Using HV Charge

Discussion in 'Clarity' started by David Towle, Sep 3, 2019.

  1. David Towle

    David Towle Active Member

    I remember seeing several negative posts on this site re using HV Charge, but for a couple reasons decided to start using it myself: 1. Gas is much cheaper than electricity here at this time, and 2. I'll likely be selling my house in Spring and I don't want it to look like my solar panels are way undersized for the house. They're fine for the house alone but the PHEV is putting me well into the negative.

    Since the beginning of summer I have been getting between 49 and 50 mpg on every tank after subtracting off EV usage. I do like to use EV for local short trips and want to continue doing that. For a test I filled the tank while I had 10 miles of EV range left. I used HV Charge several times, both on highway and around town, so that when I refilled with gas I was at 10 miles EV again. And what gas mileage did I average for the 100% gas fueled travel? 49 mpg. It looks like HV Charge has excellent efficiency. So I think I am done charging this car until I sell my house.
  2. neal adkins

    neal adkins Active Member

    If electricity is cheap or one has free charging then its foolish to use hv charge. However i have found another good use for hv charge. On a long road trip, with ev range low, i use hv charge when clinbing a 15 mile upgrade. I also use sport mode. I found the ice didn't raise the rpms as high and maintained a speed of 65mph easily. I have tried this 3 times now and noticed better performance. Meaning the ice ran at a more normal rpm with no angry bees. The battery has a high demand when climbing and accelerating at the same time. Hv charge helps supply the needed power to the traction motor thus reducing the draw on the battery.
  3. Mowcowbell

    Mowcowbell Active Member

    Good to hear that HV charge is so efficient. I've only engaged it once just to see if it actually works, but find EV usage is my preference. I like pulling into my garage on a hot day without a hot ICE engine that will heat up the garage even more. Most of my trips are less than 10 miles in length, meaning the ICE would never fully warm up if used.

    Have you used the gas vs electricity spreadsheet to confirm if gas is really less expensive? Gas would have to be less than $1.38 per gallon to be cheaper than the electricity in my area (.11 per kWh)
  4. Fast Eddie B

    Fast Eddie B Well-Known Member

    Good points raised by all.

    I think having the HV CHARGE option is nice, but have only tried it once while parked to nudge my EV miles back above 10 where I try to keep it when I can’t charge.

    But I think physics tells us it has to be somewhat inefficient, given losses converting gas to electricity and then to propulsion, compared to just using gas more or less directly for propulsion, especially when “gear mode” can come into play. More efficient would have to be freezing EV miles remaining by going to HV mode manually at a predetermined point, rather than allowing it to drift below and then dragging it back up with HV CHARGE.

    But whatever works! There’s no one “right” way to drive a Clarity! And it’s nice to know that HV CHARGE mode is not glaringly inefficient.
    sniwallof likes this.
  5. ClarityBill

    ClarityBill Active Member

    Will it go into gear mode while in HV charge mode? I have not seen it.
  6. Fast Eddie B

    Fast Eddie B Well-Known Member

    Good question. I have no idea.
  7. David Towle

    David Towle Active Member

    I don't find the spreadsheet to be very accurate, it depends how you drive, but anyway my electricity price is .21 per kWh and my gas is $2.39 so even by that method it shows gas is cheaper.
    I forgot to mention: One anecdotal advantage of HV Charge is the more consistent load makes the cruise control work much better. In Sport I get a 4 mph speed variation on hills in HV or EV (5 in normal or econ), but in HV Charge its only 2 mph. This is the way a cruise control is supposed to work.
  8. David Towle

    David Towle Active Member

    It never has while I've used HV Charge. It might be able to if the terrain was flat.
  9. David Towle

    David Towle Active Member

    On hilly terrain the generator can't run when you are going downhill so it needs to gain more charge during the uphills. That precludes gear mode.
  10. Robert_Alabama

    Robert_Alabama Active Member

    If you use HV Charge when battery is more than 60% full, isn't that pretty much the same thing as using HV only? I wouldn't expect a drag in economy when using it like that. Does HV charge hold state of charge more than HV when engaged above 60% SOC? I haven't used HV Charge at all in the Clarity. In my Chevrolet Volt, when the battery is depleted, using Mountain mode to replenish the battery to about 40% causes a pretty good hit in economy, like 25% hit in mpg for the miles gained in the battery. I'd suspect the same kind of hit to mpg for HV charge if you use it just to replenish the battery. If you are just using it to hold the battery charge (turned on when over 60% state of charge), I doubt it would be much different to the economy of just using HV. Am I missing something?
  11. assorted

    assorted New Member

    No, it will not go into gear mode during HV Charge. Tried this a few weeks ago to find out.
  12. Clarity_Newbie

    Clarity_Newbie Active Member

    David Towle

    Below is a link to a post reference some rudimentary data collection whilst in HV charge mode. Thought it might add to the discussion.

    Bottom line is an increase in RPM's relative to "normal HV non-charge mode" which is to be expected. No noticeable noise increase per @neal adkins

    As a side note...I did read somewhere that HV charge mode is most efficient at speed...stop n go traffic least efficient.

    Hope this helps!
  13. neal adkins

    neal adkins Active Member

    If above 58 percent soc hv charge is not available. I get a message in the display stating to plugin to complete charge if abouve 58percent
    Robert_Alabama likes this.
  14. Robert_Alabama

    Robert_Alabama Active Member

    That makes sense. Thanks.
  15. David Towle

    David Towle Active Member

    HV Charge doesn't work over 60%. As I said on the Clarity there seems to be no hit on economy for using HV Charge to replenish the battery.
  16. fotomoto

    fotomoto Active Member

    What is your local mileage strictly using HV mode (or "auto" with 2 bars EV)? It should be higher than HV+.
  17. David Towle

    David Towle Active Member

    No as my data showed overall it was the same (combination of local and highway though). I would agree the HV Charge probably works best at steady speed rather than local mileage, probably low steady speed like 40-50 mph.
  18. 2002

    2002 Well-Known Member

    I agree that in theory using charge mode followed by EV to use the built up charge should be less efficient than just using regular HV. But we have heard anecdotally on this thread and other threads that it is apparently not that much less efficient. The tests we hear about are always very limited, in many cases just based on one test run, and sometimes the tests claim that HV charge is equal to, or as claimed in a couple of other threads even more efficient than regular HV. Of course it's easy to dismiss limited test results, but I think they are useful in providing at least preliminary data, even factoring in the uncertainty of the limited tests they do point to charge mode as being at least in the same ballpark as regular HV and not wildly inefficient as we have sometimes assumed.

    This is different than what I have read about Prius Prime where people do report charge mode as being noticeably less efficient. But Prius Prime has a more elaborate "real" CVT system and some clever gearing which allows the gas engine to directly power the wheels at pretty much any speed. So with Prius Prime using the gas engine to generate electricity is almost always going to be less efficient than directly powering the wheels.

    Clarity on the other hand went with a much simpler and presumably lighter weight transmission where the gas engine only has one gear available to directly drive the wheels, and so it is only used at certain speeds and power demands. Most of the time the Clarity gas engine is powering the wheels through the electric generator. Not as efficient as direct drive but I am guessing that they decided that the tradeoff is worth the cost and weight savings of having a full transmission. Especially since for in town driving people will be using a lot of plug-in EV, and on highway trips the steady speeds will make gear mode available much of the time.

    So what we are left with for the most part is just losses from storing and retrieving electricity using the battery, compared to using the electricity immediately to drive the wheels. Presumably above 58% charging becomes less efficient which is why HV mode is restricted to SOC below that range. But in the range where it is allowed the losses are presumably minor.

    More elaborate and accurate tests would factor in gear mode, i.e. test runs at speeds that in HV use gear mode a lot, then do the identical test run using a combination of HV charge and EV.

    But I think based on the limited data that we have so far, charge mode is probably only slightly less efficient than regular HV, however not enough to worry about if wanting to use it for aesthetic reasons, like reducing engine noise on a hill climb, or wanting to have EV range available at your destination, especially when you forget to place a sticky note on the dash reminding you to turn on HV when you leave the rest stop.
  19. Robert_Alabama

    Robert_Alabama Active Member

    I think where HV charge may show a hit to economics would be the following example:
    1) Run in EV mode until ICE starts (2 bars on battery for most of us)
    2) Fill the tank with gas and record odometer reading
    3) Leave gas station and put car in HV Charge mode
    4) Drive until battery is back to about 50% charge
    5) Put car back in EV mode and drive until ICE starts (2 bars on battery)
    6) Refill tank, record gallons gas burned and calculate miles driven from previous fillup - Calculate mileage as Miles driven/Gasoline burned
  20. David Towle

    David Towle Active Member

    That's probably a good idea since you won't have lots of regular HV miles to obfuscate the HV Charge performance like I may have had. I will post more combined data as I get it.

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