Cruise Control Triggers ICE?

Discussion in 'Prime Technical Discussion' started by PiPLosAngeles, Dec 8, 2019.

  1. jerrymildred

    jerrymildred Senior Member

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    Cold battery with high current draw sounds plausible to me.
     
  2. m8547

    m8547 Active Member

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    But in both cases, on the 45mph road and on the highway at 65mph, I was on level ground and the battery was perfectly capable of providing plenty more current. I speculate that maybe the charge current was limited more than usual, but I didn't have a chance to look at that in Hybrid Assistant. I guess for whatever reason the cruise control wants the ability to use regen or engine braking instead of just the friction brakes (even though it is capable of using the friction brakes). So if regen is limited it tries engine braking, which turns on the engine and triggers a warm-up cycle.

    In the case where the cruise control turned on the engine at around 20% charged, I think there the discharge current was limited from parking outside around 32 degrees overnight, so it kind of makes sense to turn on the engine to help, even though it's not strictly needed. It will let you get closer to the discharge current limit with the cruise control off. For example I've seen it stay in EV mode with a discharge current limit as low as around 30kW. But if you push it and get too close to the discharge current limit for too long, for example try to accelerate quickly for more than a couple seconds or go up a hill on the highway, it will turn on the engine.
     
  3. vvillovv

    vvillovv Active Member

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    I've seen in the log while the wife was driving the engine fire on a decent uphil at 65mph.
    But the ambient temps were frigid - in the single digits F. It completely threw me and my experiment graphing miles/Kw in EV mode during frigid temps last year. I started a thread but never posted the results because the ICE fired and kept on firing at that same hill during those temps.
     
  4. m8547

    m8547 Active Member

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    Yeah, there's a pretty big hill on the highway on my way to work. If I go straight from my house I usually reach the top of the hill with about 50% charge, and I can make it in EV mode no matter what temperature (my record is 9 degrees F). But if it's a cold day and I do any errands on the way to work, I'll have about 20% less charge than usual by the time I reach the hill. In that case the engine will often turn on just before I crest over the top, which seems like a waste.

    Another issue when the engine turns on like this is it doesn't go through a warm-up cycle. Since the car thinks you're not getting enough power from the battery, the engine immediately starts driving the wheels. That can't be great for it to start from cold like that.
     
  5. Bob Comer

    Bob Comer Active Member

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    That sounds very plausible, though it I can't understand why our cars are so different. You're not setting the speed lower than what you're going I assume, so it doesn't need regen or engine braking right away.
     
  6. m8547

    m8547 Active Member

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    To be clear, it only happens when the battery is cold, for example in the morning after the overnight temperature was in the 20's. And now that I think of it, the most recent time might have been when I let it charge in the evening the night before, rather than setting a charge timer to finish charging at 7am like I usually do. It seems less likely to turn on the engine if the charge is "fresh" even if the battery temperature is similar.

    I wonder if everyone's batteries have different current limits even in the same conditions, based on usage history of the battery? I have only 17,000 miles on mine, but I use EV mode heavily, at least 30 miles a day with some big hills on the highway, and I usually accelerate briskly whenever I can.
     
  7. sam spade 2

    sam spade 2 Senior Member

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    A bit of explanation is needed.....maybe.
    Edit: (I see that has been provided in subsequent posts......so never mind.)

    IF the engine really stays on indefinitely while the car still indicates that it is in EV mode, then you have a fault that needs to be fixed.

    Just for grins, what happens if you set the cruise, switch it to another mode for a minute or so and then go back to EV ??

    The real cause might be that ever present OCD !! :whistle:
     
    #27 sam spade 2, Dec 17, 2019
    Last edited: Dec 17, 2019
  8. Bob Comer

    Bob Comer Active Member

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    I suppose that's possible. I drive a lot like you, though no hills and in addition to my 30 miles of EV a day, I drive about 50 more under HV. I'm not a light foot either on the accelerator...

    I tend to use my EV in the warmer part of the day, and we're overall more warm here... (South Carolina coast) It rarely gets in the 20s.
     
  9. vvillovv

    vvillovv Active Member

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    Backing off acceleration and/or speed at known times or circumstances that fire the ICE can help the driver keep the ICE off. That (backing off the go pedal ) can be a lot harder to do than it is to say. It's almost like training new muscles to work in the opposite direction of normal, and that is usually exhausting until the muscles are trained and exercised.

    And if the driver knows when the cruise is going to fire the ICE and it's not a totally hap hazard affair, the driver could try canceling cruise and feathering the go pedal past those nasty spots in the trip.
     
  10. m8547

    m8547 Active Member

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    In the case of cold battery and >90% SOC, the cruise control turns on the engine instantly, as soon as you set a speed, even if you're just coasting on a flat road.

    For big hills, oddly enough the engine often seems to come on when I'm most of the way to the top and already letting off the accelerator. The hill on my morning commute has a steep section, but it is more gradual at the top. But it's somewhat random. I tried going slower, around 60 instead of 70, but that didn't seem to make a significant difference. I can't go any slower or completely let off the accelerator without slowing down traffic.

    At low SOC with a cold battery it's pretty hard to predict when it will decide to use the engine, but very gentle acceleration does help prevent it. It might be better to switch to HV mode in advance, to avoid what I call a "hard start" where the engine immediately starts powering the wheels with no time to warm up.
     
  11. Salamander_King

    Salamander_King Senior Member

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    Internal Combustion Engine (gasoline based engine as opposed to battery operated electric motor)
     
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  12. Bob Comer

    Bob Comer Active Member

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    Internal Combustion Engine, i.e., the gas engine...
     
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  13. vvillovv

    vvillovv Active Member

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    Don't expect instant changes in the way the car behaves. If you've been driving one way for 500 or 1000 miles, than try to change the cars behavior by experimenting with it a few times at certain points in the trip.

    The car has memory or data history it uses a lot. It's described as adjusting to the drivers driving style. Further, the car mixes some history data with some current data from the senors.

    How much of each (history and current) data is used at any one time, I doubt anyone fully understands yet.

    It takes a while for the car to adjust the way it operates, when using the new data the computers in the car have to work with.
    Often, more time than most driver have while driving normally in traffic or the same daily commute

    Some things displayed on the dash, for example: the driving score are quickly calculated and displayed and can change rapidly between each stop the car makes in a trip. Other calculations are more subtle and much harder to notice on any one set of gauges a driver normally has displayed on the dash regularly.
     
  14. PiPLosAngeles

    PiPLosAngeles Active Member

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    Not only that, but it turns off the instant you cancel cruise control and back on when you engage it ... even if you repeat a dozen times (if the engine is already warm). All while speed and engine effort remains constant.
     
  15. m8547

    m8547 Active Member

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    I watched that on Hybrid Assistant after the engine warmed up and I was driving in EV mode on a flat highway. Turning on the cruise control caused a short blip of engine braking each time, for some reason. That is probably what starts the engine in the first place, since even a blip will cause it to go through the warm-up cycle. It seems like a bug, because I can't think of any logical reason why it would do that under some conditions (cold battery and high state of charge) and not normally, since normally activating the cruise control in EV mode does not cause engine braking.
     
  16. jerrymildred

    jerrymildred Senior Member

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    I don't remember seeing anyone with a 2017 Prime having this issue. Could it be a bug introduced in the 2018 MY?
     
  17. PiPLosAngeles

    PiPLosAngeles Active Member

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    Are you sure it's engine braking? Mine always punches the gas for a brief instant, even if you're already coasting downhill when you set it. Like it's trying to "throw a rev." I just figured it was to sense the current engine load situation. Either way, that could explain the engine starting but not why a warm engine would continue to run while cruise control is engaged.
     
  18. m8547

    m8547 Active Member

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    Not sure. I think I remember seeing negative engine power (braking) on hybrid assistant when I tried, and I can also see that on the Hybrid Reporter graph of my drive (but it's very small, not sure if I can zoom in). I tested in EV mode last night (engine never went on), and it did always punch the accelerator for an instant if I was coasting.
     
  19. m8547

    m8547 Active Member

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    It looks like maybe both, but I can't really tell. The blips on the zoomed in section are where I was testing it after the engine had warmed up.
     

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  20. m8547

    m8547 Active Member

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    Here's where I was testing it last night. Nothing interesting to see.
     

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