ice turns on when battery is fully charged ?

Discussion in 'Gen 3 Prius Technical Discussion' started by privilege, Mar 28, 2021.

  1. privilege

    privilege Member

    Joined:
    Mar 17, 2021
    104
    37
    0
    Location:
    Birmingham
    Vehicle:
    2011 Prius
    Model:
    Three
    2011 3 model

    I noticed when we were in the mountains that if the battery is fully charged and we are decelerating, sometimes the ice will turn on...

    then I tested it on a long hill in town, and it did the same:
    traction battery 100%
    long downhill
    ice turns on for thirty seconds or less

    does anyone have an idea why it's doing this ?
     
    Data Daedalus likes this.
  2. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    4,930
    2,010
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    It is the hybrid equivalent of engine compression braking probably.
    There are several things that will turn the engine ON when it is not really needed to power the car.
     
    privilege likes this.
  3. Data Daedalus

    Data Daedalus Senior Member

    Joined:
    Jul 6, 2013
    1,003
    1,161
    0
    Location:
    Wembley, London
    Vehicle:
    2008 Prius
    Model:
    II
    I experienced this in my Gen 2 last Friday, after having descended a long shallow incline on my commute home - while using regenerative braking to charge the traction battery.

    The onboard BMS ensures the battery doesn’t charge or discharge beyond the 80% to 40% range in real terms. This is NOT reflected on the MFD - what looks like a 100% SoC is actually 80%. This is done to prolong the life of the NiMH Traction Battery pack.

    Occasionally, after descending a hill with regenerative braking in operation, the SoC can crawl over 80%. The BMS burns off the excess energy in the Traction Battery by using an electric motor to spin the engine while you’re at standstill, waiting for the traffic lights (though it could happen any time before then).

    In the Gen 2, you’ll notice the top most green bar illuminated before this happens. If it doesn’t, I tend to move off and drive in EV mode (without actually selecting it), until the green bars drop to blue. I normally use cruise control to maintain speed at 40mph (UK) and it will normally default to EV on a warmed engine with a full to the brim Traction Battery).
    Cruising further down a less shallow incline at that point (there is such a spot on my commute) means I can get almost a mile of hyper mile travelling before the ICE kicks in when I arrive at the next flyover.

    Last summer, I managed 68.1 mpg on a full tank of fuel, by taking advantage of brake regeneration on inclines and using cruise control judiciously on my commute to and from work.
    The lack of traffic on the roads due to the pandemic coupled with several weeks of a heatwave more than likely aided in achieving those figures.


    iPad mini 4 ? Pro
     
    privilege and jerrymildred like this.
  4. Data Daedalus

    Data Daedalus Senior Member

    Joined:
    Jul 6, 2013
    1,003
    1,161
    0
    Location:
    Wembley, London
    Vehicle:
    2008 Prius
    Model:
    II
    I believe engine compression braking only kicks in if you select B on the “gear” selector.
    I’ve had my engine spinning - but NOT using any fuel while at a standstill at the bottom of a long hill with a fully charged battery, and also when waiting for the electronic gates to open when leaving the office.

    The ECU on the Prius is governed by trying to cut emissions. Ergo, when I have a full battery leaving work, the engine stops using fuel while I wait for the gates to open, and uses the battery / electric motors to keep the engine spinning (up to operational temperatures), until I start moving with fast acceleration.


    iPad mini 4 ? Pro
     
    privilege likes this.
  5. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    4,930
    2,010
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    Your belief is wrong.
    Setting the cruise at reasonable speed and then descending a steep hill will result in action similar to B.
    So will going down that steep hill with no accelerator pedal input, I think, but not as pronounced.
     
    Pulse07 and privilege like this.
  6. meeder

    meeder Active Member

    Joined:
    Jul 8, 2019
    183
    119
    0
    Location:
    Doesburg, The Netherlands
    Vehicle:
    Other Hybrid
    Model:
    N/A
    When you use adaptive cruise it constantly uses engine braking when a slower vehicle is in front of you.
     
  7. Data Daedalus

    Data Daedalus Senior Member

    Joined:
    Jul 6, 2013
    1,003
    1,161
    0
    Location:
    Wembley, London
    Vehicle:
    2008 Prius
    Model:
    II
    You’re right ; cruise control engaged going downhill will induce engine compression braking - I experience this daily; almost as if I’m flying an aircraft descending towards a runway with air brakes fully deployed. Always fascinated by the way the ICE compression braking kicks in. Very effective!

    If you’re descending without using cruise control, engine compression braking on the Gen 2 will not engage, it’s regenerative braking only - unless you specifically select B (or the battery is already fully charged - but if it automatically switched to compression braking under normal circumstances, why would we have a B selection at all?)
    I’ll read up on it again just to be sure, but that’s what I’ve picked up both from the manual plus 7.5 years experience of commuting daily with my Gen 2 (a.k.a. The Spaceship)


    iPad mini 4 ? Pro
     
    privilege likes this.
  8. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    4,930
    2,010
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    Not exactly.
    Just reducing the forward propulsion force and letting the wind resistance slow you down doesn't quite qualify an "engine braking".
     
    privilege likes this.
  9. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    4,930
    2,010
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    Can't say for sure 'cause my C doesn't see mountains ........ever.
    But it seems to me that it should have a "safety" setting to supplement the regen when you accidentally enter a huge grade too fast before the battery gets "full".
    Maybe not.
     
    privilege likes this.
  10. meeder

    meeder Active Member

    Joined:
    Jul 8, 2019
    183
    119
    0
    Location:
    Doesburg, The Netherlands
    Vehicle:
    Other Hybrid
    Model:
    N/A
    When going downhill or if it has to slow down for another vehicle it immediately revs up the ICE to about 3000rpm to help the car slow down. It's the same behaviour when you put it in B and then apply the brakes to slow down the car.
     
  11. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    4,930
    2,010
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    Those are two entirely different things you mentioned and I have NEVER seen that happen "immediately" upon releasing the accelerator, except when going down a STEEP grade with the cruise ON.
     
  12. meeder

    meeder Active Member

    Joined:
    Jul 8, 2019
    183
    119
    0
    Location:
    Doesburg, The Netherlands
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I am talking on situations with cruise on. Without cruise it doesn't spin up the ICE.
     
  13. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    42,944
    30,729
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    I’ve noticed once in a while the engine will run (with good charge level, car stopped), after a protracted drive. Not sure why, due to overheating, of engine or hybrid battery maybe.
     
  14. meeder

    meeder Active Member

    Joined:
    Jul 8, 2019
    183
    119
    0
    Location:
    Doesburg, The Netherlands
    Vehicle:
    Other Hybrid
    Model:
    N/A
    It could be for cooling of the transaxle.
    The oil pump in the transaxle only works when the ICE is running.
     
  15. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    4,930
    2,010
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    Well then, yes, that is normal.

    Why would it surprise you if you have manually accelerated to a speed higher than the cruise setting, removed your foot from the gas and then have it be aggressive in trying to regain the set speed ?

    Same thing will happen if going down a steep hill.
     
Loading...