Engine runs at full charge in Econ for no reason?

Discussion in 'Clarity' started by jwb, Mar 13, 2019.

  1. jwb

    jwb New Member

    I've had my 2018 Touring for a month and it's got 1000 miles. Most days I only need the battery and I always leave the car in Econ and do not engage HV mode. On Saturday I took a 150-mile trip and the car behaved as expected. But since that trip, whenever I turn the car on in the morning the engine runs for about five minutes and then shuts off again. This is baffling since the first five minutes of my drive involve coasting down a mountain. Does anyone have an explanation for why this engine runs?
  2. kevosuki

    kevosuki New Member

    Something to do with absorbing the extra energy to prevent battery damage when going downhill on a full charge. As a compromise I wish Honda did what other EV manufacturers do and implement a hilltop reserve mode. Nothing you can do about it other than blasting the heater before your drive or charging to 90% instead of full.
  3. ClarityBill

    ClarityBill Active Member

    There are a couple 'strange' reasons the engine (ICE - Internal Combustion Engine) will operate in EV mode.

    Kevosuki mentioned the extra regen issue, when the battery is fully charged.

    Below 15F ambient temperature, the battery is limited and the ICE will run to power the vehicle. After things warm up, the battery is able to power the car. (Below -22F the battery cannot operate, and the car is not allowed to start.)

    Anytime the ICE starts, it will run until the ICE is properly warmed up. This will be 2-5 minutes, depending on the starting temperature.
  4. jwb

    jwb New Member

    There's not a feature where I can set it to charge to 95% is there?
  5. KentuckyKen

    KentuckyKen Well-Known Member

    This has been extensively covered in several threads. It is a well documented fact that the Clarity will run the ICE when the state of charge (SOC) is full in order to protect the battery from being over charged. This will occur sometimes after charging when found downhill or hitting the brakes hard. You will notice that after charging, the amount of regen is limited for a few miles or so. We still don’t know exactly why the system needs the engine to come on to do this, we just k ow it does.
    Several posts have shown running the Climate Control to burn up some charge will prevent this and keep the engine from coming on. I have found that on my slight hill just using the brake pedal instead of then paddles works for me.
    insightman likes this.
  6. Mark W

    Mark W Active Member

    Does anyone have a theory as to why this is necessary for Honda to program it this way? How do full BEV cars handle this since there is no engine to run? Do Chevy Volts do this?
  7. jwb

    jwb New Member

    I guess what was interesting to me about this is it did not happen even one time in the first 1000 miles, and now it happens every time.
  8. Mark W

    Mark W Active Member

    Hilltop Reserve Mode on the Chevy Bolt allows you to set the car to only charge the battery to 90%. The idea being that if you live at the top of a hill, regenerative braking can still be utilized on the downhill so that you don't have to use the friction brake as much going down the hill. I would much rather that the Clarity make you use the friction brake when the battery is full, rather than start the engine.

    This video explains it. You can skip to the 2:18 part to skip how it is set on the Bolt if you want. I wish the Clarity had this feature.
    jwb likes this.
  9. Dan Albrich

    Dan Albrich Active Member

    I also live on a hill, but it's not a big one. Thanks to KentuckyKen I've found for small enough hill, just use breaks and avoid paddles when battery is full.
    I also find turning on the defrost keeps me from over-filling the battery. i.e. I just tap "FRONT" before I go down my hill-- which here in Oregon, I need anyway.
  10. kevosuki

    kevosuki New Member

    Chevy volt does not do this. Engine will never run unless it's too cold (ERDTT).

    No there isn't. When I had my clarity I had to manually change my charge times everyday to float around 85% charge.
  11. The Gadgeteer

    The Gadgeteer Active Member

    This has been throughly discussed elsewhere but in short what I understand is the Clarity is using the excess energy to spin the engine with one of the motors.

    It might seem like it is “running” in the same way an ICE is “running” when the a fuel cutoff engages when coasting in gear/drive. It is normal behavior and once your battery is topped off it is saving your brake pads.

    If you do not like it there are things you can do to charge less and use up your brakes more.

    Now to the mystery part... why wasn’t this behavior in the first 1000 miles?
    Anything different?
    Is the temperature different?
    Driving habits different?
    Use of less climate control/heat?
    Charging level/times different?
    Different charger?
    Was the engine used at all before the trip? Not sure why this matters but I am working on a theory.
    Anything else different even if it seems unrelated?
  12. Robert_Alabama

    Robert_Alabama Active Member

    @Gadgeteer, as an unsolicited supply of info, I have fought (and won to my satisfaction) the issue of regen starting the ICE. For me the problem materialized once winter weather hit (I think the regen allowed by Honda when battery is near full charge is seriously restricted in colder weather). I hadn't been using the heat since I was leaving a relatively climate controlled area and my commute is short. It was very soon after a full charge and occurred when stopping from about 40 mph for a left turn in a short distance. I have been able to stop the behavior by starting the defroster set on high heat about one minute prior to the regen event and then turning it back off as soon as I made the left turn. I suspect once the temperature warms sufficiently, the regen won't start the engine again (no defroster will be required) until next winter.
  13. The Gadgeteer

    The Gadgeteer Active Member

    @Robert_Alabama you provide a very good data point. Your theory on the software restricting at cold temperature makes complete sense to me. I also like your solution since a minute of extra heat isn’t a bad thing in cold weather.

    I do wonder if we can figure out what @jwb situation is and what changed for him. I simply do not believe the trigger is him having taken a 150 trip in the past. There has to be something else.
  14. RickSE

    RickSE Active Member

    I had some very odd behavior happen and wondering if anyone can help me understand what happened. I left work today on EV with a full battery like I have done every day for the past six months. Car was set to Econ mode. About a half mile down the road I noticed that the ICE was on. I got in the highway and the ICE stayed on - which I figured was not a big deal because it probably had to warm up. After 10 miles the ICE was still on. The display showed EV, I still had Econ mode set, but the ICE was on and only white bars displayed on the speedometer. I switched to HV thinking that I could then switch out of HV and shut off the ICE. Instead - and still in HV - the car went to EV. This happens in HV on the highway when I’m not pulling much out of the ICE. Usually it’s on a flat road at 55, or on a slight downhill. So now I’m in HV mode, using only the battery and the ICE is off. Switched off HV mode since at this point I had plenty of battery left. The ICE went on! Switched to HV mode and the ICE went off. Car drove fine the whole way in that I had plenty of power but I don’t understand what happened. Perhaps today is Opposite Day? I’m in Boston and the temp was about 55 so it’s not like it was freezing or unusually warm.
  15. ICE was probably running a systems check (which it will do from time to time to keep everything in order).

    Sent from my iPhone using Inside EVs
  16. The Gadgeteer

    The Gadgeteer Active Member

    Yup, likely system check(s).
    Let’s gather some data points.
    How many miles do you have?
    What is your rough % of EV vs. ICE driving?
    How old is the gas in the tank?

    The HV part is new but not shocking. Has it been an extended time since switching into and out from HV?
  17. Monir

    Monir New Member

    I had that happen to me as well. I believe the ICE comes on for few reasons: system check, warming engine on cold days, moving oil around engine and probably programmed to get rid of gas that is sitting in tank too long. I dont think much of it because it happens rarely and it happens on long duration of gas fill ups. Clarity is sort of taking care of itself in some way.
  18. vin seeram

    vin seeram Member

    In his review of accord hybrid, Alex has an interesting point on the honda way of doing it. @16:45
    Last edited: Mar 22, 2019
    MPower and KentuckyKen like this.
  19. RickSE

    RickSE Active Member

    I’ve put about 20 gallons of gas in over 6k miles, so I’m running about 85% on EV. I was using HV a bit more over the past month because of the EV range loss in the cold of February. I think I run the ICE for 5 - 10 miles 2x per week.

    It probably was some type of automatic system check that had to run it’s course.

    What was odd to me was what happened when I switched to HV because that was “normal” behavior in that the car cycled between ICE and battery depending on what I was doing. Car ran normally this morning so I guess I’ll see the behavior happen again in 6 months.
  20. KentuckyKen

    KentuckyKen Well-Known Member

    I don’t think our Claritys have the Volt programming that won’t let the gas get more than 1 year old. My Clarity was happy let my tank stay full with no loss of gas gauge bars for over 8 months and 6,000 miles. I did have a very, very few ICE starts but none lasted more than a few minutes and the gas usage was negligible.

    While we can’t select an EV only mode, I am quite satisfied that it’s a “virtual EV” mode that lets me drive all EV local but keeps the ICE healthy and ready to engage without any significant gas usage.
    I’ve managed to go one year and 8,000 miles on only 13 gal of gas. (Yeah, I don’t take many out of town trips.) Love this car!!
    insightman likes this.

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