Re: (ET) ICE to electric conversion

["Darryl McMahon" <darryl econogics com>]

"Todd Lynch" <jd4020d_69 hotmail com> wrote:

> Hi all,
> 
> I have been watching the list for a while and have looked for an 
> Electrak 
> for sale in southern Minnesota with little success.  With all the talk 
> about
> updating Electraks to use a more modern controller, I was think about 
> how much
> more it would take to convert an ICE garden tractor to electric.  I 
> already have a
> John Deere 112, of approximately the same era the Electrak was made, 
> with a bad
> engine, along with a mower, tiller, and sickle mower.  I was thinking of 
> mounting
> an electric motor where the current ICE engine is mounted to run the 
> accessories,
> and mount an separate motor by the transmission to drive the wheels, any 
> thought?
> 
> I would greatly appreciate any thought or recommendations you might have 
> such as size and type of motor would work best for this type of 
> application 
> etc...
> 
> 
> Thanks,
> 
> Todd Lynch

Todd,
such conversions are certainly possible, and have been done.

Some things to consider.

Hydrostatic transmissions waste a lot of energy as heat (which is why they 
usually
have lots of cooling fin area on their casings).  I don't know your 
proposed donor,
but if it has a hydrostatic transmission, I'd look for another base for 
your
conversion.  However, given it's vintage, I expect it is not hydrostatic.

Every gas tractor I am familiar with uses a single engine for both 
traction and
powering the devices.  You will need to size your electric motor 
accordingly.  Most
electric tractors have used multiple motors; one for traction and one or 
more
additional motors to power other devices.  Gasoline engine and electric 
motor 
rating
systems are different.  Gasoline engines are rated on the maximum power 
they can
produce under optimized conditions.  Electric motors are usually rated 
based on the
power they can produce continuously for one hour, often under specific 
less-
than-ideal conditions.  My rule of thumb is 4:1 - if an electric motor is 
rated at 
1
hp, it is roughly equivalent to a 4 hp gasoline engine for power.  Not 
everyone 
will
agree with that.  For a lawn or garden tractor, I think you should be 
looking for a
2-4 hp electric motor.  For comparison, the electric motors used in golf 
carts for
many years were nominally rated about 2 hp.  The electric motor will 
typically
accept power demand over its ratings for short periods without problems - 
so long 
as
it can disperse the waste heat afterward.

Presumably you plan to power your tractor with batteries.  They are a DC 
electrical
source.  Further, most tractor applications want relatively steady-speed 
operating
capabilities.  Therefore, I recommend you look for a shunt-wound, 
compound-wound or
separately-excited DC motor (rather than a series-wound motor or AC 
motor).  There
are universal motors, but I have not encountered them in 10 hp (peak) and 
up power
ratings.  Permanent magnet motors are usually equivalent to shunt wound 
and would 
be
acceptable, but again, I'm not aware of many of the right size for a 
garden 
tractor.
 I'm not going to be much help on sources, but I'm sure other listers can 
help out
in that department.  While golf cart motors are about the right ratings, 
they are
usually series-wound and often use a mated gearbox to provide bearing 
support for
the output shaft, so are not usually good candidates for this sort of 
application.

Power from the batteries to your electrical devices will be delivered in 
watts,
which is volts x amps.  So for the same power, more volts means less amps. 
 Less
amps means lighter gauge wires.  On the other hand, anything above 48 
volts DC can
be nasty.  The Coast Guard permits up to 48 volts around water without 
special
permits.  The new generation of golf carts are standardizing on 48 volts.  
The Elec-

Traks and their brethren standardized on 36 volts.  The traditional golf 
carts
standardized on 36 volts.  The next generation automotive accessory 
standard
(sometimes referred to as 42 volts) is really a 36 volt nominal standard.  
Much of
today's materials handling equipment runs on 36 or 48 volts.  Many of the 
early
electric cars (early 20th century) ran on voltages between 36 and 48 
volts.  A lot
of experience has led back to the same conclusions.  I recommend you 
benefit from
that experience and stay with a voltage in the same range.  This will also 
provide
you with some parts sources for various electrical components you will need
(batteries, fuses, motors, contactors, controllers, chargers, etc).

So, look for a motor with an operating voltage rating in this range.  
Next, find 
out
what the operating speed for the motor is at nominal voltage.  I expect 
you will
want something in the area of 3000 rpm as the rated speed.  If it is 
signficantly
different, you will likely want to do some belt and pulley gearing to get 
this
effective speed at the point where your electric motor joins up to the 
transmission
and power-take-off.  You might have lots of torque, but if the RPM is too 
slow, you
won't be happy with the performance of your machine.  (If it's too fast, 
you'll 
have
some different issues, but you still won't be happy.)

While the venerable ETs used contactor and resistor controllers, I would 
recommend
use of a modern solid-state controller if your budget permits.  If not, 
resistors
and contactors will work.

Don't skimp on gauges (voltmeter and ammeter minimum), fuses and at least 
one 
manual power disconnect.

Most electric motors make electric reversing pretty simple to implement.  
However,
if your existing donor has a mechanical reverse in good working order, I 
would 
stick
with that, and go with the simpler wiring that goes with running the 
electric motor
in one direction all the time.

The electric motor will have to be mounted to turn in the same direction 
as the old
gasoline engine did.  I don't play with many small gas engines, but I 
think most
spin counter-clockwise (CCW) as viewed from the output shaft.  And while 
most
electric motors can be reversed, they usually do have a preferred 
direction of
operation.

Once you have a bit of a plan, or questions about suitability of 
components, I
recommend you share them here.  There is a truly amazing amount of 
knowledge and
ingenuity (and a little bit of lunacy) available here.  In general, a very 
helpful
and sharing community on this list.

These links might provide some inspiration.

http://www.austinev.org/evalbum/038.html

http://www.austinev.org/evalbum/196.html

http://www.austinev.org/evalbum/411.html

http://www.austinev.org/evalbum/065.html

http://www.austinev.org/evalbum/216.html

http://www.renewables.com/tracpage1.html

Hope this was helpful.

Darryl McMahon


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