Long trip driving recommendation

Discussion in 'Clarity' started by Atul Thakkar, Apr 11, 2018.

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  1. Atul Thakkar

    Atul Thakkar Active Member

    Let's say I am planning to drive 700km mostly on freeway( 424 miles ) , stay over night at motel for 2 days and then return trip back , another 700km. total driving 1400km ( 850 miles)
    Hoping that will not find charging station at motel most likely and have to fill up gas for at least two times.

    In above scenario, what is the best mode to be selected for efficient green driving ?

    I am thinking: drive first 20 to 30 km in Econ Mode and rest in HV mode..
    This will preserve the battery for longer term for HV mode.
    Does it makes sense ?
    Any suggestions are welcome , thanks.
    AndyBA likes this.
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  3. K8QM

    K8QM Active Member

    That's pretty much what I've found. Basically EV in towns or stop and go driving and HV on the highway.

  4. jdonalds

    jdonalds Well-Known Member

    Just remember to select HV every time you power up the car. It's cancelled at every power down. If you don't the battery will be drained.
    dstrauss likes this.
  5. PHEV Newbie

    PHEV Newbie Well-Known Member

    That's pretty much what I'd do except I'd go to HV as soon as you get on the highway. The last trip we took, I went to HV mode with about 90% charge. Over the next 200 miles, it dropped to about 70% before it just held the charge indefinitely. Along the way, it just used the battery whenever needed to supplement the ICE or when it was most efficient. I never depleted the battery and I got about 48 mpg over a 1200 mile trip. The system has less to work with if you deplete the battery, which likely reduces the efficiency and causes the ICE to rev like crazy when it needs extra help and there isn't much (like on long upgrades).
    WindsorBoy, dstrauss and Kendalf like this.
  6. Viking79

    Viking79 Well-Known Member

    If you climb any mountain passes be sure you have battery charge as well. Starting HV mode at about half the EV range and you will be fine. Should you forget you can always use HV Charge mode an hour or so before your mountain to charge it back up (not sure how long it takes).

    The ICE has about 100 hp, so think of a 4000 lb car with load and only 100 hp and how it would do on the highway. It will be fine with speeds up to 100 mph even with a slight headwind and minor inclines. Long steep inclines will show any problems. Long enough where they drain battery reserves and steep enough where they exceed the engines ability to make power.

    For HP calculations like this I look at the ecomodder tool, here are the parameters I used, had to guess at Cd and engine efficiency so I was pessimistic:
    Last edited: Apr 11, 2018
    daar likes this.
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  8. KentuckyKen

    KentuckyKen Well-Known Member

    Yes, and ditto for all the other posts.
    If no large hills, you can EV to approximately 50% and then switch to HV. HV will switch through all the modes as necessary to give you the best power and mpg. It will maintain your charge at what some have reported to be 58%, so its OK to use some battery early in trip, as long as you have no steep hills and you don’t get close to depleting the battery. If you do, you will get high revs and less efficiency as the algorithm will not be able to incorporate battery usage as freely as it could otherwise. By not depleting the battery all the way ( to 0 EV range and 2 bars on gauge) on the hwy, I have never gotten the “angry bees” high revs; just kind of an occasional fast idle kind of revs.
    If you anticipate not being able to charge at destination and driving more than your EV range in city driving there, then I would start out in HV to have full EV for the city driving. HV mode seems less noisy and more efficient on the hwy.
    daar likes this.
  9. Atul Thakkar

    Atul Thakkar Active Member

    Thanks all for your help and time.
  10. K8QM

    K8QM Active Member

    Here's true confession time - I occasional need to do a 140 mile round trip to visit an elderly relative. Since there are usually lots of car errands to run during my visit I've found that if I leave an hour early I can park at a local civic center that has free level 2 charging, walk about a half mile to a breakfast place, stroll back and kill more time walking around until it's time to go visiting. Typically the 45 minutes to an hour of charge time gets me close enough to a full charge that I've been able use EV during all the errands and still have enough to run efficiently in HV on the return trip.

    A friend has taking to calling me a charging *insert word generally used for a person of ill repute*!

  11. Tailwind

    Tailwind Active Member

    Can someone please do the math and explain to me why using HV mode on the highway (rated at 40 mpg) is better than using the battery down to 0 EV range and then letting the car automatically switch to HV? Then being in HV mode when driving around at the destination when HV mode is rated at 44 mpg. Where is the benefit to saving battery power to operate in EV mode in stop and go driving? Stop and go driving is where a hybrid thrives!

    It seems to me that what is being advocated above is the exact opposite of what would be most efficient.
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  13. jdonalds

    jdonalds Well-Known Member

    HV mpg won't be as good as 44 mpg in city driving. Also there is a general belief that HV mpg will be worse on the highway if the battery is drained.
  14. Tailwind

    Tailwind Active Member

    Why would HV mode mpg not be as good as 44? And why would HV mode mpg be worse when the battery is drained? What information makes you (or someone else) say that?
  15. KentuckyKen

    KentuckyKen Well-Known Member

    HV mode when motive battery is fully drained is not the same experience as HV mode with some charge remaining.
    The computer algorithm is limited in what modes it can choose and when and how often it can cycle through them when there is no battery charge to occasionally draw on. You will also have the chance of higher engine reving/noise especially on hills or under strong acceleration. Try it both ways and you’ll see what we’re talking about.
    You are correct in that using as much EV/battery as possible is more efficient than the using the ICE. Most have found that switching to HV before the battery is completely discharged is more efficient and less noisy. You have to choose how close to zero you go based on conditions. It also has the benefit of saving the battery for in town driving at your destination where EV is better than HV.
    I doubt you can get the best mpg on the hwy in HV mode with the battery completely depleted for the reasons mentioned above. You can bet that The EPA HV mpg was not arrived at using a Clarity with a completely drained battery.
  16. jdonalds

    jdonalds Well-Known Member

    The engine is best used on long stretches of road where the car is being driven at a constant high speed like 70mph when the engine can physically connect to the wheels with the clutch. The Atkinson Cycle engine is most efficient in this scenario. Atkinson Cycle engines have lower torque so are less efficient at accelerating. They shine when being used at a constant RPM.
  17. daar

    daar New Member

    I have done one long trip of 180 miles/290 Km in the one month which I have owned my Clarity. My strategies were inline with most of the comments above. Here are a couple other pointers from my one long drive:
    . Use Sport mode for highway merging. You can switch ON/OFF sport mode while driving the car; and it changes effortlessly in EV or HV mode.
    . I would recommend to not go past the acceleration pedal's detent point; as I understand that you will need to pull over to stop the ICE from running.
    . I used LKAS and ACC for long highway stretches. Both these system worked fairly well on a clear sunny day.
  18. jdonalds

    jdonalds Well-Known Member

    I'm wondering if Sport mode might make the ACC behave better. I find that when the ACC slows my car behind a truck and I pull out to pass the car accelerates at a snails pace. Perhaps I'll try Sport the next time I am on a trip out of town to see if that helps.
  19. ManKo

    ManKo Member

    The EPA’s hybrid gas mileage is indeed obtained with the EV range fully depleted. Many have reported getting closer to 50mpg on the highway when using the vehicle in HV mode before depleting the battery (perhaps because the engine doesn’t have to rev so much when there is adequate battery remaining). When the EV range is fully depleted there is still approximately 12% charge remaining, which is similar to the capacity of a standard hybrid battery pack - so I’m not sure why the motor has to rev so much when accelerating normally from a stop sign/light.
  20. KentuckyKen

    KentuckyKen Well-Known Member

    When EV range is fully depleted (EV range at 0, 2 bars remaining on gauge), there is indeed some charge remaining but it is inaccessible/unusable. This is to prevent the battery from being completely discharged which would lead to early battery failure. The motive Lithium ion battery is approximately 17 kW and we get to use about 14 kW or so of that total capacity. This is why HV mode goes to 0 and kicks in with 2 bars remaining on gauge. The motor revs high with a fully depleted (2 bars remaining) battery because it has no e-power cushion to draw on and can’t cycle through its most efficient modes of motive power. It’s trying to put some charge in the battery so it can do so.

    I can’t remember where I read it, but I thought HV mpg was measured by allowing all modes to be cycled through but no net battery power allowed. So charging/discharging the battery was allowed which is how HV mode works most efficiently. Could be mistaken on that because I can’t find it on the EPA site and can’t remember where I read it. Note that Honda measures the mpg and reports it to the EPA who only confirms the results 15-20% of the time. So you can bet that Honda does everything allowable to get the best numbers possible.

    I have taken only a limited number of hwy trips, but I have noticed better mpg in HV mode with battery not fully depleted (more than 2 bars remaining). And I don’t get the “angry bees” high reving.
  21. Atul Thakkar

    Atul Thakkar Active Member

    Tailwind , I see following reasons.
    1) In hilly area , combination of Battery and Engine will be better for overall experience , life of car and engine.
    2) This is 2nd reason is most important reason. Let's assume that there is some battery juice left , which I can deplete it in return trip very near to my home. I do not need to rush to deplete the battery at very early stage of trip.
    3) If Battery is depleted , will it still run on Hybrid based on remaining two bar ? My answer is most likely no , so good idea to leave juice in battery. All other Normal Hybrids have around 3.2KW battery, so we need atleast that much Juice.
    4) In worst case HV-, 2nd click option will allow me to charge battery when deemed necessary
  22. Tailwind

    Tailwind Active Member

    I take issue with the assertion by several posters that HV mode is somehow "stunted" when having no EV range left, i.e., only two bars of battery charge. Is it your (those of you putting this theory forward) assertion that a true hybrid Clarity (if such a vehicle existed) would get better mileage than a plug-in hybrid does when the high voltage battery is depleted to the point of no EV mileage?

    I assert (with no more facts to back it up than have been presented by people holding the opposite view) that the two remaining bars of battery charge when the vehicle switches to HV mode makes our car just like any other hybrid. There is battery capacity available to aid the ICE when necessary, as well as unused battery capacity to store energy when there is excess energy, like going down a steep enough hill or when regen braking.

    I say that when the battery is depleted, the car acts just the same as a true hybrid. Mostly driven by the ICE, sometimes aided by the battery and sometimes only by the battery. This has been the behavior of my car that I have observed when the EV mileage has reached 0.
  23. KentuckyKen

    KentuckyKen Well-Known Member

    Tailwind, I’m not saying the Clarity is “stunted” in power or drivability when motive battery is depleted down to 0 EV range/2 bars and it automatically enters HV. Just that in that scenario, in my particular Clarity, the ICE runs more frequently and at higher rpms than if I select HV mode with a little usable capacity (more than 2 bars) remaining.
    So the only fact I have to offer is my experience with just one car which admittedly is not a very representative sample size. It could very well be that at 0 EV/2 bars the computer algorithm will allow flow from battery without any ICE charging. I infer from the way my car acts that this is not the case due to behavior noted above and the fact that my mpg is different. But until Honda divulges all its secrets, who really knows? Please add your facts to the puzzle we’re trying to solve.
    I guess we need more people to try it both ways on identical longer trips to know for sure.
    And as always YMMV (literally and figuratively ).

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