HV Charge Mode - observations/questionsfrom one day Road Trip!

Discussion in 'Clarity' started by jpkik96, Jul 21, 2018.

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  1. jpkik96

    jpkik96 Member

    All - I drove my Clarity Touring approx 450 miles today and used HV Charge Mode 2x on the highway during the return when the EV range fell below 10 miles. Note - It was pouring rain on the return as well! Overall the Clarity was great for a road trip and with the exception of lackluster windshield wipers that others have noted the Clarity handled the rain really well! I have a few observations as well as practical questions to more experienced owners on its usage

    1. Fuel economy understandably suffers when using HV Charge Mode. Traveling 65-70mph, my instantaneous mileage (as measured by Clarity's onboard computer) dropped from approx 40mpg when using HV Charge mode only to under 30mpg when using HV Charge mode.

    2.) It takes 2-3 minutes once HV Charge Mode is engaged to actually start charging the battery.

    3.) It took approx 50 miles running the Clarity in HV Charge Mode to increase the EV range battery from approx 10 miles to 26 (where it automatically stops charging at the 58% HV Charge mode max.

    1.) Could bad weather like I experienced on my return today impact the overall efficiency of using HV Charge Mode? I don't see why it would but thought I should ask

    2.) Assuming one does not have to worry about substantial climbing substantial mountains during a long trip, can you just try to keep the Clarity with 5-10 EV miles in reserve and just run it in HV mode? Given the fuel economy penalty, I am questioning if I should continue using it....

    As always, thank you for your review, reply, and feedback!
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  3. Viking79

    Viking79 Well-Known Member

    1. Water on road increases resistance. Heater use may or may not, the engine doesn't generate much heat when getting 40 mpg at 80 mph, it might run in a less efficient mode when heater is on (hypothesis, not tested). Extra electric range added won't be counted in instantaneous mpg display, that will be counted in average once you use the electric range later.
    2. Don't bother with HV charge unless in mountains. The car has plenty of power to drive in HV mode even with depleted battery. If you want to reserve your range for destination just use HV mode early on and remember to engage again after stops.

    I had no trouble running HV with a depleted battery at 75-80 mph or more, even in mountains on a 1800 mile or so round trip I got 40 mpg. I don't know that reserving battery did anything to prevent high RPM engine running, the car just does that, especially at high elevations in the mountains. It is just something to get used to.
    Last edited: Jul 22, 2018
  4. jpkik96

    jpkik96 Member

    Viking79 -

    Thanks for your review and feedback! Interesting comment about water, resistance, and using HV Charge mode. Definitely spent the majority of yesterday's trip in driving rain! Given the fuel economy penalty, I came to the same conclusion last night about limiting my use of HV Charge mode going forward but wanted validation so thank you! The Clarity was very comfortable to drive on a long trip and even engaging HV Charge Mode and I did not notice/experience the high RPM engine running (aka "Angry Bees") others have mentioned. Thanks again!
  5. Young J Kwak

    Young J Kwak Member

    Used HV Charge mode on a 60mi drive when EV range fell below 15mi.
    I didnt think to look at the instantaneous MPG change, but will the next time I do.

    Approx how much MPG loss are people noticing between HV vs HV Charge?

    Also, I also heard the high RPM engine noise several times on the 60mi drive - mostly when I was traveling >70mph.

    Thank you for sharing the info you have preliminarly gathered.
  6. DaleL

    DaleL Active Member

    The only reason that I can see for using the HV Charge mode is to have a 20 mile or so emergency range reserve on a long trip. This is because the gas tank is so small. Otherwise, on a long trip, one that requires stops at a gas station, just use the HV mode most of the time.

    As Viking79 posted, water on the road increases the rolling resistance to the tires. The water is pushed out of the way as the tire rolls forward. It takes energy to do this and thus reduces the fuel economy.

    On short trips, the most efficient method is to just use up all of the battery range first. The Clarity will then transition to the HV mode on its own.
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  8. Atkinson

    Atkinson Active Member

    I tried HV recharge last night for the first time in the middle of a 100 mile trip.
    When on HV mode, engine is locked to axle at about 2300 RPM (for my highway speed at the time).
    Switching to HV Recharge, engine clutch disengaged and raised to 3000 RPM.
    I switched back to HV mode shortly afterward since it was just a test.
    My preference would be to use shore power to recharge instead of beating up the drive-train.
  9. insightman

    insightman Well-Known Member Subscriber

    What is "shore power?" I'm unclear how using the engine to turn the starter motor/generator to recharge the battery is beating up the drive-train. The normal function of the engine is to turn the starter motor/generator to generate electricity.
    David Towle and DaleL like this.
  10. bobcubsfan

    bobcubsfan Active Member

    Page 19 in manual:
    When the vehicle is in HV Charge, priority is given to the charging of the High Voltage battery. While the battery is being charged, the engine may run at a higher RPM than usual. The time it takes for the battery to be charged to 12 segments varies depending on driving conditions.

    So which is higher RPM? HV or HV Charge? For me, HV Charge appears to use gas to charge the battery. Maybe that is true with HV. The few times I have used HV the car switches between HV and EV.
  11. Atkinson

    Atkinson Active Member

    HV on the highway (45MPH or higher) engine is (generally) clutched to the final drive axle.
    HV Recharge is more like the scenario under 45, where the engine spins at whatever speed it takes to run hybrid style to drive and charge.
    Engine seems to stay around 2000 RPM for HV (slight moan detectable) , but I have very little experience with it since EV is perfect for under 45 MPH short trips and HV works quiet and is well adapted for longer highway trips.
    3000 RPM is no problem for the car (HV Recharge Mode), but it sounds a little thrashy to me, plus I am still in love with serenity and silence of EV drive.
    I didn't mean it hurts the car, but it's hard to justify using the engine/generator for recharging when I can just connect a charger while parked.
    Shore power: As I understand it, when yachts pull into a dock, they stop using their generator/battery power and connect a cable to shore power.
    Full disclosure: not only will I never own a yacht, I will likely never see the inside of one (unless they need wait-staff!)
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  13. insightman

    insightman Well-Known Member Subscriber

    Thank you. I was wracking my brain, trying to figure out if "shore" was meant to be another word, but misspelled. Shore power is only available when docked--HV Charge mode works on-the-go. I believe the consensus on HV Charge mode is that it's there to prevent having to climb a significant grade with a depleted battery.
  14. Atkinson

    Atkinson Active Member

    Or get one hell of a running start before the grade.......
  15. insightman

    insightman Well-Known Member Subscriber

    Unfortunately, the Clarity cuts off all electric power assist at 100 mph (as has been a Honda hybrid tradition beginning with my 2000 Insight).
  16. The Gadgeteer

    The Gadgeteer Active Member

    I am resurrecting this thread just to ask a simple question because I have never run HV Charge mode for long enough to observe this myself....
    Once HV Charge mode brings the battery to 58% what does it do? Does it revert to Normal mode or HV mode or some other mode? My guess would be HV mode.
  17. jdonalds

    jdonalds Well-Known Member

    You are correct. HV mode.
    The Gadgeteer likes this.
  18. I was first exposed to the term "shore power" after we bought our travel trailer, where its used to mean AC power from a receptacle, as opposed to "boondocking", where you're powered by batteries or solar or a generator. I always assumed it had nautical origins.
    Last edited: Sep 15, 2020
  19. jdonalds

    jdonalds Well-Known Member

    I just prefer to drive around on city streets in EV mode. On long trips where I'm driving in HV on the highway I'll switch to EV when I exit onto city streets. Then if the charge drops more than I'm comfortable with I'll run HV Charge to bring it back up.

    My experience with HV Charge is exactly like the OP where mpg drops from about 40 to 30. It certainly isn't efficient to use HV Charge but I'm glad it is there and I do use it on trips.
  20. MrFixit

    MrFixit Well-Known Member

    I don't have direct experience with HV charge, but I think you are deceiving yourself with this argument...

    While you are getting 'reduced mileage' from being in HV Charge, you are storing energy in the battery so it is not really lost.
    To demonstrate this, use the OP's numbers. If he drove 50 miles at 30 mpg (in HV charge) he consumed 1.67 gallons. But, as also reported by the OP, he gained 16 miles of EV range during this 50 mile stretch (EV range went from 10 to 26). These miles are now in the bank and don't cost him any more gas to use them.

    This means that he actually got 66 miles for his 1.67 gallon expenditure instead of only 50. So, in reality he really got 39.5 mpg (66 miles / 1.67 gallons).
    Not an efficiency hit at all !!
    David Towle likes this.
  21. Phil_Meyers

    Phil_Meyers Active Member

    I was going to say the same thing. When in charge mode, yes your mileage will drop like a rock, because your also storing that energy. A rough estimate is about 20mpg when in charge mode, because your also putting about 20 miles into the battery per hour...rough estimate but i don't think it's far off.
  22. MrFixit

    MrFixit Well-Known Member

    I don't believe there is anywhere near a 20 mpg 'hit' in HV Charge.
    The OP and a subsequent comment indicate more like a 10 mpg 'hit', which seems plausible to me.
    But regardless, as discussed, it largely comes out in the wash due to the stored energy.

    Bottom line - Don't hesitate to use HV Charge. Any efficiency hits are minimal. This is particularly true with 'low' gas prices.
    David Towle likes this.
  23. Phil_Meyers

    Phil_Meyers Active Member

    The car gets about 40mpg give or take a little. To get 40 miles of battery would take more than a gallon, considering all losses.

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