[ausev] Small On-Board Generator

Sun Nov 25 17:15:36 GMT 2007

On Sat, November 24, 2007 9:53 pm, Sarah & Erik wrote:

> There are a couple new things to take a look at before you use a
> generator to run your EV. Generators can have messy electrical outputs
> that can fry your charger (unless you can get one to straight DC
> output which is great, but hard to find off the shelf). They can have
> voltage spikes or not a true sine wave which your charger counts on.
> Some are fine, you just have to check.

I recall a Manzanita PFC charger getting toasted by a cheap generator. A
while back, don't remember details (make, model etc)

> Some generators are really
> nasty smelling too - I understand Honda generators run fairly clean. A
> cheap generator can put out the emissions of dozens of cars in a short
> time.

One of the reasons I feel that Wilderness EV's promotion of small
generators is highly irresponsible is that in reality, *all* generators
are this way, because the laws that govern their production and sale don't
have the same requirements for emissions. There are no catalytic
converters or decent mufflers, there are no EGR valves or evaporative
emissions systems (charcoal canisters, etc) or control computers on small
generators -- and no manufacturer will add these components until they're
forced to. Like any appliance employing a small gas engine, they put out
orders of magnitude more non-CO2 emissions than cars sold today.

> Another thing is that if you have a generator powerful enough to
> keep you driving for a while you need to keep an eye on your motor
> temperature. My motor can get pretty warm in the summer after a run,
> but I only go so far at once.

True. EV motors are rated for continuous horsepower, and the short range
of most EVs means you can in most cases ignore these ratings.  As your
range increases by way of lithium batteries or auxiliary generators, you
have to size your motor at least to the average power required for the
maximum speed you want to drive, or increase the motor's rating by adding
forced air cooling. Not a dealbreaker, but something to consider.

> understand the concern about running out of juice. It takes a pretty
> stout generator though to be useful for anything but a true emergency
> and those get heavy. One of the handheld ones will take a good while
> to charge you up full.

Consider the numbers. It takes somewhere in the neighborhood of 20hp to
keep a small vehicle going at 55-60mph depending on aerodynamics, tire
rolling resistance, brake drag, etc -- as a convenient rule of thumb, this
ends up amounting to somewhere around 20kW minus motor and drivetrain
losses. 20kW is a big generator; you'll likely not find one with a small
gas engine. I've seen one up to 15kW, and that wouldn't fit in most cars.
Some time ago Northern Tool used to sell a huge 20kW generator head which
would be adequate, but at full output it required a 50hp engine, which
puts you in motorcycle or small car engine territory. That's a lot of
weight, which means you need a trailer and a bigger motor.

The sensible (but difficult) way to do this is to custom engineer an
engine and generator to spin at crazy speeds, so you win the battle with
RPM instead of engine displacement and generator size. Capstone
microturbines were one example of this, and I believe that GM may be
working in that direction for the Volt. AC Propulsion ran a horizontally
mounted twin cylinder Kawasaki motorcycle engine at very high speed
(10,000+ rpm) for their experimental Long Ranger trailer. Something you
can't even find mentioned on their site today, though they have some
archive pictures that show it.

  --chris

>
> Erik
>
> On Nov 24, 2007 6:55 PM, John Penry at Texrocks <jpenry at texrocks.com>
> wrote:
>>
>> I ran across a website a while back that listed some common gas
>> generators.
>> http://www.e-volks.com/hybridconversion.html
>> Beware of the noise and emissions created by these.
>>
>> John in Seguin
>>
>>
>>
>> ----- Original Message -----
>> From: Casey Martinez
>> To: ausev at austinev.org
>> Sent: Saturday, November 24, 2007 8:23 AM
>> Subject: [ausev] Small On-Board Generator
>>
>> Dear EVers,
>>
>> I am in the market to buy an EV soon and I would like to know if there
>> are
>> any for sale that this group may know about. I am considering all
>> options
>> right now.
>>
>> Also, how practical would it be to keep a small generator in the trunk
>> of my
>> future EV so that when my batteries are low on juice I could stop and
>> get
>> some hydrocarbons and charge my battery bank? I understand the charge
>> may
>> take some time and that it would be stupid to store liquid fuel on board
>> due
>> to weight factors but I wanted to hear what this group would have to say
>> about this idea.
>>
>> Thanks everyone for reading and have a happy holiday season. I have
>> enjoyed
>> reading these messages over the last year or so and I look forward to
>> seeing
>> yall at the Sustain A Ball on the first.
>>
>> Sincerely,
>>
>> Casey Martinez
>> 512-797-7518
>>
>>
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