Braking regeneration

Yeah I have noticed that, does feel weird.

 

Huh, not sure what you mean. So that jarring braking can happen when one wheel is over a funny object? Haven't noticed this yet myself but my brakes really jerk occasionally even with a very light foot just pulling into my driveway or coming to a relatively slow stop at the traffic lights.

It's like coming to a slow stop and then tapping the brakes like a millimeter more somehow triples the stopping power all of a sudden. In certain little instances, the modulation is terrible like this.

 

Once in a long while I get something like that (again 3rd gen). It's always in reverse, and just after start up. The brake modulation is GONE; the slightest touch on the brake pedal and they're LOCKED.

First time I noticed I'd started backing up in a street side parking spot, in preperation to exit. I was getting close to the car parked behind, touched the brake and came to a brutal/sudden stop. Thought for sure I'd misjudged distance and hit him, but nope.

 

The Prius approach works better in "mixed" households where one person is the tech geek who understands and enjoys playing with all the nuances of driving a Prius, and the other person couldn't care less about the technology and wants to just drive the car like they have driven cars all their life.

 

The most usual thing people notice is it feels like the brakes ungrab for a split second. The car detects the funny object and thinks "hmm, I'd better hurry up and switch to friction in case the traction is sketchy here", and in doing that it backs off the regen right away and the friction is a little slower to reach the same level, so there's that split second of ungrab.

When my brakes feel extra grabby, kinda the opposite feeling, they've usually picked up some surface rust from a night in the rain.

 

That's a funny and probably extremely correct way of putting it. Essentially the most vanilla approach to make a car for the person who wants something forward thinking and efficient but without making any real changes to how they are used to a car driving. Maybe they'll drive more conservatively since the car presents you with information regarding your stats on efficiency.

Otherwise, it's exactly like any other car! Gets me from A to B and with half the gas! What is modulation? What is a CVT? Etc etc.

I really dig the car. I will say that I think my next car will be a Tesla but I got the Prius to save money now and it's a way of waiting and seeing what new things Tesla comes out with in a year or two, which is probably plenty of time for them to make me wish I had waited if I bought a Tesla now. I can afford one but I can really only justify it if I make it count.

Thank goodness I was too poor to get a Model S 3 years ago.

P.S. still too poor but those are like 1/3 or so the MSRP now. Surely the more recent ones will hold value several times better. And if not, wow, good for Tesla for outgrowing their previous generations of cars that quickly.

 

What is disturbing on the Gen 4 is that if it thinks you could hit something it "helps" and makes the brakes extra sensitive . Really disturbing when the car detects incorrectly.

 

OK, I have resisted the title misspelling all I can.

Ways to break regeneration

1) shift to N. In N there is no regeneration.
2) stay under 7 MPH. below 7 MPH, the motors are turning too slowly. It is always friction braking.
3) panic brake every time. if the computer senses panic braking it switches to friction brakes.
4) fill the battery. Once the battery is 'full' no more regenerative braking can happen.

I just had to answer the topic in the title.

 

We've got kinda the same thing: brake assist.

It doesn't seem to depend on forward obstacle detection, just how fast you go on the pedal. But that also means you don't need a fancy newer Prius to have it. 2010s have it.

I don't know if it has ever triggered for me. If it did, I guess that means it wasn't very disturbing.

 

The level below full auto braking to a stop for an obstacle is the car applying brakes to slow the car. If the car starts doing that because of a false positive while the driver applies the brakes, it could seem like more braking than expected.

 

You missed the obvious one. A large enough crash will break regeneration and acceleration too.

That breaks regeneration? How is it then repaired??

 

Well, as they say, "Them's the breaks!"

 

I think it is time to put the brakes on this thread.

 

HA! What better way than with a dead end pun.

Good stuff. I think the point has been made and the questions answered.

Thank you all! Overall the braking is just fine. It is just way too touchy on ocassion and not so predictably and that's my only gripe with them. Can live with it, not a big deal. Learned that the car uses combined friction and regen braking based on the pedal input and I didn't know that before, which if I had, I would have been more understanding of the complaints I had initially.

 

You just experienced some of us crazy wise old folks. We enjoy fun while social distancing.

 

I am curious about your Tesla, if you go down a very long hill where one would need engine braking to keep the brakes from overheating in a gas car, and the Tesla battery is fully charged, how does it shed energy to protect the brakes?

 

Good question. It would probably just disable regen like it does in super cold weather since batteries hate being charged when really cold.

However, this probably wouldn't happen. The battery is massively bigger and I imagine even a 90% charged battery is able to take more regen than a mostly discharged Prius.

 

Thinking about a 'worst case', the Mt. Washington NH Toll Road rises 4618 ft in 7.6 miles. A Tesla S with driver is about 5000 lbs. The potential energy at the top is E=mgh, switching to metric E=2270 * 9.8 * 1410 = 3.1E7 Joules or 8.6 kWh that needs to go somewhere to avoid melting the brakes. Tesla S battery is 60-100 kWh so you are right, even at 85%-91% charge, a Mt. Washington descent could be done on regen alone. That's one hell of a battery!

 

Unless it's really cold outside.

That's cool you did the math. I just went off of a feel-based guess from what I understand about how much range both cars have on the battery.

Thanks for sharing! Interesting to know what the worst case would be haha.

I also love the idea that at higher altitude, gas cars lose mpg due to less oxygen but electric cars gain it due to less drag from the thinner air.

 

I don't think air drag at any highway elevation is much of a factor. As a kid in Colorado, I used to fly kites clear out of sight. My house wasn't even in the mountains and it was about 1,000 feet higher than the top of Mt. Washington.

But oxygen availability for engines or lungs is a huge factor.