More EV Power Regen via PDA Deceleration Assist?

Discussion in 'Gen 5 Prius Fuel Economy & Prime EV Range' started by reptilian, Jun 27, 2024.

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  1. reptilian

    reptilian New Member

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    I've had the '23 Prius XLE less than a year, love the additional power and MPG both improved from the 2019.
    Now that I've had some time with the many driving features and assist modes, I recently enabled PDA Proactive Driving Assist. While it's meant as a safety feature, I immediately noticed an increase in regenerative braking, which I believe is based on the sensitivity and car distance settings. I found it comfortable and noticeable in city traffic.
    This totally reminded me of what a Tesla feels like, as anyone will tell you, the regenerative braking is heavy on EVs, so much that you barely use the actual brake pedal (good for your brakes' lifespan).
    It got me thinking, hmm this whole time I've had PDA disabled (several months)... I wonder if I'll get more MPG now? More use of the electric motor... more "braking" regen?

    While using the actual brakes also performs regenerative braking, I did notice something on the instrument panel while using PDA. If you have the EcoZone view on, with the green & white bars, the white EcoZone stays lit while the PDA "deceleration" is active. But if you brake instead of using PDA, the white EcoZone disappears immediately.
    It makes me wonder if there's a difference in energy regenerated from deceleration (which I believe is like engine braking) and actual braking. If anything, it might create a smoother transition from stopping to starting, like it keeps the electric motor ready instead of turning it off (?).

    I'll see over time if my current hot summer 50MPG average increases.
    Either way, I prefer the feel of the PDA deceleration and less lifting of the foot to the brake pedal. Theoretically, it should at least be less wear and tear on my brakes, while also a safety feature.
    If you haven't enabled PDA, try it and post your thoughts for in-city stopping and starting. It's similar to adaptive cruise for lower speeds. Not the same thing, but I believe it also works in conjunction with adaptive cruise on the highway as well. It slows your car down for you before using any brakes. I wonder if the brake lights come on when this happens.

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    #1 reptilian, Jun 27, 2024
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  2. Tom Mulloy

    Tom Mulloy Junior Member

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    Interesting post. I will have to try the PDA mode. I just sold a 2023 Chevy Bolt EUV. One feature was one pedal driving. With OPD enabled the regen braking was such that I rarely had to use the brake pedal. The Bolt also had a paddle control that, when used, made the regen braking much more pronounced. Speaking of regen braking, I just watched a Prius Prime road test YouTube video and the driver frequently used the B drive mode, kind of like the Bolt's OPD. I'd be interested in comments about using B mode during normal driving. Thanks. TM
     
    #2 Tom Mulloy, Sep 19, 2024
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  3. CooCooCaChoo

    CooCooCaChoo Senior Member

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    Please, for the love of God, don't start the whole B Mode driving thing again. We just got done debating it, twice already AFAIK.

    As for PDA, any regenerative braking it does does not out perform manual braking. PDA is mainly to prevent accidents that would've been caused by an inattentive driver or to reduce the seriousness of a crash. If you want more regenerative braking, you should ride the brakes. Riding the brakes in a regular car eats up the brake pads and is bad practice, but in hybrids/EVs it increases the amount of regenerative braking. The mechanical pads don't get used until very low speeds.

    Edit: ^^^ or hard/sudden braking applications.
     
    #3 CooCooCaChoo, Sep 19, 2024
    Last edited: Sep 19, 2024
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  4. Danno5060

    Danno5060 Active Member

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    I believe that regenerative braking is where the hybrid system takes the wheel energy and puts the kinetic energy into the traction battery. Dynamic braking is where the extra energy is sent to the ICE engine (downshifting with a manual transmission is dynamic braking). Both would be saving on your regular (friction) brakes but you only get the energy back (increasing MPG) in regenerative braking.

    Light touch on the brake pedal - regenerative. Firm press on the brake pedal - friction. Once I understood this, I found I was looking out further for traffic lights, braking longer and easier. Of course, that seems to piss everyone else off because I'm in the way of them getting to the red lights in time for them to be able to stop. I don't know why it's so important for them, but those red lights seem to call to everyone else on the road. They seem to really get pissed if it's green by the time they get to the light too.
     
    #4 Danno5060, Sep 19, 2024
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  5. reptilian

    reptilian New Member

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    Yeah, I realize that's nothing to do with B mode...
    But I encourage you to try PDA mode for yourself and watch the white EcoZone bar when the PDA mode kicks in. It behaves differently than a brake press, which makes the white bar disappear.
    Can someone explain why the EcoZone displays differently while in PDA mode?
     
    #5 reptilian, Sep 19, 2024
  6. reptilian

    reptilian New Member

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    I wonder if PDA "braking" is the same thing as if you were to light touch brake yourself? It could be something different due to the EcoZone view. I need to test a light touch brake while in PDA mode to see if the white line disappears.
    FWIW, my mileage has not changed, but 50.0MPG in a hot summer is pretty good! Using Eco & PDA mode always on.
     
    #6 reptilian, Sep 19, 2024
  7. AndersOne

    AndersOne Active Member

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    Why would it be different? Unless youre a very harsh braker.

    I use it all the time but its more a convenience feature - over time it learns too, where to regen automatically as shown by "green leaves" in the navigation system.
     
    #7 AndersOne, Sep 23, 2024
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  8. reptilian

    reptilian New Member

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    Because in PDA mode, the white EcoZone bar behaves differently than a brake press, which makes the white bar disappear. If you have PDA disabled, and press the brake (I think light or hard doesn't matter), the white EcoZone bar disappears, as if it's saying "you pressed the brake, you are no longer in the EcoZone"... but when PDA engages the brake, the car stays in the white EcoZone.

    That's my question, why would it be different? It's something I've noticed.
     
    #8 reptilian, Sep 23, 2024
  9. KMO

    KMO Senior Member

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    The white bar you're talking about is the suggested maximum throttle indicator, isn't it? So hiding that when you're braking seems reasonable - your foot isn't on the throttle. And I guess it stays up if you're not pressing any pedal?

    So PDA isn't changing behaviour of indicator at all? It's purely a guide to user input, based on user input?
     
    #9 KMO, Sep 23, 2024
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  10. reptilian

    reptilian New Member

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    Ok, I did a little test today. I've answered my own question.
    Turned off PDA mode, tested light braking (very light)... it behaves the same as what PDA mode does for you.
    PDA mode is effectively handling light braking for you. Which DOES increase MPG if you don't feather the brakes.
    I didn't realize how light you had to press for regen braking (thanks to these forums for helping me figure that out).
    In PDA, the white bar stays up because the mode is constantly light braking for you. If you press a firm brake, of course, the white line disappears.
    Mystery solved. PDA mode is helpful for light braking, therefore should increase MPG for most people (although mine just won't seem to budge above 50.0MPG, maybe the fall & winter will help with that).
     
    #10 reptilian, Sep 24, 2024
  11. darkstar3274

    darkstar3274 Junior Member

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    so now the one question I think was unanswered-does the PDA mode when in operation actually turn the brake lights on? (no manual pedal press light or otherwise)
     
    #11 darkstar3274, Sep 25, 2024
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  12. KMO

    KMO Senior Member

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    I'm pretty certain the general rule is that if there's significant deceleration for any reason, the brake lights come on.

    Interestingly, the Japanese Prius has brake light indicators in the instrument display that aren't present in other countries, which would help reassure you.

    upload_2024-9-25_11-38-10.png
     
    #12 KMO, Sep 25, 2024
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  13. AndersOne

    AndersOne Active Member

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    That can be easily checked too by looking into the mirror when decelerating at night. (EDIT: Yes I checked it )

    It looks exactly the same for the new C-HR in Europe. Given its technically the same car as the Prius I was honestly very confused why this feature was not included. On the other hand I have a feeling the Prius in Europe (and even the US?) might be depriorized regarding software updates despite all having similar platforms. The C-HR navi (same 12") just got an update that seems to have new features not available in the prius yet...
     
    #13 AndersOne, Sep 25, 2024
    Last edited: Sep 25, 2024
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  14. KMO

    KMO Senior Member

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    The C-HR is about a year newer.
     
    #14 KMO, Sep 25, 2024
  15. AndersOne

    AndersOne Active Member

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    Yes but how would that explain the points discussed above? Did not prevent the older Japanese Prius from having this feature first and everything else is mostly the same technically - especially the navi. In any case, I hope we get the OTA soon as well.
     
    #15 AndersOne, Sep 25, 2024
  16. reptilian

    reptilian New Member

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    Yes, that's a hard thing to test while moving in traffic. I would assume that slowing down of ANY kind would engage the brake lights.
    Back to the PDA braking, I did notice something else. The PDA mode seems to brake much harder than I could while keeping the white EcoZone bar still lit. I could light brake and get the white bar to stay there. But there are many times (coming to a stop light with a car in front of you) that the PDA braking is quite heavy, while the white EcoZone bar is still showing. I'm pretty sure if I pressed the brake with the same force, the white bar would disappear. I need to double check that, I'll do another test soon.
    And then the question remains, is the PDA braking getting more regen than you would with your foot?
     
    #16 reptilian, Sep 25, 2024
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  17. KMO

    KMO Senior Member

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    If you can grasp that the brake lights are linked to slowing down, why can't you grasp that your Eco Zone bar isn't?

    The brake lights are to indicate to some-one else that you are slowing down - it doesn't matter why.

    The white bar above the Eco Zone text, as the manual says, is "a reference operation range for using the accelerator pedal according to driving conditions such as starting off and cruising.".

    It's totally logical to remove that when your foot is pressing the brake. If you're not pressing anything, your foot could be lightly resting on the accelerator. If it chooses to keep it up when you're not pressing anything, it's not logical to hide it because the car is slowing down. The slowing down isn't the reason to remove it, it's the foot being on the brake.
     
    #17 KMO, Sep 25, 2024
  18. darkstar3274

    darkstar3274 Junior Member

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    nothing about grasping not grasping people are asking questions-everyone is not super logical (at least I am not)
    in any event when I used the B mode on my previous '22 PP, people would hate it behind me (stopped doing it w/o in conjunction with manual brake press) as they could see me slowing down but without the brake light
     
    #18 darkstar3274, Sep 25, 2024
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  19. reptilian

    reptilian New Member

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    While I see your point here, by that logic, why does the white EcoZone bar stay there when my foot IS on the brake, during a light press? If it knows my foot pressed the brake (lightly), it should hide the white bar, right?

    For some reason, the EcoZone bar is there and seems to stay there when PDA brakes more heavily for me coming up to a stopped car.
    The white bar disappearing could be just a visual interface event triggered by a harder foot press, or it's possible that the regen is actually behaving differently when PDA brakes for you.
     
    #19 reptilian, Sep 25, 2024
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