Hypermilers in Clarity?

FWIW, here’s my strategy.
I start my out of town (longer than EV range) trips with a full charge and hit HV when I get on the highway or Interstate. Then it’s HV with no angry bees (under 1,000ft) until I get with in EV range of my destination and I exit HV “mode”. This works if I’m charging at destination which has always been the case for me. If I couldn’t charge at destination, I would leave it in HV the whole trip and exit HV “mode” when I got to within EV range of home on the return leg.
This scheme is my way of maximizing the efficiency of EV by using as much of the full charge per trip as I can without provoking the angry bees.

From combining everybody’s posts I think if there are no steep hills or high altitudes, that I could let the charge deplete to 2 bars or 0 usable charge and let the algorithm automatically shift to HV without losing driveability or quietness. But I haven’t gotten up the nerve to try it yet and with my current strategy, I don’t have to worry about the terrain to get max efficiency and low noise.
And it would only take one HV button push at start and one at destination or home if the Clarity would just remember the last mode it was in!

 

Awesome, thanks for the information!

 

The CVTs used in the gen 1 Insights included an acceleration clutch. It is completely different from the Engine Drive clutch used in the i-MMD system.

 

The hybrid system in the Clarity is basically the same as the new Insight and Accord hybrids. This is what Motor Trend wrote about the similarly sized Accord Hybrid:

"All trim levels of the Accord Hybrid can achieve 47/47 mpg city/highway. At least that's according to the EPA. Our own test numbers reveal much better fuel economy: 53.3/49 mpg. For the math-inclined, that's a 13 percent improvement in the city and a 4 percent improvement on the highway, compared to the EPA numbers."
https://www.motortrend.com/cars/honda/accord-hybrid/2018/2018-honda-accord-hybrid-first-test-review/

That might explain why so many of us have gotten HV mileage far higher than the EPA estimates for the Clarity. I still believe that with the bigger battery carrying a significant charge (but not full, which would not be ideal), the Clarity is able to achieve hybrid mode mileage on par with the Accord Hybrid despite its greater weight.

 

I matched that 49 mpg hwy on a 500 mile round trip from Lexington KY to Elizabethton TN. Speed limits 60-75. Started with a nearly full battery and HV kept the SOC with no angry bees.
(Local mixed driving (55 mph max) is giving me 135 to 145 MPGe.)

 

I'm finding it difficult to compute miles per gallon. Of course there is the at-the-pump method, taking the total miles traveled divided by the gallons added to the tank. But even that is unsatisfying. Or there is the car's MPG readout which is a total puzzle how it comes up with a number. Honda, of course, doesn't tell us anything.

In a pure hybrid, like the Prius, all of the propulsion comes from gas in the tank. The small battery does supply power to the electric motor for short periods, then the ICE drives the wheels directly the majority of the time. Recharging the battery comes from running the ICE or through regen. But in the Clarity the only time the ICE is directly connected to the wheels is when the clutch engages at higher speeds and even that isn't a steady connection because it turns on and off frequently, mostly off in my observation. Also if I watch for the little circle that tells when the clutch is engaged I see that the electric motor is still driving the wheels along side the ICE/Clutched. Or the car will actually switch back to EV mode and use regen to charge the battery if there is a downhill section of the highway. Where is the pure MPG data here?

So the majority of the time the car is either being driven by the electric motor using power from the battery, or from the electric motor being driven by the ICE and the battery. The ICE isn't connected to the wheels like a Prius. Sometimes the ICE is powering the electric motor and putting juice back into the battery. Sometimes both the ICE and battery are supplying power to the electric motor. So what I see is converting gas used for miles traveled is greatly complicated by the fact that a second source of power, namely plugging the car in to charge the battery, are in play.

It seems to me that a more sensible measurement would be KWH per gallon rather than miles per gallon. Still I have little interest in that measurement either. This is because the main function of the ICE is to run the generator (I suppose its an alternator really), not drive the wheels. Since the ICE is rarely directly connected to the wheels an MPG measurement has little meaning to me. From what I can see there is no time, or very little time, that the ICE is directly driving the wheels by itself. How can we imagine any of the numbers we have translate into miles per gallon?

As noted many times on this forum the rpm of the ICE has little or no relationship to the speed of the car. We might be driving slowly but the ICE is rev'ing high. Perhaps this averages out in the mpg calculations though.

For most here on this forum driving around day-after-day in EV mode is the norm. We're using no gas. And for a few of us we're charging from solar systems for free. This kind of use doesn't supply any mpg data at all. If I were to switch to HV mode around town and hypermile it would be like pushing on a wet noodle; a waste to time and energy. We do have the car automatically reset the B counter each time we charge the car, and use that counter to observe miles driven in EV mode. But we've pretty much ignored MPG. We do compute miles per gallon on long trips and usually get about 42-44 driving mostly in the 70-75 mph range. Since there is almost nothing we can do to improve that, short of slowing down, we just take it at face value.

 

I agree with you that it's a challenge. The best I could do is the pump method for straight HV mode. I keep the car in HV mode from pump to pump. If the battery is below 80%, I might lose a mile or three of EV range between fill ups and I just subtract that off the top and then divide miles driven by gallons used. I think that's the most accurate way (assuming the gas pump is accurate) to determine HV mileage.

 

I assume your daily drives are more than the EV range then? Or is your electricity too expensive?

 

I think the most accurate and honest way to calculate mpg in HV mode would be not to use any NET battery charge which would be “cheating” if you did. So I start my long trips in HV with a full charge and tank. HV mostly maintains the SOC. Then it’s just miles from Trip A odometer driven div. by gal at the pump used. I then end my round trip filling up with the same pump at the same rate of fill to account for variances in when different pumps shut off.
Then at home I charge and it’s usually just a kW or so to top off the charge. So to be absolutely accurate, you have to account for the small amount of net charge used/lost from the battery in HV mode.

Here’s how I try to account for this and I’m asking the Clarity Brain Trust to see if this is legit and if there is a better way to figure this.
The Mulroney sticker says the EPA/DOT uses 31 kW per 100 miles. (I do better than this at 24 to 25 kW/mile, but my statistics are only in mixed driving under 55 mph so I’ll use their #s.) So I divide the net kW used or lost in HV by 0.31 miles/kW to get how many miles I gained by using that amount of charge. Then I subtract that from my total miles which reduces the mpg slightly.

For example:
500 m trip, 10 gal = 50 mpg but also used 2.5 kW. So 2.5 kW div by 0.31 miles/kW = 8 miles gained by battery. Then 500 - 8 = 492 miles and div by 10 gal = 49 mpg.

OK, now my head hurts from all this math. Could y’all tell me if that’s the best way to get an accurate mpg in HV?

 

I took my round trip about 800 mile trip, mostly on gas and I averaged 45-47 mpg using the method of keeping a good amount of battery during the trip. Thanks for the advice!

 

No, I'm actually in all EV for my daily drives. I measure HV mileage during road trips. I know the mileage is terrific but I'm curious to find out what it actually is outside the battery. I find that speed makes a big difference. You'll experience remarkable HV mileage if you drive on roadways that are slower (50 - 55 mph).

 

Great thread. I have a few additional questions to add to the fray.

On trips that will use all the available battery, I operate much like Kentucky Ken. Essentially, I use EV mode at slower speeds and HV mode on the freeway or at faster speeds. If I enter the freeway with a full battery, I let it go down a bar or two then engage HV mode. In my experience, the battery depletes very quickly at 75mph in EV mode. At the end of my trip, once the distance to my destination is equal to my EV range remaining, I switch out of HV mode and arrive home with the battery depleted.

All that being said, I am curious about using HV Charge mode while on the freeway. If I'm already running the ICE, why not have it run the wheels and charge my battery continuously (assuming battery is below 59%)?

From the thread discussion, HV mode returns 42-45 MPG efficiency (in general). HV Charge mode returns less (35-38 perhaps, though this is an assumption as I have not seen anyone test it yet). Do we know if the reduction in mpg from charge mode puts more or less equivalent charge to the battery? For instance, if I get 35 mpg instead of 42 mpg, but while using that one gallon of gas my battery is charged by greater than 7 miles, it would seem charge mode is more efficient, especially if I am using the ICE to power the wheels/motors anyways.

In the end, I'm looking to determine the most fuel efficient mode at different battery and speed regimes when on long road trips. Attached is a chart that may help show the question better.

 

I believe HV is more efficient than HV charge on hwy so you may as well just keep it on HV unless you will do some heavy city driving at the end of your journey or when you need to deplete the rest of your EV mileage. I think the reason for this is HV charge has to store the energy in the battery and them deliver it to the traction motor resulting in loss of efficiency. HV most of the energy is transferred directly to the traction motor resulting in less loss.

 

Are you saying that in charge mode the ICE can't concurrently charge and power the traction motor?

 

it can do both but you want to send a minimal amount to the battery only as a buffer as needed , sending excess is inefficient and that is why HV charge is not as economical as HV. My personal opinion is to rarely use HV charge ever. I may never end up using it, too much thinking and most of the time it will be more inefficient than leaving it in HV.

 

No, I think @JCEV is saying that the loss of gas mpg when in HV Charge cannot be exceeded or even fully recouped by latter electric MPGe from the electricity concurrently generated. The laws of thermodynamics prevent you from getting something for nothing. The generator itself is not 100% efficient and the process of charging and discharging the battery is not either. So there will always be losses to heat from friction, magnetics, electronics, and battery chemistry.
For these reasons, HV Charge is only useful to me if I’m heading to a significant climb and have a mostly depleted battery. Then I accept the reduced efficiency in order to have enough charge to have better power and better chance to avoid the high reving angry bees when I hit the climb.

You are making the most efficient decision already to use HV at hwy speeds and then switch EV so that you arrive with as close to 0 usable SOC or 2 bars as possible.

Based on your chart, the only time I would use HV Charge would be the single scenario of 2 bars/over 50.
I would never let my SOC get fully depleted before or on a long hwy trip, but if you handed me a Clarity in that state, I would use HV Charge to have enough usable SOC to allow the algorithm to be able to cycle between all it’s possible power flow so as to increase drive ability and efficiency and decrease the possibility of the angry bees. And I would not do this on any significant climbs; just on the flats.
IMHO, I think it’s better to avoid having to use HV Charge whenever you can. For example, on a long trip if I knew I could not charge at my destination, I would not switch to EV to maximize the use of the more efficient electric propulsion, but would trade that gain for not having to drive HV on a depleted battery on the return leg which would be such a wretched experience that it would force me to use HV Charge some. Then I would switch to EV when in range of home on the return leg.
EV is always more efficient than HV and almost always more economical. (Only time it may not be more economical is with high priced pay EVSEs and low gas prices.)

That’s just my opinion and my bias against courting the high reving angry bees. You would also need to take into account the cost of away from home public charging and gas prices to really parse this out since I’m assuming by efficiency you are also including economy.

 

I wish HV Mode would remain selected after powering down the Clarity PHEV the way NORMAL Mode and ECON Mode do.

After stopping during a long trip, it's easy to forget to re-enable HV Mode. Later, after miles of silent driving in EV drive mode, you discover you've used up all the charge in your [expletive deleted] battery. With the battery depleted, you have a reason to use HV CHARGE Mode for the reason KentuckyKen describes, except that the person who handed you a Clarity in that state was you!

I've wracked my brain, trying to come up with a valid legal, financial, mechanical, or user-interaction reason for HV Mode to go away when the Clarity is restarted. Is Honda trying promote traveling under EV power, even if inadvertent? I contend it's more likely that a driver who selects HV Mode would want to stay in that mode. Perhaps "Retain HV setting" could be an additional setting if Honda didn't want to make retaining the HV Mode selection the default behavior.

For now, I guess an "HV MODE!" sticky note on the steering wheel will have to suffice on long trips.

 

LOL. We must have a common ancestor somewhere. I did the same thing (twice) and lost ~10 miles EV charge before I realized it. Then I had to do more math to figure out my true mpg since some net charge was used. Grrrrr.
I’m going to have to make something to hang on the wheel like the Airforce’s red ribbons that say “Remove before flight”.
Maybe “Go back to HV, stupid!”

 

I believe the best solution for consumers would be to allow these settings to be customizable.

Want HV to stay on all the time? No problem... configure it that way in the settings.

I do think it is a good idea for the car to default to EV mode, until it’s not.

 

I think you used about $1.25 in fuel and would have only used about 70 cents worth of electricity.

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