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

Yet another engine start condition!

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by chuckp, Mar 14, 2012.

  1. chuckp

    chuckp Junior Member

    Joined:
    Mar 14, 2004
    26
    8
    0
    Location:
    Seattle, WA
    I live at the top of a hill and had noticed that every day I leave the house the engine starts at some point near the bottom of the first hill, say about 250 feet vertical altitude. If I am, say, on the level or going uphill no such engine starts happen (unless the other "start" reasons happen). After carefully studying this strangeness I have concluded that, because the battery is full at the top of the hill, the regen starts to over fill the battery and for some reason this starts the engine! If I stay on top of the hill and drive around for a bit, then go down the hill I don't get the engine start! I wonder why...
     
  2. devprius

    devprius /dev/geek

    Joined:
    Jan 2, 2006
    979
    291
    0
    Location:
    San Francisco Bay Area, CA
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    It may not be actually running the engine, but rather just spinning it (no fuel & spark) to drain off the excess energy.
     
  3. Tracksyde

    Tracksyde Member

    Joined:
    Sep 21, 2011
    1,429
    761
    0
    Location:
    So Cal
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    I think you are right. This happened to me once. I also go downhill over the first half mile of my drive. One time, the engine started. I wasnt using the heater and I am always careful not to start the engine through throttle input. However, when it happened that day, I figured I wasn't being careful and gave it too much throttle (even though I coast much of the way down the hill).

    Your experience sounds like it explains my engine start last week that I couldn't explain. That may also explain why my EV range continues to drop each morning. It's possible it assumes I regen, on average, X amount, so it leaves a little buffer? I have my Kill-A-Watt on tonight. I'll check tomorrow to see if it's taking less charge than normal. I may be able to get a SoC % tomorrow morning via Torque. I'll report back tomorrow morning.
     
  4. Matt M.

    Matt M. Member

    Joined:
    Feb 1, 2012
    117
    11
    0
    Location:
    San Francisco Bay Area
    Vehicle:
    2012 Prius
    Model:
    Four
    I can't answer your question, but, the more I learn about how the "Hybrid Synergy Drive" works, the more amazed I am at how complicated it is!
     
  5. ryogajyc

    ryogajyc Active Member

    Joined:
    Aug 30, 2004
    985
    165
    0
    Location:
    Reseda, CA
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Advanced
    I don't think it would leave the battery slightly uncharged as a buffer. I think the EV range drops b/c it is counting all the electricity it regens going downhill and burns off using the engine as electricity consumed, so your watts/mile goes up, lowering your EV range.
     
  6. Tracksyde

    Tracksyde Member

    Joined:
    Sep 21, 2011
    1,429
    761
    0
    Location:
    So Cal
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Hmm.. I guess leaving a buffer wouldn't be the best thing to do from an technical/engineering standpoint. But I've only had the engine start on me once in this unexplained manner. However, my EV range has been going down almost every day. I still make it to work on all EV with anywhere between 0.6 and 1.4 EV miles though.

    In any case, I'll post my Kill-A-Watt reading tomorrow. The one time I used Torque, my SoC on a full charge was 85.1%. So we can compare that to tomorrow's reading.
     
  7. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    313
    0
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    because its a plugin your leaving your home with a full battery..
    so going downhill just after that you wil have no more room for energy storage.
    its the same with the non plugin prius after a long downhill regen the ice wil bleed of energy
     
  8. usbseawolf2000

    usbseawolf2000 HSD PhD

    Joined:
    Sep 22, 2004
    14,487
    2,994
    0
    Location:
    Fort Lee, NJ
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    This is the same behavior with the regular noplug Prius. When the battery is full and the regen brake (MG2) continue to pump more electricity into it, MG1 will spin the gas engine to dump the excess electricity.
     
  9. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    maybe you should leave home with a partially charged battery. then you can get some 'free' electricity.
     
  10. OilFreedom

    OilFreedom New Member

    Joined:
    Oct 21, 2011
    79
    25
    0
    Location:
    San Diego, CA (Carmel Valley)
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    This is a similar strategy that many Leaf owners use... If you don't need max range, then charge the Leaf's battery to just 80% (automatically) or 90% (manually end charging). This way you get the benefits of regen coasting and braking. If the car begins a trip with a 100% charge, then only the conventional brakes are used to slow the car when the brake pedal is pushed, and there is no little or no coasting regen. You lose the energy capture opportunity during this time, but it protects the battery. Once the state of charge drops down a bit, then you get the regen benefits again.

    Note: A 100% battery charge on the Leaf really is a 100% state of charge. A "full" charge on a PiP may be less than 100%.
     
  11. Tracksyde

    Tracksyde Member

    Joined:
    Sep 21, 2011
    1,429
    761
    0
    Location:
    So Cal
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Last night's charge on the Kill-A-Watt was 3.11kWh. When I left my home, I was seeing 85.1% SoC. Its maybe a quarter mile out of my neighborhood, onto the street, then to the first stop sign. I watched the SoC but after dropping to somewhere around 83%, it was only able to regen back to 84.3%. I guess if I was really trying, I may be able to regen back to 85.1%? maybe more, triggering the ICE?

    Anyway, on the way to work, I used Siri on my iPhone 4S to log EV range remaining and SoC (just tell Siri "take note 12.1 and 85.1" and it'll create a note with "12.1 and 85.1", pretty cool).

    I'm not sure if this data is really applicable to anyone else since I don't know why my car shows 12.1 miles of a full charge versus 13.3 or even 11.1 for some other people (or even myself at other times).

    EV Miles Remaining ... SoC

    12.1 ... 85.1% (fresh charge)
    10.3 ... 76.1%
    10.2 ... 75.7%
    9.7 ... 72.5%
    9.0 ... 69.0%
    8.0 ... 63.9%
    7.0 ... 59.2%
    6.0 ... 53.7%
    5.8 ... 52.9%
    4.8 ... 48.2%
    4.1 ... 44.3%
    3.0 ... 38.4%
    2.2 ... 34.9%
    2.0 ... 34.1% (parked car)

    On a side note, I made it to work today with the most amount of EV miles remaining today, 2.0 (I usually see anywhere from 1.4 to 0.6).

    This was all city, no freeway, maybe half 40-45 MPH and half 45-50 MPH. The last 4-5 miles of my drive were pretty smooth, not too many red lights, very little traffic. This also includes an elevation drop of about 400 feet (mostly within the first 6 miles, I would say). Total trip to work is 13.3 miles.
     
    1 person likes this.
  12. usbseawolf2000

    usbseawolf2000 HSD PhD

    Joined:
    Sep 22, 2004
    14,487
    2,994
    0
    Location:
    Fort Lee, NJ
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    The depth of discharge is 52% (85.1 - 34.1). You went 13.3 miles with it. You are getting good with it. ;)

    The 3.11 kWh charge was to fill up yesterday's drive. It wouldn't be useful to apply it to this morning drive.
     
    1 person likes this.
  13. Tracksyde

    Tracksyde Member

    Joined:
    Sep 21, 2011
    1,429
    761
    0
    Location:
    So Cal
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Hmm.. thats right.. I never gave it much thought. I'll try to plug my Kill-A-Watt in at work. My charge timer is set for 3PM so I have time to get out there.
     
  14. Allannde

    Allannde Just a Senior

    Joined:
    Jan 7, 2006
    874
    138
    0
    Location:
    Washington State
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Advanced
    Or you could try putting the car in "B" going down the hill. It is my understanding that "B" provides engine braking and less regen. I use it all the time for long down hill runs when I don't want to ride the brake.
     
  15. andi1111

    andi1111 Member

    Joined:
    Jan 13, 2012
    270
    63
    0
    Location:
    EU
    Vehicle:
    2012 Chevy Volt
    Model:
    N/A
    B mode in demo PiP increased the level of regen without any throttle pedal applied. It did not run the ICE to do it.
     
  16. ryogajyc

    ryogajyc Active Member

    Joined:
    Aug 30, 2004
    985
    165
    0
    Location:
    Reseda, CA
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Advanced
    Are you sure about this and how do you know the ICE isn't being used? My understanding is that the ICE isn't really "run"/burning gas when it is used for engine braking in B mode. Instead, the engine valves are just left closed like a regular ICE, so air pumping losses slow the engine rotation and cause it to brake.

    Another possibility is that the Plug-in can brake harder with regenerative brakes since the battery can accept more power than a Liftback battery. In which case, it might be able to simulate engine braking with regen brakes, until the battery fills. If so, then once the battery is full, the Plug-in would have to switch to real engine braking. Was this test with a full battery?
     
  17. drees

    drees Senior Member

    Joined:
    Oct 31, 2007
    1,782
    247
    0
    Location:
    San Diego, CA
    Vehicle:
    2008 Prius
    Some owners who live on large mountains manually stop the charge even lower than 80% - 60-70% has been used by at least one owner.

    "100%" on the LEAF is around 94% full. "80%" on the LEAF is around 75% full.
     
  18. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    the thing is, if you fully charge, you're paying for the electricity. using b mode or any other method going downhill from your start isn't really giving you any advantage. once you figure out how much charge you're picking up on the down hill leg by experimentation, like oilfreedom and drees said, you'll know how much charge to put in it before leaving, saving yourself some dough and the grid a bit of juice.
     
  19. Tracksyde

    Tracksyde Member

    Joined:
    Sep 21, 2011
    1,429
    761
    0
    Location:
    So Cal
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    My Kill-A-Watt read 2.77 kWh when I left work.

    So that makes it 208 Wh/mile? I guess the 400 foot elevation drop helped a bit too, eh? :D
     
  20. usbseawolf2000

    usbseawolf2000 HSD PhD

    Joined:
    Sep 22, 2004
    14,487
    2,994
    0
    Location:
    Fort Lee, NJ
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Does that include additional miles going out for lunch?