Best I can tell, its exceedingly likely the motor is doing the braking until the car comes to effectively a stop and the booster applies the brakes. The rear motor most likely can generate sufficient braking at very low speeds, that's surely what it feels like is happening, and there is no audible noise of the brakes being applied. I'm not sure why everyone is convinced this isn't possible. I'd imagine the tuning is more challenging as the speed approaches zero, but permanent magnet motors aren't typically terribly challenged by low speed generation. Tesla claims this drive mode increases range, and its easy to feel the braking force gently approach zero as the speed nears zero. On a slight incline the vehicle struggles to stop before applying the brakes. Plus the brakes are hydraulic, I don't see any metric to eliminate the feel in the pedal of the line pressure increasing as the brakes are applied electronically. The car has no magical way to apply the brakes without having some impact to the feel, it literally is effectively pressing a second pedal electronically under the hood.
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
One pedal mode uses the brakes?
- Thread starter BlueWRXPride
- Start date
It was about 20 deg over night. The dotted line was full up to the middle of the bar, and when coasting at speed, there was zero green showing no regen. Someone on here did mention that if I had the heat on (which I did) it could have possibly negated any actual regen to make it look like nothing, it's hard to say for sure.
WilliamG
Hinge Fanatic
I would not assume that at all. The motor is definitely capable of reducing power to slow the car down to 0, even on a slope. I demonstrated this in a video last week. This consumes energy at low mph.
WilliamG
Hinge Fanatic
And say for argument’s sake even if regenerative braking doesn’t work below 60mph, the car is still able to electronically brake using the motors (consuming power, of course). This is what I found happened at ~5mph decelerating to 0mph.
jdcollins5
Member
Elektrek posted an article when they first received the Release Notes for 36.2.1. In describing the new Hold feature they quoted Musk as saying that at slow speeds it would use “blended braking” in which he described a blend of regen and friction brakes.
Yeah, that's totally possible as well. I'd think you'd feel that, as the loading on the drive train would reverse. At low speeds when quiet enough I'd imagine this is somewhat noticeable or potentially audible in the inverter carrier frequency.
One more thing to be aware of, the motor has significant reduction, so its turning a fair bit faster than the wheels are.
No doubt there are situations where it needs to use the friction brakes to stop the car. On flat ground, id say its quite likely the regen goes lower than it did before for sure.
The brakes do not apply at all in my car until it comes to a complete stop and it goes into hold mode.
I don't know how people can be saying they feel the pedal go down before then.
I can only think IF there really is some braking for some people, it is when they are charged to near 100% in very cold conditions maybe?
I don't know how people can be saying they feel the pedal go down before then.
I can only think IF there really is some braking for some people, it is when they are charged to near 100% in very cold conditions maybe?
WilliamG
Hinge Fanatic
I don’t think at low speeds it should make any difference even if the battery is at 100%. The car is capable of using reverse torque and consuming energy - to slow the car down (like in my video above). I haven’t tested this at 100% battery, though.
I’m going to do the foot-behind-the-brake-pedal test today. If I don’t feel any movement of that pedal at 5mph and below I’m going to stick with my assumption that there’s zero friction braking going on when the car is slowing itself, at any speed, when you come off the accelerator.
Of course, if Tesla would just tell us what’s going on, it would simplify this discussion greatly.
What makes you think you can tell if the friction brakes are being lightly applied before stopping? You cannot tell without access to the CAN bus or by visually observing the friction brakes.
WilliamG
Hinge Fanatic
We can only go with what we observe at this point. You can’t prove a negative, after all.
I may go stick some painters tape on a front rotor and drive around without physically touching the brake pedal. That should prove it. If the tape doesn’t get trashed, no friction brake usage.
Your assumption is correct AFAIAC. There is no movement. I already tested it when Hold mode arrived. This whole thing about brake blending is either a big mis-understanding or there are specific conditions needed for it to happen, so if someone is adament they can feel the pedal move, they better post up all the conditions and all the settings on their car so we can all try it.
I'm working partly on the assumption that the elecromechanical brake booster will cause the pedal to move and partly on feel of how the car slows.
I admit, these are not definitive ways to prove it and that still troubles me slightly.
This is how it is described by Tesla in the manual:
"When Model 3 stops, the brakes are automatically applied without you having to put your foot on the brake pedal."
Unless someone is prepared to install pressure sensors in the brake lines, I'm not sure it's going to be easy to prove definitively.
CAN data available currently doesn't include brake pressure, only brake on/off which is probably sensed from a switch on the pedal.
I suppose there are probably more important things going on the world, but this is intriguing...
CAN data available currently doesn't include brake pressure, only brake on/off which is probably sensed from a switch on the pedal.
I suppose there are probably more important things going on the world, but this is intriguing...
Presumably this is practical to demonstrate to some extent. Put the roll mode on, mark a pattern on a front rotor with a marker, slow to ~5 and hit the brakes normally. Observe the damage to the marking on the rotor, clean and mark a fresh line. Turn hold mode on, and repeat the same thing to see for any notable difference to the damage on the marked line. It's possible if the brakes are in good shape the line would mostly or entirely be gone from a 5mph stop, and have significantly less damage if the car regens to near zero before applying the brakes.
TT97
Active Member
WilliamG
Hinge Fanatic
Yes. To me it means when the vehicle stops, the friction brakes are applied.
It’s the same language as saying: when the vehicle stops it’s safe for pedestrians to cross the street.
So it’s the same thing as saying when the vehicle IS stopped.
The online manual says one thing, the actual car option says it a little differently, using the word “blend.” In this case I don’t think there’s any tangible blending per se, - just actually engaging friction brakes at 0mph.
Attachments
The manual is poor at getting into all the intricacies of this. It does not say WHEN exactly the brakes are applied. It also indicates that it will use regen at slower speeds, but doesn't say whether that is affected when you are in a limited regen scenario whether by reason of cold or by high SOC. It also doesn't say whether there is any blending of regen and physical brakes.
I unfortunately do not have any colder weather in the near future to be able to test in the cold induced limited regen condition. I do have access to CANbus data but as Electric Dream stated, brakes is only an on/off metric.
How do you differentiate providing power to slow down the motor vs regen braking power?
