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Noticed that braking from cruise control suppresses regen

Discussion in 'Gen 3 Prius Main Forum' started by ChapmanF, Nov 26, 2016.

  1. ChapmanF

    ChapmanF Senior Member

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    Maybe this has been observed before, but it has taken me about 6 months of driving my Gen 3, with a ScanGauge in place, to notice something that surprised me.

    Most of the time, I notice pretty strong regen currents (sometimes up to 80 amps or more) when applying the brakes normally. It seems to routinely regen at higher rates than my Gen 1 did.

    But then I noticed that if I have cruise control on, and then I brake by simply applying the pedal (so it cancels the CC and applies the brakes in one step), I get much lower regen, seldom more than 15 or 20 amps. I tried that a few times to make sure it wasn't a fluke, and then I tried first canceling cruise (by pulling the stalk toward me) just before applying the brake pedal, and sure enough, it is back to nice eager regen in that case. Same happens if I tap the pedal once to cancel cruise, release, then brake again normally.

    It seems that the car is programmed to favor friction braking if the pedal is pressed while on cruise control. I guess this could make sense, if we already know it's programmed to favor friction in abrupt/urgent braking cases; that might just mean Toyota programmed it to see brake-pedal-cancels-cruise as a sign of possible urgency.

    I'm now working on training myself to cancel cruise with the stalk, then brake, whenever there's no urgency.

    There was a bunch of related discussion on this old thread about brake-light switch misadjustment, but, oddly enough, that discussion came very close several times to where someone might have noticed this effect, but nobody did ... maybe because it's not really that noticeable without a ScanGauge.

    -Chap
     
    #1 ChapmanF, Nov 26, 2016
    Redpoint5, marlinsmobile and Tideland Prius like this.
  2. drysider

    drysider Active Member

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    I have not noticed this, but will look. Have you tried tapping the brake to drop out of cruise and then braking?
     
    #2 drysider, Nov 26, 2016
  3. ChapmanF

    ChapmanF Senior Member

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    Yes. Tapping first, then braking, has the same effect as canceling with the stalk, then braking. Normal regen in both cases.

    -Chap
     
    #3 ChapmanF, Nov 26, 2016
  4. Tideland Prius

    Tideland Prius Moderator of the North
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    Do not have a scangauge so I haven't noticed it (since it's still regen-ing, that's all I feel. Without hard numbers, I wouldn't be able to tell between 15-20A and 80A)

    Thanks for the heads-up. I normally cancel first since I'll let the car coast but I'll keep that in mind.
     
    #4 Tideland Prius, Nov 26, 2016
  5. bisco

    bisco cookie crumbler

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    what happens going downhill when cruise is trying to hold speed?
     
    #5 bisco, Nov 26, 2016
  6. ChapmanF

    ChapmanF Senior Member

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    Regen, as often discussed before. I just thought here to draw attention to how using the brakes to cancel cruise also biases the car toward friction (just for that use of the brakes), because I hadn't seen that discussed before.

    -Chap
     
    #6 ChapmanF, Nov 26, 2016
    bisco likes this.
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