Electric cars, unclean at any speed

[P-hack]

It doesn't have to be a converted car, and it doesn't have to be a complicated driveline (situation dependent).

If you have a mostly flat trip and constant speed, just rig up a small diesel (yanmar style) and a sprag clutch and chain/sprocket it to a wheel to run it at peak bsfc at the hiway speed. The control is basically throttle, the engine can stop instead of idle, and start when power is requested with minor circuitry (golfcart style). Need an educated guess at optimal engine size.

If you need extra range at other speeds and want to be efficient about it then you need a gearbox/clutch.

The inefficiency of the generator problem does not disappear. Though there may be some warranty concerns with bypassing the plug.

[NeilBlanchard]

The losses of the generator are more than offset, I think, by the fact that the engine runs at a single RPM - right at its peak efficiency, all the time. No idling either.

Also, if the engine has to move the vehicle by itself, then it has to be powerful enough to meet the peak torque required; whereas in a genset, the battery can be a buffer, and the engine only has to meet just above the average torque required plus the losses.

Being a smaller engine, it can warm up faster, and the cooling system can be proportionally smaller, the fuel tank can be smaller, and the cooling system will have less areo drag, and it can be closed off when not in use. And a serial/series hybrid avoids the need for any multi-gear transmission or clutches.

Typical plug to wheel losses are about 15%, by the way.

[P-hack]

Originally Posted by NeilBlanchard

The losses of the generator are more than offset, I think, by the fact that the engine runs at a single RPM - right at its peak efficiency, all the time. No idling either

Do the math and show your work. What about when the battery is full? A good driver will keep it close to peak bsfc also.

[NeilBlanchard]

When the battery is full, the genset is shut off completely.

With a multi-gear transmission, a engine while it is accelerating the vehicle is *by definition* almost never at peak efficiency. With proper gearing, it can achieve maximum efficiency on flat ground with no wind. Add an up hill and or a head wind, and the engine is forced off-peak. How much off peak? These are large factors not in the control of the driver.

Electric motors have a very flat efficiency curve that is 2-3X higher than an internal combustion engine. The recent serial hybrid *airplane* claims a 25% improvement in fuel mileage.

World?s First Aircraft With Serial Hybrid Electric Drive - Siemens Global Website

Why are we discussing the merits and challenges of various hybrids on this thread? We already have a thread on parallel hybrids:

http://ecomodder.com/forum/showthrea...ids-15069.html

And we have threads on serial hybrids:

http://ecomodder.com/forum/showthrea...ids-13213.html

http://ecomodder.com/forum/showthrea...ker-14852.html

http://ecomodder.com/forum/showthrea...ike-19843.html

[P-hack]

"the vehicle is *by definition* almost never at peak efficiency. " that is not how good drivers use them, and series takes away the best tools of efficient driving, assuming everyone is an incompetent boob. You have not looked at the system as a whole either.

[P-hack]

Define the scenario, pick your components, make series promotion a science and not a religion.

[P-hack]

Originally Posted by NeilBlanchard

...The recent serial hybrid *airplane* claims a 25% improvement in fuel mileage.

World?s First Aircraft With Serial Hybrid Electric Drive - Siemens Global Website...

Just read that,
" In the future, the technology, which is intended for later use also in large-scale aircraft, will cut fuel consumption and emissions by 25 percent, compared to today's most efficient aircraft drives"

and with a wankel?!?

I read it on the internet, it must be right. Because carrying two 35kw engines and feathering one in cruise is beyond comprehension (too guaranteed to work actually).

[NachtRitter]

Originally Posted by RedDevil

So we're ditching the genset option because the Leaf's max charge rate is not high enough?
It does not have to charge the battery, right? It just can feed the EV's engine directly.

We accept that converting a car to an ICE pusher trailer with all the controls is feasible.
Circumventing the max 'charge' limitation to match the power used under load should not be harder that that imho. With twice the power generated the problem disappears.
Then the range is limited only by the generator's tank size.

OK, let's assume that. Recall that the Leaf in my example consumes 16 - 21kWH at 65mph (without a trailer). Granted, that's taking into account the losses from charger to battery and back out from battery through controller to motor... so there would be fewer losses going direct to controller and then to motor, but as has been said the whole path is pretty efficient already so we're not saving all that much, right? And again, we haven't accounted for the additional drag of the trailer, so using "best case" numbers wouldn't pass the snicker test.

Assuming a 21kW genset (where the 21kW is peak and continuous is 20kW, such as this one: Mobile Isuzu 21 kW Diesel Generator (Note that this one is already on a trailer, and weight is already at 1875lbs)), consumption is 1.8gph. Does that beat the theoretical pusher's "worst" of 1.2gph? Nope.

The problem is that the ~21kWH consumption is steady-state flat cruise consuming the 0.33kWH/mile... That's not real world... In the real world, a driver has to accelerate, slow down, climb grades, descend grades, etc... if your going to depend on the genset to drive the motors directly, then it has to be sized to handle the peak power draw of the worst case portion of the trip. For that kind of worst case, the 21kW genset isn't gonna cut it, and a bigger generator is gonna consume more fuel.

Granted, it might be possible to have the controller pull from the battery pack when the motor draw exceeds the rating of the genset, though to me that sounds complicated... and the EV's battery isn't getting recharged, so if regen (which is also lossy) from downhills & deceleration can't keep the battery charged, then eventually battery pack will be drained and the "just right-sized" genset won't be able to get the EV going from a stop or get it up a hill anymore. How soon that happens depends entirely on the route.

Bottom line: even if you sized the genset to drive the electric motors directly for steady state 65mph cruise, the fuel consumption is higher than the pusher...

[jamesqf]

Originally Posted by redpoint5

I just don't ever see battery electric vehicles becoming economical/practical for long distance trips.

Humm... Perhaps you'd better let all those Chevy Volt owners know this? 'Cause as far as I can see, the only difference is that you're putting the IC engine & generator on a trailer, instead of inside the car.

[gone-ot]

Originally Posted by jamesqf

Humm... Perhaps you'd better let all those Chevy Volt owners know this? 'Cause as far as I can see, the only difference is that you're putting the IC engine & generator on a trailer, instead of inside the car.

...which provides the opportunity of parking the IC eng & gen trailer while operating the car only in the city where trips are short duration.