available until you have used some of the battery charge.
When the temperature of the battery pack is above 70F the Tesla has full regenerative braking. Between 50F and 70F the Tesla vehicle has some regenerative braking. Below 50F there is very limited or no regenerative braking. Overnight, parked, the temperature of the battery pack in the Tesla will fall and be close to the ambient temperature in the garage or outside air temperature. You can minimize the reduction in regenerative braking by preconditioning the Tesla vehicle in colder weather. Preconditioning the Tesla vehicle will automatically warm the battery pack as well as warm the passenger cabin. In winter plan on preconditioning for at least 15 minutes or more before driving. The Tesla vehicle does not have to be plugged in to use the preconditioning feature however the battery must have at least a 20% state of charge. A typical preconditioning cycle in winter will use 2% of the battery charge (maybe a bit more) depending on how cold it is and long the preconditioning is left running before you drive.
When the battery pack is charged over 85% then regenerative braking is limited. When the battery fully charged or almost fully charged then no regenerative braking is available until you have used some of the battery charge.
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Great explanation @jcanoe ! Thanks for that, really interesting. Since I charge to 85% every night that explains why I haven’t felt it. Also answers my questions on preconditioning.
thesmokingman
Active Member
It's a car, stop asking it too be a swiss knife.
I keep thinking back to MME's going down a steep Italian road found dead on side of road, can't handle their own amount of regen...
I keep thinking back to MME's going down a steep Italian road found dead on side of road, can't handle their own amount of regen...
bobby g
Member
Thanks, I didn't know that. I had a g2 Volt before my M3 and it scared me once until I learned that regen didn't work with a full charge. I stopped and rebooted the car.
I too am pleased with the regen on my car but that system you describe might make it better yet.
Again, thanks
