Best (reasonable) highway speed for fuel economy.

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Mass Clarity owner said:
Started off with full tank and full battery for each leg. Our strategy was to start each leg with EV mode for the back roads, then use HV on the highway. And switch to EV mode if we encounter a slowdown or stop and go during construction/traffic. Adn then end the trip on EV (local roads).

This exceeded my expectations for how the car would perform. And we felt very comfortable with the car's seats (former car was a civic) and ride smoothness. And everyone we visited was impressed with the car (of course, they'd never heard of the thing).

I think if one had the patience, you could do even better by driving at 63-65 mph. I think the reason that the efficiency is poorer (compared to other cars) at speeds such as 80mph may be due to the Atkinson engine, which does not have the typical gearing/overdrive capabilities of typical ICEs.
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It's great how one can just get in and drive a Clarity without thinking about maximizing efficiency. It works just fine like that. However, I love how the Clarity lets me fiddle with the way it operates, trying to come up with exactly the best strategy for stretching every gallon and every electron.

I've always wished Honda would offer optional software to let drivers tweak the system even more, or at least provide current data about its decision-making processes. For example, it would be cool to see a graph of the multiple factors lining up to activate Engine Drive Mode. Another example would be a graph showing the factors determining when the engine starts up--especially when the battery is fully charged.

There was an unpolished, home-built kit available for the gen-1 Insights that gave drivers direct control over motor operation and regen. Hypermiling clubs had to establish a separate classification for Insights with those mods because their 100+ mpg capability could blow away the efficiency of unmodified Insights. I was too afraid of damaging my Insights to install one of these kits so I rarely topped 85 mpg.
 
neal adkins said:
Hi Landshark. I feel like i have allready answered many of your points of contention in my previous post. I got the info about the 6.6 kwh 32 amp charger from a honda web page. I keep an open mind about causes of battery degradation and don't claim to be an authority. But i am happy that i have no noticable loss of ev range.
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Neal, thanks for the reply. From my perspective the questions have not been answered. That’s fine. There’s knowledge to be gained from no answers as well.

None of us completely understand how this vehicle works. Even the handful of members who have probed every orefice and analyzed every bit of data available still have questions. That’s why, when someone makes a statement about a feature or function of the car, we sometimes ask for clarification or an explanation.

I’ll ask a couple more questions. How have you determined that you “have little to no battery degradation”? Have you recently had a reading/measurement taken of the battery capacity?

I’ve been operating the vehicle for nearly 2 years, primarily in the same environment, area and terrain with many repeated routes. I haven’t noticed any loss of range, yet a recent battery capacity reading, from a Honda dealer, which I paid for, yielded a result of 49.9Ah. This was followed up by another reading from a forum member who had a device to read the data and it produced the same result. Unfortunately, I don’t have a capacity reading from the PDI from the selling dealer. I’d suspect it would have been in the 54-55Ah range. I was surprised by the reading because more often than not the car goes beyond the 47
mile EV range on just batteries. I haven’t noticed any loss of range, yet I have reason the believe, based on the data, that the battery capacity has declined by ~10%.

I believe that you are mistaken in believing that HV charge uses the onboard 6.6kW charger to charge the batteries. If you believe you are correct, show us the data to support your statement. That’s all I ask.
 
insightman said:
For example, it would be cool to see a graph of the multiple factors lining up to activate Engine Drive Mode.
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Here’s a graph, with 2 factors, speed and torque. Unfortunately, there is only a number at the top of the torque axis, nothing on the speed axis. We do know that EDM engages at speeds above 45mph. And I can confirm that it can remain engaged up to 90mph.
439861BB-0F7C-487B-9B41-1E692A43DD6A.webp
 
Landshark said:
Here’s a graph, with 2 factors, speed and torque. Unfortunately, there is only a number at the top of the torque axis, nothing on the speed axis. We do know that EDM engages at speeds above 45mph. And I can confirm that it can remain engaged up to 90mph. View attachment 11993
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Thanks. Yes, that's how it works, but I want an animated graph on my center display that lets me see the factors converging to cause the EDM clutch to be engaged. After it's engaged, I'd like to see a line for increasing acceleration or load on the system approaching the point where the EDM clutch disengages.
 
Landshark said:
Neal, thanks for the reply. From my perspective the questions have not been answered. That’s fine. There’s knowledge to be gained from no answers as well.

None of us completely understand how this vehicle works. Even the handful of members who have probed every orefice and analyzed every bit of data available still have questions. That’s why, when someone makes a statement about a feature or function of the car, we sometimes ask for clarification or an explanation.

I’ll ask a couple more questions. How have you determined that you “have little to no battery degradation”? Have you recently had a reading/measurement taken of the battery capacity?

I’ve been operating the vehicle for nearly 2 years, primarily in the same environment, area and terrain with many repeated routes. I haven’t noticed any loss of range, yet a recent battery capacity reading, from a Honda dealer, which I paid for, yielded a result of 49.9Ah. This was followed up by another reading from a forum member who had a device to read the data and it produced the same result. Unfortunately, I don’t have a capacity reading from the PDI from the selling dealer. I’d suspect it would have been in the 54-55Ah range. I was surprised by the reading because more often than not the car goes beyond the 47
mile EV range on just batteries. I haven’t noticed any loss of range, yet I have reason the believe, based on the data, that the battery capacity has declined by ~10%.

I believe that you are mistaken in believing that HV charge uses the onboard 6.6kW charger to charge the batteries. If you believe you are correct, show us the data to support your statement. That’s all I ask.
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Here's a link where they confirm the onboard charger specs. They are different than i remember reading 3 years ago.https://www.forbes.com/wheels/cars/honda/clarity-plug-in-hybrid/2019/
 
Landshark said:
Neal, thanks for the reply. From my perspective the questions have not been answered. That’s fine. There’s knowledge to be gained from no answers as well.

None of us completely understand how this vehicle works. Even the handful of members who have probed every orefice and analyzed every bit of data available still have questions. That’s why, when someone makes a statement about a feature or function of the car, we sometimes ask for clarification or an explanation.

I’ll ask a couple more questions. How have you determined that you “have little to no battery degradation”? Have you recently had a reading/measurement taken of the battery capacity?

I’ve been operating the vehicle for nearly 2 years, primarily in the same environment, area and terrain with many repeated routes. I haven’t noticed any loss of range, yet a recent battery capacity reading, from a Honda dealer, which I paid for, yielded a result of 49.9Ah. This was followed up by another reading from a forum member who had a device to read the data and it produced the same result. Unfortunately, I don’t have a capacity reading from the PDI from the selling dealer. I’d suspect it would have been in the 54-55Ah range. I was surprised by the reading because more often than not the car goes beyond the 47
mile EV range on just batteries. I haven’t noticed any loss of range, yet I have reason the believe, based on the data, that the battery capacity has declined by ~10%.

I believe that you are mistaken in believing that HV charge uses the onboard 6.6kW charger to charge the batteries. If you believe you are correct, show us the data to support your statement. That’s all I ask.
Click to expand...
Landshark said:
Neal, thanks for the reply. From my perspective the questions have not been answered. That’s fine. There’s knowledge to be gained from no answers as well.

None of us completely understand how this vehicle works. Even the handful of members who have probed every orefice and analyzed every bit of data available still have questions. That’s why, when someone makes a statement about a feature or function of the car, we sometimes ask for clarification or an explanation.

I’ll ask a couple more questions. How have you determined that you “have little to no battery degradation”? Have you recently had a reading/measurement taken of the battery capacity?

I’ve been operating the vehicle for nearly 2 years, primarily in the same environment, area and terrain with many repeated routes. I haven’t noticed any loss of range, yet a recent battery capacity reading, from a Honda dealer, which I paid for, yielded a result of 49.9Ah. This was followed up by another reading from a forum member who had a device to read the data and it produced the same result. Unfortunately, I don’t have a capacity reading from the PDI from the selling dealer. I’d suspect it would have been in the 54-55Ah range. I was surprised by the reading because more often than not the car goes beyond the 47
mile EV range on just batteries. I haven’t noticed any loss of range, yet I have reason the believe, based on the data, that the battery capacity has declined by ~10%.

I believe that you are mistaken in believing that HV charge uses the onboard 6.6kW charger to charge the batteries. If you believe you are correct, show us the data to support your statement. That’s all I ask.
Click to expand...
I did a post about 2 weeks ago on a rather impressive ev range test. I drove a few miles to top off with gas, then continued to the freeway still in ev mode. I drove a few miles at 60mph, then accelerated to 64 mph for the duration of the test. Recap: With some cargo and a full tank of fuel i got exactly 47.3 miles total before ice came on. While driving with air conditioner on and mostly at 64 mph.
However i do agree it's likely that there is some battery degradation. But i have no data on the condition of the battery.
 
Landshark said:
Yes, the car has a 6.6kW onboard charger. This is how the battery is charged when the car is plugged in to a 120V or 240V power source.

In HV Charge mode, the battery is charged by the engine driven generator/starter motor.
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Yeah, that makes sense. It would not be logical to think that in HV mode the generator somehow uses the same charging circuitry as the EVSE to charge the battery.
 
Landshark said:
Yes, the car has a 6.6kW onboard charger. This is how the battery is charged when the car is plugged in to a 120V or 240V power source.

In HV Charge mode, the battery is charged by the engine driven generator/starter motor.
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I think remembered seeing a Honda video that said the charge rate in hv charge mode was 240v at 32 amps. So its like a level 2 charger.
 
neal adkins said:
I usually only use hv charge at highway speed to prepare for significant grades or to gain some charge for upcoming city driving. It takes about 25 to 30 minutes to gain the 58 percent soc in ideal conditions which yields 26 miles ev range.
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I don't think the car uses the onboard charger at all when in HV charge or regen mode. From your post above, lets say it can gain 50% SOC in 30 minutes. That's roughly twice the speed at which it would gain that level of SOC at 240V and 32A. So it must be charging at closer to 14 kW on average. I think this is why Honda limits the SOC percentage in HV charge (they don't want to charge the batteries at this rate as they near 100% SOC).
 
Robert_Alabama said:
I don't think the car uses the onboard charger at all when in HV charge or regen mode. From your post above, lets say it can gain 50% SOC in 30 minutes. That's roughly twice the speed at which it would gain that level of SOC at 240V and 32A. So it must be charging at closer to 14 kW on average. I think this is why Honda limits the SOC percentage in HV charge (they don't want to charge the batteries at this rate as they near 100% SOC).
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I remember seeing a video by Honda and they said it was 240v 32amp onboard charger. I have been searching for that video with no luck so far. In hv charge the time/distance varies significantly, possibly depending on the temperature of the battery. I have gained about 50 percent in 30 minutes at 70 mph before. Sometimess it takes longer. My main point was that it hasn't lead to much loss of range in my car. I still get about 47 miles. My clarity has almost 33000 miles on it and almost 3 years old.
 
"Technically, the 20 miles downhill, cost you all the energy it took to get up the hill. You just paid in advance. We’ll never be able to recapture 100% of that energy."
-> Agree. No doubt about that.

"The EV range estimate after a long descent is a deceptive beast..."
-> While the guess-o-meter (GOM) may read bizarre stuff like 80 or more miles coming down a mountain, I think the key point is that the car can travel a long ways down hill without *consuming* your range. So the ride down the mountain, I plan to have substantially the same energy (HV/EV range) as I had when I started down. And of course there are places that essentially level out even coming down a mountain, and yes you do use range, but depending on the mountain you're coming down you may find the regen does enough to cover all of the flat spots.

So while the GOM may report something silly. Odds are you'll go down the mountain using very little actual HV/EV range. It's the ground covered that amazes me the most. And admittedly, our gas-only 'brothers' also get better mileage coming down, but they're still consuming, and not breaking even on range. So one might not want to try arriving at the ski resort on 1/4 tank in a gas-only car, but it works just fine for my mountain pass in a Clarity.

Maybe for another post, Clarity has me noticing the profiles of common trips I do. Some consistently exceed expectations on mpg. I sort of track these in the back of my mind, and plan accordingly. And so too, my actual cost at the pump is low on these travels. One example is Eugene, OR to the coast at Florence, OR. It's about 65 miles each way, call it 130 round trip, but I utilize less than 1/2 a tank. The profile of the trip permits long stretches where the gear icon mode is shown. I tend to fill before ever needing more than 6 gallons, so call it $10 to go to the beach and back (I live in Eugene). What a bargain. (estimated with gas at $3.40/gal).

-Dan
 
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PHEV Newbie said:
My Subaru Outback gets less than 20 mpg at those speeds. At 55 mph, I can get 32-34 mpg in the Subie. It rides high so forget about aerodynamics. The Clarity is super aerodynamic hence the bigger gap in mileage at higher speeds. The Outback is also a smaller car, both shorter and more narrow. BTW, 0-60 in the Outback is just under 10 seconds while it's about 7.6 seconds in the Clarity so I don't get better acceleration for the poor gas mileage.
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Is the Clarity super aerodynamic? It seems to have a drag coefficient of .32, whereas my '16 Sonata plug in comes in at .24. Am I missing something?
 
Of course, the quick answer is you're missing 0.8.

The Clarity is more aerodynamic than it would have been had Honda left off the underbody panels, rounded the rear wheel-well cut-outs, eliminated the air-curtain vents that deflect the wind from the wheels, and installed functional windshield washer jets on the hood. It is not super-aerodynamic like any car the manufacturer claims has a cD of 0.24.
 
jeko44 said:
Is the Clarity super aerodynamic? It seems to have a drag coefficient of .32, whereas my '16 Sonata plug in comes in at .24. Am I missing something?
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Regardless of that number, with a Sonata you're missing about 19 miles of ev range compared to the clarity's 47. And also a few thousand dollars in tax rebates.
 
neal adkins said:
Regardless of that number, with a Sonata you're missing about 19 miles of ev range compared to the clarity's 47. And also a few thousand dollars in tax rebates.
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Believe it or not, it qualified for the same tax credits and rebates as the Clarity, but I get your point about the ev range. I was just comparing the dc.
 
insightman said:
Of course, the quick answer is you're missing 0.8.

The Clarity is more aerodynamic than it would have been had Honda left off the underbody panels, rounded the rear wheel-well cut-outs, eliminated the air-curtain vents that deflect the wind from the wheels, and installed functional windshield washer jets on the hood. It is not super-aerodynamic like any car the manufacturer claims has a cD of 0.24.
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No doubt.
 
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