1. Attachments are working again! Check out this thread for more details and to report any other bugs.

B drive

Discussion in 'Prime Main Forum (2017-2022)' started by Northerner, Aug 11, 2020.

  1. Northerner

    Northerner Active Member

    Joined:
    Feb 26, 2020
    121
    103
    0
    Location:
    Midwest
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    I tested the B drive going down a hill and posted in another thread that after I shifted into it (on the fly) that the car slowed to a near stop before I shifted back out of it to roll down hill faster. The response received was that it needs to be a pretty steep grade to leave your foot off the gas and keep rolling and recharging the battery at the same time. However, for hills with lesser slopes, pressing the gas pedal does not, at first, burn any gas but just slows the rate at which the battery gets recharged. This is a paraphrased interpretation.
    This possibly incorrect understanding led me to trying to go down a hill in B drive again, this time ready to put my foot on the gas and also (importantly) watching the HUD display.
    I was overwhelmed by what came up (TMI!). What I think I saw was that when I put my foot on the gas pedal I could exceed the neutral energy-use position fairly quickly. However, when I did (in B drive) it appeared I was burning battery power rather than burning actual gas.
    Did I read it correvctly?
    In other words, when going down a steep hill, does B-drive have a default that requires it to use up the battery’s energy first - and then use gas only when the battery is depleted?
     
    #1 Northerner, Aug 11, 2020
    Last edited: Aug 11, 2020
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    110,156
    50,059
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    i think you need a scan gauge or the like
     
    #2 bisco, Aug 11, 2020
  3. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,557
    10,324
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    If the hill really is steep, it shouldn't use any battery power or gas at all. It should be feeding electric energy back into the battery.

    Just in case we have different definitions of steep, try another test the next time you are on that hill. Going downhill at normal travel speed, shift into Neutral for a bit, then watch your speed.

    If it is steep, then gravity will pull it to go faster. Switching back to B mode, with just the right gas pedal touch to maintain speed (or D mode with cruise control), it should be charging the battery, not depleting it.

    If it is not steep, then the car will gradually slow down. In this case, it will require a shift back to D (or B) and some gasoline or battery power to maintain constant speed. And you'll need to adjust your definition of "steep".
     
    #3 fuzzy1, Aug 15, 2020
    jerrymildred likes this.
  4. Tideland Prius

    Tideland Prius Moderator of the North
    Staff Member

    Joined:
    Oct 2, 2004
    45,024
    16,244
    41
    Location:
    Canada
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    If the accelerator is twitchy, then try a ECO mode. Lightly pressing the accelerator pedal in B has the same effect as in D - it reduces regeneration for gliding and of course as you continue to depress, it’ll propel the car forward.

    Note that on steeper hills, the engine will eventually come on in B mode to vacuum pump, especially if you’re gaining speed - the computer thinks there’s not enough to slow you down so it turns on the engine to provide more braking power.
     
    #4 Tideland Prius, Aug 15, 2020
    jerrymildred likes this.
  5. jerrymildred

    jerrymildred Senior Member

    Joined:
    Oct 28, 2016
    11,518
    14,128
    0
    Location:
    Tampa, FL
    Vehicle:
    2017 Prius
    Model:
    Two
    Exactly! If D will maintain the speed, B will slow you too much. I haven't used B since May last year when we were in Colorado. And then, not very much. At the risk of over-simplifying things, you basically use B anywhere that would necessitate downshifting a manual transmission.
     
    #5 jerrymildred, Aug 16, 2020
    fuzzy1 likes this.
  6. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    7,035
    2,790
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    Why did you NOT put this at the end of the other thread ????
    Scattering discussions like this all over the place in fragmented threads just creates a mess.
     
    #6 sam spade 2, Aug 16, 2020
  7. Northerner

    Northerner Active Member

    Joined:
    Feb 26, 2020
    121
    103
    0
    Location:
    Midwest
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    I had two thoughts when I started a new thread. One was that a title like Prime vs CRV wasn’t giving the B drive discussion its due credit and part was because of my confusion over what the HUD display is telling me when I go down a hill in B drive - or in any other mode, for that matter.
    It appears we can watch that display while coasting down a hill and know instantly what is happening with the battery (quantitatively?) as we press the brake and accelerator.
    I have long since decided to drive the Prime and not the CRV so the other title no longer had a connection to this subject.
     
    #7 Northerner, Aug 16, 2020
    Last edited: Aug 16, 2020
  8. Austin Longenecker

    Austin Longenecker Member

    Joined:
    Sep 24, 2018
    123
    66
    0
    Location:
    Austin Tx
    Vehicle:
    2010 Prius
    Model:
    N/A
    You don't have to listen to that guy, he trys his absolute hardest to be wrong. Posting a new thread for a new topic was the right choice.

    I use B occasionally when going down steeper hills, but here in Minnesota, only a few locations in the bluffs has steep enough hills for it to be very beneficial. In town I use it to slow down. Never had the chance to test it in the mountains.
     
    #8 Austin Longenecker, Aug 16, 2020
  9. jerrymildred

    jerrymildred Senior Member

    Joined:
    Oct 28, 2016
    11,518
    14,128
    0
    Location:
    Tampa, FL
    Vehicle:
    2017 Prius
    Model:
    Two
    You must be referring to the only person I've ever ignored on any forum. He does get things right sometimes, but he seems to make everything an attack. The less he knows, the more belligerent he becomes. The phrase "Hmmm. I didn't know that." isn't in his vocabulary.
     
    #9 jerrymildred, Aug 17, 2020
    Austin Longenecker, fuzzy1 and Raytheeagle like this.
  10. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    7,035
    2,790
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    It is not nice to tell lies, Jerry.
     
    #10 sam spade 2, Aug 17, 2020
  11. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,557
    10,324
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Q.E.D.
     
    #11 fuzzy1, Aug 17, 2020
    jerrymildred likes this.
  12. Austin Longenecker

    Austin Longenecker Member

    Joined:
    Sep 24, 2018
    123
    66
    0
    Location:
    Austin Tx
    Vehicle:
    2010 Prius
    Model:
    N/A
    Truth
     
    #12 Austin Longenecker, Aug 17, 2020
    jerrymildred likes this.
  13. alexcue

    alexcue Active Member

    Joined:
    May 27, 2014
    346
    311
    0
    Location:
    So Cal
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    I used B in my last regular Prius, but to be honest, I've never even used it (forgot it was there) on my Prime.
     
    #13 alexcue, Aug 20, 2020
(You must log in or sign up to post here.)