Electric cars, unclean at any speed

[rmay635703]

Originally Posted by P-hack

compared to a tdi that is %95 efficient (assuming some effort in driveline optimization) at driving the wheels under optimum conditions.

Now if you want to use "peak bsfc" as your argument, we are assuming peak bsfc in both "pusher" and "generator" here.

But if the tdi direct drive has to "compete" with the generator, the "at the wheels" bsfc for the tdi is like 206 gm/kwh. Whereas the same efficient engine running a generator is like 301 gm/kwh.

Find me a 220cc motor with the same BSFC range as the TDI you quote

[P-hack]

Need to see someones work backing up their belief that series is more efficient, regardless of the starting bsfc. Otherwise it is just a religion.

[rmay635703]

Originally Posted by P-hack

Need to see someones work backing up their belief that series is more efficient, regardless of the starting bsfc. Otherwise it is just a religion.

There are practical reasons why one would do series, it has nothing to do with religion (or efficiency).

Understand I don't really support a series F150 from a fuel economy standpoint.

In my case I use series because
1. I have a generator and a means of coupling to my production EV with cheap/free off the shelf items that I already have.
2. My kei van does not have a reasonable method of attaching a motor to a wheel.

So basically in my case its a practical reason,
AKA Mechanically I am capable of attaching a trailer hitch mounted pad and generator. (any idiot can do that but building and controlling an efficient pusher I could not, nor would I be able to have it ready in any reasonable period of time even if I could)
AKA electrically I am capable of attaching the generator to the ev which has the DC taps in the ass end where the generator sits.

I have not yet figured out fuel economy beyond the rated amounts of fuel the genset uses to produce the current required to run the dead man "charger". Which is hypothetical.

In my case doing this allows a handfull of trips to be run 30+ miles on EV and 5-12 miles on gasser above and beyond that amount.

Thus far doing it the last 3 months we haven't even used a tankfull on the genset. (1.3 gallons)

By using the genset it allows my father to use the EV as opposed to the Dodge Ram Crewcab (11mpg if driven by him) or the suburban (not much better) for the full distance.

So in my particular circumstance, even if I am only getting say 22mpg on the EV portion of an occasional trip it is still far superior to running the dodge at all or suburban for that matter. (hypothetical is around 27mpg strictly by the steady state number, I assume 25mpg to make up for accel)

Most of my fathers miles are EV but by using the genset it enables him to use the EV instead of something far worse on the odd trips to seem to go past his tired battery packs range.

[IamIan]

Originally Posted by P-hack

here is a modern tdi:


1. motors are not always at peak efficiency.
A. generally not efficient at slow speed, starting at about 0% efficient at very low rpm.

Finally... he sees the light


The Pusher ICE starts at 0% efficiency ... just as you write here ... while the same minimum is not the case for the generator.

The generators fuel to electrical conversion efficiency is independent of vehicle speed ... be it x% at 0 MPH ... or the same x% at 50 MPH ... or the same x% at 100 MPH... same is NOT true for the ICE pusher via transmission to the wheels ... just as you write here ... The ICE starts at 0%.

Originally Posted by P-hack

B. efficiency is still largely load dependent. Peaking around 90-95%

ie = Depends on the situation
He's seen the light.

Originally Posted by P-hack

2. Controllers are not %100 efficient, say %90 (large heat sinks)

Why are you using antiquated low efficiency controllers?

How about without even using (state of the art) ... but still several years old ~99.2% link

Originally Posted by P-hack

3. The generator has losses going from mechanical to electrical, like %80 efficient.

Why are you intentionally stacking the deck by using antiquated low efficiency motor to go with the antiquated low efficiency controller?

How about without even using (state of the art) ... but still several years old ... ~98% efficient Link

Originally Posted by P-hack

These are just swags, but let me total them up for this example so we have at least a starting point. Lets say demand is optimal.

.95 * .90 * .80 * .95 = 0.65 efficient in steady state mode with optimum load.

Your math is wrong.

The 95% was for load ... or Transmission efficiency ... not ICE efficiency... ie there should only be one .95 in the above equation.

The posted BSFC has a peak efficiency of 196 g/kwh which is about ~39% efficient from fuel to drive shaft.

Correcting that but still using your antiquated low efficiency devices you get:
.39 ICE(Fuel to Mechanical) * .8 Motor (Mechanical to Electrical) * .9 (Controller) * .8 Motor (Electrical to Mechanical) *.95 Transmission = ~21% Efficient.. still better than the ICE start at 0% you pointed out above.

Using better devices ... that are still several years old ... and no where near as good as State of the Art ... we get:

.39 * .98 * .992 * .98 * .95 = ~35% efficient ... with still using the 95% efficient transmission ... a direct drive BEV would get a peak of ~37% Efficient from that same ICE.

What do you know ... results depend on situation.

Originally Posted by P-hack

compared to a tdi that is %95 efficient (assuming some effort in driveline optimization) at driving the wheels under optimum conditions.

It's NEVER 95% efficient ... the BSFC peaks at ~39%.
.39 * .95 = ~37% peak

like I wrote before ~37% peak is a higher peak than the generators ~35% peak... we'll ignore for the moment the ~37% direct drive BEV peak.

Originally Posted by P-hack

But if the tdi direct drive has to "compete" with the generator, the "at the wheels" bsfc for the tdi is like 206 gm/kwh. Whereas the same efficient engine running a generator is like 301 gm/kwh.

Remembering that the Generator can get it's ~35% efficient at ANY vehicle speed ... but the same is not equally true for the Pusher ... with the finite limits of it's transmission.

At any vehicle speed the Generator can still get the ~35% efficiency.

But the finite transmission on the pusher means it can't do the same ... it's efficiency will vary with the torque and RPM of the wheel ... down to a minimum of 0% Efficiency as you posted at the top.

Even if we gave the ICE Pusher a bit of help by avoiding those 0% points ... and instead just looked at it's worst BSFC points ... which on that BSFC is ~270g/kwh which would be ~28%
.28*.95 = ~26% efficiency.

Which is what I wrote before ... the ICE Pusher will have a lower minimum efficiency under various vehicle travel conditions.

Originally Posted by P-hack

So lets play the load the battery for peak bsfc game now, but first note that pretty much any operating condition above 3 bar will be to the advantage of the direct drive in this graph already.

Nope ... not until it gets past ~35% ... which is about ~220g/kwh ... which this posted BSFC has areas worse than that as high as 15 bar at low RPM ... and doesn't even start to get above that until around ~7 bar at any RPM.

Originally Posted by P-hack

5. lithium batteries are 80%-90% in charge/discharge efficient under optimal conditions.

Incorrect.
under optimal conditions they are above 95%... round trip.
See page 21
pdf Link

Originally Posted by P-hack

6. Say you have a %90 efficient charger and bms, which is also dependent on state of charge and current.

See above ~99.2% efficient controller that includes regen to charge the batteries.

And there are some people who don't use a BMS ... but even if you did ... it consumes only tiny tiny tiny % of the total net power and energy... not even 0.1%.

Originally Posted by P-hack

So aside from the fact that you can't ever touch most of the bsfc graph with a generator in front of this tdi driving the wheels, you are looking at a generator efficiency of
.65 * .90 *.90 = 53% efficient when loading the generator for bsfc (assuming all the electrical are in a fairly optimal operating range). That is a wheel bsfc of 369, below the very bottom line on the bsfc chart.

See above for corrections ... of other situations.

Originally Posted by P-hack

Now you may take issue with the specific numbers here, but the point is clear, there are a lot of losses in the series proposal.

There can be ... that is one situation... that you are focused on... with numbers you pulled from thin air ( no references ).

What you seem to keep trying to avoid ... is that there are other situations that can result in smaller hits to the generator ... and larger hits to the ICE Pusher.

Depending on the situation ... see above ... with references ... the pusher can be bellow 27% efficient when vehicle speed and travel conditions force force the ICE into less efficient points on the BSFC ... due to finite limits of the transmission ... while the generator could sustain above 35% at any vehicle speed and travel conditions ... because it is not connected to the road... and wheel RPM and torque don't effect the generator ... but do effect the ICE pusher.

Originally Posted by P-hack

I have heard speculation about higher peak BSFC with rpm targeting but I have never seen any actual data, nor do I know that a cvt wouldn't still be more efficient than an "electronic torque converter" in maintaining target rpm.

See above.

As for the cvt ... same things apply ... it has it's limits ... and can not keep the ICE at peak efficiency under any wheel RPM and torque.

Under some situations the cvt will do better ... and in other situations the cvt will do worse than a manual transmission.

Originally Posted by P-hack

Sending all your ICE power through a generator to drive your EV wheels certainly seems like an inefficient solution all around, and requires %54 more engine in steady state for the same power at the wheels in this example.

See above.

- - - - - - - -

A bit of an extreme example ... but might be a useful thought exercise:

Think about why freight trains and cargo ships ... have pretty much all stopped using mechanical transmissions ... and instead pretty much all use ... a combustion generator to provide electrical power to an electrical motor that actually moves the train wheels or the ship propeller ... is it a giant conspiracy? ... do they love to waste energy and fuel on less efficient options? ... I don't think it is either of those ... I think in their different situation the pros and cons clearly leaned against the mechanical transmission and very much in favor of the generator / electrical combination instead.

Originally Posted by P-hack

Need to see someones work backing up their belief that series is more efficient, regardless of the starting bsfc. Otherwise it is just a religion.

See above... for some example situations ... do NOT try to make this a black and white always A or always B ... as I have been pointing out over and over again ... that is NOT how it works ... who wins ... depends on the situation.

[P-hack]

I stopped reading after looking at how load/rpm dependant that controller is, and seeing it as "predicted" instead of measured, and seeing you quote 99% efficiency, please put your "ideal" system together, and then we can compare it to an ideal pusher with an ideal driver. I am not convinced you see the light yet. You are saying there are ALWAYS scenarios where series will be more efficient, time to back it up. And no assuming that the driver is stupid, they can coast and accelerate efficiently and use the terrain, I am not designing a pusher for the average idiot..

[Frank Lee]

Originally Posted by jamesqf

4WD with two of the wheels aft of a flexible coupling, so what is that going to do on a slippery surface where there's little friction to resist sideways forces? Can you spell "jackknife"?

If you have to traverse icy mountain slopes with some regularity this may not be the best option.

On the other hand, I don't think making a stable pusher in those conditions is technically unfeasible.

[Frank Lee]

Originally Posted by rmay635703

Find me a 220cc motor with the same BSFC range as the TDI you quote

That 95% is only for the driveline, not BSFC. Find me a gen set that is 95% efficient...

Some of these posts are so long my A.D.D. is kicking in.

If you look at the path of power the explosion of fuel in the cylinder takes to get the torque to the road to make the whole mess move, direct mechanical drive gets the win.

You only get to attach all these conditions to the pros and cons of how to get there.

A serial genset is the most "plug-n-play" but it isn't the most efficient. As rmay points out, if it keeps a guy outta a Ram, it is more efficient. But if it keeps a guy outta an EV capable of all the range needed, or an EV with a proper parallel ICE, or even just a very efficient ICE vehicle, it is less efficient. That was the bone I had to pick with the otherwise excellent Zing trike.

How frequently is this auxilliary power unit going to be called upon? How much capability i.e. range and performance does the APU need? Does it have to be readily available at all times or is one allowed to go home from wherever and get the APU? How user friendly or idiot proof does the APU have to be? This is exactly what the hybrid engineers especially the Volt guys have had to wrestle with.

[IamIan]

Originally Posted by P-hack

I stopped reading after looking at how load/rpm dependant that controller is, and seeing it as "predicted" instead of measured, and seeing you quote 99% efficiency, please put your "ideal" system together, and then we can compare it to an ideal pusher with an ideal driver. I am not convinced you see the light yet. You are saying there are ALWAYS scenarios where series will be more efficient, time to back it up. And no assuming that the driver is stupid, they can coast and accelerate efficiently and use the terrain, I am not designing a pusher for the average idiot..

You pulled numbers out of thin air ... with ZERO references.
Then you knock the numbers I give with references?


There is no one single IDEAL for all situations ... there is no ALWAYS for all situations.

You will get different results from different situations... which is what I have been consistently writing ... over and over again.

One situation is a smart driver ... another situation is a stupid driver ... ready for it ... different situations give different results.

And smart driver or stupid driver are possible situations for either system.

But sure ... I'll even give another situation to you ... how about a mass produced motor controller with 10+ year old technology in it.

Attached ... The 2004 Prius motor controller... testing done by DOE in 2006.. oh look It still has over 99% peak efficiency.... the previous situation with ~35% peak efficiency is a possible situation ... as is the situation where there are conditions where the referenced engine will only be at ~28% efficiency.... previous still stands.

There is no always A>B ... some situations A>B ... other situations B>A.

Sometimes the pusher is better ... sometimes the generator is better ... it depends on the situation.

[Frank Lee]

Now we are talking about controller efficiencies?

If I had an EV that I wanted to use past it's EV capabilities I would hands down, no question go parallel and put that ICE power to the wheels. It has to do with:
1) the intended usage patterns and
2) it has to do with efficiency.

If I am doing anything within city limits or up to about 10 to 20 miles out from home, I'd want my EV to handle all that unassisted, and equip it so. And in fact my EV does (the Songi bike).

However when I finally venture out of my little world, I REALLY venture out and my trips are commonly 60 to 600 miles one way out of town. On such trips I'm not willing to sit around and recharge either the original battery pack or an auxilliary pack (so that makes an auxilliary battery trailer, which would be an excellent solution for the <60 mile trips out, a moot point); I go pretty much straight through and that demands ICE power in some form.

If I'm going 600 miles I don't want to use a genset in a serial fashion; fe is guaranteed TO SUCK. Then I would be better off abandoning the whole EV concept (not dragging a heavy, costly, mostly disabled EV drivetrain and battery pack around for 1200 miles) and stick with an efficient ICE.

And that's pretty much it, for me.

Others who only ask for a wee bit of extra range, and only occasionally, have other choices: they could add a genset serially, or they could throw some more/better batteries on and stay true EV... or they could put ICE power to the ground too, as fooling around with all this Rube Goldburg equipment is ALL ABOUT THE EFFICIENCY... right?

YMMV.

[redpoint5]

Originally Posted by Frank Lee

If I'm going 600 miles I don't want to use a genset in a serial fashion; fe is guaranteed TO SUCK. Then I would be better off abandoning the whole EV concept (not dragging a heavy, costly, mostly disabled EV drivetrain and battery pack around for 1200 miles) and stick with an efficient ICE.

Agreed. 600 mile trip; I'm going to hop into my conventional gasoline powered car, which, according to the OP, might be more environmentally clean than an EV. In short, use the correct tool for the job.