Ok, let me try again. This discussion is about max regen deceleration. No one ever realistically considers regen deceleration above 0.3g. The driven wheel configuration of the Model 3 (either RWD or AWD) does not appreciably affect the available traction at 0.3g or lower.
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Regen Braking Preferred 3 settings.
- Thread starter LTLT
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insaneoctane
Well-Known Member
Exactly. The fact that the RWD and AWD Vehicles have generally the same deceleration is more evidence that traction limitations are NOT in play. The limitation is Tesla's kW cap. It seems to be 60kW to 70kW for the S/X
I'm sure there's a balance between the force of the regenerative braking and the rate of charge the battery can safely accept. We know from supercharging that the charge rate tapers and I don't think it's practical to have a regen rate that changes dramatically based on how low the battery charge is.
I personally am familiar enough with the regen braking, that I coast to a near-stop under most standard traffic situations. I'd be annoying if that changed constantly as the battery drained.
What would be nice though is if the regen increased to the maximum possible in conjunction with pressing the brake pedal. I suspect though that there's some compatibility issues between the ABS and regenerative braking systems and regen would need to disengage and let ABS handle braking in the event of traction loss.
I personally am familiar enough with the regen braking, that I coast to a near-stop under most standard traffic situations. I'd be annoying if that changed constantly as the battery drained.
What would be nice though is if the regen increased to the maximum possible in conjunction with pressing the brake pedal. I suspect though that there's some compatibility issues between the ABS and regenerative braking systems and regen would need to disengage and let ABS handle braking in the event of traction loss.
There's a difference between deceleration and power that's important to remember. It's the deceleration that we feel and want to control. The power is the limit, but it's only a limit at high speeds. For example, the Bolt EV has a max regen power of 70kW, but in it's highest regen mode the peak decelerations only produce up to about 50kW because the speeds are relatively low. Bottomline, Tesla could change the deceleration profile (to increase deceleration from regen) without needing to increase the max regen power.
You're describing blended brakes, which have been used in most other EVs since the Gen 1 Volt and LEAF. Here's the off-the-shelf component Tesla could have included in Model 3 but chose not to: iBooster. The biggest criticisms I've seen, and share myself, of blended brakes are discontinuous transitions between regen and friction brakes that are awkward to predict and control by the driver.
The ABS functions are currently well integrated with regen systems on Teslas and other EVs.
I had assumed based on all the warnings about changing to low regen in slippery conditions that there were issues. I have an X and haven't had any snow/ice since getting it, so I haven't seen how it reacts.
My only other EV is my motorcycle and I've tried hard to avoid situations where my ABS has to engage.
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insaneoctane
Well-Known Member
Agreed. If Motor Trend's plots are to be believed, then regenerative braking is applied in a fairly linear fashion with approximately fixed deceleration. From there, your SOC will dictate the max charge rate, and would correlate to different possible deceleration rates for different SOC and I'm not necessarily talking about temperature effects here, more SOC charge limits. You can pick a conservative deceleration that encapsulates most SOC conditions and maintains linear and constant deceleration. That is probably what Tesla has done to avoid having a highly variable deceleration rate. I still wish it were higher max and controlled in the GUI!
Robert Llewellyn (fullycharged) recently tested the Tesla Model S 100D, and noted its regenerative braking was significantly stronger than that of his own Model S 85 RWD. It's true that magnetic braking power for the Model S was limited to 50 - 60 kW a few years ago, but there is now reason to believe they may have increased it for dual-motor models, either through software of hardware (rectifier capacity) changes. My earlier comment was that AWD gives you the POTENTIAL for twice the braking power, and that is true, and relevant.
It's certainly doable. Formula E racers can generate well over 100 kW of regenerative braking power (from the telemetry graphics displayed during the race), from the rear wheels only.
I don't remember ever reading that Tesla intended to limit regenerative braking deceleration to 0.3 g. Certainly they could easily achieve more than that on dry roads without compromising stability, using all four wheels. In slippery road conditions (sand, water, ice, snow), where even 0.3 g cannot easily be achieved, four-wheel braking will give you substantially more braking effectiveness than using only the two rear wheels.
50-60 kW regen power is an arbitrary limit going forward in EV development, as is 0.3 g braking deceleration. It's like saying (in the past) that cars would not need to have more than 100 hp or go over 60 mph.
It's certainly doable. Formula E racers can generate well over 100 kW of regenerative braking power (from the telemetry graphics displayed during the race), from the rear wheels only.
I don't remember ever reading that Tesla intended to limit regenerative braking deceleration to 0.3 g. Certainly they could easily achieve more than that on dry roads without compromising stability, using all four wheels. In slippery road conditions (sand, water, ice, snow), where even 0.3 g cannot easily be achieved, four-wheel braking will give you substantially more braking effectiveness than using only the two rear wheels.
50-60 kW regen power is an arbitrary limit going forward in EV development, as is 0.3 g braking deceleration. It's like saying (in the past) that cars would not need to have more than 100 hp or go over 60 mph.
I don't think SOC is really that limiting for regen. I base that on the Bolt EV, which has a relatively conservative fast charging profile. DC fast charging peaks around 55kW (0.8C) at about 55% SOC. However, it's possible to regen at 70kW at ~92% SOC. Above that it does limit regen power, but regen is drastically higher power and SOC than fast charging. I think the high regen is possible because it only happens for a few seconds and then only rarely at such high levels.
I fully agree that AWD gives you much more potential for regen brake deceleration. However, nobody brakes harder than about 0.3g during typical driving. If you did, your passengers will start to comment on your poor driving skills and it wouldn't take long for you to get rear-ended. So while it's certainly possible to design a regen system to brake harder, the average driver will not use it nor care that it exists. (Performance oriented or track driving is a completely different scenario.)
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Futuresystem
Member
"You're describing blended brakes, which have been used in most other EVs since the Gen 1 Volt and LEAF. Here's the off-the-shelf component Tesla could have included in Model 3 but chose not to: iBooster. The biggest criticisms I've seen, and share myself, of blended brakes are discontinuous transitions between regen and friction brakes that are awkward to predict and control by the driver."
The blended brakes in our Mitsubishi PHEV are absolutely brilliant, with the shift between pure regeneration and brake activation being all but imperceptible. The other thing I love about the PHEV is the five levels of regen, selected via flappy paddles.
Having said that, I usually use level 5 in the PHEV (max regen) where my wife normally uses level 2, the automatic default setting.
When I did 400 odd kilometres in a model S in late 2017, there were only two regen levels available, selected on the centre screen. Being used to regen on our PHEV, I found the model S regen excellent, and did nearly all the driving with just one pedal. (Somebody earlier mentioned three levels of regen- not correct as far as I'm aware unless there has been a software update changing that.)
It would be really nice however if there were more levels of regen available in the S, X, and 3, and preferably very easily changed whilst driving.
Different levels are very nice to have depending on the type of driving you're doing at the time, eg: suburbs, main roads, freeways etc.
Cya (from downunder)
The blended brakes in our Mitsubishi PHEV are absolutely brilliant, with the shift between pure regeneration and brake activation being all but imperceptible. The other thing I love about the PHEV is the five levels of regen, selected via flappy paddles.
Having said that, I usually use level 5 in the PHEV (max regen) where my wife normally uses level 2, the automatic default setting.
When I did 400 odd kilometres in a model S in late 2017, there were only two regen levels available, selected on the centre screen. Being used to regen on our PHEV, I found the model S regen excellent, and did nearly all the driving with just one pedal. (Somebody earlier mentioned three levels of regen- not correct as far as I'm aware unless there has been a software update changing that.)
It would be really nice however if there were more levels of regen available in the S, X, and 3, and preferably very easily changed whilst driving.
Different levels are very nice to have depending on the type of driving you're doing at the time, eg: suburbs, main roads, freeways etc.
Cya (from downunder)
Right, so would maybe a paddle on the steering wheel, like the Volt Gen 2 has, which allows the driver to use more regen when circumstances are appropriate, but otherwise use the brake pads when not pressing the paddle?
There are a lot of times when I drive my M3 around, and I'm in Low regen mode (thereby able to coast more, and not use any energy, or a lot less, when coasting) where I'd love to use regen to brake, but I can't because Low adds no additional regen when I brake.
Glamisduner
Active Member
I like blended brake feel on the highway and regular regen when driving around town. That's kind of what I have on the volt (although it's just high low like the tesla) the difference is that on low mode, you get the blended braking still so you ALWAYS get strong regen. ( I think you get some on high regen as well)
Contrary to the directions, I find 0 regen is best for efficiency on the highway if your not stopping. If you pop into neutral and let the car accelerate a bit down the hill then up then next one then pop it back into cruise control as you hit your original speed.
Regen is a great way to capture energy when you need to slow down, but is not as efficient as just rolling.
Or add a paddle to the wheel so I can leave it in low regen and just pull the paddle when I want to slow down without using the brakes. It sounded dumb to people at my work to have one more thing to worry about, but for me it just makes sense to have a paddle when you don't need to slam on the brakes. Save the brakes and charge your car!
Contrary to the directions, I find 0 regen is best for efficiency on the highway if your not stopping. If you pop into neutral and let the car accelerate a bit down the hill then up then next one then pop it back into cruise control as you hit your original speed.
Regen is a great way to capture energy when you need to slow down, but is not as efficient as just rolling.
Or add a paddle to the wheel so I can leave it in low regen and just pull the paddle when I want to slow down without using the brakes. It sounded dumb to people at my work to have one more thing to worry about, but for me it just makes sense to have a paddle when you don't need to slam on the brakes. Save the brakes and charge your car!
The discussion about regen comes up here often and it;s always about what setting would be best or preferable. Once you think about it the same as the accelerator, then you can forget all settings and hand pedals and different strength. Just like you can modulate power from zero to full power with the accelerator, now you can also modulate regen from 0 to full with the same foot pedal. And you don't even have to switch pedals!
The confusions and different preferences are all rooted in the old way ICE vehicles work. Unlearn it and forgot it. You have one pedal that lets you adjust positive and negative torque from zero to max. That's the best and simplest way to do it and it works great once you get your old habits out of your head.
You don't need a hand pedal or different settings to adjust how much power the accelerator gives you. Regen is the same way. You adjust to with the same foot as you like. Light, soft, strong, all the way, whatever you want, it's all linked to your foot.
The confusions and different preferences are all rooted in the old way ICE vehicles work. Unlearn it and forgot it. You have one pedal that lets you adjust positive and negative torque from zero to max. That's the best and simplest way to do it and it works great once you get your old habits out of your head.
You don't need a hand pedal or different settings to adjust how much power the accelerator gives you. Regen is the same way. You adjust to with the same foot as you like. Light, soft, strong, all the way, whatever you want, it's all linked to your foot.
Glamisduner
Active Member
Id like to feel this way but I do not. It's hard to get your foot right into that perfect spot where your not getting regen or using power, compared to just lifting your foot off the throttle or slightly pressing the throttle. Especially on the higher regen mode where the same amount of movement in the pedal creates higher variance.
Every time you lift slighly too high and start to regen rather than coast your losing efficiency.
However tesla's high regen did seem easier than high regen mode on my volt, but still I think a paddle would be ideal. GM did a great job there.
Glamisduner
Active Member
Do you think a higher regen mode will be released?
See post 2 of this thread.
Exactly How Strong is the Regen?
See post 2 of this thread.
Exactly How Strong is the Regen?
I'd be happy if the Tesla provided the same regen settings as my Zero motorcycle. Two sliders that let me determine the coasting regen from 0-100% and the braking regen from 0-100%.
I think the upper limit on the regen is ultimately based on how much power the motor can safely generate, convert and pump back into the battery, At 90% charge on my Model X, the regen is already capable of higher power generation that I'd receive plugged into a supercharger. At lower states of charge, the regen should be capable of higher regen, but I like the fact that the coasting regen is consistent regardless of battery state, with the exception of the battery being too cold or too close to 100%.
I'd be nice if the coasting regen provided the steady max 60 kW of regen, but could increase to 90 kW through blended braking with the friction brakes, depending on what the battery could accept.
I'm not sure how much more efficiency it would really add though, because the consistent regen allows me to slow down under almost all circumstances without needing the friction brakes. Only in abrupt stops would I mitigate energy lost to the brakes and that just doesn't happen often.
Exactly!
You might be 78 years old, but in your mind you are young and able to learn quickly. That's something young people should be able to do, but I think sometimes their ego gets in the way of learning and adapting.
Fusion
Member
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