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Regenerative braking, traction / stability control, ABS question

Discussion in 'Gen 3 Prius Technical Discussion' started by 5 Speed, Sep 20, 2017.

  1. 5 Speed

    5 Speed Member

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    2011 Prius
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    Two
    So everyday when I get off the freeway where I live I have an incline up to a stop sign and usually when I get off the freeway there are no cars behind me so I try and maximize the regenerative system up to the stop sign by just applying the brakes enough to get the regenerative symbol on the dash up towards but not to the max. The off ramp has a major bump in the middle and quite often I feel what I assume is the regenerative braking system drop completely out almost like my brakes have failed momentarily and they it activates about a 1/2 second later but it is a strange feeling because there is no braking action for that brief moment. Am I correct to assume what is occurring is since my vehicle is only using the regenerative brakes when I hit the large bump that the stability control turns off the regenerative system momentarily ? If I push the brakes harder I believe the mechanical brakes would activate? Can I see the regenerative brake system with my ScanGauge and verify what I believe is happening?
     
    #1 5 Speed, Sep 20, 2017
  2. Grit

    Grit Senior Member

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    I
    Check to see if there is a recall on your vehicle using your VIN # to verify that exact issue.
     
    #2 Grit, Sep 20, 2017
  3. bisco

    bisco cookie crumbler

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    yes, road imperfections activate safety systems, because they don't know that it isn't something dangerous.
    can make your heart skip a beat though.
     
    #3 bisco, Sep 20, 2017
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  4. 5 Speed

    5 Speed Member

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    no recalls outstanding except for the airbag bracket
     
    #4 5 Speed, Sep 20, 2017
  5. fotomoto

    fotomoto Senior Member

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    No, it's the ABS/brakes kicking in and cancelling regen. There's a momentary surge/lurch feeling during the transition and Toyota's software (G2&3 not sure about 4) isn't the best at it. It's a FAQ. I can do it at will in my 2006 at a major intersection with a bumpy railroad track crossing in the slow down zone.
     
    #5 fotomoto, Sep 20, 2017
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  6. FuelMiser

    FuelMiser Senior Member

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    It's definitely the ABS taking over and releasing braking action momentarily, and it would not matter if you were in the friction braking zone or simply in the regen zone. When the wheels rise over the bump, they lose a bit of traction (less contact with the pavement) causing them to slow down in relation to the vehicle speed. This is interpreted as loss of grip (skidding if you will) and the ABS releases brake action to allow the wheels to speed back up to vehicle speed. In theory, this will happen to any car with ABS, but seems to affect the Prius more than most, probably due to the complexity of managing regen braking combined with friction braking.
     
    #6 FuelMiser, Sep 21, 2017
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