Play It Cool

These brackets on the driver side of the engine bay played an important role in their previous life by supporting the relay board. The board will no longer be needed, but the brackets are perfectly suited to support the liquid cooling system for the Curtis controller. Another bonus is that the original engine electrical harness branched from the main harness under the brackets, leaving a way to power the cooling system when the key is turned on. For the record, the ignition wire is the black one.

.

All of these items were purchased from Koolance, a supplier of radiators, fans, pumps, reservoirs, nozzles, tubing, and everything needed to keep electronics cool. Their usual customers are computer gamers who overclock their systems for speed, so these components should adapt well to chill the power MOSFETs in the Curtis controller. Everything is designed to fit together simply and easily. The only modification I made was a 90 degree bend in the pump mounting bracket, so the pump and reservoir can sit upright while the radiator lays flat. I also made sure to buy the nozzles from Koolance, as normal US thread formats are incompatible with all their European standard fittings. Here’s a couple links where you can read more about BSP versus NPT.

.

These two mounting plates will attach the radiator to the existing brackets in much the same way as the original relay board. Fashioned from 1/16 inch aluminum using my bench vise, rubber mallet, cordless drill, sheet metal snips, and a file, they are fastened directly to the mounting holes on the underside of the radiator with Allen screws. That’s the bottom of the pump on the right.  The front mount on the left will be slotted into a groove in the forward relay bracket, and the pump-side plate will be screwed onto the rear bracket.

.

Here is a test fit of the complete cooling unit on the mounting brackets. The pump cover has been removed and replaced with a reservoir base and a clear tank, which seals with O-rings. Koolance advised me that their nozzles are designed for finger-tightening only, but I gently applied additional torque with small pliers as a countermeasure against road vibration. Also, the BSP thread standard does not require Teflon tape, so none was used. The spousal unit says this looks like a two-burner stove and blender for quesadillas and margaritas. No argument from me.

.

Now we’re looking at the underside of the controller cooling plate, with hoses clamped to the nozzles which direct coolant through channels cut in the topside of the plate. The bottom face of the controller mates directly to the top of the plate, sealed around the circumference with a large rubber O-ring. These two hoses will be connected to the output side of the pump, and to the input of the radiator, completing the cooling circuit. The cooling plate is machined specifically for the Curtis 1238-7601 AC Controller, and was purchased from HPEVS. Here’s a similar plate fabricated by students at the University of British Columbia’s Electric Car Club.

.

Here’s how the cooling system looks at home on the driver side of the motor/battery bay. All connections are not yet complete, but the hoses, wires and plug for the pump and fans will be tucked underneath for a clean look. The coolant circuit will run from the reservoir to the pump, to the controller cooling plate, to the radiator, and then back to the reservoir to complete the loop. The module just above the fans is the key switch relay, which is unrelated except that it shares primary switched ignition power with the cooling system.

.

Here’s how the harness ended up looking. The previously mentioned black ignition wire got tapped for the pump and fans, as well as the ignition relay and future tach signal isolator. All power to the cooling system routes through the Radio Shack multi-pin connector at the center of the shot.

.

After hooking everything up and applying primary power to the harness using my 12 VDC bench supply, the PMP-400 pump was unresponsive, so I RMA’d it back to Koolance for a look-see. They confirmed the pump worked fine in their shop, so I emailed them the specs for my 12V supply. Their Hungarian manufacturing facility reported that I was providing a higher voltage than the pump would accept. The pump operates within 8 to 13.2 VDC range – just under the 13.8 to 14.5 volt output of my DC bench supply. I needed to drop a couple volts, so my friend Steve suggested I use a DC-DC voltage reducer. Some searching online led me to PowerStream Technologies, where I found the exact box to output a rock steady 10.27 volts to the coolant pump with a capacity of 3 amps. That figures out to 30 watts, which is well above the 20 watt maximum draw of the pump. In the shot above, my bench supply is feeding the voltage reducer from the left, and the meter shows the output voltage on the right. You may notice the label states an output of 9.2 VDC, which is the original spec before PowerStream modified it on request to output approximately 1 volt more.

.

Here is the cooling system in full regalia and filled with Koolance’s day-glow freezy juice. The voltage reducer found a good home on top of the fans, where it will stay ventilated. The LED illuminated fans were no more expensive than the boring industrial black ones, so I jumped on the bling wagon. They’ll make an eye-popping impression when I open the deck lid at night. A thermostat might be warranted in the future, but for now the cooling system will always be pumping when the contactor is engaged. This corner of the motor compartment is not entirely immune from weather, and even though the pump is sealed and the fan motors are brushless, I’m already thinking about building a sneeze guard to shunt any moisture away from the gear.

.