Inconsistent EV behavior

Discussion in 'Gen 4 Prius Technical Discussion' started by Ranko Kohime, Oct 9, 2018.

  1. Ranko Kohime

    Ranko Kohime Member

    Joined:
    Oct 29, 2017
    62
    29
    0
    Location:
    Ohio
    Vehicle:
    2017 Prius
    Model:
    Two Eco
    tl;dr: My Prius unpredictably idles when it shouldn't, this is a relatively new behavior, and I have mild autism.

    To be clear: this thread is not about the EV mode button, but rather the ICE engaging or dis-engaging as shown in the HV indicator. Any mention of EV mode refers to ICE stopped while in motion.

    First, I'm going to define normal behavior. Around 73mph, the ICE will kick on to protect MG1. It won't necessarily consume fuel to do so, if for example we have gravity available to avoid high current draw from the traction battery. For some reason, cruise control alters this, forcing ICE to spin at speeds above 63mph, more often with fuel consumption. I find this weird, but since purchasing my '17 Two Eco, it has been consistent.

    I am measuring fuel consumption using a ScanGauge, and verifying that it's reading actual fuel consumption by taking measurements at the injectors themselves.

    What has NOT been consistent, however, is the behavior I have experienced on and off for the past 5k miles or so. (I'm at 51k as I type this)

    At some point the system decided that consistent behavior was over-rated, and EV mode went from 73 down to 62 without CC active, and with CC active any speed over 35 required the ICE to spin, ALWAYS with fuel consumption. It did this for 2, perhaps 3 weeks, then returned to normal.

    While it was doing this, it was still switching to battery power when appropriate, and the ICE would spin ~990 rpms, and consume around 0.2 GPH, effectively idling.

    I've seen no degradation of battery power, based upon voltage readings, amperage draw readings, etc, and the engine is always hot (>80c) when this even becomes an issue, so i doubt that I'm not in at least stage 3 or 4.

    Things that I thought might have an impact:
    • I had an unrepairable hole in one tire, and due to budgetary constraints, replaced it with a used tire of a different size (all that was available at the time). This tire is a 195/60-15, whereas the stock are 195/65-15, and it was rotated to the rear to avoid ratio grind in the differential. I would think that if perhaps THIS was the problem, then I would get some kind of ABS error, or some kind of code at least, but no codes.
      Before anyone asks: I'm getting new tires as soon as the budget allows.

    • I skipped the 45k service, as the dealership stated they only change the oil at 10k intervals anyway, and I'm not keen on paying for just a tire rotation when I don't need service otherwise. I reset the service gauge myself, and thought that might have something to do with it, but the problem persisted after the 50k service.

    • Around the time this started, I began towing a trailer on a regular basis. I thought that perhaps the added load was causing the computer to go into some different mode, but this too has outlasted the behavior, and the last time I towed, I had the CC set at 60, and while the load causes it to go into EV mode less, it does still go into EV mode on downhill areas.

    As an aside, this next bit HAS been consistent as long as I've owned my Prius: When decelerating, and the traction battery reaches a high state of charge while still decelerating, the ICE will kick on. Depending, I think, on pack temperature, it may do this around 60, or 70 SoC, but it definitely does it above 80 SoC. When it does it at lower SoC, it merely idles the ICE, using fuel, instead of putting it into B mode automatically. I really do not see the purpose in this. I CAN see a purpose behind using the ICE in B mode to reduce battery stress, but this is not being done if the ICE is spinning at idle on fuel.

    And why not one more gripe for good measure: B mode is extremely difficult to control. It almost always has too much braking, and controlling it via the accelerator pedal IS possible, as in it was an actual intended feature, but the sensitivity is JACKED, even with the drive mode in ECO.
     
  2. alanclarkeau

    alanclarkeau Senior Member

    Joined:
    Feb 24, 2016
    5,189
    5,896
    0
    Location:
    near Brisbane, Australia
    Vehicle:
    2016 Prius
    Model:
    N/A
    Your mention of the ICE kicking in when the battery gets to a high state of charge - yes, they all do it, we're not sure why. It will do it once after warming up and a certain amount of driving - if you press the EV Button it will say something like "EV Mode UNAVAILABLE". Often, 2 mins later, it will revert to normal again. As you suggest, it could be something to do with pack temperature, but without access to the engineering team who designed the safeguards, we just enjoy the car with that idiosyncrasy.

    I'd suspect "B" Mode is something you would use rarely - I've only used it twice in 2½ yrs - but what you say is consistent with what it does.

    The "HV INDICATOR" - is very approximate, particularly the EV light. I'm certain that the ICE wasn't running at times, but the EV light didn't show. I threw it away after the first 2 weeks of driving my Gen 4 (the bar-graph is in your HUD anyway). This has been discussed many times on PriusChat. Instead I put up the ENERGY MONITOR which shows much more accurately what's going on:
    upload_2018-10-9_17-31-8.png

    Keep enjoying your PRIUS.
     
  3. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    81,487
    35,212
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    normal

    prius is inconsistent to the human brain, if nothing else
     
    alanclarkeau likes this.
  4. Ranko Kohime

    Ranko Kohime Member

    Joined:
    Oct 29, 2017
    62
    29
    0
    Location:
    Ohio
    Vehicle:
    2017 Prius
    Model:
    Two Eco
    There are a few occasions I've noticed it stutter, the EV light shows even though the ICE is still spinning, the light goes out and then back on as the ICE stops for real, (about 1-1.5 secs total time), but other than that, it is VERY consistent in reporting the state of the ICE.

    To be clear, I don't consider the car being driven from the traction battery to be EV mode unless the ICE is stopped, even if the energy display shows no energy moving to/from the ICE. If the ICE is out of the equation, it should be stopped.

    I knew there was a reason why I'm fanatical about software freedom...

    As for B mode, I use it daily. Any hill where I gain speed with the accelerator fully released, (and there are a few in my normal driving circuit), I use it. It's a lot like downshifting a manual transmission, which is why it's there.
     
  5. Ranko Kohime

    Ranko Kohime Member

    Joined:
    Oct 29, 2017
    62
    29
    0
    Location:
    Ohio
    Vehicle:
    2017 Prius
    Model:
    Two Eco
    Strap in for some reading children, I'm in a typing mood. (viciously yanks carriage return)

    I'm at 133k now, and doing a lot more highway towing than when I started this thread. I'M ALSO MAD AS HELL! [​IMG]

    There's now 3 different clearly defined stages of what I call digital madness. OR THERE WERE 3 CLEARLY DEFINED STAGES UNTIL YESTERDAY!!

    I'll include a soundtrack here for proper effect. Just put it on in another tab while you read.

    The previously detailed issue reared it's ugly head again, and I noticed something this time I did not previously: the idle charge limits on the traction battery. These days, since I'm on the road a lot, I stop in truck stops, and it's simply cheaper to sleep in the car than to get a hotel room, so I do. On hot nights, I keep the system in Ready mode, and run the A/C. Normally, the system will start the ICE to charge the battery as it is switching from 27% down to 26%, and then charges until 40% at a rate of around 15-16 amps, with a calculated GPH of 0.40 as according to my ScanGauge. I average about 0.3 gallons consumed per average 8 hour night. I'll refer to this as mode A. Until yesterday, the cruise control functioned normally in mode A.

    Mode B changes these idle charge limits slightly, to 32% and 45%. Charge rate drops to 11A, and GPH remains unchanged at 0.40. This equates to a significant increase in fuel consumption over the course of a night as it takes longer to charge the battery. It also changes the cruise control functionality to eliminate EV mode percentage at set speeds above 40. The aforementioned inability to run EV mode above 63 applies.

    Mode C *expletive deleted* changes this to 40% and 55%, and further reduces the charging rate down around 5A, while again, not in any way affecting GPH. This results in well over a gallon being used overnight. The real punch in the nads is not just cruise control, but also the EV mode speed, which now forces the ICE on if heaven forbid you hit 58 mph, and will not let the ICE stop until you drop below 52. Fortunately, this mode simply seems to have resulted from bad spark plugs, a few start cycles after replacing them, I was in the above modes again.

    At no point in ANY of these modes is the system even making the pretense of possibly protecting the battery. I regularly see 70A being drawn off of it, for several seconds, before the ICE takes over.

    This last trip, starting out I was in A mode. Ahh, glorious A mode! And, can you believe, with the cruise control set at 55, the MPG started in the high 70's, and after 150 miles was at 84 MPG!
    [​IMG]

    Then it all went downhill. The cruise control went into mode B. But the battery still let me get down into the 20's, so clearly I was in mode A! My MPG quickly tanked, and the rest of the tank wound me up in the low 60's. What's worse, is that I cannot do better with my foot.
    [​IMG]

    Hey Elon, could you bring out the Tesla pickup a little sooner, please? Thx.

    ETA: by the way, yes, I'm well aware that weather conditions and road conditions have an effect on MPG, my mind makes unconscious calculations based on both of these.
     
  6. alanclarkeau

    alanclarkeau Senior Member

    Joined:
    Feb 24, 2016
    5,189
    5,896
    0
    Location:
    near Brisbane, Australia
    Vehicle:
    2016 Prius
    Model:
    N/A
    It sounds quite normal. "low 60's" - towing on the highway - I reckon that's better than excellent - what speed are you driving? What battery do you have?

    Did you notice battery temperature? At higher temperatures, it won't go into EV MODE except for very short spells, and will almost immediately run in ICE Mode to protect the battery. But, once the battery cools, back to normal again. That cycle is quite normal.

    Is your battery fan filter clean?

    [Sorry - I don't understand what you meant by A, B or C Modes.]
     
    kithmo likes this.
  7. kithmo

    kithmo Couch Potato

    Joined:
    Apr 25, 2010
    2,086
    2,331
    44
    Location:
    South Yorkshire, UK
    Vehicle:
    2016 Prius
    Stop messing with "B" mode, just leave it in "D" normal mode (not ECO or PWR or EV) and drive it. That will give you an indication of what is normal behaviour and what is not. Then you can start comparing the different modes if you really must.
    If all else fails then, as Alan says above, check your battery fan filter is clean and the intake, just in front of the rear seat, is clear of obstructions.
     
    alanclarkeau likes this.
  8. Ranko Kohime

    Ranko Kohime Member

    Joined:
    Oct 29, 2017
    62
    29
    0
    Location:
    Ohio
    Vehicle:
    2017 Prius
    Model:
    Two Eco
    I have the Two Eco, so a lithium battery. Both 80+ and 60 MPG comes from deadheading; no trailer. Trailer MPG ranges from 45 down low 20's. 55mph, most of the time.

    I checked the battery fan and filter, there was no dust on either the filter or the fan blades themselves, and I've never heard the fan run, actually. Having very acute hearing, I was expecting it since others have noticed it.

    The only time that I've ever witnessed battery performance be restricted is in winter on a cold startup. Even with the interior of the car scorching from sitting in the sun during the day, I've never experienced the battery performance be limited from heat, I consistently see it willing to deliver or regen 70A or more.

    Since I have the rear seat removed, (for a homemade cargo platform) I have easy access to the battery case, and even after extended city driving, the case isn't even noticeably warm, relative to the cabin temperature.

    These are "states" that the hybrid system gets into: I detailed all of the observations I made in the post you quoted.

    The modes I mentioned have nothing to do with the Drive modes. The Drive mode setting only changes the response curve of the accelerator pedal, I leave it in Eco full time, as I want the greatest granularity of control. Given careful foot control, there wouldn't be any difference in fuel economy between the different modes, they are merely to personalize to one's driving style. Which itself would probably dictate economy.

    B mode, on the shifter, is the equivalent of down-shifting a manual transmission vehicle. I am aware of the appropriate times to use it. ;)
     
  9. kithmo

    kithmo Couch Potato

    Joined:
    Apr 25, 2010
    2,086
    2,331
    44
    Location:
    South Yorkshire, UK
    Vehicle:
    2016 Prius
    On the Gen 4, ECO mode not only changes the pedal response, it also dumbs down the climate control, so there will be a difference in fuel economy.
    I don't know why you would want the pedal to grainy o_O but the best control of the pedal is in normal mode, a straight line of pedal position to pedal response.
    No offense intended, but ECO is for heavy footed drivers.
     
  10. Ranko Kohime

    Ranko Kohime Member

    Joined:
    Oct 29, 2017
    62
    29
    0
    Location:
    Ohio
    Vehicle:
    2017 Prius
    Model:
    Two Eco
    I thought that was what PWR mode was for... :D

    And all the better with the climate control, honestly. I keep it in ECO too.
     
  11. alanclarkeau

    alanclarkeau Senior Member

    Joined:
    Feb 24, 2016
    5,189
    5,896
    0
    Location:
    near Brisbane, Australia
    Vehicle:
    2016 Prius
    Model:
    N/A
    Yes, this is the mapping of ECO, NORMAL and PWR:
    upload_2019-9-6_22-53-22.png

    Mostly - it changes the sensitivity of the accelerator pedal.

    Personally, if I'm driving using accelerator (which is rare), I use ECO as the accelerator is more sensitive. Most of my driving I use NORMAL in DRCC, unless it's tight traffic where I want it to not leave gaps ahead, I use PWR.