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

Engine Comes on Downhill W/O Full Charge

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by Harpua-Prime, Sep 22, 2017.

  1. Harpua-Prime

    Harpua-Prime New Member

    Joined:
    Sep 22, 2017
    4
    2
    0
    Location:
    Seattle
    Vehicle:
    2017 Prius Prime
    Model:
    Plug-in Advanced
    I have a 2017 Prius Prime Advanced and have 1000 miles on the car. I live at the top of a hill and go on a 10% slope every morning.

    For only the past 4 mornings, the ICE has switched on during the downhill portion of my commute and the past two days, the battery has NOT been fully charged (to test and avoid this new issue).

    Although it didn't happen during the first 950 miles, I wondered if this was related to the battery being full and then avoiding the overcharging. But the past two mornings, I've left my battery 3/4 and then half-charged and the engine is STILL coming on about halfway down the hill with normal breaking and temps in the 50s. Again, this didn't happen with the same route for the first 950 miles of driving.

    Car is in EV Mode - Normal.

    Any ideas? Thanks.
     
  2. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Did you have windshield defogger on? Here is the list from the manual that would turn ICE on.

    EV driving may be canceled automatically in the following circumstances:
    ●When vehicle speed is more than approximately 84 mph (135 km/h).
    ●When power is needed temporarily, for example when the accelerator pedal is depressed firmly or when accelerating suddenly.*
    ●When the temperature of the hybrid system is high. The vehicle has been left in the sun, driven on a hill, driven at high speeds, etc.
    ●When the temperature of the hybrid system is low.
    ●When the heater is switched on when the outside temperature is below about 14°F (-10°C).
    ●When the windshield defogger switch is pressed. (→P. 491, 501)
    ●When the system determines that the gasoline engine needs to be started. The gasoline engine may also operate in circumstances other than those listed above, depending on conditions.
    *: When traveling in the EV auto mode only
     
    Mark57 and dalcon95 like this.
  3. Mark57

    Mark57 2021 Tesla Model 3 LR AWD

    Joined:
    Aug 14, 2009
    2,945
    2,735
    0
    Location:
    OK
    Vehicle:
    Other Electric Vehicle
    Model:
    N/A
    Welcome to the site.

    You're scaring me with how much you're reading that manual. j/k ;)

    Excellent post. I'd forgotten about some of those.
     
    Harpua-Prime and Salamander_King like this.
  4. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    that last bullet point is a knock down round house tko. got everything covered like my local weatherperson.
     
    arthur92710 and Salamander_King like this.
  5. Harpua-Prime

    Harpua-Prime New Member

    Joined:
    Sep 22, 2017
    4
    2
    0
    Location:
    Seattle
    Vehicle:
    2017 Prius Prime
    Model:
    Plug-in Advanced
    Thanks for the reply. Climate system was off, outdoor temperature about 55 degrees, in EV mode, speed about 40-45, defogger switch not pressed, not left in the sun (in garage overnight)....

    Again, this never happened for the first 950 miles on the same route and has for 4 mornings in a row. This morning, the battery was about half charged and I was certain it wouldn't happen but sure enough...

    It's more the change from the norm that concerns me that something has failed.

     
    bisco likes this.
  6. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    doesn't make sense, you're in ev, not ev auto, correct?
     
  7. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Yap, basically Toyota can program the car to turn on ICE whenever it wants to. :LOL:
     
    bisco likes this.
  8. Harpua-Prime

    Harpua-Prime New Member

    Joined:
    Sep 22, 2017
    4
    2
    0
    Location:
    Seattle
    Vehicle:
    2017 Prius Prime
    Model:
    Plug-in Advanced
    Correct. Very frustrating as I can already expect the skeptical service call.....

     
    bisco likes this.
  9. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Is it affecting overall EV range and/or mpg? I have seen on my car while on EV mode with still charge left, turn off EV on uphill some times, but wasn't paying much attention, so I don't know if that happens every time the car is uphill or not. Your's is happening downhill, correct?
     
  10. Harpua-Prime

    Harpua-Prime New Member

    Joined:
    Sep 22, 2017
    4
    2
    0
    Location:
    Seattle
    Vehicle:
    2017 Prius Prime
    Model:
    Plug-in Advanced
    Mine is downhill. It lowers MPG because the engine has to do a full warm up so I'm driving on engine for the next 3-4 minutes until it turns off a few miles down the highway. My Ford C-MAX Energi used to kick in the engine going up that hill above 40 mph but I've never had it happen so far in the Prius Prime. And, as I mentioned, this issue never happened until this week.

     
  11. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,850
    4,017
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    It happens to me also on a particular decent. I don't take that route often enough to identify the cause, but the first two times it happened I was in B mode and the last time I used the floor brake and it didn't happen.

    Not sure.
     
  12. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    is your heater temp set to 'min'?
     
  13. Pdog808

    Pdog808 Active Member

    Joined:
    Mar 30, 2017
    411
    271
    0
    Location:
    Los Angeles
    Vehicle:
    2018 Prius Prime
    Model:
    Prime Premium
    What @bisco mentioned is very valid. I have had my climate control come on if my A/C is set to 74 degrees and the outside temperature is in the 60's.

    Very irritating as I certainly do NOT expect my climate control to be activated unless I turn on my fan. Nonetheless, I have felt warm air flowing through my vents with the fan off and recirculate set to off. When this happens, I have to quickly set my climate control temperature settings lower as the heater chews up my battery levels.
     
    dalcon95 likes this.
  14. Flaming

    Flaming Active Member

    Joined:
    Aug 9, 2017
    138
    122
    0
    Location:
    QC , Canada
    Vehicle:
    2017 Prius Prime
    Model:
    Technology
    While charging , if the battery is too cold , the charger will limit the current going in the Li-on Battery to avoid damaging it until the battery reach the correct temp specs.

    now the speculation :
    If everything is off ( defroster , etc ... ) Maybe 55 degrees is borderline for the '' Cold range '' and the ICE turn on while going downhill because the car is protecting itself from overcharging and want to limit the current going in the Li-on Battery.. the extra energy has to go somewhere .. i think the ICE start to eat it
     
    HypersonicPrime, jaqueh and bisco like this.
  15. HypersonicPrime

    Joined:
    Oct 1, 2017
    74
    59
    3
    Location:
    NC, USA
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    If you haven't used your engine in a while or if it thinks the fuel is getting stale it might turn it on; however, I believe it gives notifications at least for the stale fuel. @Flaming's guess is probably more likely due to the conditions.
     
  16. Andyprius1

    Andyprius1 Senior Member

    Joined:
    Feb 4, 2013
    2,327
    859
    1
    Location:
    Cool CA
    Vehicle:
    2017 Prius Prime
    Model:
    Plug-in Base
    Use eco or ev/eco, I maintain my charge to full, even going up 1000 feet. ( I save it for the return trip )
    On the next downhill portion, it’s less steep, I 80, so I lose a portion of the mpg, but still save the original charge. Now at 26, summer = 35. On the return I’ll start using EV about 20 miles out and still end up with charge left on the car at arrival. Load changes are constantly occurring, so terrain is everything.
     
  17. Andyprius1

    Andyprius1 Senior Member

    Joined:
    Feb 4, 2013
    2,327
    859
    1
    Location:
    Cool CA
    Vehicle:
    2017 Prius Prime
    Model:
    Plug-in Base
    Right, it is said that the engine is not really running, but simply eliminating that extra energy, ??? Other items you mention are built in load factors that quickly get normalized. If one forgets and turns the heater, defroster too high then the mpg and charge make take a big hit.
     
  18. Andyprius1

    Andyprius1 Senior Member

    Joined:
    Feb 4, 2013
    2,327
    859
    1
    Location:
    Cool CA
    Vehicle:
    2017 Prius Prime
    Model:
    Plug-in Base
    Today, had 20 miles of charge left, distance to home 22.2 miles, mode: ev/eco, altitude ~ 2000 feet.
    Result: upon arrival 199.9 miles per gallon. Not the phoney figure that shows when starting car, but actual mpg. WHY I don’t know, the afternoon was clear and warm, that’s the only thing I can figure..........
     
  19. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,850
    4,017
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    Mine almost always shows that because I used no gasoline (all Ev mode). I don't see what's unusual.