Help: ICE running with full battery when not in HV Mode

Discussion in 'Clarity' started by Rachel Sherman, Apr 20, 2022.

To remove this ad click here.

  1. Rachel Sherman

    Rachel Sherman New Member

    Hi all, I'm a fairly new Clarity owner, I've had my 2018 for about 3 months. Twice in the last week, after charging (L2), I've turned the car on, and noticed a minute or two later that the engine is on, the car does not say 'EV' on the dash, and I don't have the blue bar on my power meter indicating EV power availability, despite a full charge. Switching mode to HV and back does not solve the problem. Turning the car off and on again seems to solve the issue, though one of the two times this happened I had to turn off/on twice before it resolved things. Has anyone else had this happen? Pretty frustrated to be having this issue when I specifically chose the Clarity over other PHEVs because of it's 'EV as default' design philosophy.
  2. To remove this ad click here.

  3. jdonalds

    jdonalds Well-Known Member

    Yes it really irritates me when the engine runs even though I don't want it to. We can drive our Clarity for months without us causing the engine to start.

    What I've found is these things:

    1) The best way to keep the engine from running is to use ECON non-HV mode and don't push the accelerator pedal past the detent.

    2) Honda has designed the car so the engine will periodically run, and keep running for a few minutes. Supposedly this is to both lubricate and warm-up the engine.

    3) If the battery is full and if the regen is working the engine may come on to dissipate some of that regen power.

    I've noticed that Honda's method of getting the engine to run is to switch ECON off. Then I don't have to depress the accelerator pedal past the dent for the engine to come on.

    When I get in the car sometimes ECON is switched off even though I have not done that. If I catch it and switch ECON back on I can prevent the engine from coming on.
  4. Robert_Alabama

    Robert_Alabama Well-Known Member

    I’d bet on 3) above from @jdonalds above. Very likely it is from regenerative braking with the battery full. Even in Econ mode (which I always use), the engine will start if the battery is full and you decelerate very much. I’ve gotten much better at avoiding the engine start with gentle deceleration for the first couple miles after a full charge. If you have to go down a big hill/mountain right after a full charge, you may not be able to avoid it. In the winter, you can turn the heat up at the start of the drive to help give some room for the regeneration energy and avoid the engine start. I’ve also had some luck with using the defroster early in the drive in warmer weather. Hope this helps.

    Also, it is not recommended to turn the car off and back on to get back in EV mode. I’ve read It isn’t good for the engine or exhaust system as it can allow water condensation issues by not getting to a high enough temperature. That seems reasonable that it could lead to a problem.
    Last edited: Apr 20, 2022
    Daniel M W likes this.
  5. MrFixit

    MrFixit Well-Known Member

    Although there is some debate about this, this behavior is highly likely to be normal. It is dependent on the circumstances, particularly when regeneration is used with a full battery, but occasionally the engine will start for no apparent reason. These random occurrences are very infrequent and I believe Honda is doing some kind of routine maintenane cycle. As mentioned, make sure you are always in Econ mode and engine starts should be 'rare' unless you have a specific scenario that causes them (like living at the top of a hill which always uses regen when you start out with a full charge).

    My recommendation is don't try to stop the engine by switching modes, turning it off, etc. It is very likely running for a reason and artificially terminating it defeats the legitimate purpose of the run. It will turn off on it's own. Sometimes the occasional maintenance run seems to last a long time (maybe 10-15 minutes). It seems like a very long time when you don't really want it to run, but it is mostly just idling, and probably serving a legitimate purpose.
    Madmartigen likes this.
  6. Mowcowbell

    Mowcowbell Well-Known Member

    I time my charging sessions so that I never charge the battery beyond 80%. Never had the ICE come on like mentioned above. It only comes on if I floor the pedal beyond the detent position, or by manually pressing the HV button.
  7. To remove this ad click here.

  8. megreyhair

    megreyhair Active Member

    This annoys me as well when I know I didn't step on the gas far enough to go pass the green arc and the batt are full. Driving in ECON doesn't help. It still comes on. Would be nice for it to come on when the batt is some what discharged so it can charge the batt a bit
  9. RataTejas

    RataTejas New Member

    Also don't forget that this is still an ICE car in some ways. The 12v auto battery needs to be charged/discharged regularly, as well as mentioned earlier, it just runs occasionally for lubrication/self preservation reasons.
  10. Rachel Sherman

    Rachel Sherman New Member

    Thanks all. I'm always in econ mode and I'm never going past the detent. This is occurring when I'm going about 25 mph in my neighborhood immediately post charge. I guess it must be the full battery/regen combo since this has been after charging both times. No big hills or anything though, pretty normal flat city driving, but maybe just the stop light/stop sign stop-and-go is enough regen on a full battery to trigger this? Just odd to me this happened twice last week and never in the 3 months before. I wonder if the warmer weather causing the battery to hold charge better is contributing to the sudden change.

    Also, both times were charging after relatively long drives where I was in HV for a while, so it's not an issue of the ICE needing to run because it's been unused.
  11. Frankwell

    Frankwell Active Member

    Actually the 12V battery is charged by the HV system not the engine, whenever the car is in READY mode it it charges the 12V whether the engine is running or not. The 12V battery is also charged whenever the car is charging. Although only while charging, just being plugged in won't charge the 12V battery.

    That is quite possible, especially if the first stop is near your house. What might help is to try and lighten the braking when you make your first stop. Next time you are out driving notice the power needle and how it shows regen, which is whenever the pointer is below the line. You will notice that when you brake for a stop the pointer will at first be below the line indicating regen, but as you get within the last few seconds before coming to a stop the power needle moves to "neutral" as it switches to only the friction brakes. So when you leave your house with a full battery try to go a little slower if possible up to the first stop, and when you are approaching the stop try and start slowing down earlier so that you can press the brake pedal just enough to start slowing down but without causing regen. Once you get below about 10 mph you can press the brake pedal as hard as you want and it won't go into regen. Of course if someone is following behind you this may not be practical, but when no one is behind you give it a try.
  12. To remove this ad click here.

  13. rodeknyt

    rodeknyt Active Member

    I have the same issue with my 2018. I live on a hill and I have to put the car in neutral until I get to the flatland to avoid having the engine start. This topic has been discussed since the beginning. I have noticed, though, that folks with 2019 and newer models don't seem to have this happen (or at least as often). Could be Honda made some changes that a software update wouldn't fix in the 2018s.
    gedwin likes this.
  14. That task is handled by a DC/DC converter/charger. The car has no alternator. Discharging and charging any battery will decrease longevity. The 12V in a car is not a deep cycle battery. It will last longer if kept fully charged and not subject to unnecessary discharge and charge cycles.
  15. ClarityBill

    ClarityBill Active Member

    In winter months, the heater will keep the full battery /regen problem from happening as much. I live at the top of a hill, so I turn the seat heater on full, and turn on the heat, to avoid the problem. At the bottom of my hill, I adjust the heat to my comfort level.

    A stop sign after full charge can cause the engine to run.
    Dan Albrich likes this.
  16. Andy Lo

    Andy Lo New Member

    Hi Rachel, I think it is normal. I have my 2018 for a few years now. It occasionally switches to non-EV from EV modes. I think what it tries to do is run through things for the gas engine side for maintenance purposes. I have also heard from the service manager at my dealer that when sufficient water condensation building up in the exhaust line, it will automatically switch to non-EV mode to try to get rid of them. I do notice the switching happening more often in winter times. It switches back to EV mode by itself every time after a few minutes.
  17. CHinVT

    CHinVT New Member

  18. CHinVT

    CHinVT New Member

    Hi, Rachel.
    I am also a relatively new Clarity owner, got a 2021 in September, and I don't notice the HV coming on yet after a "full" charge. But it's still cool in VT, and just getting up to 50+ miles of EV on a charge. Usually the first mile or so is downhill with a stop sign at the end, so I am picking up EV miles on the way down after the charge. But I agree with those who think it's related to regen after the full charge. I'll pay closer attention as the weather warms.
  19. Frankwell

    Frankwell Active Member

    That's an interesting theory but I have never heard that one before. Kind of makes me wonder what type of sensor could survive in the hot exhaust line yet still be sensitive enough to detect moisture when the system is cold. Maybe that type of sensor is more common than I think, but it seems like that would be a more expensive type of sensor than you would normally find in a passenger vehicle.
  20. JRath

    JRath New Member

    Honda Engineers who read this could take away some valuable suggestions:
    1. Add an "End When 80% charged" option to Charge Schedule in HondaLink
    2. Have the car use the friction brakes to slow it down rather than starting the engine when it's already at 100% charge.
    3. Option, add something like "Mountain Mode" so it won't take the battery down to 0% while driving.
    We've had our 2018 for 4 years and we love it. But it is almost infuriating to see the engine start up within my subdivision when I've (accidently) charged it to 100%.
    Frankwell, Robert_Alabama and Kestrel like this.
  21. Honda engineers don’t read this forum. Even if they did, it isn’t likely they would be able to do anything other than what the bean counters want them to do.

    Personally, I’d never use a “End when 80% charged feature”.

    Just select HV before depleting the battery if you expect demanding driving conditions.

    I’m starting to agree with the theory that the engine starting when the driver thinks about using the brakes with a fully charged battery is a 2018 issue. Hard to believe that there would be a difference in software. We always fully charge out 2019 and have never had the engine start when applying the brakes.
  22. Robert_Alabama

    Robert_Alabama Well-Known Member

    I agree that the engine ever starting when I have a full battery is an annoyance, but it is a small one in the grand scheme of things. I have a 2018 and have 33k miles on it. It's almost 4 years old and I have driven it 64% battery 36% gasoline (it's always our travel/vacation car so it gets a good bit of highway driving on some pretty long trips). I've burned 301 gallons of gasoline in that time, and I'd bet heavily that approximately 1 gallon of that is due to the engine starting with regen and battery is full. In the grand scheme of things, it's just not worth the effort of worrying about for me. Maybe I've gotten a lot better at avoiding it, but it's been a very rare occurrence in the past couple of years and I can't even remember the last time it happened, but it was at least a couple of months ago.
    MrFixit likes this.
  23. Greg DoClose

    Greg DoClose New Member


Share This Page