What could make a puff, puff sound?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Isaac Zachary, Jan 16, 2023.

  1. Isaac Zachary

    Isaac Zachary Senior Member

    Joined:
    Jan 20, 2018
    2,228
    1,090
    1
    Location:
    USA
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I noticed the other day there was a strange noise when we started going down a long decent. It sounded like steam puffing, maybe like water dripping on something hot. It was kind of randomly spaced out between puffs. It made one, then a couple seconds later another, then 4 or 5 seconds, then a couple, and so on.

    I hope it's water (there's been a lot of snow and ice) that started dripping on the hot exhaust. But it seemed to come from the back. The passengers in the back heard it coming from behind them and mainly from the side the battery intake vent is. Could this be the battery offgassing from not using a B mode? Battery was one bar lower from fully charged when this happened.

    PS. This was in my Avalon Hybrid, but I thought I'd post it here as it's a 2013 so I imagine the battery is similar to a 3rd gen Prius.
     
    #1 Isaac Zachary, Jan 16, 2023
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    111,711
    50,869
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    not using b mode would only affect your brake pads. maybe melting ice on muffler is a good theory
     
    #2 bisco, Jan 16, 2023
    Isaac Zachary likes this.
  3. Isaac Zachary

    Isaac Zachary Senior Member

    Joined:
    Jan 20, 2018
    2,228
    1,090
    1
    Location:
    USA
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I noticed when engine braking the battery doesn't charge as much. It charges like when taking your foot off the accelerator.

    Without engine braking (B mode) then using either brakes or the cruise control make the battery charge at a much higher rate.

    For the record, I was not riding the brakes, but rather using cruise control on a grade that it was enough to hold the vehicle back.
     
    #3 Isaac Zachary, Jan 16, 2023
  4. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    26,052
    17,028
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    You've nailed the purpose of B mode exactly. It charges the battery less aggressively (which sometimes requires more use of the engine-as-vacuum-pump to burn off energy), which is useful if you know you will be on a long descent where the battery is going to be maxed out by the bottom anyway, and the lower charge rate at least goes easier on it.
     
    #4 ChapmanF, Jan 16, 2023
  5. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    111,711
    50,869
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    In 20 years, I’ve never gone down a descent long enough to matter
     
    #5 bisco, Jan 16, 2023
  6. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,558
    10,334
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Come out west, you can take scenic mountain routes that will do it several times the same day.
     
    #6 fuzzy1, Jan 16, 2023
  7. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    111,711
    50,869
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    No doubt, but I’d fly and rent a gasser
     
    #7 bisco, Jan 16, 2023
  8. Isaac Zachary

    Isaac Zachary Senior Member

    Joined:
    Jan 20, 2018
    2,228
    1,090
    1
    Location:
    USA
    Vehicle:
    Other Hybrid
    Model:
    N/A
    There are hills here that you can B mode the entire way down, not touching the brakes even once, and still end up with a full HV battery.
     
    #8 Isaac Zachary, Jan 16, 2023
    bisco likes this.
  9. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    26,052
    17,028
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    In "USA", no less!
     
    #9 ChapmanF, Jan 16, 2023
  10. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,558
    10,334
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Probably thousands of them. I've been down just dozens.
    ... and plenty where the foot brake is still required to hold down to safe speeds. I run into this every trip to and from dad's place.
     
    #10 fuzzy1, Jan 16, 2023
    Isaac Zachary likes this.
  11. CR94

    CR94 Senior Member

    Joined:
    Dec 2, 2014
    2,660
    1,149
    0
    Location:
    Northwestern S.C.
    Vehicle:
    2011 Prius
    Model:
    Two
    Plenty places in the East, too. Bisco needs to venture out of his neighborhood more.
     
    #11 CR94, Jan 17, 2023
    fuzzy1 likes this.
  12. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    111,711
    50,869
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Why?
     
    #12 bisco, Jan 17, 2023
    CR94 likes this.
  13. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    111,711
    50,869
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    We’re 1400 miles from home, completely flat the whole drive
     
    #13 bisco, Jan 17, 2023
(You must log in or sign up to post here.)