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"B" mode...what for?

Discussion in 'Gen 5 Prius Technical Discussion' started by peternumber2, Feb 14, 2024.

  1. Doug McC

    Doug McC Active Member

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    ONLY IF you’re thinking and terminology matches whoever decided which terms should be treated as index terms. Kind of like trying to find something in WalMart: you have to think like a WalMart employee.
     
  2. vvillovv

    vvillovv Senior Member

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    LOL and hope you're thinking like the right kind of employee that knows who will know if they don't know what you're looking for.
     
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  3. sylvaing

    sylvaing Active Member

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    I've read the manual myself and I don't know if it's because it's the traduction to English but some section of the manual are hard to figure out what they are trying to say.
     
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  4. sylvaing

    sylvaing Active Member

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    I don't think it makes much of a difference. It's more like for coincell type batteries that it makes a difference.
     
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  5. fuzzy1

    fuzzy1 Senior Member

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    At least where I worked the longest, technical writers had become fairly well respected positions embedded among the engineers.

    The next place where I worked (as a contractor, not an FTE), I don't remember having any of them ever included in our meetings ...
     
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  6. Doug McC

    Doug McC Active Member

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    Yipes! You could have a career writing for the next Owners Manual! LOL
     
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  7. ChapmanF

    ChapmanF Senior Member

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    Well, that's what I was getting at. Using an index (a) requires work by the document creators at creation time, and (b) works best if they were thinking like you do.

    Using Find... in a PDF viewer does not require anything to have been done up front, and you can search for whatever you want and turn up wherever that text happens to be in the document.
     
  8. vvillovv

    vvillovv Senior Member

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    And he's thinking that if the regex used in the query is even in the doc somewhere / anywhere.
    Sure you could adjust the regex if you get a null output, but that also requires some experience with the construction and proceeding translation, such like @sylvaing refers to up in post #43
     
  9. vvillovv

    vvillovv Senior Member

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    since unix people tend to dislike top posting and myself being a bit out of league with prep and translation of docs, just wondering if you or anyone else has noticed the newer / newly released info formatting and organization of either grep, find ? There are plenty of others now with new multi-page additions being introduced. Was it ever like that where you worked ?
     
  10. sylvaing

    sylvaing Active Member

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    That's assuming the PDF manual isn't just a photocopy of a real manual. I've seen these for old owner's manual. Worst of both worlds.
     
  11. fuzzy1

    fuzzy1 Senior Member

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    Being retired for a decade, and out of the HP*UX world for two decades, I have no connections to anything new.
     
  12. KMO

    KMO Senior Member

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    When you have two manuals for two variants published simultaneously, and they differ in the description, it's usually best to assume that there is a real functionality difference between the variants that they're trying to convey.

    In this case the PHEV has the whole "regeneration boost" section that the HEV manual lacks, but the other bits seem unaltered. So I think we should initially assume there's some HEV/PHEV difference. It may be that their wording is just trying to explain the two higher B modes.

    But reading it, it kind of seems as if it's saying that with all 3 settings the algorithms have been shifted to primarily being closer to a general single-pedal drive mode, and away from the "downhill" mode. That would make sense for a vehicle with bigger battery with more scope to soak up downhill charging.

    There's the bit "When Regeneration Boost cannot be used: [...] Regenerative braking may be restricted in the following situations.
    When the amount of charge of the hybrid battery (traction battery) is high. [...] When Regeneration Boost is continually used".

    Which would to me suggest a reversion to engine braking. I've always felt the "engine braking" talk around "B" is overstated - people often suggest B has gone to engine braking immediately. I think it's true it has previously always biased it towards starting energy bleed-off sooner.

    So - without any testing and purely trying to parse manuals - I think they've rejigged B in the PHEV to initially not go anywhere near energy-bleed off, and just increase no-pedal-input regeneration, as long as the battery isn't nearing full.

    I concede that they may have not touched the algorithms at all, and it's just the manual writer getting creative, but they DID add the 3 settings, which suggests they could well have decided to mess with the algorithms in that area, not just change a constant to a setting.

    Thinking about the conservative way they layer their systems, it would be very much their style if "regeneration boost" is actually a new algorithm in front of the old one. When conditions are right (good temperature, low battery etc), they use that one. When they aren't, they revert back to the original tried and trusted downhill/energy-bleed-off algorithm.
     
    #52 KMO, Feb 17, 2024
    Last edited: Feb 17, 2024
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  13. sylvaing

    sylvaing Active Member

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    When glancing at Hybrid Assistant while braking going downhill, I can see the Charge Current Limit (CCL) green peg creeping up the graph (ie. less regen power allowed to reach the battery) in my Gen4 Prime and that's with a battery not even close to full charge as this graph is showing.



    My guess is if I were to be in B mode then, the engine would start to offer compression braking as the battery itself is taking less and less braking power.
     
  14. Lantaral

    Lantaral Junior Member

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    In the Gen 3, it is immediately obvious when B mode moves into engine braking. And it only occurs after the battery bars are entirely filled, and then a bit more.
     
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  15. Doug McC

    Doug McC Active Member

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    FWIW: The Car Care Nut has a video on B Mode (of course it will contradict the beliefs of some people, which is always dangerous in today’s society).
     
  16. Lantaral

    Lantaral Junior Member

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    Watched it some time ago. If I recall correctly, he said that B mode wasn't well documented but that he believed it first filled the battery, then revved the engine to permit effective engine braking.

    The portion of B mode that fills the battery is fuel energy efficient, but once the battery is filled and B mode moves into engine braking, the system needs to use fuel battery power in order to slow the car. He said this engine braking is fine for the car, and creates no unusual engine wear.

    Though personally, hate the sound of B mode when it moves into engine braking. Reminiscent of flooring a car in neutral. If the hill isn't too big, will personally move into drive mode when it reaches that point.
     
    #56 Lantaral, Feb 17, 2024
    Last edited: Feb 17, 2024
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  17. sylvaing

    sylvaing Active Member

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    You mean this video?



    I tried B mode a few times and in one of those times, when going down a hill, it did spin up the engine and when I was down the hill, the engine kept running until it warmed up and then shut down (after several minutes running). I'm wondering why did it warm it up if there was no sparks going while going down the hill in the first place...
     
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  18. Lantaral

    Lantaral Junior Member

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    Perhaps the engine braking portion of B mode is time limited. It seems to run the engine at or near maximum RPM.
     
  19. Mendel Leisk

    Mendel Leisk Luddite

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    I may have missed some in the preamble, but around 7:15 he gets to the meat.
     
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  20. sylvaing

    sylvaing Active Member

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    Next time, I'll watch what Hybrid Assistant is saying regarding MG1, the engine RPM and the fuel flow.