Regenerative vs. Friction Braking

Technically I do not know the answer but if Gen4 is anything like Gen2 your brakes make never need replaced, put it that way

 

Yes, on my 2012 v if I stay in 2 out of 3 white bars at the bottom, then friction braking kicks in at about 7 MPH. (the motors are turning too slow to be effective at lower speeds)

At freeway speeds, it is easy to brake too hard, as there is a lot of energy to absorb. At lower speeds harder braking is still regenerative.

 

As long as the CHG area is not full you are not using the hydraulic brakes. If the speed is less than x mph they are applied and the CHG area reduces even if you keep the same pressure on the pedal.
At high speed the CHG area fills up quite quickly and at any speed if you brake more beyond that mechanical brakes are applied together with regenerative braking.

 

I've noticed if I've washed the car and it's sat for a day or two, built up some surface rust on the rotors, I'll hear noise for the first block or two. That indicates to me the friction brakes are being used. I would say the friction brakes are always used to some degree; it's not completely one or the other.

 

In both my Gen-2 and Gen-3 I could feel the spot in the brake pedal when regen was augmented with friction and vice-versa when regen cut out as I neared a full stop. I believe that you can have regen only, both regen and friction, and friction only during different phases of slowing to a stop.

 

No they are not used, but for sure they set close to the disc. When there is rust it builds a little thickness, that is what you feel/hear.

 

When rolling I hear nothing. Touch the brakes I hear a raspy sound. Sounds like friction brakes to me. Again, I'd say it's a blend, not so black-and-white. Hey, I'll just live with my delusions.

 

I never did brakes, never looked at them on my gen 2 for 200K miles. I'm a smooth driver, and rarely doing any hard braking. The gen 2 switched to the friction brakes at 3 MPH. It was very noticeable. I think my new gen4 switching but is much smoother doing it. The friction brakes in the gen4 feel a little grabby compared to the gen2, but there new. Hope the brakes on the gen 4 hold up like my old Prius.

 

Mendel, RTFM.
From the manual, when you touch the brake pedal and engage regenerative braking the pads are brought very close to the discs. but pressure is not applied. That is causing the sound, the pads are close enough to clean the disks.
Now, the -reason- they are brought that close is to minimize the delay when switching between regenerative braking and friction braking. Perhaps to quiet our constant complaining of braking delay etc.

 

Could be.

 

I need that scrape off the rust early in the morning when backing up. Since I always back up first I do not know what happens pulling forward after sitting all night. But they definitely work at first start up at slow speeds. Good safety feature as they need to be used on a regular basis to keep the parts from corroding together.

 

From the scangauge I can confirm (assuming the report from the vehicle sensor is accurate of course) that the friction brakes are not used until the CHG bar is full with a few exceptions:
1. Under 7 mph only the friction brakes are used
2. If the car goes over a bump while braking, the friction brakes will sometimes engage. If this happens, the regen seems to cut out (current to the battery drops from a max of 80-90 amps down to 5 or so) and the friction brakes will be used for the rest of that stop. The loss of the regen brakes I think is what people feel as a braking loss since they are actually pretty powerful.
3. I'm not 100% sure on this one, but at very high SOC (over 70%) it seems that the friction brakes might creep in a little bit sooner.
4. In N, the car uses only friction brakes, no regen.

 

Yeah, I see there's an XGauge for this, interesting.

 

I couldn't have it explained better. Thanks!

 

I never really understood regenerative breaks. My Mom has a Gen3, and I was explaining how it works the other night... she had no idea. In fact, prior to being a first time owner... and learning how to drive the car for max. regen benefits - I knew nothing about it. Then learning much more about it on this forum (and still learning)... I hadn't a clue.

It's a hard concept to get across with Toyota's marketing efforts.