My 2001 Focus EV Conversion

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The Basics 

I wanted to do the conversion as inexpensively as possible while making sure it was reliable.  Once I purchased the car my search for the items needed for my conversion began in earnest. 

In it's simplest form 5 major items are needed for an EV.

They are:

• • The electric motor

  • A transmission

  • Batteries (lots of them)

  • A controller (which basically controls the speed of the motor)

  • A method of charging the batteries

I will detail my decisions on each of these in other entries.

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The Motor

Finding the motor was one of the first tasks I set out on.  During my research I found that electric motors designed specifically for EV conversions are available, but are quite pricey.  I also came across many conversions that used the drive motor from an electric forklift.  I decided I would try the forklift motor route and if that proved to be unsuccessful I would purchase a motor designed for this application.  I scoured eBay and Craigslist for motors without success.  Then I realized that calling a local forklift repair business may lead me to a motor.  At work we have a small walk behind forklift and I found out it was serviced by Mac's Service in Detroit.  I called them and spoke with Brett Karas and explained to him what I was trying to do.  He found a motor from a Yale forklift that fit my needs (A series wound motor 9 inches in diameter).  This was in January 2011 two months after purchasing the donor car.

How does one connect the motor to the transaxle?

For my conversion I decide to go the "clutchless" route.  I should mention that I chose the car I did because it had a 5-speed manual transmission.  While not impossible to convert an automatic, it would require additional work primarily because an automatic transmission needs fluid constantly under pressure.  This is normally provided by the gas engine via the torque converter hub, but with an electric motor there would be no pressure at a stoplight. 

From everything I have read you typically only use 2nd and 3rd gears (as well as reverse) when using an electric motor.  I also learned that it is possible to shift without the clutch since the electric motor does not have to idle and it has less inertial mass than a gas engine.  I decided to couple the motor to the input shaft of the transmission directly (Hence the term "Clutchless"). 

After creating a cardboard template of the motor and it's output shaft I decided that if I cut the output shaft of the motor and the input shaft of the transaxle I could mate them together with a 1/2 aluminum plate separating them.  But now I had to figure out how to connect the output shaft to the input shaft.  The drive motor output shaft is splined and came with a large gear on one end .  I considered having a splined coupler machined that would connect the two shafts together.  This sounded expensive and I was also concerned if there was any runout of the shafts it may lead to a vibration.  I then looked into using a LoveJoy connector.  These are commonly used for PTOs and in industrial applications to couple two shafts.  I found some posts lamenting failed LoveJoys so scrapped that idea.  Then I had one of those "aha" moments.  If I could weld the gear from the electric motor to the original clutch disc I would still have the benefit of the dampening springs and the play that is found in the center of the clutch disc.  The play would allow for a small amount of misalignment between the shafts. Not that I plan on having any :).

(maybe I could use dowel pins to hold the alignment)

Below are pictures of the process of creating my coupler.

To insure there was minimal runout (making sure the gear is centered) I clamped them together and mounted them to the motor shaft.  A dial indicator was used to insure the runout was less than .005".