The Zing! (Custom-built prototype hybrid tadpole trike)

[pete c]

Glad to here my BS meter doesn't have to go into the shop for calibration.

Even at 60 lbs or as much as 80, I think you are well within the window of calling it portable and would look real hard at setting it up that way. You could even sell some sort of tripod, or maybe quadpod with a small electric winch that could allow grandma to lift it out.

Being an air cooled single (it is a single, in'it?) I would think it would be kinda noisy. Is this the case? I suppose you could use some sort of noise cancellation through the stereo to combat it.

[Ken Fry]

Originally Posted by pete c

Glad to here my BS meter doesn't have to go into the shop for calibration.

Even at 60 lbs or as much as 80, I think you are well within the window of calling it portable and would look real hard at setting it up that way. You could even sell some sort of tripod, or maybe quadpod with a small electric winch that could allow grandma to lift it out.

Being an air cooled single (it is a single, in'it?) I would think it would be kinda noisy. Is this the case? I suppose you could use some sort of noise cancellation through the stereo to combat it.

Wow, another right-on response. It is a single and it is kinda noisy. Way back in a previous life I custom-designed and built expansion chambers, I built a huge muffler for a motor cycle chassis dyno, etc... so I wouldn't have though myself clueless about noise... but the first muffler I built for the POC was a disaster. Honda has my admiration (for their really quite generators) , as do NVH guys.

Amenities have not been the deal for the POC -- it is pretty much stuck together with chewing gum and popsicle sticks. So I just rubber mounted the whole rear subframe without giving real thought to it. How bad can the vibration be (?), I thought. Bad enough to cause intense bleeding of my backside in about 10 minutes. (Ok. I'm lying. But it was both noisy and shaky.) Now the motor-generator unit is mounted on isolation mounts within the subframe, and the vibration is fine. The noise was cut back dramatically be adding the original muffler to the end of my kluged one. But i'd like it to be quieter.

Active noise cancellation may be my fallback if I can't tame the noise more. Honda uses it, as you may know, with their variable displacement V6.

Thanks again,
Ken

[pete c]

What sort of lifespan are we looking at with the engine? Air cooled thumpers running flat out aren't really known for being the longest lasting engines ever made. Being a honda, I guess it will be as good as that breed of engine can be.

On the bright side, it's a 500 dollar motor. If you burn one up every 2 years, WGARA?

[Ken Fry]

Quote:

1. How does efficiency change with load and rpm for the generator?

2. How does efficiency change with load and rpm for the motor?

3. How about the controller?

4. What is the overall efficiency in terms of vehicle speed and load?

5. And is energy moving "through" the batteries? What conditions affect the charging/discharging efficiency? (not counting regen)


6. Like we don't consider ICE engines to be really 35% efficient because of operating conditions, we should not make the same mistake with electrical drivetrains, no?

Not sure if the quoting will make sense, but these q's were asked in another thread. They are great questions... in fact, spot on. I find it irksome when I talk to a motor manufacturer and they cannot give me anything other that a full load dyno run for an electric motor. Even more irksome, when based on this run, I calculate efficiency, and find that it peaks at 80 or 85% (including controller losses) but the marketing spin claims the motor/controller combo is generally over 90% efficient.

Specifics:
1. The motor generator unit in the POC runs at constant speed and near constant load. If load drops, it shuts off (in the POC I do this manually). So in practice, the generator only runs when the battery bank can absorb all the power it can produce at its peak efficiency load and rpm. In the POC the amperage is not allowed to go outside the range of 50-60 amps. In that range as speed the generator is within 1% of 89% efficient. (I use 85% in my spreadsheets.) There is nothing but wires (and a contactor) between the generator and batteries in the POC. (In the production version, there are diodes.) So the POC generator produces 58V x 55A continuously: 3190 watts. The engine output must then be 3190/.85 = 3752 watts. That's 5.03 hp. At that load, the POC engine is about 24% efficient. If the batteries are somewhere in the range of 30% to 70% charged, and I go up a hill, the load on the engine increases, and its efficiency (in the POC goes up to 26%, which is as good as it can get (without modifying it for closed loop, Atkinson cycle etc.) The batteries then have to take over most of the load, and because they are relatively big (huge in comparison to a Prius-like hybrid) they do not sag much. They have no difficulty in putting out 600 amps (10C) briefly, whereas the generator can only put out 60 amps. In the POC, the batteries cannot put out more than 5C (300 amps) because the motor controller sets a limit than keeps the motor from glowing red hot.

2. This is the killer. Motors are remarkably level in efficiency (in other words the curve is pretty flat) but vendors rarely seem to show the very light load part of the curve, where it has to drop off to 0% when the motor is just starting to move, and functioning only as a heater. So the only way that you can asses efficiency is to plug the actual values (which you can get from some manufacturers with prodding... or can generate in a shop with a dyno). Azure Dynamics publishes pretty good data that covers most of the operating range without driving themselves crazy. Others just assume you don't care or that you are willing to do your own dyno testing. I guess the situation is just like it is for commercial engines, where some vendors provide actual BSFC maps, but most just provide a single BSFC curve based on full load dyno testing. For my application, the latter is not a problem, because I operate very near the middle of the peak. But there are times when the drive motors operate at much less than peak efficiency. So in modeling for Urban (especially) and Highway (to a lesser extent) You have to insert actual figures for particular loads and RPMs.

Failing to do this gives you the equivalent of the mpg calculator on this site which is completely useless for anything other than a single speed where you are certain of the actual BSFC, at that load. If you put in some average, then there is one speed for which the calculated mpg is correct, and it is incorrect for every other speed. This makes mpg as low speeds (where engine efficiency might be 8%) completely bogus, if you use 20% as an average. In my view, the calculator should produce only one line, for a particular speed and load.

Short of paying the $25,000 for EPA style dyno runs, modeling with actual efficiencies at actual loads and rpms is the only way to get meaningful MPG figures. On-road testing is just too variable for a vehicle developer's use. (Read about the trials and tribulations of coast down testing on this site to get a feel for variability.) Once you've got 100 cars out there and people are responding to the EPA site, then averages of many people and many conditions closes in on the EPA numbers.

3. The controller: these days, it might as well be considered wire: 99% is often quoted as "typical most of the time". (With a 150kW motor 1% is 1500 watts -- about like a stove burner. Don't touch the controller.)

4. The overall efficiency in terms of vehicle speed and load: This is all over the place for a plug-in hybrid. As a simple rule of thumb, you can take a steady state condition for 45 mph, going up a 2% grade, and in a minute of two get an MPG figure which is close to the combined EPA figure... for many vehicles. But otherwise there is not single efficiency number that works -- it changes a lot with speed and load. The guesstimate I mention is only useful for deciding to go ahead with a project, at which point you have to gather up all the relevant data or do the testing of components. If you a hobbiest, then none of this matters all that much, other, than, I suppose, as background. Call Honda for the BSFC maps for a CBR 250 , and you probably won't get much help.

5. Is energy moving through the batteries? There is a level-road, still-wind cruise speed at which the engine has to provide all the energy to more the car. At that condition, all the energy effectively bypasses the battery. In the more typical case, in which the engine comes on for 20 minutes and then shuts off for perhaps a similar time, the the losses in and out of the battery matter. With lead acid, these can be a deal killer. With Lithium X they tend to be small in both directions, often 95% in and 95% out, but worse if you get up to 80% charge... at which point you should not be charging.

Conditions: Mainly temperature, which is why most systems are actively heated and cooled. Secondarily, charge rate, with either way high or way low being not so good.

6. Yes, we should not make those "generality" mistakes for either vehicle type. If you model with a particular "average" efficiency, the model does not work. After you have done real modelling, then you can work backward and say that the overall drive train efficiency is X, (if you wanted to do so) for a particular stated condition... but then some journalist would pick up that figure and use it completely inappropriately.

Sorry for the long post. This stuff is hard to simplify without conveying the wrong info. You clearly "get it", but there are others who may be reading who need a little more detail. Performance prediction spreadsheets can go on for many pages, and the guesstimates or calculators at electric motor vendor sites rarely work right -- in practice they are not useful even for comparison shopping because, for example, the efficiency curve of a PMAC motor and an AC induction motor are quite different. At a target speed and load, the difference in efficiency can be 50% vs 80%, even if the motors are "appropriately" sized. If one is too big and another too small, then the differences can be greater.

Really good questions.
Ken

[dcb]

You da man Ken, thanks for the details.

Here is a rather optimistic graph for an electric motor for the readers (expensive large motor maybe?), I assume a generator is similar:



But both the generator and motor have islands of peak efficiency, like an ICE BSFC graph, except in a series configuration the individual inefficiencies are multiplied by each other. Mating the generator island to a bsfc tuned internal combustion engine is doable with an energy storage scheme, but the motor end still will be sub-optimal for most of the operating range, and battery losses when vehicle demands are not just right.

And of course constant cruise operation just screams for the additional expense of a clutch and sprocket hanging off the engine.

Ever looked at hydraulic energy storage?

[Ken Fry]

From Doug in another thread:

1. There will be a range where your 32 percent efficient IC will have excess power over cruising, and yet your batteries won't accept the excess amps the generator will accept.
In this case, the generator will not operate at peak efficiency, or the generator will start cycling on and off.

A lot.

2. By the way, where do we purchase one of these 32 percent efficient IC engines? Sounds pretty neat.

From DCB in another thread:

3. Not only 32%, but, 32% air cooled gas engine. I was under the impression that liquid cooled gave a slight efficiency gain due to maintaining optimal head temps.

1. I think this may be answered in my novel above. You are basically correct. There is a meaty part of the battery charge profile during which the engine is very close to fully-loaded. It takes many minutes to complete a cycle, unless the vehicle is just sitting in a parking lot -- although even then it takes a while -- it's charging at 1C, so it could take an hour if the batteries were flat and you wanted them full... but the microprocessor will not allow them to be full, because the load tapers off too much. Once the load drops, the engine shuts off. It won't cycle back on again until the driver pushes the start button. As I mentioned somewhere, this could be automated based on GPS, so that you always arrive at home with a low charge, given distance, terrain, etc. but I'm not going to do that. I think that drivers will be able to figure out their own desires re charging. Making the generator start up at automatically at 30% charge or any other SOC, would be simple for the same microprocessor, but I prefer driver control, because if you have a 40-mile commute, the engine would otherwise be starting up (maybe half the time) at distances of 10 to 0 miles from home, depending on things like temperature and traffic. A lot of people, I think, would prefer to say no to gas, other than for long runs (and will be willing to take the hit in overall battery life that the deeper cycles entail).

2. I think you already have an IC at about 32% peak efficiency with your Civic engine. Without a huge amount of work you could get it up to 36 - 38% peak efficiency, by modifying it for Atkinson cycle. You'd loose low end torque and the ability to idle smoothly. My engine has about the same cylinder volume as a Prius or your engine. It will be available only from me, as far as I know -- there has not been a strong market for efficiency in commercial engines, but at least closed loop injection is showing up. My mods effectively cripple the engine for other uses.

3. I think that water cooling makes emission control easier. Head temperature can be adequately controlled with good control over mixture and timing, without going outside the emission limits for motorcycles.

[dcb]

Originally Posted by Ken Fry

...As a simple rule of thumb, you can take a steady state condition for 45 mph, going up a 2% grade, and in a minute of two get an MPG figure which is close to the combined EPA figure... for many vehicles.

This was an interesting insight as well. It is obviously something you or someone you know reverse engineered to obtain, so huge caveats apply, but could be useful in situations that are not too far off the beaten path.

[dcb]

Originally Posted by NeilBlanchard

I think The Zing! will show how efficient a serial hybrid can be. ...

That is just silly, so many things are different about the zing than a regular vehicle aside from the drivetrain, it would be like saying Allans streamliner shows how efficient a hybrid is NOT.

214 mpg with DIY aerodynamic fairings on a Honda 125cc motorbike

And the series/parallel issue is kinda silly too, it should be apparent that there will always be modes of operation where parallel is simply the most efficient way to get the power to the ground, so it should always be a part of the driveline layout. With the right technique (and sufficient gear selections), the advantages of series goes away and then some, but the driver cannot ever fully compensate for having an extra lossy transmission of power i.e. ICE->gearing?->generator->battery%->motor->transmission->wheels.

vs
ICE->transmission->wheels. (regen motor/gen/storage optional)

[pete c]

Originally Posted by dcb

And the series/parallel issue is kinda silly too, it should be apparent that there will always be modes of operation where parallel is simply the most efficient way to get the power to the ground, so it should always be a part of the driveline layout. With the right technique (and sufficient gear selections), the advantages of series goes away and then some, but the driver cannot ever fully compensate for having an extra lossy transmission of power i.e. ICE->gearing?->generator->battery%->motor->transmission->wheels.

vs
ICE->transmission->wheels. (regen motor/gen/storage optional)

Always is a big word. It rarely applies.

A vehicle that will see considerable run time on the ICE certainly should have direct drive. Ken has opted to go with the KISS approach, which I happen to be a big fan of. Too many engineers muck things up by wandering away from it.

[sendler]

Better to make some wise compromises in order to get the project on the road than to constantly try to cater to everyone's wishes to get the perfect design that never gets built. RIP Aptera.