In the honda civic hybrid is the power train parallel, ie either the
gasoline or the electric engine or both can drive the wheels, or does
the gas engine drive the generator which charges the battery which
powers the electric motor which drives the wheels? Is this series
arrangement simpler or are the computers which select the mix of
electric and internal combustion highly reliable and more practical?

Dear jhalsey:

The answer to your question is that both the gasoline engine and the
electric motor can drive the wheels.  I believe this is done because
the series arrangement would be less efficient.  There would be energy
losses in converting the mechanical energy of the gasoline engine to
electricity and then converting it back to mechanical energy.  For
example, charging the battery generates waste heat.  Furthermore, both
a generator and an electric motor would be required, whereas only an
electric motor that can also act as a generator to charge the
batteries is required by the current design.

Interestingly, Honda and Toyota have taken different approaches to
which element is the primary source of power during initial
acceleration.  The Civic Hybrid uses the gasoline engine primarily and
the electric motor to provide additional horsepower and torque.  In
contrast, the Toyota Prius uses the electric motor primarily and uses
the gasoline engine to assist.

Both the cited Honda and Toyota web sites have graphics to convey how
the vehicles' power trains work.

Technology Review magazine in its April 2004 issue indicates that
"Honda's models -- which include a hybrid Insight and Civic, and an
Accord due this year -- have less electrical power and are more
expensive to produce than Toyota's...."  (Page 40)

http://www.technologyreview.com/articles/mag_toc_april04.asp "Technology Review"

Sources:

"Engineering, 2004 Civic Hybrid"
http://www.hondacars.com/models/engineering.asp?ModelName=Civic+Hybrid

"The latest version of Honda's Integrated Motor Assist (IMA) system
thrusts the Civic Hybrid to the forefront of hybrid technology. On the
electric side of the power-producing equation is an ultra-thin
brushless DC motor. Assisting the engine as needed, this highly
efficient, compact unit increases total torque output by a whopping
66% at 1000 rpm."

"Electric Motor: The IMA electric motor works in conjunction with the
gasoline engine, and supplies additional torque in assist mode."

"Power Control Unit (PCU): The PCU controls the flow of electricity
between the IMA motor and battery pack, supplying energy to the motor
when needed."

"Acceleration: When accelerating or climbing hills, additional
horsepower and torque are needed. The electric motor assists the
gasoline engine using electric current stored in the
nickel-metal-hydride battery pack."

"Cruising and Deceleration: Primary power comes from the engine when
cruising.  The motor functions as a generator and charges the battery
pack."


"Prius Hybrid Synergy Drive System"
http://www.toyota.com/vehicles/2004/prius/key_features/hybrid_syn_drive.html

"Low Speeds: From initial acceleration to low speeds, power is
provided by Prius' quiet electric motor using energy supplied by the
battery."

"Heavy Acceleration: Prius delivers smooth, seamless power as the
power split device manages input from the gas engine and electric
motor."

"Highway Cruising: for exceptional Highway performance, Prius' gas
engine powers the wheels and electric motor by the generator."

Search Terms: "Honda Civic hybrid" "Toyota Prius"

Sincerely,

Wonko

i have done a fair amount of research into the available hybrids as of
april 2001 (the date of my purchase of a Honda insight).

First off:  Toyota's initial approach was that the vehicle should be
capable of driving with only the electric motor active.  This was
accomplished by binding the drive-train to two seperate power devices
(that being the gas engine and the elctric motor) simultaneously. 
This is made possible by use of the Continually Variable Transmission
(CVT, you'll find that most [all?] hybrids have this now).

Think of the CVT as a spinning cone; place a cylindar against it such
that the cone spins the cylindar.  Now recognize that if you slide the
cylindar toward the peak of the cone, to a part where the cone's
diameter equals that of the cylindar, then you have the equivalent of
a 1-to-1 gear ratio.  similarily, you can slide this cylindar toward
the fatter end of the cone, you can change the gear ratio smoothly as
you do so.  This method allows for multiple 'cylindars' to be involved
- hence the ability to connect more than one power source to the drive
train. (basically, Toyota does connect the power sources to the drive
train in parallel)

Second Point: Honda's inital approach was different.  Honda initially
put the electric motor in series with the gas engine.  This method
allows for a standard transmission (which cannot be used to replace
the CVT in Toyota's method above).  I happen to own a 2001 Honda
Insight with a manual transmission.  I do not recomend the manual, as
certain aspects of a hybrid vehicle make an automatic transmission a
more pleasant option.*(more on this later)

By placing the electric system in series with the gasoline, Honda
greatly simplified the system.  The previous poster's qoute regarding
Honda's method being more expensive to produce:

"
Technology Review magazine in its April 2004 issue indicates that
"Honda's models -- which include a hybrid Insight and Civic, and an
Accord due this year -- have less electrical power and are more
expensive to produce than Toyota's...."  (Page 40)
"

may not reflect the actual hybrid technology so much as the rest of
the vehicle's components.  (the Honda Insight is extremely
lightweight, built of mostly aluminum - even using rolled aluminum for
many of the structural components - which is very expensive.  you
don't want to know how much my replacement 'magnesium oil pan' would
have cost if it weren't under warranty).

Toyota's gas/electric hybrid system is much more technically elegant. 
Toyota provides a system that can dynamically start the gas engine and
use it to drive a generator which in turn runs the electric motor.  In
Honda's system, the electric motor IS the generator, theren't seperate
parts for this, and therefore it is impossible to recharge the
batteries while accelerating in most circumstances (extremely high
tach often charges the batteries when you would think they should be
drainging, discussing this veers off the topic).

I hope this sponaneous post was clear and concise enough to provide
some insight to the Insight (all bad puns are intended, regardless of
any author's attempt to suggest otherwise).  I will monitor this
discussion, if you have questions about my specific experiences i'd be
happy to share them.

*(previous comment, clearified)
Rechargable batteries must be 'conditioned' (at least most types of
them do, including those found in our hybrids).  Conditioning
basically consists of:
A. completely drain the batteries
B. recharge the batteries with little or (hopefully) no drain during
the charge cycle

The car's computer decides when to do this, with no warning at all to
me, the driver/owner.  I sometimes pull up to a stop-light with plenty
of stored power in the batteries, only to lag the motor badly when i
try to drive off.  upon inspection it is always clear: the computer
decided to condition the batteries while i was stopped, and is in the
process of recharging them.  This is not quite as horrible as it may
sound, but certainly an anoyance that would be circumvented if i had
an automatic transmision (for which the computer could alter the shift
points during a conditioning phase, preventing me from having to care
that conditioning happens at all).  ironically, a good deal of my
decision in purchasing the Insight rather than the Prius came down to
the transmission (at the time, Hybrid Civics were a thing of the
future).  I had reasoned that with a low-power engine i might need an
manual transmision to get acceptible acceleration in an emergency case
or when i simply wanted to 'go fast'.  i was wrong, DC motors have
exceptionally higher torque output and i'd have been very happy with
the automatic.  que sera sera.

-jared