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Limits of regenerative braking

Discussion in 'Gen 2 Prius Technical Discussion' started by Ethereal, Mar 22, 2007.

  1. Ethereal

    Ethereal New Member

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    I've searched for this to be addressed and don't see where it has.

    Since regenerative braking is power limited (whatever the max rating of the motor-generator, charge controller, or other "bottleneck" component is) rather than force limited, like friction braking, and since P=F*v, it seems that it should be possible to decelerate twice as hard at 20 MPH as at 40 MPH without exceeding the limits of the regenerative system.

    Does anyone (calling all Toyota tech-heads!) know if this is actually how the regen system functions?
     
    #1 Ethereal, Mar 22, 2007
  2. D0li0

    D0li0 New Member

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    <div class='quotetop'>QUOTE(Ethereal @ Mar 22 2007, 05:16 PM) [snapback]410539[/snapback]</div>
    I haven't logged any data specifically for this question, but you may find some of what you are looking for within my PiPrius Logs. The graphs don't show all of the logged data so you may want to grab one of the .zips for a high speed trip and take a look at the deceleration figures as I exit the freeway from ~60mph to ~0mph... Actually if the SOC is high or CCL is low it might not accurately reflect normal regen, the 2006.07.23 logs were all in stock mode so there should be lots of data there. I'm sure that I've seen somewhere someone else's analysis of braking but can't find it at the moment.
     
    #2 D0li0, Mar 22, 2007
  3. qbee42

    qbee42 My other car is a boat

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    That depends on what you mean by "decelerate twice as hard". Your thinking is correct; the regen braking on the Prius is limited by the amount of power converted to electricity. For a given battery SOC and temperature, the Prius can absorb a given number of amps, so the braking becomes a matter of constant power, not constant force.

    Tom
     
    #3 qbee42, Mar 22, 2007
  4. sola

    sola New Member

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    I have just wanted to start a new topic about this.

    Does anyone know what is the maximum regen rate? I've heard that in certain situations it can reach 50% of the the kinetic energy previously gathered by acceleration.

    How/when can this be achieved? What is the best strategy to maximize the amount of the regenerated energy?
     
    #4 sola, Mar 30, 2007
  5. ScottY

    ScottY New Member

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    The max regen current is ~100Amp. I think the absolute max is like 125Amp or something.

    Someone did gather data on the amount of regen vs. deceleration. Can't find that now. I'm sure others will find it faster than I can.

    EDIT: ok, found it, http://vassfamily.net/ToyotaPrius/CAN/brindex.html
    Looks like I'm pretty fast too. lol.
     
    #5 ScottY, Mar 30, 2007
  6. Ethereal

    Ethereal New Member

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    <div class='quotetop'>QUOTE(ScottY @ Mar 30 2007, 06:53 PM) [snapback]415141[/snapback]</div>
    The fuse in the service plug is 125A, so that's one absolute limit.

    The vassfamily.net spreadsheet appears to only address decelerating at various constant states of pedal depression, not progressively depressing the pedal to decelerate harder as the car slows.

    Anyone out there with a CAN-View experimented with initial mild deceleration at high speed with increasing decel as the car slows?
     
    #6 Ethereal, Mar 31, 2007
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