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Slow stopping wastes battery?

Discussion in 'Gen 2 Prius Technical Discussion' started by tom1l21, Apr 29, 2009.

  1. tom1l21

    tom1l21 Member

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    I noticed that if you try to come to a very nice gentle stop that you infact are wasting some battery. When I see a stoplight ahead and I am too close to do a full out coast to the light, I apply the brakes in a manner that will get me to the stop line just as I approach 0mph. I like to do the gentle stops where you can barely feel the brakes react. The problem is that as I ease up on the pedal, the battery is then used to creep. So essentially I am creeping with the battery (this is all around speeds about 4-3mph) and also using the brakes to slow down. I have found that if I don't gently ease up on the brake at the stop light line and just keep it pressed down at the same pressure I used to slowly stop from say my initial speed of 30mph, that I will not use the battery at all, but will get a small "jerk" from the brakes. It is not like I am slamming on them, but I don't get that very soft slow down that I used to do with my previous car. My question is, is this wasting the battery if I do the slow stop or am I wearing down the brakes if I do the little firmer stop?

    Also, on a side note, how come whenever I hit the brakes while in Cruise control, the car jerks a bit. I know that you are supposed to use the throttle and coast to control speed in CC, but if I anticipate that I will get to close with just trying to coast (dropping down a few mph from the CC clicker) I will hit the brakes instead. It seems that I have to press the brakes say 15% before the CC will notice that the brake was hit and then I get that small jerk feeling. My old car used to just slow down immediately and disengage CC with just the slightest tap on the brake.
     
    #1 tom1l21, Apr 29, 2009
  2. Celtic Blue

    Celtic Blue New Member

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    The friction brakes kick in at 7 mph and the regeneration stops, so once you get that slow you aren't regenerating anymore. The transition from regenerative braking to friction brakes at low speeds is often noticeable when you first drive a Prius, and especially the first time you have to do a moderate stop in heavy traffic and feel the brief pause in between the two modes.

    It's best not to try to let the car "creep" at stop lights for the reason you mentioned. When I have to stop I go ahead and firmly apply the brakes at the end so that the motor doesn't try to hold me in position.

    Haven't really used the cruise.
     
    #2 Celtic Blue, Apr 30, 2009
  3. Simtronic

    Simtronic Active Member

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    I have noticed the same and like to drive smoothly and progressivley, I certainly don't want to waste battery power when comming to a stop so I find myself slipping it into neutral as I reach 8 mph. Below 7 mph there is no regeneration and the brakes are just working against the battery. I believe this is for hill starts to prevent roll back but it can compromise stopping.
    Simon
     
    #3 Simtronic, Apr 30, 2009
  4. efusco

    efusco Moderator Emeritus
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    For best conservation of energy/fuel economy it's always best to anticipate stops and begin slowing as far ahead of time as possible. But, as pointed out, once you get below 7mph regen stops and you're better off getting completely stopped and keeping firm pressure on the brake.
     
    #4 efusco, Apr 30, 2009
  5. qbee42

    qbee42 My other car is a boat

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    As for coming off cruise, I prefer to pull on the cruise control lever. A quick pull with your right fingers and you are off cruise control without any fuss. In an emergency, or when braking is required, the brake pedal disengages cruise control just as you described. I prefer the larger trigger threshold on the Prius, as it allows a slight touch without disengaging.

    Tom
     
    #5 qbee42, Apr 30, 2009
  6. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    i usually "park" it for long lights or situations when i am a ways back from the light since it takes several seconds before i can move when the light does change... hate wasting power on illuminating those tail lights i guess...hehehe
     
    #6 DaveinOlyWA, Apr 30, 2009
  7. 2009Prius

    2009Prius A Wimpy DIYer

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    The only issue maybe that people behind you see your brake lights off and they start to move forward ... :eek:
     
    #7 2009Prius, Apr 30, 2009
  8. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    NO PROBLEM WITH THAT!!!

    need that insurance money to get my new 2010!!
     
    #8 DaveinOlyWA, Apr 30, 2009
  9. jayman

    jayman Senior Member

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    With whatever vehicle I'm driving, once there are cars stopped behind me, I put it into Park. If nobody is behind me, in Drive with the foot firmly on the brake pedal
     
    #9 jayman, Apr 30, 2009
  10. David Beale

    David Beale Senior Member

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    Evan commented "long ago" that the current "wasted" during "creep" is only about 2 Amps, so it's not very significant.
     
    #10 David Beale, Apr 30, 2009
  11. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Put it in Neutral when you get to 7 MPH. It will not creep in N and you can stop as slowly as you want.
     
    #11 usbseawolf2000, Apr 30, 2009
  12. timberwolf

    timberwolf New Member

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    Being in Neutral does not allow the ICE to charge the HV battery. Is the SOC of the HV battery being considered before deciding to select Neutral?
     
    #12 timberwolf, Apr 30, 2009
  13. icarus

    icarus Senior Member

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    Except you'll get paid 60 cents on the dollar from the adjuster,,, and you will have to spend months fighting for that. My sister was hit in her '99 Subaru Outback by a 24k Pepsi truck at a light. Low book on the Sub was $4500, high book was 6k. They offered $3k. The car was fairly high mileage,(125k) but had just had a clutch an other major service, and we were expecting it to go to 250k. After months of haggling she got $4 because she needed the car. (This didn't include the medical that eventually resulted in a suit!) If they had been fair on day one with the car,,, then the medical would have been much simpler!

    Icarus
     
    #13 icarus, Apr 30, 2009
  14. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Below, 7 MPH it won't regen in D anyway. My suggestion was to prevent creep feature from consuming a small amount of battery. To me, it is not worth worrying about it.
     
    #14 usbseawolf2000, Apr 30, 2009
  15. timberwolf

    timberwolf New Member

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    I wasn't thinking of braking regen, but ICE charging. If the Prius is not moving with the ICE idling at the lights in Neutral the HV battery won't be charging. I am guessing that if the ICE were running before switching to Neutral that the ICE would continue running when stopped?

    It doesn't worry me either, I'm quite happy to sit at the lights with my foot on the brake.
     
    #15 timberwolf, May 1, 2009
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