DriveEV Logo
JeepEV: Electric Vehicle Conversion Project
Motor Controller

< Part One >



Part One: Part Two: (Update)
Selecting a Controller

     During the planning stage of my conversion, another important choice I had to make was what kind of motor controller to use. In an Electric Vehicle, the motor controller is basically the brains behind the go. It is solely responsible for controlling and delivering power between the batteries and motor. This means that there is high-voltage electricity present at the controller box as well as high current which runs through it. The high power switched by the controller causes it to generate a good amount of heat. Being that I'm in Texas, heat is always an issue when it comes to using power electronics. The hotter a motor controller gets, the less current (and thus power) it is able to switch to the motor, due to built-in protection devices that prevent the controller from melting down.

     There aren't too many manufactures that currently make Direct Current controllers for EVs. A popular choice for lower-current DC applications is the Curtis 1231C controller. This was the controller I too was originally planning to use in the Jeep. However, I received some good advice to try and find a higher-current (and thus more powerful) controller since the Jeep is a large, heavy vehicle. Also stories about these controllers overheating in the Texas summer made me finally decide to send back the Curtis controller and search for another.

     After listening to other people's stories and recommendations, I decided a better controller for my application would probably be a Raptor series controller made by DC Power Systems (DCP). However, DCP just stopped making controllers and I wasn't sure if I'd be able to track one down. The good news is that I was finally able to locate a Raptor 600 controller from an EV parts supplier. This controller has a maximum battery-loop current rating of 600 Amps verses 400 Amps with the Curtis 1231C. It also came with some extra features such as a built-in motor rev limiter, precharge circuit, and tachometer sensor output (more on that later).

Motor Controller Page Photo Motor Controller Page Photo Motor Controller Page Photo
The DCP Raptor 600-Amp motor controller (No Longer in Service).



Mounting the Raptor controller (OLD)

     Before I could use the controller, I had to select a place for it and make a mount for it. The Raptor needed a space that would provide air flow while not allowing water to enter the controller casing. I chose the area above the power steering gear box, which is in the front driver's side area of the engine compartment. The space provides plenty of air flow, but doesn't protect the controller from water. That issue was addressed later.

     I then began making the mount. First I began be cutting some 3/16" thick flat steel into four pieces. Next I welded the four pieces together so they made a rectangle the size of the controller's footprint.

Motor Controller Page Photo Motor Controller Page Photo Motor Controller Page Photo
A rectangle is made out of flat steel which matches the controller's footprint.

     Next, I set the controller on top of the rectangle I had just made and marked through the mounting holes of the controller onto the rectangle. I then drilled the holes out through the rectangle. Then I began working on the means to bolt the controller mount to the rest of the vehicle. Before I began making the mount, I had decided to attach one side of the controller mount to the front most battery tray, and the other side to the metal floor area off to the driver's side of the power steering gear box. I cut two pieces of "L" channel to use as tabs and then cut two pieces of square tubing. The tabs were welded to the pieces of square tubing which were then welded to the bottom of the rectangle I made earlier.

Motor Controller Page Photo Motor Controller Page Photo
"L" channel and square tubing are welded to the rectangle
to create tabs for bolting the mount down.

     Next, I used the same method stated above to create tabs on the opposite side of the rectangle. These will be used for bolting to the metal floor area. With all the tabs finished, I drilled holes into them for bolts. Two 5/16" holes are drilled on the battery tray side of the mount, and three 1/4" holes are drilled on the flat metal area side of the mount. A last piece of 3/16" flat steel was then welded to the tabs and rectangle on one side to provide part of the mount for the DC/DC converter.

Motor Controller Page Photo Motor Controller Page Photo Motor Controller Page Photo
Two last tabs are welded on and holes are drilled. Also a piece
of steel is welded on to help support the DC/DC converter.

     With all the welding complete, I primed and then painted the mount a silver color. The last mount related thing was to weld a piece of "L" channel to the side of the front most battery tray. This tab is what the two tabs on the passenger side of the controller mount bolt onto.

Motor Controller Page Photo Motor Controller Page Photo Motor Controller Page Photo
The controller mount is primed and painted. Lastly, a
piece of "L" channel is welded to the front battery rack.

     Once the mount was installed in the Jeep, I placed the controller to ensure the proper fit, and began routing wiring to it. I didn't finalize its installation just yet because it had to be removed again so other components could be installed first.

Motor Controller Page Photo Motor Controller Page Photo Motor Controller Page Photo
The controller is installed on its mount at the
front driver's side of the engine compartment.



Raptor Throttle Switch Installation (OLD)

     The Raptor comes with the throttle switch included. The throttle switch is the device responsible for telling the controller how much power to apply to the motor. The Raptor's throttle switch is an inductive switch. It consists of a coil of wire with a magnetic slug in the center. As the slug is pulled through the coil, a small amount of power is created. The controller measures this and adjusts it's output to the motor accordingly.

     I chose to mount the throttle switch directly to the firewall near the accelerator pedal and next to where the speedometer cable passes through. There was already and existing hole there where the throttle cable used to pass through. I used a unibit to enlarge the hole, then mounted the throttle switch.

Motor Controller Page Photo
The throttle switch is mounted to the firewall.

     After mounting the throttle switch in the firewall, it was time for me to attach some form of linkage between the accelerator pedal arm and throttle switch. The throttle switch has an O-hook on one side for this purpose. So, I decided to temporarily connect them together using a zip-tie. I've since learned that zip-ties have an infinite amount of uses! However, after attaching the pedal arm to the switch and pushing the pedal through it's range of motion, I discovered that there was too much resistance in the pedal. This was happening because the switch was offset to the left of the end of the accelerator pedal arm. Unfortunately, the throttle switch could not be moved, as the firewall has limited space for drilling new holes. So Instead, the accelerator pedal arm met my Sawzall!

     I used the sawzall to cut the accelerator pedal arm (which is a cylindrical rod) almost in half. I say almost because instead of moving the pedal or throttle switch, I decided to bend the arm to the left. So I cut the rod through most of the way then bent it. After verifying the bend was far enough to the left, I filled the cutout gap with metal by welding it shut. Next I needed to lengthen the pedal arm by about 5". To do this, I took a short piece of flat steel and welded it to the existing "fork" at the top of the arm. Lastly, I drilled a hole in the flat steel so it could be tied to the throttle switch. The accelerator pedal now pulls the throttle switch slug straight out and all is good.

Motor Controller Page Photo Motor Controller Page Photo Motor Controller Page Photo
The accelerator pedal arm is cut, bent, then
re-welded shut. It is then extended by about 5".


Remember, More photos are in the Photo Gallery!