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Why do people say the feeling between regen braking and regular braking is so different?

Discussion in 'Gen III 2010+ Prius Main Forum' started by luvmypriushybrid, Jul 21, 2011.

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  1. luvmypriushybrid

    luvmypriushybrid Junior Member

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    I know this thread belongs in the Technical Discussion, but there are so many more people viewing in here...

    I have a question about the feeling people complain about when it comes to regenerative braking compared to regular braking...
    I own a 2010 Prius and this is my first hybrid. For years I have been reading, especially in car magazines, that the regenerative braking in the Prius leads to a squishy feeling brake pedal, and that you can "feel" when the regen is taking place via the brake pedal.

    Of course when I brake it feels different than it did compared to my 2008 Honda Fit Sport I had...but what kind of "feel" from the brake pedal should I be looking for when I am in regen mode?

    Also, when I take my foot of the gas, how do I know if I am applying too much or not enough pressure on the brake pedal to engage regen braking? I always try to apply a little pressure at first, and then more as the stop is coming nearer...always making sure the bar in the "charge area" of the Hybrid System Indicator never goes all the way to the left.

    I would really appreciate any input, opinions, personal experience, etc. you all have...and sorry this was SOOOOOO long...
    thanks!!!
  2. airgas1998

    airgas1998 New Member

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    Re: Why do people say the felling between regen braking and regular braking is so different?




    try to keep charge bar at 1/4 to 1/2, as others on here have said before brake like you don't have any.
  3. Dark_matter_doesn't

    Dark_matter_doesn't Prius Tinkerer

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    Re: Why do people say the felling between regen braking and regular braking is so different?

    The big braking complaint for Gen III Prii has been a "floaty" non-braking feeling when using the brakes on a rough surface. The root cause was "excessive" delay transitioning between regen brakes & hydraulic brakes, and this was fixed in last year's recall by reducing the transition time in software.

    I sense no brake feel difference between my Prius and my other conventional vehicles. Toyota has done an excellent job of making a Prius operate just like any conventional car and concealing what's really going on under the hood.
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  4. pictone

    pictone New Member

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    Re: Why do people say the felling between regen braking and regular braking is so different?

    I sense a huge difference between the braking in my 2011 Pruis vs. every other car I've ever owned, most recently a 2007 Sonata. This is especially prevalent when moving slowly. It feels like the brakes don't even engage until the pedal is pressed a good distance. I'll be thinking that I have plenty of distance to come to a stop, and then must suddenly floor the brake because the car hardly slowed at all.
  5. mad-dog-one

    mad-dog-one Prius Enthusiast

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    Re: Why do people say the felling between regen braking and regular braking is so different?

    I can detect a slight difference between regen and Friction braking, although I have no complaints about this Prius feature. The fact is, when I drive other cars that don't have regen, not recapturing spent energy using regen seems absurd.
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  6. macman408

    macman408 Devil's Advocate General

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    Re: Why do people say the felling between regen braking and regular braking is so different?

    I have no idea about the squishy feeling, other than they might be complaining about the stroke simulator, since the Prius norally won't directly connect the pedal to the hydraulic brake system, unless there's a failure. This shouldn't feel different between regen and not, though.

    For best regen, you should keep the CHG bar mostly full, but not past full. People say you should *drive* like you have no brakes, because any time you brake, it means you accelerated more than you absolutely needed to. But the regen system has some constant losses, and some losses proportional to the amount of braking; so given that you have to stop, you're better off braking harder (but not filling the CHG bar completely) to minimize the length of time and hence the constant losses. (To make up numbers, say the losses are 10% plus 3 arbitrary units. If you brake at "10", you lose 10%*10+3=1+3=4, or 40%. If you brake at "100", you lose 10%*100+3=10+3=13, or 13%. So it's important to have the braking be much higher than the constant losses, even though these numbers are just illustrative.)
  7. cproaudio

    cproaudio Speedlock Overrider

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    Re: Why do people say the felling between regen braking and regular braking is so different?

    I always brake at 95-99% of the CHG bar. It gives the maximum regen without touching the friction brakes. It works really well without effecting the flow of traffic.
  8. Skoorbmax

    Skoorbmax Senior Member

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    Re: Why do people say the felling between regen braking and regular braking is so different?

    I find regen and normal transition to be incredibly, almost imperceptibly smooth.
  9. luvmypriushybrid

    luvmypriushybrid Junior Member

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    Re: Why do people say the felling between regen braking and regular braking is so different?

    Thanks guys...I have noticed, for instance, when getting off an interstate ramp...coasting all the way to the light without using the brakes that much produces very little battery charging.
    In another instance, I keep my speed higher than when I was coasting approaching the light. I then use more force on the brakes being careful though to keep the charge bar close to 100% before coming to a stop. Now under that circumstance, I noticed the battery charge was about 3-4 bars HIGHER than coasting.
  10. xs650

    xs650 Senior Member

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    Re: Why do people say the felling between regen braking and regular braking is so different?





    When I test drove a couple of Prii and got mine a year ago, I noticed in tended to almost over run the place I intentioned to stop. After a few hours in the car I started automatically correcting. Not a problem, just an observation.

    One small problem I have with Prii brakes is that is is very difficult to avoid the slight jerk feeling as you come to a stop. In other cars I can stop smoothly enough that you can't feel exactly when the car stops rolling, but not in a Prius.

    It is also difficult to creep ubber slow through the blow dryer in a car wash. When I get the car going as slow as I want, it stops. There is no smooth control available below about 1/2 mph.

    My 400 hp Corvette is easier to finely control under all three of those scenarios than my Prius.
  11. macman408

    macman408 Devil's Advocate General

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    Re: Why do people say the felling between regen braking and regular braking is so different?



    Coasting is what you want to do. If you keep your speed up, it means the car is burning more gas to do so. Some, but not all, of that wasted gas will be recovered into the battery for later, but it's not the most efficient way to drive. Coasting means you aren't using gas at all (even though the engine will keep spinning until you drop to 43 mph).
  12. Tideland Prius

    Tideland Prius Moderator of the North Staff Member

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    Re: Why do people say the felling between regen braking and regular braking is so different?



    Gliding would be even better (Coasting means there's some regen as indicated on the HSI).
  13. kgall

    kgall Active Member

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    I'm one of those who can't tell the difference--can't tell by feel when the "crossover" to friction braking comes in the Prius.
    On your how much pressure question--whenever you are in the charge area you are doing regeneration, so far as I can tell.
  14. jdcollins5

    jdcollins5 Senior Member

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    If you want to feel the difference between regen and friction braking, the next time you are doing light regen braking, like when pulling up to a stop light, shift to neutral. This will disable regen and enable friction braking.

    In my car I have to press the pedal a little harder with friction brakes for the same amount of deceleration.

    Most of the discussions on this has to do with the transition from regen to friction when you are lightly braking and go over a bump or slick surface and the ASB kicks in.
  15. macphile

    macphile New Member

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    When I test drove, I felt the brakes were really tight. I don't know if they're less tight in my Prius than they were in the test drive or if I was just aware of it and being more careful, but I've not noticed any major difference that I wouldn't be able to just attribute to it being a new car and a different manufacturer and model. I paid attention to the regen today, though, on the display. It's fun to watch the arrows change around as you do things. It was still showing regen even with my foot off the pedals, though? I was also watching as I waited at the drive-thru and the engine started up to charge the battery. Anyway, I can't say I notice any alarming difference.
  16. ProVega350

    ProVega350 Junior Member

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    I am a hot roder so I am always looking for performance. In the case of a Prius that means maximizing miles/gallon. We have owned our '11 Prius III for three months, so I am no expert, but I'll give you my observations.

    When I am slowing/stopping I watch the Instantaneous fuel consumption (MPG) gauge and the car ahead of me. I push on the brake pedal to maximize the MPG gauge. If you listen, you'll hear the generator changing the battery. If I haven't started my braking soon enough and am at risk of not stopping in time, I'll push harder to bring the car to a stop.

    You will feel and hear the difference between regenerative and friction braking with time.
  17. Sabby

    Sabby Member

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    It is different but I believe it works well. The regen braking is more to me like a "pre" braking with a feeling similar to downshifting a manual car prior to braking. It provides some added drag without major braking. If I have plenty of distance and can anticipate all I need is the regen braking. If more braking is needed I press harder and concentrate on stopping the car and take little note of what is doing the braking.
  18. Rebound

    Rebound Senior Member

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    Regenerative braking is an effect very similar to downshifting a manual transmission car, only much smoother. I don't have any problem with my Prius brakes. I'm usually a very gentle driver. I drive cars to make them last. So I always brake gently and gradually, and the Prius is fine. The brakes I don't like are ones that are too sensitive and grabby, like they're made for jackrabbit starts and stops.

    I've panic-stopped my Prius several times, literally slamming the brakes, and they always worked perfectly. No lag at all, the friction pads just grab like they should.
  19. qbee42

    qbee42 My other car is a boat

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    Re: Why do people say the felling between regen braking and regular braking is so different?



    This isn't because of regenerative braking, but because of the control algorithms. Your Prius is mostly drive-by-wire, which means your foot on the brake is really a request to the computer, which then decides how much brake to apply. Because of this, the designers of the Prius could have decided on any sort of brake feel. They went with a very linear map, where half pedal produces half braking.

    Most cars are not so linear: some grab up front, others not much to the end. It's all in the mechanics, or computer interface. All of the Prius controls are like this. The accelerator is evenly mapped, and steering is uniform, which leads many car enthusiasts to complain that driving a Prius is like driving an appliance.

    Tom
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