Efficiency of the Clarity Generator

Michigan after 600 kwh’s jumps from $0.169 per kWh to $0.269 per kWh. So 14 kWh would cost $3.76. So it may be cheaper to use gas than hv charge. Costco gas now $1.19 a gallon.

 

Not only is electric driving better for the environment, but I enjoy driving on EV so much that I don't mind paying the higher price for electricity. Meanwhile, Honda execs pat themselves on the back for making the decision not to bring the electric Honda e to the US.

 

Yeaahhh...before the gas price drop it cost only slightly more to run the car on electricity and I justified home charging because I didn't have to stop at the gas station but now that gas prices have dropped it definitely makes more sense running it on gas out here in Hawaii!

 

I estimate the Clarity's gas engine driven generator capacity is between 60 hp (45 kW) and 91 hp (68 kW).

The lower estimate of 60 hp comes from the traction motor's 181 hp (135 kW) rating minus the high voltage battery power limit of 121 hp (90 kW). In other words, in order for the traction motor to output 181 hp, you need electric power from the battery of 121 hp plus another 60 hp from the gas engine generator. In reality, you need even greater power input because the traction motor is less than 100% efficient.

From that, and other factors, I estimate the engine driven generator capacity is closer to 91 hp. Higher generator power is needed to account for efficiency loss and for times when the high voltage battery is limited to a power rate less than 121 hp (when the battery is hot, cold, or at a lower state of charge). During these conditions, in order to protect the battery, the controls reduce its power output to perhaps 2/3 (or lower) of its peak. At 2/3 of the peak 121 hp, you get only 81 hp (60 kW) from the battery. To maintain good driveability Honda engineers likely designed the Clarity engine generator to provide up to ~90 hp to combine with the reduced battery output in order for the over 4,000 lb car to still have reasonable power and acceleration.

When your battery is very hot, very cold or is at a very low state of charge, your battery power rate decreases further (ultimately dropping to zero hp).

Another means of estimating the gas engine generator capacity is to note in the cutaway drawings showing it next to the traction motor, you see they both have the same stator diameter, presumably the same rotor diameter, and the only difference is the 181 hp traction motor looks twice as thick (axial direction). From their relative thickness, you could estimate the engine generator is half of 181 hp, or ~91 hp.

The greatest possible generator power would be if the gas engine generator is capable of converting all of the engine's peak 103 hp into electric power (assume 90% efficiency), you then get 93 hp (69 kW). I estimate 90% efficiency (compared to likely more efficient common industrial induction motors in the range of 90% to 97%). If the Clarity engine generator is only 88%, then we are back to 91 hp (68 kW). Now the estimated 90% is its highest efficiency (peak of the curve), and it will be somewhat less efficient over the rest of its operating range.

For HV Charge mode, I've observed gaining about 1 mile of EV range for every 3 to 5 miles of freeway steady state driving (60 to 75 mph). At 60 mph I could gain 20 miles of range in an hour, and assuming a freeway average of 350 Watt per mile, that is 7 kW for one hour, or 7 kWh. At 75 mph I gain 15 miles of range, which is 5.3 kW or 5.3 kWh. This is from memory, I'd have to run some timed tests to be more accurate. Of course Watt per mile varies based on speed, weather, etc., so as they say, "...your mileage may vary."

 

Dang man.....you lost me! Haha I'm not as electrically savvy as you lol. So what would you think would be more efficent.....running the car in HV mode all the time or running it HV charge while on the highway and then EV around town until it runs out...(like I had posted earlier I am not charging my car at all....running it only on gas)

 

I also never plug in. Tests I posted a while back indicated the same efficiency either way, but I prefer using HV Charge on the highway till done, then for around town use the quiet EV mode, this also reduces the polluting cold startups of the engine.

 

You may get a faster charge when driving at speed. I’ve only used HV Charge a few times, all at speeds of 55+.

The first time was with batteries depleted, 0 EV range. After a 3-5 minute “warm up” HV Charge brought the batteries up to 10 bars, 50% in approximately 30 minutes. I did not note the EV range after charging, probably 20-25 miles. The car was only a week old at the time, so a driving pattern had not been established for the computer to estimate EV range.

The manual states that HV Charge will bring the batteries to 12 bars, ~60%, when driven at high speeds for ~1 hour. That would be a charge rate slightly higher than what can be provided by a L2 device.

 

For me, I don't like the sound of the engine revving up and then settling back when in town (or stop and go) driving HV, I call this start/flare-up/stop. So I like to always have enough EV to do all in town driving, and then use HV for commutes to work (geez, it's been a over a month now since last commuting to the office). And here in central CA gas is just now getting low enough to be less than electricity, but I still plug it in.

To answer your question, I think both ways are efficient, but HV charge at freeway speeds (to then have EV in town) may be slightly better. In town HV driving, the frequent engine start/flare-up/stop I think is likely less efficient than building up charge while on the freeway (when the engine can stay on longer and at higher loads where it is comparatively more efficient than at light loads around town). The best possible gas engine efficiency is to start it once, warm up, then run continuously at its peak efficiency to charge the battery, then stop. The gas engine is less efficient at low loads, and starting/warming up is also less efficient.

For Honda engineers, it was likely a design trade off between maximizing efficiency and annoying engine behavior when driving HV mode in town. They couldn't just start the engine and run it for a long time at a higher load (peak efficiency) as that would be even more annoying than the start/flare-up/stop it does now.

If gas prices continue to drop, I may try plug in charging less and HV charging more, just to see what that is like. The times I have done HV Charge, I've found it least intrusive at speeds around 55 to 65 mph steady state cruising on flat highways.

I really wish Honda would have given us geek nerds access to all of the energy/efficiency info. Its all in the control system, they just didn't give us a screen to conveniently access the data.

 

I was just thinking that too yesterday....wish there was a Honda Engineer to answer some of these questions. I tried what all of you suggested yesterday.....HV charge while on highway and then EV charge around town. It didn't seem to change the overall mileage much (i.e. EV range+hv range+miles driven) so I think I may keep driving like that as well just because I agree with you all....the constant on off of the gas engine around town is kinda annoying.

 

Sorry...ment to write EV driving not charge

 

While reviewing this thread, it came to my attention that 15+37=52, not 82. Maybe a typo?

After running the engine for an hour and going nowhere, the computer decided that your HV range was going the way of the Dodo bird. Sometimes it’s smart, other times it is stupid. In either case it is reacting to past performance, so don’t try to use it to pick stocks.

The photo above is an example of stupid. After cresting a mountain summit in HV with ~48 miles of EV range, I descended for ~9 miles in EV and got home with 80 miles of EV range. Only one bar was added to the charge level while range increased 32 miles. After a full charge the display showed 102 miles.

I got about 42 out of it.

 

You would have easily gone 102 miles on that charge, if not more, had you continued descending...

 

Indeed. If Rowerpilot1111 is on Maui or the Big Island, I’d like to see the results after a descent of Haleakala or from the Mauna Kea Observatory.

 

Lol...no...on Oahu...but that would be a cool observation! Yeah...sorry...previous post was a typo...was supposed to say 67 not 37

 

Assuming that you are a paddler, did you ever have the good fortune of knowing my friend, Loren Ching? He was the Steersman on many Molokai Channel crossings. He lived on the Big Island and was our next door neighbor for many of the 18 years that we owned a townhouse there.

In a story that may sound awful to some, he had a heart attack while paddling and was presumed dead before he hit the water. He went out doing what he loved most.

 

Oh no! That's tragic! At least it was while paddling. I've only lived here for about 3 years so not familiar with him

 

In past years, I've stated loudly on this forum that I'd pay good money (say, $1K) for an optional all-info screen. I was hoping Honda's bean counters would read my suggestion, see it a guaranteed ROI for minimal effort, and have one of their programmers do it. They must have had a version of the screen we nerds crave during the car's development! However, that screen might have been on a laptop rather than on the Clarity's micro-FLOPS (macro-flop) tablet.

 

Unfortunately the active management required makes running a home economically on a generator unfeasible, without a huge capital investment in a computer controlled load sensing variable output high capacity generator and a battery bank. Even the “expensive” $10k to $20k whole house generators like Generac, which are extremely popular backups, can do nothing more than start up at full throttle like a lawnmower and wastefully run at a fixed speed, whether you are running your entire max electrical load, or just charging an iPhone, at any moment. You need to add another $10k for variable speed generators with sensing controllers and a battery bank in order to make the system smart enough to be truly efficient with gasoline to power a home. While possible, it is never cost effective.

Many wealthy off grid people, and many corporations, indeed do make such an investment, usually based on their unique needs. But for most anyone who can just use a reliable grid, it makes no financial sense.

However the Clarity has the entire smart system and battery bank built in right from the factory, allowing variable output that responds immediately and efficiently to power demand. For this reason it instantly makes financial sense for propelling a Clarity, to use the cheapest fuel.

A valid question, and I know you jest, but due to the massive capital investment required just to save money on fuel, it makes no financial sense to do so for a home. But it totally does make financial sense to do so for many Clarity owners right now, with zero additional capital investment. So Apples and oranges really.

 

Umm, many inverter type generators will vary throttle to match load or will have a switch setting to do this. They are a little more expensive, but not hideously more. A nice 4,500 W one will run ~$650 to $1,000 and 2,000 W ones ~ $400. (Remember, generators are rated at starting Watts or temporary output while the continuous load will be less. In this case around 3,500 W.)

They will save 30-50% on fuel since they don’t run full tilt all day and have <3% distortion ana a good sine wave so they are very safe for electronics and appliances with electronics. I have not researched whole house permanent mount ones since I am not in that market.