When to Kick in ICE to Add Just a Few Miles Range

Discussion in 'Prime Main Forum' started by mr88cet, Jul 16, 2017 at 2:06 PM.

  1. mr88cet

    mr88cet Active Member

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    A few times now I've had a drive home where I would likely end up a couple miles short trying to drive it all strictly on EV. My thought had been to kick in HV at some point in the drive when I'm going at 40-50MPH, where it should get pretty-good mileage, let gas power the car through the unavoidable warm-up cycle, then switch back to EV.

    Today I did that, and looked more carefully at was happening, and discovered that that strategy doesn't work at all!

    Thinking back to our Gen-2, what I saw happening was that the battery continued to be drained at the same rate as in EV mode through the mandatory warm-up cycle. It essentially remained in EV mode through the warm-up cycle, meaning that all it does is waste a warm-up cycle's worth of gas during that time, and not save a few miles of battery capacity as intended. It wants to warm up the engine at a constant, medium-low RPM.

    It appears that it the best strategy, if you want add a few miles in HV is to just continue in EV until you run out and let it switch over all by itself. When the battery is drained down to the HV range, it seems more likely to actually use the ICE to do useful work.

    Thoughts?


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  2. joachimz

    joachimz Active Member

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    Once the ICE is warmed up, it will start charging the traction battery and bring it back up to the level prior to switching to HV, this might take a few miles but I have observed that behavior multiple times.
    The other option would be to switch it into charge mode, I have however not done that on a "cold" ICE, it might not charge during warm-up but might bring it up to previous charge level quicker than the above ...
     
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  3. Prius from Dad

    Prius from Dad Senior Member

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    I tried something similar and found the battery is used during warm up. After warm up, the battery will deplete some when in HV battery mode. It seems to deplete faster than it can regen. I ended up doing what you said, use EV until it runs out, then after warm up, try to maximize HV battery usage.
     
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  4. bisco

    bisco cookie crumbler

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    unless you're going to arrive at your destination before the warm up cycle finishes, it seems pointless, efficiency wise.
     
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  5. NJ-PrimeAdvanced

    NJ-PrimeAdvanced Junior Member

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    There is a recent thread on this where some folks have a commute of just under 30 miles and they run out of EV just before they get to work or just before they get to home and a cold ICE kicks in with just less than a mile to go... and they have to sit there with the engine switched off until it warms up before they can switch off... they were wondering how they can squee an extra half a mile out of the EV range so that that the cold ICE doesn't come on... is CHG mode the answer? is HV mode WELL BEFORE the answer? no one knows.
     
  6. bisco

    bisco cookie crumbler

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    find a charger at the half way point?
     
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  7. priuscatprimeguy

    priuscatprimeguy Senior Member

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    or use gas, or get yourself a BEV:D
     
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  8. Pdog808

    Pdog808 Junior Member

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    My rule of thumb is to swap to HV when I am relatively sure I will be able to drive at least 10 minutes at speeds above 50 MPH. Sometimes you guess right, sometimes not. EV efficiency drops off so sharply at higher speeds (50 MPH is my rule of thumb) that it just makes sense for me to swap to HV.

    Also, I'm a bit paranoid about stressing the traction battery at extended high speeds (higher current draw = higher battery heat). Wish there was more data on this, though.
     
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  9. heiwa

    heiwa Junior Member

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    Lee Jay had a thread "When you need a tiny bit more EV range..." and talked about ICE turn off switch to utilize hybrid portion of th traction battery. Another mentioned that Ford has such switch if I remember it correctly. Perhaps in2018 model will have such a switch.

    Posted via the PriusChat mobile app.
     
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  10. mr88cet

    mr88cet Active Member

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    Uhmmm... Why wait for the ICE to finish warming up? Just shut it off immediately.

    As a footnote, however, I'm not certain, but I *think* I've seen one or two cases where I kicked in HV mode at 75MPH, and it did in fact switch over to ICE power. Again though, not certain of that...

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    #10 mr88cet, Jul 17, 2017 at 6:41 AM
    Last edited: Jul 17, 2017 at 6:48 AM
  11. fotomoto

    fotomoto Senior Member

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    That was me, it's called EV+, and no it does not have a switch; rather it is an automated feature that learns via GPS common destinations like home, work, etc. In the OP scenario (a general destination) it would not activate.
     
  12. heiwa

    heiwa Junior Member

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    That is a clever engineering, though some may prefer a manual switch! Thank you for the correction.

    Posted via the PriusChat mobile app.
     
  13. FuelMiser

    FuelMiser Active Member

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    It's been a rule of thumb since at least Gen 3 that you should let the ICE finish its warmup cycle before shutting it down to avoid engine rattle/shaking on subsequent starts. In non-Prime models, this usually only happens when you need to move the car a short distance (in/out of the garage, for example) and the ICE starts up. But in Prime, I suppose there is this other situation when you would be at the end of your trip with an ICE that has come on but has not completed its warmup.
     
  14. alexcue

    alexcue Active Member

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    I guess I missed that memo, err Rule of Thumb, on my Gen 3.
     
  15. mr88cet

    mr88cet Active Member

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    So then, assuming that you aren't going to fire up the car (ICE or not) for … say an hour, why would it shake or rattle on subsequent starts (or at least shake or rattle any differently from having finished the warm-up cycle)?


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  16. FuelMiser

    FuelMiser Active Member

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    This was covered in several threads, to my recollection. A quick search yielded this, Engine Rattle on Startup | PriusChat
     
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  17. alexcue

    alexcue Active Member

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    Thanks, Wowzers, that's an ugly sound, and mine never made it in 36k miles I drove it. Must have been lucky!
     
  18. Krzysiek_KTA

    Krzysiek_KTA Junior Member

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    Ii happened to me quite few times I run out of EV juice couple of hundred yards from home and the ICE kicked in. I reached home before warm up cycle was completed. Never had any issue after shutting off the ICE well before warm up cycle was done ( no rattling noticed ever).
    Anyway I did not like arriving into garage with ICE on, therefore whenever I am sure I won't make it on EV I engage CHG mode at speeds above 50 mph and add some EV juice.
    Performance- wise It those speeds I can't tell the difference between HV and CHG mode.
    It might not be the most efficient way but for sure it maximizes EV driving (which I do like ).
     
    #18 Krzysiek_KTA, Jul 18, 2017 at 2:29 PM
    Last edited: Jul 18, 2017 at 8:26 PM
  19. bisco

    bisco cookie crumbler

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    hopefully, the cold start shake rattle and roll has been fixed in the gen 4 engine.
     
  20. Prius from Dad

    Prius from Dad Senior Member

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    This is something I experienced with my 2012 v. There was no warm up issue, it just happened once in a great while when I would start up on my trip home in the afternoon after driving 35 miles in the morning.
     
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