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Braking and regeneration

Discussion in 'Gen 2 Prius Main Forum' started by bumblbe, Mar 4, 2007.

  1. bumblbe

    bumblbe New Member

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    Greetings:

    I have had my Prius for just over 24 hours and am lovin it even though it doesn't have the kick of my Porsche Boxster S.
    A quick question (I have tried a search)
    I there any easy way to tell when you are braking hard enough just to regenerate electricity vs braking too hard and generating heat at the brake discs along with regeneration??
    Thanks

    Bill
     
    #1 bumblbe, Mar 4, 2007
  2. Gadgetdad

    Gadgetdad New Member

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    <div class='quotetop'>QUOTE(bumblbe @ Mar 4 2007, 05:32 PM) [snapback]400066[/snapback]</div>

    Good question, I have wondered if there really is any regeneration with the application of the brakes. I suspect that it is only engaged as a coasting regenerator with the brakes just slowing the car down further/faster.

    Anybody know for sure? :huh:
     
    #2 Gadgetdad, Mar 4, 2007
  3. hobbit

    hobbit Senior Member

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    #3 hobbit, Mar 4, 2007
  4. Tideland Prius

    Tideland Prius Moderator of the North
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    No but there are several "tests" that you can do to check.

    1. when you're braking, hold the position until to come to a complete stop. When you reach ~12mph, you'll feel the brakes "give" as it switches over to friction braking. That's one way to tell that you've been regenerating. If you don't feel that split second "give" then that probably means you were using the brake pads all along


    2. Now how to tell how *hard* I've been braking? Same method as above - brake and hold that pedal position. When you reach ~20mph, shift into B. Under 22mph, when you shift into B, the engine won't come on to engine brake and you'll be doing maximum regeneration. So, when you brake and shift to B, if you were already near or at maximum regeneration, you won't feel difference in the car's behaviour. If you were not (say you were lightly braking), then when you shift into B, you'll feel the extra drag as the PSD max regens.

    What does all this mean? It means the lighter the drag, the harder you were braking and still in regenerative braking. If you feel a strong drag when you shift into B, then press harder next time you stop.


    Using these two methods should help you get a feel of
    a. which system you're using to brake
    b. how much you were regenerating


    Hope this helps.
     
    #4 Tideland Prius, Mar 4, 2007
  5. Betelgeuse

    Betelgeuse Active Member

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    If it's the summer and you have the windows down, you can often hear the whine of the generators running (it's a little hard to explain, but it's high-pitched and different from any sound a non-regenerating car makes).

    Basically, the rule of thumb is that, unless you really slam on the brakes, you're probably regenerating. You can brake pretty darn firmly and you will still be regenerating.

    Does anyone know if the animation on the MFD (i.e. green arrows going from wheels to battery) actually indicate regeneration? Or are those arrows shown even if you're friction braking?
     
    #5 Betelgeuse, Mar 4, 2007
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  6. Tideland Prius

    Tideland Prius Moderator of the North
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    No they don't. Unlike the Escape Hybrid, ours just simply show regen (heck, even if you're friction braking, I think it still shows regen).

    On the Escape Hybrid, the more you regen, the thicker the line/arrow.
     
    #6 Tideland Prius, Mar 4, 2007
  7. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I explain regeneration by comparing it to hydroelectric generators.

    In the same manner that you can apply electricity to a motor to create mechanical motion, you can mechanically turn the motor to generate electricity. In hydroelectronics, the motor is turned by the water. In the Prius, it's the wheels mechanically linked to the motor that generate the electricity.

    This is why I sometimes correct people when they insist that the Prius recharges the battery only when you brake. In reality, anytime you are moving forward and not accelerating, the wheels are probably turning the motor, generating electricity, and recharging the battery.

    Wanna see the demonstration: [Click here]
     
    #7 TonyPSchaefer, Mar 4, 2007
  8. hendji

    hendji New Member

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    As a Prius driver, I have driven my 2012 Prius more than 110,000 miles and many of those miles have been on steep and long mountain passes. On the downhill glide, my battery quickly recharges on regeneration braking. Once it is fully charged, braking is provided by engine compression (with high PRM’s) and friction braking that wear down pads.

    I would love to see a means to allow a Prius driver to use extra battery energy to climb a long uphill so the battery will be more discharged at the top, to allow for additional regeneration braking on the downhill glide.

    Perhaps there is already a way to do this, and I have not discovered it.
     
    #8 hendji, Oct 22, 2014
  9. Britprius

    Britprius Senior Member

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    This is possible on the UK/EU gen2 Prius by pressing the EV switch. The only drawback to this is the limited speed at which this is possible. This must be under 31 mph. An override for this to say 45 or 50 mph would be very useful.
    I live near the top of a hill and use this every time I return home. I know the precise point to press the switch to finish my journey on electricity only. Since I live out in the country on a narrow (8 ft 6 inches wide) dead end road the speed limitation is not a problem. When I leave home by the time I get to the bottom of the hill my battery is at full green bars.

    John (Britprius)
     
    #9 Britprius, Oct 22, 2014
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  10. Tideland Prius

    Tideland Prius Moderator of the North
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    Well another solution is to get the PiP with the larger capacity battery. You can recharge the 11-15 miles back on the downhill portions if you're able to get into Charge Sustain mode before (or while) going uphill.
     
    #10 Tideland Prius, Oct 23, 2014
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