Another theory for HV-charge vs HV

Discussion in 'Clarity' started by Walt R, Oct 26, 2019.

  1. Walt R

    Walt R Active Member

    There have been a couple of threads suggesting that HV-charge may behave better (for some set of preferences) than HV, and there have been many complaints related to how aggressively the ICE is revved in HV.

    Thinking about what it would truly mean to be a "range extender" rather than just a hybrid engine, I have a theory to offer regarding the ICE algorithm in HV-charge and how it could differ from HV.

    A true range extender would just generate electricity to charge the battery, and not care about the driving conditions. It would likely sit at some highly-efficient load and RPM combination which output somewhat more kW than a long-distance steady cruise is expected to use. In the normal SOC range it would not respond to SOC, and the EV drivetrain would operate the same as it does in EV, even when the kW demand is higher than the ICE output.

    Contrast this with the goal in HV, which is to maintain SOC. The ICE varies its output frequently to respond to varying driving demands so that SOC does not vary much. This leads to behavior such as high revs even when there is ample battery SOC to drive the vehicle up high grades in EV mode.

    So, is it possible that, intentionally or not, Honda's engineers have made it where HV-charge keeps a steadier RPM and thus a more pleasant driving experience for those who enjoy quiet, smooth, and powerful EV operation? I haven't taken enough long (and mountainous) trips lately to get direct experience. What are the thoughts of those that *have* driven varying terrain in HV-charge?
  2. KentuckyKen

    KentuckyKen Well-Known Member

    Great theory. However my Clarity has only been driven in HV (with plenty of SOC) on out of town trips and has never given me any problem what so ever, like angry bees, power issues, etc. Even on steep hills at 55 to 70 mph, it ran perfectly with only a very moderate rpm increase much like a gas-mobile downshifting our of overdrive or high gear.
    Full disclosure: I’ve only driven 800 miles in HV out of my 13,000+ total and only up 2 steep hill climbs.
  3. Sandroad

    Sandroad Well-Known Member Subscriber

    Seems logical to me. I only drive my Clarity in the flatland of southern Michigan and northern Indiana/Ohio so I have no hill or mountain driving experience. I’ll try HV charge mode sometime to see what it does.
  4. neal adkins

    neal adkins Active Member

    From what i have read, the ice sometimes serves to supply electricity directly to the electric traction motor. So my theory based on my experience, is that in hv charge, more electricity is sent directly to the traction motor that in turn reduces the draw on the battery and helps keep the soc more stable and thereby reducing the need for high revs( during a high/lengthy battery demand situation like a long steep climb.
  5. My theory would be the exact opposite.

    HV Charge would send electricity to the batteries in order to charge them up to the cut off point of 58% SOC. It may or may not allow any generated voltage to go directly to the motor. We just don’t know.

    HV mode would send all or some of the generated voltage directly to the motor. Depending on the position of the right foot it may send some to the motor and some to the batteries to build or maintain the SOC.
  6. neal adkins

    neal adkins Active Member

    Living up to your name landshark. Haha. But you could be right. Charge mode could only charge the batteries. As you said, we don't know for sure. But i do know what i read as stated above. But either way the end result is the same. More electricity in the system when its needed most is a good thing.
  7. The wife and I thought the car looked like a Landshark, especially in Solar Silver. I was pleased to find that the name was available.

    Some may be too young to remember the Landshark from SNL.
    insightman and David Towle like this.
  8. neal adkins

    neal adkins Active Member

    It seems to me, as i have learned Honda's approach to engineering is the kiss approach. Thats why i thought the electricity would just take the path of least resistance and go straight to the traction motor when there's a high demand. However I am probably one of the least quailified to 2nd guess anything about this cars engineering. Just going by what i have read. Maybe some of the more qualified can weigh in.
  9. HagerHedgie

    HagerHedgie Member

    In lower speed conditions on windy, hilly roads hv charge is nice because it keeps the RPM smoother. It seems to be of some benefit in cold conditions as well.
    I think it’s most beneficial purpose Is to maintain a state of charge near 50% when you are spending an extended amount of time away from a charger. That way the battery isn’t sitting in a near depleted state for weeks or months on end.

    Sent from my iPhone using Inside EVs
  10. Tek_Freek

    Tek_Freek Active Member

    Won't the diagram on the instrument panel tell you? It shows what the engine is sending power to doesn't it?
  11. neal adkins

    neal adkins Active Member

    The vehicle energy display does shows the energy flow from the ice and to/from the battery, and where the energy is going. So i will look closely next time i climb the mountain in hv charge and see if the ice energy flows directly to the wheels as the artical i read suggest.
  12. MrFixit

    MrFixit Well-Known Member

    I like this thought... I have found that HV mode does 'maintain' charge level (some have reported a steady loss of charge). But - it seems impossible to maintain charge during a long HV trip because of 2 things... First, whenever you stop and re-start, it establishes a new charge 'setpoint' which is invariably a little lower than what you had previously. Also, I think everyone (in spite of good intentions, and post-it notes) forgets to engage the darned thing every time!. On a 'long' trip with a lot of stops and starts, it becomes virtually impossible to maintain charge level.

    This seems like a good use of HV charge mode - to provide 'makeup' charge for losses due to human error (failure to re-engage) or setpoint losses due to re-engagements.
    HagerHedgie likes this.
  13. laptop

    laptop Member

    Hi, how did you find ‘driven miles’ for EV and ICE please?

    Sent from my iPhone using Inside EVs
  14. MrFixit

    MrFixit Well-Known Member

    For the ICE miles, multiply the number of gallons used by 45 and you will be very close. The rest of the odometer miles are EV.
  15. Lowell_Greenberg

    Lowell_Greenberg Active Member

    The Clarity seems to be a series/parallel hybrid, heavily weighted towards the series side giiven its relatively high capacity battery when compared to traditional hybrids. In keeping with this philosophy, its efficient Atkinson engine is comparably weaker relative to the car's weight than for example a Prius Prime. For example, I believe the Prime/regular Prius use the same engine.

    Apparently, the Clarity- left to it's own devices, will run the battery down to a minimum set point and then rely on its gas tank/engine for the remainder of the drive. Since the engine, while highly efficient, is weak in relation to the car's weight. It will apparently strain, for example, going up a steep hill with a fully depleted battery and operate at a constant/louder RPM. Further the ICE will not drive the wheels in this situation.

    Manual modes allow the driver, who knows the intended trip to proactively act to maintain a SOC- so the car can maintain all of its drive options and have smoother operation. Presumably, if the car was smart enough, the user could input the trip information and based on distance, temperature and elevation- optimize operation. But it can't.

    Another byproduct of its default mode is that it allows the battery to go down to two bars- where for battery longevity, it would be preferable to maintain a higher SOC between re-charging cycles. The engine would allow it to do this. One could argue that this is unnecessary given the useful life of the vehicle- but I have my doubts- particularly if you plan to hold on to the car for 10+ years.

    Sent from my SM-G975U using Tapatalk
    Last edited: Oct 27, 2019
  16. DaleL

    DaleL Active Member

    The Clarity PHEV is at its heart an electric vehicle. The engine will only directly couple to the drive train at full acceleration between 45 and 65 mph. All other propulsion is from the 181 hp traction motor. The battery can supply up to 121 hp and the engine generator can supply another 60 hp.

    When driven in the hybrid vehicle mode, the engine runs as efficiently as possible to generate electricity for both the battery and the traction motor. Periodically, the engine will turn off and the the battery will provide the power. The alternation between engine power and battery power maintains the battery at approximately the same charge level.

    HV Charge mode just keeps the engine running to power the traction motor and charge the battery.
  17. Not true, unless I’m misunderstanding what you’re saying. I can watch “gear mode” regularly cycle in and out at very modest throttle settings given the right parameters.
    MPower and insightman like this.
  18. MPower

    MPower Well-Known Member

    That is my experience. If you are cruising along at whatever speed in the 40s and above, gear mode engages. If you ask for more power, gear mode will disengage. At first I thought it would only engage on the flat, but paying more attention, I discovered that it engages even as I drive through the mountains, as long as the throttle is not asking for more power.
    insightman likes this.
  19. KentuckyKen

    KentuckyKen Well-Known Member

    I do it the old fashioned way with pen and paper since Honda did not implement this feature in software.
    I start all my out of town trips in HV directly from charging and at end of trip switch to EV and fill up to calculate mpg. This accounts for virtually all my ICE usage except for the infrequent and short System Checks. And since I don’t take many out of town trips, I’m at about 96% EV,4% HV, ams 0% HV Charge.
  20. David Towle

    David Towle Active Member

    Its a lot more sporadic than that at least on my car. It of course goes out of gear mode on downhills, and over the course of a trip it cycles between times when it goes to gear mode on slight uphills and flats (typically 75% of the time) and times when it doesn't (25%). And in the winter it comes in much less, I've gone through entire tanks of gas on highway trips where it never goes into gear mode at all.
    Dan Albrich likes this.

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