Efficiency of the Clarity Generator

Well I actually kinda answered my own question for anyone else interested. I had 98 miles range (0 electric) and ran my car in my driveway on HV charge mode for 1 hour. When I came back it was showing only 82 mile range (15 ev and 37 hv). Also you can't lock your doors and anyone can just drive away with the car. I left my FOB in my house and tried driving away and the car let me ! so no...it is not as efficient to run the car this way. Still don't really know why this feature is available if it's that inefficient

 

The only time that I use the HV charge mode is on long trips. The Clarity only has a 7 gallon gasoline tank. When the low fuel light comes on, there is one gallon left, about 42 miles. Having a few miles of EV range reduces my range anxiety. Also, the Clarity drives nicer in stop and go driving as an EV. So once I'm off the interstate, I switch from HV mode to EV mode. One cannot do that if the EV range is zero.

 

Yeah.....definitely agree the car is more enjoyable driving as an EV just as far as the noise of the engine is concerned. I think because of how the motor is connected and how the engine just basically charges the battery it actually drives exactly the same as HV or EV...just louder as HV lol. If you turn music up to cover the noise you can't really tell much if your in EV or HV mode

 

Not sure you can tell much from using HV charge on an idling car in a driveway. The typical use case is while doing highway cruising (where a normal ICE car would be using very few HP). At those speeds, and with wind and road noise, the engine is pretty much unnoticeable (at least in my car) and is probably running at an efficient rpm).

 

Law of physics, no machine is 100% efficient. You cannot convert fuel range to equivalent electric range - there are conversion losses in heat, mechanical, and electrical. You would never convert X number of fuel miles into the same X number of EV miles for a 1:1 maintaining of total range. Plus you are using energy (pumps, lights, etc) while the car is sitting there in your driveway.

 

Then why not just run it on the highway in hv mode vs hv charge? And then save the EV for city driving

 

That’s exactly what most owners do.

 

I see...

 

Because of high electric prices here I never plug in. I use HV Charge on the highway to build up the battery, then run it down on around town errands. Doing this I average overall 40 mpg in the winter and 50 in the summer. And the engine does not have to go through the inefficient, polluting warmup near as often as if I used HV around town.

This will change soon when I move to Florida where electric prices are half of Connecticut.

 

I'll have to try that and see how it works out here! Thanks!

 

The manual recommends using HV Charge while driving at sustained high speeds, not stop and go traffic. Probably so the engine cooling system functions as designed. No mention is made of using HV Charge while parked. There is a recent thread where it was suggested that one of the reasons HV Charge was added to the car was for dealers to charge the batteries periodically while the car sat on the lot.

Some owners, in areas with cheap gas and high electric rates, use HV Charge, theoretically when appropriate, to charge their batteries rather than charging with electricity. I’d recommend using HV Charge while driving so that you are actually going from point A to point B while simultaneously charging the batteries, rather than just burning gas while parked.

In warm weather it is not unusual to get 50-60 miles in EV in urban driving or rush hour traffic.

 

Yeah...it helps that it's always warm weather out here in Hawaii Haha =D

 

Just as a note, when you are idling stationary with HV Charge Mode on, it is charging at around 2400-2500 watts (until cut off at above 58%). The engine is producing approximately 4.5 HP at a pretty efficient fuel burn since it is an Atkinson cycle, which means it is converting all but about 1 HP into power into the HV battery. The wasted calculated HP is likely into the combustion heat and the required cooling, the vehicle systems, charging the 12v battery, and mechanical losses. However it is pretty efficient all things considered, and I continue to be impressed by Honda's engineering on this car. I am fairly certain it is as efficient as most purpose built small "work site" generators in that wattage range. I am still doing some more tests to refine this data, but the above should be within 10% as far as the total exchange numbers. I am the least certain about the idle (1200 rpm) HP, but the numbers are pretty close.

Note, this is IDLE info - when in cruise the HV Charge can dump substantial energy into the battery, especially when you are in steady state or coasting. Way more power than level 2 charging.

Cheers,

Cash

 

Awesome info! Thanks!

 

Level 2 charging is actually in the range of 7000+ watts. 30 amps x 240 volts = 7,200.

I at first found it very difficult to believe that HV Charge mode, while also expending energy to maintain forward motion of the car on the highway, has yet enough additional energy to come anywhere close to dumping 7,200 watts into the battery at the same time it is propelling the car...BUT...as I typed this reply I started changing my mind. It might.

Maybe I'm misunderstanding what @Cash Traylor was trying to point out in his last sentence. Maybe he meant during regen/slowing down? Yes for very short periods of time I can see larger than 7200 watts going into the battery...only while decelerating. But not while highway cruising. And maybe I'm totally wrong. I have zero data.

Other than 1.5 years ago when I was doing some napkin math in post #45 in this thread, and other posts before it, I did speculation/unrelated comparisons, and I had myself convinced the size of the generator under the hood of the Clarity was somewhere in the 25,000 to 28,000 watt range when the engine was spinning at wide open throttle/redline: https://www.insideevsforum.com/community/index.php?threads/angry-bees.4163/page-3

So if I'm anywhere close to correct, the engine has gotta be screaming redline murder to put out that kind of power, which I believe only occurs when under major propulsion load (accelerating foot to floor up steep and sustained incline with low battery charge), and at that point nearly 100% of the generator's engine is going straight to the electric motor, with likely zero or even negative power going into the battery. As soon as load drops (reach the top/get off the gas pedal), RPMS almost immediately drop, because the battery can never accept a huge wattage load like that for any amount of time (think supercharger damage to the battery). So HV Charge would never have reason to spin the engine that fast when charging, because the battery simply can't accept a sustained high wattage charge that fast without damage.

There is a huge difference between generator peak capacity (I'll speculate 25,000 watts for Clarity), and the amount of wattage a battery can accept for a sustained amount of time without damage (I'll speculate 7,200 watts for Clarity). Programming needs to straddle this gap safely and efficiently while propelling the car.

Cash, as for "idle". Most car engines, when warmed up, actually idle about 650 rpm. Yet you stated 1200 rpm is an "idle" speed. That seems like a very fast cold-engine idle. So I'm unclear what you meant about idle as well. Maybe that's the slowest RPM that HV Charge allows? Surely it idles slower with HV Charge deactivated. Not challenging anything...just curious. I think I'm misunderstanding what you were trying to describe. Thanks.

In the end, I'm willing to speculate that Honda programmed HV Charge to spin at whatever speed it needs to spin, while maximizing battery input to that of about L2 charging (7000-ish watts), and to never exceed it for fear of damaging the battery. But that is pure speculation with nothing to back it. And I bet this higher wattage to the battery only occurs while the car is in motion...not while sitting still, which is where you measured your 2,500 watt/1200 rpm level. And lets guestimate it takes nearly 3,000 rpm to generate L2 charging wattage of 7,200. If true, NOBODY wants a car "idling" and sitting still at 3,000 rpms. Angry bee complaints galore. So Honda probably slowed it down to your 1,200 number only for car sitting still in HV Charge mode, just so owners and other people nearby would maintain their sanity.

So I'm waffling all over the place here cuz I have no idea what I'm talking about. But I have a lotta semi-educated guesses. Sorry folks.

 

Makes sense. And if your 30% efficient number is correct, it means you need nearly 35hp out of the gasoline engine to produce that 7200 watts. I can see this being in line. Clarity's 1.5 L engine likely is producing 35 hp when running somewhere in the 2,500 rpm range...

All wild estimates, but they all kinda make sense.

Then again many 7,500 watt generators come with 13 HP and 14 HP engines...

So maybe it doesn't all make sense. Calling me a "Generator expert" is a huge stretch too LOL. And even if I were, it might be irrelevant with regards to Clarity. I'll step aside now. I'm confusing myself as much as everyone else.

 

Just as an addition like I wrote in my previous post.....i got about 15 mile EV range idling in HV charge mode for about 1 hour...so for 2.5 hours (the length of time to fully charge with level 2) that would equal 37.5 miles which is a little less than level 2 charging.

 

And Hawaii is home to the highest electricity rates in the country at 27.5 cents per kWh!

You'd think with all that geothermal/wind/solar available there it would get put to use? The issue there is being an isolated electrical grid that can't trade with adjacent grids... https://blogs.scientificamerican.com/plugged-in/3-reasons-hawaii-put-the-brakes-on-solar-and-why-the-same-won-t-happen-in-your-state/