Toyota Prius Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
105 Posts
Discussion Starter #1
I've seen some people (especially magazines) confusing these terms. For example, calling Prius "parallel" and Civic "series" hybrid. Or vice-versa.


PARALLEL = Car can be pushed by both engine and/or motor. The power flows along a parallel path. Example: Prius & Civic

SERIES = The car is pushed *solely* by the electric motor. The gasoline engine recharges it, so the power path is connected in series. Example: EV1 w/ gasoline generator trailer.
 

·
Registered
Joined
·
12 Posts
The Prius because of its unique power split device has characteristics of both a parallel and a series hybrid. Like a parallel hybrid it can move when powered by the electric motor alone, but the internal combustion engine (ICE) cannot supply power to the drive wheels unless it is also supplying power the generator. The power split devise sends some of the power directly to the drive wheels like a series hybrid, and some of the power to the generator which intern sends power to the electric motor. This unique configuration allows the ICE to operate like a series hybrid at its highest efficiency independent of vehicle speed and power requirements. Because only a portion of the power from the ICE is sent to the generator, smaller more efficient ICE, generator and motor can be used than in a pure series hybrid.
There is a good description of the Prius on howstuffworks.com
http://auto.howstuffworks.com/hybrid-car16.htm
 

·
Registered
Joined
·
466 Posts
Spencer said:
Like a parallel hybrid it can move when powered by the electric motor alone
A parallel hybrid does not move by the electric motor alone.
It always moves by the ICE running parallel with the electric motor.
The power split devise sends some of the power directly to the drive wheels like a series hybrid
A series hybrid does not drive wheels directly.

Regards,
[email protected]
 

·
Registered
Joined
·
105 Posts
Discussion Starter #4
Well the term "series" comes from electrical circuits, and it describes how the power flows:
Battery ---> Lightbulb ---> Radio ---> Battery

Same applies to hybrids:
Engine ---> Battery--> Motor ---> Wheels

...where the engine has NO connection to the wheels. Neither the Prius nor the Insight not use the above "series" design.



To me, a series hybrid is an electric car with unlimited range:
EV1 + generator trailer = series hybrid
 

·
Registered
Joined
·
12 Posts
A parallel hybrid vehicle can be propelled by the electric motor, the internal combustion engine, or both.

Honda’s implementation of a parallel hybrid uses a small motor that provides an assist to the internal combustion engine. This motor is not large enough to propel the car by itself. If Honda used a larger motor it would be full parallel hybrid capable of propelling the vehicle with either the motor, the engine, or both. Without clutches separating the motor from the engine they would rotate together, but no fuel would be provided to the engine when operating from the motor alone, and no electric power supplied to the motor when operating from the engine alone.

The Toyota system has characteristics of both a parallel and series hybrid. The power split device can send part of the power from the engine directly to the drive wheels like a parallel hybrid, and part of the power through the generator to the motor and then to the wheels like a series hybrid.

The operation of parallel and series hybrids is explained with words and pictures on howstuffworks.com

http://auto.howstuffworks.com/hybrid-car2.htm
 

·
Registered
Joined
·
928 Posts
It's not clear to me who has the authority to define these terms. I know the car manufacturers use them, but not always to mean the same thing.

Anyway, when Toyota and other people talk of the Prius having both series and parallel aspects, they're generally refering to the following modes:

Series:
Engine --> Generator --> Motor --> Final Drive

Parallel:
Engine --> Final Drive
Battery --> Motor --> Final Drive

But the series mode rarely stands by itself (reverse being the only case), it usually operates "in parallel" with other modes, especially Engine --> Final Drive. Plus both of the parallel paths are series paths in their own right. And there are other modes that can happen, especially Engine --> Generator --> Battery and the ever popular Final Drive --> Generator --> Battery. Hence the confusion even with the Prius. Just to make it even tougher to keep straight, there are two Motor/Generators, either of which can be a Generator or a Motor at any given time.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #7
Spencer said:
This motor is not large enough to propel the car by itself. If Honda used a larger motor it would be full parallel hybrid
Actually, the motor can push the car down the road in emergencies. 10 hp is not much power, but it's enough, and some unlucky drivers have done it. That means the Honda IS a parallel, because it has two sources connected to the wheels: (1) engine (2) motor

I suppose the Prius would best be described as a series-parallel hybrid circuit (to borrow from electronics terminology) since it operates as a series when going backwards, but parallel going forward.


Still, Car & Driver claimed the Honda Civic was a "series" hybrid. This is inaccurate. There's currently no series hybrids for sale, except the pure Electrics with add-on generators.
 

·
Registered
Joined
·
12 Posts
The Honda hybrid vehicles are mild parallel hybrids.

The Prius, however, is difficult to put into either series or parallel category since the engine power is split between the final drive and the generator. The Prius engine cannot drive the vehicle without also powering the generator. Some of the power from the engine always passes through the generator and motor before reaching the final drive.

When cursing at a steady speed on a flat road the Prius operates as shown below. The power split device splits the power between the final drive and the generator, and the electrical control system further splits it between the motor and the battery.

Prius cruising
Engine -> power split -> Final Drive
Engine -> power split -> Generator -> Motor -> Final Drive
Engine -> power split -> Generator -> Battery

In real life electrical power is transferred to and from the battery when the terrain is uneven or the vehicle accelerates and decelerates.

I know of no series hybrid automobiles, but series hybrid diesel-electric locomotives have been the standard in the railroad industry in the US for nearly fifty years. In these locomotives there is no mechanical connection between diesel engine and the drive wheels. This eliminates the need for a mechanical transmission and allows the diesel engine to be operated at its optimum speed regardless of the vehicle speed.

The Prius with its unique design has the benefits of a series hybrid without the additional size and weight of a full power generator and motor.
 

·
Registered
Joined
·
279 Posts
Azure Dynamics have a series hybrid London-taxi that is performing quite impressively in trials in the city. AC-propulsion have been running a Volkswagen based series hybrid on US roads for a while now too - but neither are available commercially yet.

However, I think Honda will almost certainly go down the series hybrid route at some stage. The problem with their system at the moment is the lack of pure EV mode, which is a distinct selling disadvantage to Toyota's system. BUT, the two companies have a huge amount of pride in their own technologies, and more to the point are bitter rivals that, not to put too fine a point on it, absolutely hate each other, so there is no way on earth that Honda would ever consider losing so much face by licensing the power split method from Toyota. (Ford, in their own research, realised that the whole splitting power thing was just the best way to go with a small battery, so couldn't do anything but sign the agreement with Toyota to use their patents. Same with Nissan too.)

So, to my mind, what is the only way out of this predicaemnt for Honda, saddled with their non-EV mode technology? Installing a bigger battery and going series hybrid. No embarrasing patent problems or meekly knocking on the door at arch-rival Toyota - the first series hybrids were buses designed by Ferdinand-Porsche in the 1920s, so the patents on that whole system have long run out! Will be very good news for those keen on plug-in hybrids, as this constant one-upmanship between the two companies may well be the catalyst required to usher in the next tier of hybrids to the market. As a note of further interest, I've noticed that Honda are forging close links with JEOL... presumably with an eye on their 75Wh/kg ultracapacitors! :wink:
 

·
Registered
Joined
·
105 Posts
Discussion Starter #10
Honda could easily convert their system to a pure EV using the Ford method:
- add an electric motor to the rear wheels
They'd still have the benefit of the transmission-linked 10hp motor to quiet the engine.



Here's the AC Propulsion link: http://www.acpropulsion.com/Products/Ra ... ailers.htm


got a link to the series hybrid taxi cab in London?

Troy
 
1 - 10 of 10 Posts
Top