ElectroClassic EV
Classic Cars Reborn into the Electric Future

Control Freak

Here is the Curtis 1238-7601 motor controller situated in the former engine bay, over the AC50 motor and between the rear battery packs. It’s sitting on the dedicated shelf that’s part of the rear battery rack assembly, all fabricated from aluminum by Aero Welding in Culver City. The B+ input terminal on the upper right of the controller connects via black 2/0 cable to the Tyco Kilovac contactor at the bottom. The other side of the contactor runs under the shelf and back to the positive terminal of cell 13 at the top of the shot. The B- input on the top left of the controller will connect directly to the negative terminal of cell 5. The controller takes the 115 volts of direct current from the battery pack, and inverts it to 3-phase alternating current which is fed to the motor on the three red cables seen above. To the far left is the wiring harness that will connect to various EV components, such as the throttle pot, the key switch relay, the data display, the low-voltage side of the contactor, and the motor encoder.

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We’re looking at the underside of the controller cooling plate, showing the nozzles and coolant hoses. This view is from the transaxle looking forward to the front of the motor. The cooling plate is a pretty hefty hunk of aluminum, and would normally dissipate quite a bit of heat on it’s own. But the channels cut in the topside of the plate will allow coolant to carry most of that heat off to the radiator, where it will be chilled and then pumped back through the plate again. More details about the cooling system will be covered in a future post.

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This gray cable sends motor data from the controller to the digital display in the cabin. The small white connector on the end was too large to squeeze through the firewall grommet alongside the existing wire bundle, so it was temporarily removed. After getting squeezed past the grommet and pulled through the tunnel, the raw leads were soldered back together and sealed up nicely with heat shrink tubing. The round LCD instrument display will live in the center console, just above the OH SH*T button (emergency disconnect). The other white/red wire with the small red button is a momentary interrupt that allows cycling through the various display readouts. It will live next to the display itself.

.The Curtis PB-6 pot box is a two-wire potentiometer that connects to two throttle wires on the controller. Those wires are inside the gray sleeve shown above, and vary the frequency and current sent to the motor by the controller. In other words, go fast and go faster. Also routed from the controller are two green and red wires that attach to a microswitch on the pot box. That switch opens the circuit when the throttle is completely closed, preventing any stray electrons from reaching the controller when the driver’s foot is off the pedal.

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This key switch relay is provided in the accessory bag with the Curtis controller, and engages the lower 24 volt side of the contactor so the controller and motor receive full pack voltage. Installing the relay on the left side of the motor bay was inevitable, since the electrical harness delivers primary 12 volt coil power straight there when the key is turned on. In addition to engaging the relay, the same coil wire will also power the cooling system. Very convenient.

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This picture shows the controller with all wiring complete and dressed-out. The only remaining task in the motor bay is to tear off the blue masking tape, connect all of the batteries with the braided straps, and install the BMS cell modules. The controller can then be connected to the main B+ and B- cables shown above, and finally the heater core, charger, and DC/DC converter will be connected to the pack via the black and red primaries that run through the tunnel from the former fuel bay. Oh, and then I’ll need to put the wheels on.

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