Slightly Depressing the Brakes increases Regen?

[cashcow]

Just noticed this and wonder how this works? If you slightly depress the brakes it does seem like you get a little bit more regen and at times I have seen a whole extra bar. If this is true are the physical brakes engaged if you slightly very slightly depress the brakes? By that I mean do they make contact with the rotors and get worn? I'm confused if they do get to touch the rotors and at the same time get more regen. Why not just have all the regen available off the bat?

 

[miimura]

This is a user experience decision that different automaker do differently from each other. Toyota developed the blended regen for the Prius, so they did the same thing with the RAV4 EV. If you drive in D, you will find that the regen increases quite a bit when you first apply the brakes. If you drive in B, you already get most of the regen before you apply the brakes, but there is still more regen in the first part of the brake pedal. Since the RAV4 EV uses conventional vacuum assisted hydraulic brakes, they are somewhat limited in how they blend the brakes. The VW e-Golf, on the other hand, uses the Bosch iBoost electro-mechanical brake booster. It is a fully digital system that provides pedal pressure feedback to the car and the car can coordinate the regen deceleration and the hydraulic pressure applied to the friction brakes. The VW implementation is much more seamless than the Toyota blended regen braking.

The Tesla Model S and X also use the Bosch iBoost system, but they don't do blended braking. When you apply the brakes it is only friction braking. They only use the iBoost system as the actuator for automated braking in ACC and AEB.

 

[TonyWilliams]

The max regen in Drive is 60 amps.

The max regen in "B" drive is 120 amps.

 

[cashcow]

That's very interesting guys thanks for the replies. Personally I would prefer if the rav4 ev would just apply all regen available instead of having to fiddle with the brakes to try and eek out every bit or regen the motor is capable of. I'm still a little unsure if the friction brakes make contact with the rotors when very slightly depressing the brakes. It does sound like they do, but can someone confirm? I see the word blended so... I'd say yes? I always thought it was more of a slightly depressed = Regen boost and no friction brakes. At least in the leaf because of the grabby brakes that is what I thought

 

[TonyWilliams]

That's very interesting guys thanks for the replies. Personally I would prefer if the rav4 ev would just apply all regen available instead of having to fiddle with the brakes to try and eek out every bit or regen the motor is capable of. I'm still a little unsure if the friction brakes make contact with the rotors when very slightly depressing the brakes. It does sound like they do, but can someone confirm? I see the word blended so... I'd say yes? I always thought it was more of a slightly depressed = Regen boost and no friction brakes. At least in the leaf because of the grabby brakes that is what I thought

I would guess the brake pads move toward the disc every single time you press the brake pedal. How much pressure is applied is the "blended" part.

 

[n3ckf]

this makes the Rav4 stop *incredibly fast*. Which means, secure anything you leave in the back of the car. I moved a toolbox 6' this evening while stopping quick behind someone who *stopped* on the freeway infront of a misplaced construction cone. The car stops *really fast* when it wants to.

 

[yblaser]

this makes the Rav4 stop *incredibly fast*. Which means, secure anything you leave in the back of the car. I moved a toolbox 6' this evening while stopping quick behind someone who *stopped* on the freeway infront of a misplaced construction cone. The car stops *really fast* when it wants to.

You might actually experiencing the Emergency Braking Assist which adds increased braking pressure when the car determines you are attempting a panic stop. IF EBA activates it actually disables increased regen from the brake pedal until you release the brake and reapply.

 

[cashcow]

Thanks Tony you are always so knowledgeable on the subject . Personally I always try to measure my distance to a stop with a blend of N, B, and regular D regen. I try not to use the physical brakes when possible, but there seem to be a lot of desperate drivers so it is difficult . Out of curiosity would you happen to know if the motor the RAV4 EV uses is regen limited? As in... it still is possible to get way more regen out of the motor, but the software only gets you get so much?

Oh and yes secure everything at high speed anything drifting around can turn into a high speed projectile on a sudden stop.... or crash....

 

[TonyWilliams]

The motor is capable of 530 amps in Sport mode, and about 480 amps in Normal operation, so clearly the motor / inverter is VERY capacble of well more than the 120 / 60 amps that it regenerates in "B" and "D" mode.

Those are just software restrictions. There maybe times (obviously) when the battery cannot except either 60 or 120 amps, like when the battery is cold or when the battery is nearly full.

I'm pretty confident the battery could probably take several hundred amps for a very short amount of time., given a warm battery below 50% full.