[ausev] adding an electric generator

[Mark Farver]

The idea of adding a gas engine as a range extender//hybrid is a
wonderful one, but engines vary significantly in pollution and
efficiency.  Small generators are generally designed for short
duration emergency and portable use, and to be as inexpensive as
possible.  As such they emit many times more pollution and use more
fuel per watt/hr that a generator designed for efficiency.

There are also some interesting issues related to speed... a portable
generator will tend to run a fixed speed so it can generate standard
60 (or 50) hz power, as such it seldom runs at itt most efficient RPMs
for its given load.  Hybrid vehicles often generate "wild" AC with a
varying frequency, and speed up and slow down the generator according
to load and use the batteries and electronics to make that compatible.

Additionally your electric motor is often undersized for the job of
moving the car down the road, and is being used well beyond its
continous current rating.  That doesn't matter when you drive a
maximum of 50miles a day, but if you use it with a generator to drive
several hours it will probably overheat.

In my experience it takes about 25-30kw of generator to move a car
down the road at a steady freeway speed taking into account the
conversion loses.  You'll find that portable units do not really get
up to that size, or tend to be quite heavy and expensive.

For the home builder so called "pusher" trailers are inexpensive to
make if you would like a range extender.  Essentially, a pusher is a
small car (Volkswagon Rabbit Diesels are popular) that has been cut
off at the firewall. and a tow hitch welded to the front.  A standard
aftermarket cruise control system and remote ignition is added, and
run into the EV.  As you get onto the freeway the EV accelerates both
vehicles to freeway speeds, then the trailer's engine is started,
shifted into gear and the cruise control used to set the speed.  The
trailer "pushes" the EV down the road, and the forces are the same as
when the tow vehicles brakes are used to stop.  Done right, the
original vehicle's pollution controls and emissions system remain
intact and you are using the gas engine in its most efficienct mode,
steady state cruising.  On days where you do not need to go the extra
distance, the trailer can be left at home.

Mark

On Thu, Sep 11, 2008 at 4:05 PM, Josh Handel <josh.handel at ktomics.net> wrote:
> Isn't this the direction the Volt and the Mazda Hybrid mule thats been
> tooling around Tokyo are going? I'm not saying that they are practical for a
> home conversion but if GM and Mazda both like the idea of all electric power
> with ICE as a generator then there has to be something to that design
> choose?
> Josh
>
> On Thu, Sep 11, 2008 at 3:55 PM, Brian Lasseter
> <blasseter.cmpe01 at gtalumni.org> wrote:
>>
>> On Thu, Sep 11, 2008 at 1:25 PM, John Flores-McLaughlin
>> <johnfm101 at gmail.com> wrote:
>> > Hi all,
>> > I'm new to the group after purchasing a 1986 toyota mr2 conversion. I
>> > have a question about adding a gas-electric generator with my charger
>> > while driving. Would this cause a current overload to my batts? here
>> > are my specs.
>> >
>> > 72 V system with 8 volt Energizer golf cart batteries, 7245 Alltrax
>> > Programmable Controller (www.alltraxinc.com) and the D&D Motor ES-15A
>> > (www.ddmotorsystems.com). The charger is onboard 72 volt - 20 amps
>> > smart charger made by Quickcharger (www.quickcharge.com)
>>
>>
>> 20A at 72V is only 1.44kw... and that little power is unlikely to help
>> you in cruising down the highway.  How many amps does your car draw
>> when you are cruising at something like 50mph?
>>
>>
>> The tricky parts though are making sure your generator is large
>> enough, clean enough to be legal on US roads, and that it generates a
>> nice sine wave for the charger.  I would direct you to the following
>> reading. Manzanita Micro http://www.manzanitamicro.com/ has some
>> specific notes on using Generators with his PFC chargers:
>> http://www.manzanitamicro.com/Appnote1R3.doc
>>
>> Also, there are some general notes on why using a generator is mostly
>> impractical (and very polluting) in the Electric Car Conversion
>> wiki-book:
>> http://en.wikibooks.org/wiki/Electric_vehicle_conversion_chapter:_technologies#Range_Extenders
>>
>> And some number crunching on the Seattle EVA chapter Wiki...
>> http://www.seattleeva.org/wiki/Generator_Emissions
>>
>> There is also some good reading in the AustinEV archives...
>>
>> http://www.google.com/search?q=generator+-HHO+site%3Ahttp%3A%2F%2Fwww.austinev.org%2Fpipermail%2Fausev%2F
>>
>> --
>> TTFN,
>> Brian "Lasso" Lasseter
>>
>> "No Sane man will dance." -Cicero (106-43 B.C.)
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