Serial Hybrid vs. Parallel Hybrid

[Derwin]

I need some help from you guys. I am unclear on what the difference between a Serial Hybrid and a Parallel Hybrid is exactly, and thought it would be a good idea to open up a new discussion about this. Especially since it seems Venture Vehicles is now going in the direction of the Parallel Hybrid.

So, for all those that want to explain this to me, and then to enter into a discussion about this, please post to this thread. Thanks for your help!

Derwin

[Baja_Traveler]

For that you have to go no further than Wiki -

http://en.wikipedia.org/wiki/Types_of_hybrid_vehicle

[Derwin]

Well, I appreciate the effort, Baja, but I was trying to strike up a conversation about this subject. pop:c:r:n12 Thanks anyway!

Derwin

[ziggy951]

Parallel is when either the Ice or the electric motor give power directly to the wheels. Series is when the Ice, or some sort of generator/genset etc, run off of a fuel and supply electricity to the battery which then powers the motors running the wheels.

Series:

Ice/Genset/Generator---->Battery/UltraCap---->Motor---->Wheels


Parallel:

Ice---->Battery---->Motor---->Wheels
Ice---->Transmission---->Wheels




With a Parallel system you always use the Ice to power the motive system. This is very inefficient as you are always using a 4 cylinder(usually), large, vehicle engine that MUST provide enough hp to actually power the car. That is why they are trying to come up with large capacity batteries so that you can plug in to recharge rather than use the Ice. Without these large batteries you wont have the 30 miles or so of not using gasoline. This is the reason I want a series system that removes the standard Ice altogether. That way the vehicle can use a smaller engine that is far more efficient to produce electricity for the system.

Someone gave me the following analogy:

A series system turns a 2.4liter Ice into a lawnmower engine and gives the vehicle just as much hp and tq.



I hope that helps, and that I got it all right. Some good visuals can be found here http://en.wikipedia.org/wiki/Types_of_hybrid_vehicle




Z

[Derwin]

Baja, That was a very good link about the differences. I love the diagrams also...... Makes it a little easier to visualize!

So, to be clear, your saying that the serial hybrid will get better gas mileage? Is that the big difference here, other than the parallel will obviously be holding a larger engine?

Derwin

[ziggy951]

That said, the series system really does allow for more variation in the type of power plant you have under the hood. Basically you need to convert the hp of the engine you use to kw. Easy to use calculator here: http://www.calculateme.com/

If the conversion gives the output you need for the electric vehicle then you have a winner. For instance, to rebute the analogy I used above, a 5hp lawnmower engine would produce appx 3.7kw. Thats not really enough for "most" people to get around in. Plus it wouldnt be very efficient because, well, lawnmowers just arent effecient.

There has been some discussion about a small rotary engine, I think some specifics have been brought up about a single rotor mazda engine. If a point could be reached on this engine that burnt all of the fuel then this would be phenominal. Unfortunatly, from what I have experienced with the mazda rotary, this just isnt possible because of the design of the engine. I think a new design would need happen but it is a bit beyond me.

I am hoping Honda will develop a highly effecient small engine(2 cylinders, or even rotary) that is designed with series systems in mind.


I have some knowledge but no solutions, for what its worth.



Z

[ziggy951]

Baja, That was a very good link about the differences. I love the diagrams also...... Makes it a little easier to visualize!

So, to be clear, your saying that the serial hybrid will get better gas mileage? Is that the big difference here, other than the parallel will obviously be holding a larger engine?

Derwin


The serial should get considerably better gas mileage because of many reasons: weight savings, smaller engine, higher efficiency engine(hopefully), and larger area for a plugin battery.



Z

[Baja_Traveler]

Guess I'm not the only one who misunderstood the phrasing of your post Derwin! - sorry to dump cold water on the thread there...

For me - a full hybrid is the only way to go, I want to be able to run on one or the other power system and not have one dependent on the other. If I want to bop over to the archery range I should be able to do it without firing up an ICE to get me there and back. Since I want this vehicle for more than it's sporting appeal, having to start an engine just to get out of the driveway to me is completely unacceptable.

[Derwin]

Well, since we see that the serial hybrid is incredibly superior, why do you suppose Venture Vehicles has decided to go the parallel route?

Derwin

[danbucks]

A serial hybrid isn't incredibly superior - it is superior, however. With a reverse planetary gearing system (aka Prius) in a II hybrid, any power source (battery, ICE, etc) can contribute whatever it can to the wheels, independent of the others (roughly).
It's actually fairly efficient (not incredibly weak).

However, it begs the question why one would?
Isn't simpler better? (i.e. no hybrid whatsoever: a single power source)
The answer must be:
a II system must be compensating for something.
In cars like the Prius, it's distance and power (from the batteries). To retain life, I believe the Prius does not let the batteries go below 80% : a total a waste of E storage, in my book (you have 20% the distance you should have).

[RAN]

Well, since we see that the serial hybrid is incredibly superior, why do you suppose Venture Vehicles has decided to go the parallel route?

Mainly because it requires many more expensive batteries to give you that 40 mile or so EV-only range.

[westonlgray]

Actually, the new Prius programs keep the batteries between 20 and 80% to extend the life of the battery. Since you have to really, really baby a Prius to avoid starting the ICE, I don't think this hurts their efficiency too much.

I really do like Honda's parallel system though because it always turns the ICE (therefore keeping it lubricated), but it also appears that it can propel the car using only the electric motor. They close off the valves to minimize the losses while using electric only, but at the same time, you minimize the cold starts of the engine which should increase life significantly. This might be a really good bridge for the next few years until the batteries improve/decrease in cost.

However, for small vehicles like Dagne, V1, they don't need as much battery as a full size car, so they should be able to go serial hybrid now.

[ziggy951]

However, for small vehicles like Dagne, V1, they don't need as much battery as a full size car, so they should be able to go serial hybrid now.


Or have a seriously kickass electric range(size limited obviously)2thumb:up


Z

[Timon]

With a series hybrid you can tune the ICE for optimal efficiency and minimal pollutants than you can if the ICE has to run over a wide range and thus can't be tuned.

From a mechanical point of view a series hybrid is much simpler with fewer moving parts. The electronics are simpler as you only have to worry about keeping the battery charged and not syncing the ICE with the electric drive.

The new Volt is a series hybrid and you can bet they designed it that way for a reason. It allows them to use virtually any power source. You can run as a plug-in hybrid with a ICE backup, as a fuel cell drive or anything else you can come up with.

I for one hopes that VV drops the parallel hybrid idea really quick.

[danbucks]

Does this mean the end of PHEV for VV?
Although a single RPM, single load ICE is more efficient (which, btw, is not precluded in a II system), I think everyone's major disappointment in a II system is the worry/expectation that fuel is a necessary evil ... at any commuting range.
Things just aren't as exciting if I can get 75 MPG on my motorcycle ... only to get the same or less in a V1, at any distance.

[MikeB]

Does this mean the end of PHEV for VV?

As far as I know, yea. Every parallel hybrid on the road either can't move without the engine starting, or can only get a fraction of it's full speed. Getting a real plug-in requires that the electric motors can fully propel the vehicle without assistance from the ICE. So either you have a parallel hybrid with some serious redundancy, or a much more optimal serial hybrid.

Of course, the decision to go with a parallel hybrid for the V1 isn't final, Steve just said they were going to explore it. I'm hoping they'll quickly see the drawbacks of that path, and go back to the original plan.

Oh, and one more important point: If they give up on making a PHEV, they also give up on any chance of a PHEV tax credit to offset some of the purchase price. Both presidential candidates have plans for a significant PHEV tax credit in the $5-$7k range, which would significantly change the affordability question of the V1.

[danbucks]

I can see why a II hybrid usually won't have a plug-in (read: small battery pack - why bother charging?), but I don't think I follow why electric motor size has anything to do with plug-in. Presumably your car is *not moving* when plugged in :) , and has a direct (well, through a separate small-scale AC/DC converter) connect from wall to batteries - the rest of the system : ICE/Motors/etc. are offline.

[RAN]

Because, Dan, the whole reason to have a plug-in hybrid is to be able to have a given range that the vehicle can travel on electricity only; if you can stay in that range, you essentially have an EV for your daily driving. For this to happen, the electric motor has to be able to power the car at speeds you're going to need, and the batteries have to be big enough to provide some kind of usable range.

Schlepping along at 20-30 MPH for 5-10 miles isn't worth having a plug.

[danbucks]

I get that (as noted). But technically there's no connection with the motor. I think we're saying the same thing (that it makes no sense for many cases in the ll case) : I just meant technically there's no barrier/tie with the motor. ... and I can think of some "unlikely" ll designs where it might still make sense (just unlikely)

[RAN]

Right. The size of the motor has nothing to do with actually being able to charge the batteries by plug-in.

[Baja_Traveler]

BUT - the size of the motor directly affects how big that battery pack has to be to feed it.

[danbucks]

Here's the rub: the V1 always had a battery pack issue ... at least (if I recall), way back when I was a young'n, the EV only drive distance was quoted on their site at 40 mi ... then it was 20 ... then it was 10 ... at which point, parallel or series system (it is irrelevant), you're hosed: who wants to plug in and charge for a measley 10 mi? (complaints were rampant on ftr)

I am curious if the ll system they are "considering" has any EV only range at all...

[D'Hag]

I have always been surprised that any manufacturer came up with the parallel hybrid idea at all. Always seemed stupid to me.

I remember an article in Popular Mechanics magazine back in the mid-1970's. They actually built a car that was powered by a 5-horse Briggs & Stratton generator, powering a brushless jet engine starter motor. NO battery packs, except for a battery to start up the generator. The fully-enclosed 2-seater (looked like an ugly Renault) would run 75 mph and delivered 150 mpg.

I guess its main problem was, it was too simple.

It was built in response to the Arab Oil Embargo of that time. Too bad we got over it back then. We'd be a lot farther along than we are now.

What manufacturers need to consider nowadays is the old KISS principle, and just get these things built!

[ziggy951]

Hmm. I wonder if could find an adequate generator to move my car. Preferably from 0-60 in 4-6 seconds.



Z

[RAN]

I remember an article in Popular Mechanics magazine back in the mid-1970's. They actually built a car that was powered by a 5-horse Briggs & Stratton generator, powering a brushless jet engine starter motor. NO battery packs, except for a battery to start up the generator. The fully-enclosed 2-seater (looked like an ugly Renault) would run 75 mph and delivered 150 mpg.

I guess its main problem was, it was too simple.

It was built in response to the Arab Oil Embargo of that time. Too bad we got over it back then. We'd be a lot farther along than we are now.

What manufacturers need to consider nowadays is the old KISS principle, and just get these things built!

I would love to read that article. While all these super high-tech prototypes we're talking about now will be great someday, it would be nice to be able to get 150mpg today.

[D'Hag]

I would love to read that article. While all these super high-tech prototypes we're talking about now will be great someday, it would be nice to be able to get 150mpg today.
I've been searching for it. Trouble is, magazine articles from back then aren't on the 'Net. Searching public libraries isn't quite like Google.

[Mark Tomlinson]

... Especially since it seems Venture Vehicles is now going in the direction of the Parallel Hybrid. ... Maybe a little late in the thread to post this, but please reread SEP's comments. He specifically said they are testing many alternatives and will chose a drive train based on some unqualified "optimum" criteria - although he did specifically call out performance.

The long and short of it is that Venture is not "going in the direction of the Parallel Hybrid". That's just the configuration they are testing at the time of the post. He even mentioned a full electric drive train, which should make some of our members smile.

[Derwin]

The long and short of it is that Venture is not "going in the direction of the Parallel Hybrid". That's just the configuration they are testing at the time of the post. He even mentioned a full electric drive train, which should make some of our members smile.


Well, if that's the case, then that's great! But, as many have noted, testing that configuration would SEEM to imply that they are indeed going in that direction. But I guess we will know for sure in time.

Derwin