Why are all auto companies either selling or planning parallel hybrids rather than series hybrids? GM & other U.S. Big Auto companies latest fool idea is the dual mode, parallel hybrid with an electric motor for low speed & and an electric motor for high speed plus an electric clutch connecting them. Sounds way complicated to me. Furthermore, why don’t they make parallel hybrids that are plug-in, is spite of the obvious advantage and great demand for this capability?

For those who don’t know, a parallel hybrid relies on both a gas motor & an electric motor for propulsion, the motor supplies extra torque for acceleration & captures some of the braking energy back to a small battery pack. Whereas a series hybrid is an electric vehicle with a gas or diesel generator to charge the battery pack.

Consider:

The series hybrid can be charged off of the power grid, for convenience & much cheaper operation (< 20% of the cost of running on gas) with no loss of performance (except range), otherwise use the onboard generator, The parallel hybrid may be able to run off the power grid if you expand the battery pack, but with reduced performance.

The series hybrid is much simpler in design & maintenance than the parallel hybrid. It does not need a clutch or transmission, no oil changes, spark plugs, fuel/oil filters except on the separate generator which can be removed or replaced easily. It does not need the complex control / interface between the gas engine & electric motor.

The series hybrid has better acceleration due to the superiority of the much larger electric motor to the gas motor in this respect.

A series hybrid recovers almost all the energy from braking, the parallel only a much smaller portion of the energy. The electric motor in a series hybrid supplies acceleration energy & recovers braking energy efficiently at all operating speeds. An Electric Motor delivers to the battery / supercapacitor about the same current braking 60-0 in 8 secs, as it takes accelerating 0-60 in 8 secs, therefore a robust fully powered electric vehicle is necessary to recover the energy lost in deceleration, that is a fully electric drive. The partial electric drive in a parallel hybrid just won't do it. Because of this and no transmission / clutch etc. it is much more efficient than the parallel hybrid.

The generator engine on the series hybrid can be much smaller, simpler and more efficient than on the parallel hybrid. It only needs to run at optimal charging speeds, does not need good torque or acceleration performance. It only needs to be large enough to supply average energy that the vehicle uses or even less if the vehicle is parked part of the time.

The generator module on the series hybrid can be easily be standardized for all electric vehicles, and mass produced as an interchangeable auto component. It could easily be replaced, exchanged or upgraded depending on requirements or the available technology. For instance, it could be a high efficiency diesel, a >50% efficiency Brayton cycle external combustion engine, a LNG fueled gas turbine, or a Fuel Cell. Check out:

www.starrotor.com/Engine.htm

The series hybrid can readily be made a true all wheel drive vehicle, without the complexity of multiple drive shafts / differentials, by using wheel hub electric motors. Added benefit of zero turning radius by running wheels on one side backwards to wheels on the other side. If a motor fails, the other motors will still run the vehicle. Also the wheel motors run >90% efficient, with NO DRIVETRAIN LOSSES, which amount to 30% to 50% of the I.C. Engine shaft horsepower in a parallel hybrid or standard ICE powered vehicle. This cannot be done on the parallel hybrid. Check out:

www.e-traction.com/Mechanical_efficiency.htm



The larger battery pack on a series hybrid is needed to store the potential energy lost by going downhill, so it can be used to power the uphill climb. The small battery pack on the parallel hybrid cannot do this, for example, the .3 kwh (utilized) battery on the Prius, is only capable of storing the energy for a small 1% grade hill for 1.5 km, anything more is thrown away, vs the series hybrid with a 4 kwh utilized battery pack, which could store the energy from a steep 12% grade for 2 km. Also the larger battery pack means lower charging currents / per cell, which leads to higher charging efficiency for braking energy recovery.


The series hybrid can be mass produced with all drive components within the chassis of the vehicle, except possibly the add-on generator module. This had long been a dream of Auto Companies. With all the weight of the major components in or below the chassis, the series hybrid is inherently more stable than the typical ICE powered vehicle or parallel hybrid. With no heavyweight engine components in front of the driver, the vehicle can be made much more safe in a collision. This would amount to at least 20% less deaths in auto accidents. Various bodies can be attached to the same frame. This cannot be done with a parallel hybrid. As such, I the series hybrid would be less expensive to make.

The series hybrid can easily be made as one of two models, an all electric with no generator but expanded battery pack or as the hybrid. The generator engine would run typically 15 to 30 hp for a normal vehicle, and weigh around 200 lbs, as would the expanded battery pack. The unused space in the front of the vehicle, normally under the hood, could be made to contain either the battery pack expansion or the generator module. It would be a matter of unplugging two connectors (control cable & power cable) and swapping them according to the owner’s preference. Perhaps, battery pack for maximum all EV range in the city commuting, or the generator module for weekends extended range. A hydraulic lift on wheels, like they sell in hardware stores for $200 would easily allow swapping the modules.

The series hybrid can easily used as an emergency portable power generation system or to supply energy back to the grid for distributed power generation, a great advantage for utilities to supply emergency peak power after transmission line and/or power generating plant failure and/or major natural disaster or terrorist attack and/or extreme heat wave. This is called vehicle to grid or V2G. Check out:

www.acpropulsion.com/Press%20releases/V2G_Demo_release.htm

The only disadvantages of the series hybrid over the parallel that I can see are:
-- that it would require a larger electric motor – big deal, the 248 peak hp motor on the Tesla is 10” by 14”, (the dual mode parallel hybrid, however, requires two electric motors)
-- it needs a generator – even smaller as it only needs to supply average power use and can be a high frequency generator optimized for battery charging
-- a bigger battery pack depending on how long you want it to operate without the generator, and how big a hill you want to be able to climb at what speed – a comparatively minor disadvantage and as pointed out earlier also an advantage
-- the power electronics would be somewhat bigger due to the bigger motor, but the control would be simpler since you don’t need to control the paralleled gas engine, a small additional expense, small increase in size of the module.

The only conclusion I can come to is that Big Auto is deliberately trying to avoid making cars that can be run off of the power grid. Do I see the ugly, dirty hand of Big Oil in this? Note that DARPA, wanting to make the best vehicle possible, having no ulterior motives, chose to build the new HumVee as a series hybrid. check out: www.military.com/soldiertech/0,14632,Soldiertech_Shadow,,00.html

Welcome.

Interesting assertions.

... and controversial too - as you would notice if you do a forum search.

Cheers;

MSantos

Evone,

The main issue is the battery and sufficient 'average' power to go up (or down) a mountain (or just a long hill) at high speed (requiring a large ICE-Generator or fuel cell). A series hybrid is mechanically simpler than a parallel hybrid, but it requires not only a higher capacity battery; the battery must be able to handle high currents without overheating. The battery in present parallel hybrids is treated gingerly to allow them to last 'the life of the car'. There are no available batteries (yet) that can hold up under the strain of being the primary source of energy for a family car at a reasonable price.

Your comment on the 'innefficient' regenerative braking of parallel hybrids is somewhat incorrect as the losses are mostly due to battery charge-discharge losses and some in the generator-motor losses which is identical to those in a series hybrid (or pure EV).

Remember, we have to be able to afford to buy and maintain the vehicle (the Tesla, a two seater, costs how much?). My 2004 Prius cost me $23,000 and has required only minimal maintenance in 67,000 miles.

Please go easy on conspiracy theorys. Big Auto (US) is just run by stupid executives with no vision. Big oil has little to say about what cars get produced and sold; all they can do to prevent efficient vehicles (and alternate fuels) is to keep gasoline prices low and that doesn't seem to be something they can do any longer. DARPA has unlimited funds (our tax money) so don't assume that their solutions suit our needs.

JeffD

Uh, welcome. However, you might have considered posting this in the "Anything goes" or "General" forums. We usually post reviews of other articles here versus starting a discussion of architectures.

Now as to your premise, do you have a quantitative vehicle model that shows advantages of one versus another architecture? Something like this could be put together fairly quickly with an Excel spreadsheet. Just curious.

Bob Wilson

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Actually, the HCH-II (a parallel hybrid) compares very favorable to the Prius (a parallel/series hybrid). There's only a 2-3 MPG difference, and the HCH costs a little less.

GM's 2Mode is also a combination parallel/series hybrid, since the battery pushes the truck unassisted at low speeds but aids the engine at high speeds. The difference in this system is that the EV components go offline when towing heavy things.

If there are any conspiracies going on, it's in the Far Right's anti-hybrid whisper campaigns (aka "you don't make your premium back in gas savings" crap) and the way that gasoline just dropped by a dollar a gallon right before an election in which the Far Right is about to have it's read-end handed to them.

I'd like to see a fully developed series hybrid. Toyota will probably develop one first while GM develops a "special edition" Hummer that runs solely on burned $100 bills.

But to get a series hybrid mainstream one (and only one) thing has to happen: the development of a large, inexpensive, high-density, baton-shaped lithium-ion cell that doesn't explode when charged. Getting the "not exploding" part is a bit of a challenge, as is the "inexpensive" part.

Welcome to the forum, by the way!

“The main issue is the battery and sufficient 'average' power to go up (or down) a mountain (or just a long hill) at high speed (requiring a large ICE-Generator or fuel cell)”



This is incorrect, as I stated a 4 kwh utilized battery is quite sufficient to supply the energy required to go up a steep 12% hill for 2 km, at 100 km/hr, it would be rare to require more energy storage than that, in which case you need only travel at a lower speed (or use a somewhat larger battery). The potential energy a 2000 kg vehicle uses in climbing that height is 1.6 kwh, the rolling / wind resistance required is typically .2 kwh which works out to 1.8 kwh @ 90% motor to wheel power efficiency. This is not a problem, even pure EV’s such as the Tzero have made the trip across the mountains:

“…Interstate 15 to Las Vegas (from Los Angelos) includes two climbs, the Cajon Pass and Baker Grade, both with about 3500 feet of elevation gain. The tzero never faltered and arrived in Las Vegas, 245 miles from AC Propulsion headquarters in San Dimas, with at least 40 miles of reserve range”



“There are no available batteries (yet) that can hold up under the strain of being the primary source of energy for a family car at a reasonable price.”



This is also incorrect. An example:

http://www.everspring.net/product-battery.htm or

http://www.hymotion.com/products.htm

Quote from the PeakOil link, although somewhat outdated technology:

“.. the Ovonic NiMH battery was shown to be capable of allowing battery electric vehicles ranges comparable to gasoline cars with its repeated demonstration of allowing a converted Geo Metro to obtain a highway range in excess of 200 miles per charge in less than ideal conditions [60], and at a total pack cost competitive with an internal combustion engine in high volume [61..”



“…not only a higher capacity battery; the battery must be able to handle high currents without overheating…”

The purpose of the high currents are to capture braking energy, effective battery currents are lower in the series hybrid because of the larger battery, hence high charging efficiency, much greater recovery of braking energy, and lower battery heat generation – all problems quite readily solved in EV’s like the Tesla or Tzero, with virtually no scale economies, and miniscule levels of R&D funding. And of course the larger battery means most energy from downhill travel will be recovered for reuse in uphill travel, not achieved in the parallel hybrid with it’s small battery.



“…we have to be able to afford to buy and maintain the vehicle (the Tesla, a two seater, costs how much…”



At $100G this vehicle outperforms a Ferrari Spider (a similar vehicle style) at $190G, with the equivalent of 130 mpg vs 13 mpg for the Spider, and this with by Detroit Standards, trivial R&D costs, almost no scale economies, and new technology.



“…Please go easy on conspiracy theorys. Big Auto (US) is just run by stupid executives with no vision. Big oil has little to say about what cars get produced and sold…”



Conspiracy theories is a mickey-mouse phrase, usually used by gullible fools, who cannot otherwise justify their naïve view of the world. The real world of politics and business interests is inundated with corporate collusion & price fixing, cartels, political patronage dealers and lobbyists, corruption, vested interests, phony “grassroots” campaigns, phony corporate funded “research”, public disinformation efforts of a multitude of types,… to name a few examples.

Do you believe George “I’d sell my soul for Oil” Bush really invaded Iraq to get at those WMD’s?

If you think there is no corporate efforts on the part of Big Oil & Big Auto and their servants in Washington, explain these quotes from:

http://www.peakoil.com/fortopic8972.html

“…After the Ovonic NiMH battery was shown to be capable of allowing battery electric vehicles ranges comparable to gasoline cars with its repeated demonstration of allowing a converted Geo Metro to obtain a highway range in excess of 200 miles per charge in less than ideal conditions [60], and at a total pack cost competitive with an internal combustion engine in high volume [61], its patent was bought out by Chevron-Texaco, who refuses to mass market the battery at a price affordable to hobbyists and small manufacturers to this day. They are so protective of the patent, that they have sued Toyota for using an allegedly copied version of the battery in its Prius hybrid [62]. There is no reason pertaining to technological limitations why these batteries cannot be placed into conversions by hobbyists and into commercially-manufactured EVs by small businesses for an affordable price. I personally suggest that those reasons are political in nature. To quote Victor Tikhonov of Metric Mind Engineering on the NiMH battery, “Not available for non-technical reasons and may never be to you and to me [63].” The Oilies can be thanked for that….”

“… The big three were caught trying to use the United States Advanced Battery Consortium to keep Stan Ovshinsky from revealing the capabilities of his NiMH battery to the public at a CARB hearing. Ovshinsky remarked, “They tried to stop us from going to California. They threatened us! I said to them, ‘Look, the Communist Party no longer runs the world. A party line cannot be imposed upon people who don’t believe in it. The consortium is set up to make sure the American public has an electric car. It was not set up to fight the mandate. We are a battery company, and we’re not going to lie to the public [77]!’” Further, battery companies were bound by GM not to reveal to the public the advances in battery electric vehicle technology they had made [78]. Ovshinsky also remarked about the viability of his NiMH battery, “The people who are saying that battery technology isn’t ready are absolutely wrong. It’s part of the party line. It’s self-perpetuating. It’s very sad. You tell a lie big enough and long enough, and people start to believe it. The fact of the matter is volume. That’s the only reason batteries are the cost that they are. [79]” Indeed, as mentioned, in volume, the price for an automotive-sized Ovonic NiMH battery pack was competitive with an internal combustion engine, assuming units for 20,000 cars were produced each year [61]… “



“DARPA has unlimited funds (our tax money) so don't assume that their solutions suit our needs”



The amount of funds DARPA spent on developing the series hybrid HumVee are trivial compared to what GM could muster on such important technology, and trivial compared to what the government funds on the phony “United States Advanced Battery Consortium” and the nutty “the Freedom Car Initiative” / Hydrogen Economy / Fuel Cell boondoggle, not to mention massive subsidies to the “cash strapped” oil industry.

That would be easier than making the not exploding gas tank. Many people are killed every year when their gas tank explodes or catches fire, from such trivial things as driving over a loose manhole cover. Gasoline is a very volatile and extremely flammable liquid (not to mention cancer causing fumes). Presumably the fuel used in a Series Hybrid would be a much less flammable / explosive diesel. The developers of the Tesla don't seem to be worried about that point, and it is a trivial problem compared to the hydrogen fueled vehicle (5,000 to 10,000 psi fuel tank) hydrogen economy crap that is being massively pushed by the pro-oil bush administration, Big Auto, and Big Oil interests.

Your statement is undoubtably based on the recent Li-Ion battery pack fires in Laptops. It is invalid to blindly extend this to automotive type batteries, which are a totally different application. Laptop batteries, are made as cheap as possible - probably the designers have less than a $25 budget per battery - protection systems would add weight and cost to a very limited size / cost system. It is easy to prevent these internal short circuits, (which occur in something like .00001% of batteries produced) with internal fusing or thermistor monitoring, not a difficult problem when you have a dedicated energy storage system, as you would have in a vehicle battery pack.

Also, this so-called series-parallel hybrid vehicle is really a parallel hybrid vehicle, and quite a different concept than I am talking about, which is a pure electric vehicle with generator option, such as found on:
http://www.fevehicle.com/services.html

Another great bonus of the series hybrid is that it also neatly avoids all patent problems with HSD, IMA etc. Any manufacturer can build one.

So why still bother with parallel? Because the battery can be very small (cheap) for a reasonable FE increase.

Don't worry though, the PHEVs are coming, the next Prius is set to be a 9-mile EV range plug-in.

http://mysite.wanadoo-members.co.uk/ecotech/ecot.htm

I don't buy this argument. The modest cost of an increased battery pack would certainly be less than the cost of the complex drivetrain, the much, larger less efficient engine. A 4 kwh utilized Li-Ion battery pack in low volume would be about $640 extra, not a large amount. Total package cost would probably be comparable, until scale economies kick in, which would bring the cost of the serial hybrid below that of the parallel, with much better performance. For the presumed customer, green friendly or fuel cost conscious, the much better mileage with also easy and far superior plug-in option (and way less expensive to run off of utility power) would make it an extremely attractive option. Oh, and I forgot to mention the much better life expectancy, much lower maintanence, and much simpler repair / upgradeability.

I would be more inclined to believe that Toyota's secret settlement with Chevron / Ovonics, on the NiMH battery lawsuit precluded using the plug-in option with their batteries. Why does the Prius' sold in North American not have the EV button on them, which the Asian & European models do have?
As for Toyota's supposed plug-in vehicle for sale in North America - seeing is believing and a 9 mile EV range is a sick joke.

Very good point, I will include it in the original post.