Just got my Clarity Plug-In a couple days ago and I have an efficiency question

Discussion in 'Clarity' started by brentac, Feb 14, 2018.

  1. dstrauss

    dstrauss Well-Known Member

    The key is 50-55; In the spirit of Crocodile Dundee "that's not highway speed, 75-80 is HIGHWAY SPEED" which is what we have all over West Texas and it sucks your battery dry in no time.
    Pushmi-Pullyu and Kendalf like this.
  2. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Yes, we do keep re-inventing the wheel over and over in this thread, don't we? ;)

    Not at all to minimize your contributions to the discussion, Dstrauss, but looking over the earlier posts in this thread, I think (just my entirely subjective opinion) the following comment best summarizes the advice, regarding maximizing EV miles, which should be given to new Clarity PHEV drivers:

    Kendalf and jdonalds like this.
  3. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Yeah, I really wish the EPA's range ratings for EVs were done as a chart, with figures for range at 35, 45, 55, 65, 75, and maybe even 85 MPH. That would really underscore just how much more energy-efficient it is to drive at a slower speed on the highway. That's not at all to say that I personally would poke along at 55 MPH on a long trip, but it's good to have an informed opinion on just how much energy one is using when driving.
  4. bobcubsfan

    bobcubsfan Active Member

    Gas mileage varies with speed too. If one has a commute of 45 miles, at 55 mph that would take 49 minutes. At 65 mph it would take 42 minutes. After that drive of 45 miles, that pretty much exceeds the range of the battery.
  5. I still feel that your goal should be to run out of energy at your charging destination, no matter how fast you're driving or what mode you're in. Even at the rate of energy usage at 85mph, the electric is still cheaper than the gas would be used in HV mode. Speed and use of the throttle/regenerative braking are the key to efficiency
  6. bobcubsfan

    bobcubsfan Active Member

    Environmentally correct. Use EV until the battery runs out.
  7. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    I've only seen one person here argue that the Clarity is actually more energy-efficient in gas-powered mode in highway driving. Based on all I know about EV engineering, energy efficiency, and thermodynamics, that appears to be a misconception.

    It's not very common to see a consensus form in an online discussion, but we do have a pretty strong one here. And that consensus is that ideally, all of your miles should be battery-powered rather than gasoline-powered, no matter how fast you're driving. We're just saying that if -- if -- you are going to run out of battery power somewhere on the trip, then it's better to switch to HV mode for at least part of your highway driving, to ensure all of your low-speed and/or stop-and-go driving is in EV mode.

    BTW, I don't think you can run the Clarity PHEV's battery pack down to zero even if you want to. PHEVs are designed to maintain a certain minimum level of charge in the battery pack. I believe in the Volt that's 30%. I dunno what it is in the Clarity PHEV, but I suspect it's something close to that.

    Now, if you're talking about the Clarity Electric (BEV), then yes you could run the pack down to a nominal 0% every day. But that would be very hard on battery life! Ideally, you should end the day with the pack at 20% or better, or at least 10%. That's not to say you shouldn't use all of the car's range when you need to; when you're on a longer trip than normal. But if you're doing that every day, then you should expect the car to permanently lose capacity (and range) faster than normal.
    KentuckyKen likes this.
  8. bobcubsfan

    bobcubsfan Active Member

    I posted this elsewhere, but here it is again.

    From the UK.
  9. jdonalds

    jdonalds Well-Known Member

    That is especially true of our situation and others who charge from roof solar. What we've done is, on a return trip home, to set the GPS to Go Home so it can show us how many miles are left. Then when the GPS indicated miles-to-home are equal to the EV range shown we switch back from HV to EV mode. That is our best bet for making the max use of EV and minimizing HV. Ideally we will run out of battery power as we pull into the garage where we plug into the Level 2 charger which is being supplied (at least partially) by solar.

    In any case I like to have about 6-8 bars of EV all the time. There are many indications on this forum that 2 bars of EV can potentially be the cause of Angry Bees, and possibly poor acceleration. This makes sense to me. It seems to me that HV normally alternates between electric only and ICE/Electric use (as shown on the gauges). The car decides it needs more power so it taps into the battery power finding insufficient energy there so it winds up the ICE to both assist in driving the wheels and charging the battery.
    KentuckyKen likes this.
  10. bobcubsfan

    bobcubsfan Active Member

    We have roof solar as well so cost is zero to charge car. Strategy for gps is brilliant.

    Sent from my iPhone using Inside EVs
    Johnhaydev likes this.
  11. descolado

    descolado Member

    I would like to add as a south Floridian with summer around the corner...my case for using HV Charge mode is to ensure my battery is topped off enough for the preconditioning to work whenever I want it.

    I do wish Honda had though this piece through more, as I’ve had a few low battery scenarios wher I wish I had mindfully charged the battery enough for this feature to be available. Seems for a lot of the great engineering on our vehicles this was an odd oversight. Minimum battery charge state should include all basic vehicle functionality imo.
  12. KentuckyKen

    KentuckyKen Well-Known Member

    That would be a great feature to add so that you could select a percentage of battery charge at which HV Charge would automatically come on and then hold at without having to do it manually. Then you would always know you’d have enough charge to precondition later. It would only take a software change to add it to the customizable features. Honda probably figured too many features would confuse the general public.
  13. M.M.

    M.M. Active Member

    I'm late to the discussion, but it looks like several people have asked what any reasonable use case for HV charge mode is without getting an answer. The answer is that, for practical purposes, it's for when your battery is empty and you know you'll be climbing a mountain on the highway.

    Logic: The ICE puts out 103 HP max, and the car weighs 4000 lbs. Going up a very long hill at high speeds (particularly if you're changing speeds frequently) is going to be seriously pushing the limits of that to not feel sluggish. By having several kWh of buffer in the battery pack, there will be sufficient extra energy to get you up those hills without the drivetrain feeling anemic, and the ICE will do its best to recharge when things level out for a bit.

    In the Volt an analogous mode is actually labeled "Mountain", and it tries to keep 50% SoC in the battery pack. The Clarity does exactly the same thing--charge to 12 segments, which is right around 50%. I haven't yet taken my Clarity over any big hills, but I drove over a couple mountain ranges in my Volt and indeed I'd see it lose a couple bars of electric charge while I was climbing a steep hill at highway speeds (which it then recharges with the ICE when the road flattens out).

    A Clarity does give you 2 bars of visible extra battery energy even at "zero", but if the hill is long enough and steep enough that might not be sufficient.

    Basically, it's there for performance reasons, not anything to do with efficiency.
    Kendalf likes this.
  14. Kendalf

    Kendalf Active Member

    Ah, that's a great use case for HV Charge. And it is another example of how these mode buttons are important and helpful because the car does not know what the upcoming road conditions will be, hence the need for driver input to set the car up for future situations.
  15. KentuckyKen

    KentuckyKen Well-Known Member

    M.M., I think the general consensus on the forum is that the 2 bars at 0 is the lower buffer that prevents battery degradation caused by repeated full discharge cycles common to all Li-ion batteries.
    As such, most think this portion of the battery capacity is not available for use.
    This theory is bolstered by many reporting high ICE reving (angry bees) when battery discharged to 2 bars/0 and high torque events such as hard acceleration or going up hills occur.
    Johnhaydev likes this.
  16. trevor68

    trevor68 New Member

    Newbie here. I willl be buying a Clarity without having the ability to plug in in my home because I live in a condo. I will be plugging in here and there in public charging stations, but not every day. I am sure that you will be wondering why not buy an accord hybrid instead. The answer is simple: federal and tax state credits.
    Now my questions for you guys, In my specific context, should I always put press the HV button when in driving so as to fill up the battery as much as possible?
  17. bobcubsfan

    bobcubsfan Active Member

    I only use HV mode if there are less than 10 miles left in EV.
  18. Tailwind

    Tailwind Active Member

    Absolutely not. HV charge mode is the least fuel efficient mode there is. Just be diligent about finding charging stations wherever possible.

    Maybe a bit of education is in order. HV mode happens automatically whenever the battery gets down to approximately 10% state of charge. Or you can select HV mode by pressing the HV button. This will not really charge the battery, merely maintain a state of charge within a narrow range. HV charge mode, on the other hand, will actively charge the battery up to something close to 60% state of charge. The actual number is something like 57%, I can't remember exactly. So you could just drive the car as if it were a hybrid and plug it in when possible. That just seems to me to defeat the purpose of a plug-in hybrid, though.

    In your situation, I would purchase an Insight. Better mileage rating and lower cost than a Clarity after taking the federal tax credit ($30k net cost vs. $28 for a nicely loaded Insight) But that's just me. Don't know what your state tax credit is, so that would make a difference, too.

    I've had my Clarity for one year come January 29th. So far I've used 26 gallons of gas in 9500 miles of driving. But I have a ClipperCreek 32 amp charger in my garage. Even at 55 mpg in an Insight, I would have used 170+ gallons of gas, so the Clarity has been great for me in reducing my use of dead dinosaurs for fuel.

    Good luck with your new car. I'm sure you'll enjoy it as much as the rest of us.
    M.M. likes this.
  19. M.M.

    M.M. Active Member

    To expand on this:

    HV Charge mode is useful for one thing and one thing only: You have an empty battery, are driving for a while and will not be charging, and know you're about to go up a mountain. That's it.

    Chevrolet much more helpfully called the same feature "Mountain Mode" in the Volt. You should use it when you have no charge but want some reserve that you will use driving up a long, steep hill that the gasoline engine alone may not be able to handle at highway speeds. Period.

    Regular HV mode (not HV Charge) just saves around whatever battery capacity you have, so can be used to manually switch from using gasoline to the battery.

    As far as how to drive your car in normal use (I'm assuming here you live in a city or at least not somewhere unusual like on top of a mountain) it's really not complicated: Leave it in EV mode and plug it in whenever you can. If there's charge, it will use it. If the battery is empty, it will switch to HV mode as necessary. That's it. Depending on how much you drive and how often you're near a charger, you might actually end up in EV mode most of the time, since you can put 40-50 miles of range in the car in 2 hours at a Level 2 charger, which are easy to find in some cities.

    If you really want to spend effort manually managing energy use, you could, optionally, manually switch to HV mode (not HV charge, just HV) when you have some energy in the battery, are driving at highway speeds, and know you will be running out of battery before you next plug in. The gasoline engine is somewhat more efficient at highway speeds (due to the mechanical transmission that kicks in around 50mph) than at slow speeds, while the all-electric drivetrain is more efficient at lower speeds

    But again, that's only if you have some charge in the battery and know you will be using more than that much before the next time you plug it in. If you have 30 miles of range and will only be driving 20 miles before you plug in for a couple hours at a Level 2 charger, just drive in EV mode. If you have 30 miles of range and will be driving 60 miles before charging, 30 of which are on the highway, before plugging in, you'd do better to put it in HV mode for the highway miles then switch to EV once you're going slower.
    Pushmi-Pullyu, MPower and insightman like this.
  20. David Towle

    David Towle Active Member

    Y'all are forgetting one important point: It all depends on local prices. At my current prices ($2.19 gas, $0.20 electric) its more expensive to run the car on the highway in EV than HV (short push). $3.00 of electricity gets me about as far on the highway as a gallon of gas (35 miles). Conversely around town $3 electricity gets me about as far as 1.5 gallons of gas (55 miles). Gotta do the calculations.

    This will go away as a factor if gas prices go back to a normal, higher level.

    Of course if you have an existing solar panel system on your home that negates all this.

Share This Page