Phoenix to Flagstaff - 2018 Honda Clarity Forum
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post #1 of 17 (permalink) Old 03-18-2019, 07:39 PM Thread Starter
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Phoenix to Flagstaff

Has anyone made this drive in a Clarity? It is a 150-mile, 6,000-foot climb into thin air which robs engines of power. In winter, temperature in Flagstaff can be as low as zero F, robbing batteries of charge.

What I want to know is how to make this trip at 75 mph while keeping engine noise to a minimum. (No “angry bees”) ‘cuz I have an ear condition which would make the noise painful.

It just occurred to me that, while it would be dangerous to drive well below the limit when many drivers are traveling at 80 or more, it would be possible to tuck in behind trucks going 40, 30 or 20 on the steep uphills if that would help.

If it isn’t practicable to make this drive in a Clarity, I’d like to know it, preferably before I buy one 🤪

There’s some great info on the subject in the thread “Driving for Quiet.” Now I’m asking what modes and speeds did YOU use to make this drive and what were the results?

Thanks for sharing your experiences.

Tom
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post #2 of 17 (permalink) Old 03-19-2019, 04:04 PM
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Try to maintain as much of your charge before starting the climb using HV or HV Charge mode. Just before the climb up turn off HV/HV Charge. I would also turn of the heat too since that is a heavy load. You should be fine.

Please report back and let us know how it works out. We can use all the data points we can get.
If fact if you can tell us if using sport mode helps that will be good to know.
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post #3 of 17 (permalink) Old 03-19-2019, 05:21 PM Thread Starter
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Gadgeteer, thanks for the information. I’m trying to decide whether to buy the car or not, so it will be a while. Can you please clarify “turn off HV/HV CHARGE mode”? If I turn off HV, what is left? Without HV, won’t the battery use up its charge in the first few miles?
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post #4 of 17 (permalink) Old 03-19-2019, 07:57 PM
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Hi,
If you are interested in playing with some of the numbers:

Well, there is a nominal 47 miles available from the 17 kWh battery. You will be gaining, overall, 6000 feet. So, according to the laws of physics (and so far everything in the universe that we know of obeys the law of conservation of energy) you will be needing to expend an extra amount of energy equal to weight of car times vertical height foot pounds, which converts to about 9 or so kWh. A fully charged Clarity will start out with a bit more than 13. So, those up hill driving segments not balanced by downhill segments (probably in segments that will add up to about 12 miles) if using strictly battery, ie strictly EV, must eat up at least 53% or so of your battery capacity. And that assumes perfect energy conversion efficiency without considering heat dissipation and extra energy usage beyond the EPA's estimated values.

It would be nice to know that in HV mode the downhill gain in charge exactly balances the uphill gain in charge. Part of the considerations would depend I presume on how fast and smooth you drive up hill vs down hill. And doesnt consider the use of audio, heat, A/C, etc.
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post #5 of 17 (permalink) Old 03-19-2019, 08:08 PM
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Sigh... Clarity battery 17 kWh, not 13 kWh. (I was thinking 17.3)
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post #6 of 17 (permalink) Old 03-19-2019, 09:10 PM Thread Starter
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That’s really interesting, Car. So I’d need 9 kWh more than if the trip had been on a level road. Let’s add a bit for misc. losses and call it 12 kwh extra. Assuming that on a level road in HZ mode the engine would charge enough to keep the battery at its starting charge ( say 50%), the question becomes: where can I pick up that extra 12 kwh?

1. How much excess can I expect to pick up in the level and downhill parts of the road?

2. How much can I pick up from slowing down to truck speed (say, 30 mph) in Hz on steep uphill parts or would there still be a net battery loss in those conditions?

I’m starting to move toward guessing that this car simply doesn’t have the battery reserve or engine power to do this trip without a great deal of high engine revving (angry bees) and/or reducing the overall speed substantially —probably both.

Not only does heating etc. play into it but imagine how much worse it would be in winter, with half the trip at 30 degrees or below, figuring in sharply reduced engine power and battery capacity!

I will try the same question on the other forum as someone has suggested. Thanks for all the help so far!
Tom
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post #7 of 17 (permalink) Old 03-19-2019, 10:43 PM
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That's where HV Charge may come in on the downhills (use gas so that more excess energy can be captured for the battery but not so much energy required by the ICE to generate the bees because at reasonable speeds we are now capturing some of the energy of height gained times mass. Easy to consider theory, not so easy to calculate in practice.
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post #8 of 17 (permalink) Old 03-20-2019, 07:47 AM
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I've driven that stretch of Interstate 17 several times and remember the long uphill climbs. Haven't driven it in my Clarity, however.

I think if you reduce your expectation of doing 75 mph the whole distance to easing up on the go pedal to maybe 55 or 60 on the uphills, and you'll find the Clarity an excellent highway cruiser.
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post #9 of 17 (permalink) Old 03-26-2019, 01:57 AM
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The math works out and you should be fine as long as you're not pulling a continuous 6k incline. By using the HV mode during the dips you should be able to eliminate the 'bees' and regen enough energy to make it without issue. Charge it fully before you take off and don't use the HVAC during the climbing pieces, and you'll be just fine. I am driving to central Oregon and will climbing to about 5k this weekend over the Cascade range. I'll monitor it and repost upon my return.
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post #10 of 17 (permalink) Old 04-02-2019, 12:04 AM
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Portland, OR to Bend, OR and back.....

So as promised I made the drive this past weekend and it went well. I didn't opt to go beyond an average of 62-65 mph the whole trip. The climb from about 700 ft to 4900 ft was fine. It seems to work mighty hard but that is more than likely thanks to the CVT and not the engine. The noise wasn't awful, but it would certainly be annoying on long drives. I'd still advise you to either pop in some earplugs or get some noise canceling headphones if you're that sensitive to noise. I did the drive without any music just so I could listen to how hard things worked. I averaged almost 57.0 mpg overall using HV mode the entire drive (376 miles total). Very happy.
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