Water Cooling for the Controller


I added water-cooling for my controller about 3 weeks after I started driving the car. It was September, and still warm enough to get the Soliton Jr. to warn me that it was running hot. At the time Evnetics had their high temperature warning set to 50 degC. The warning light on the dash would flash, and since this can mean a number of things it was bothersome. I decided to put in water-cooling because I knew it would make the controller last longer. There were some kits available that cost over $250. I decided to try making my own system. I found recommendations that the flow rate should be 1.5 gallons per minute or higher. I also found some pumps mentioned, that I could find on the Internet. They were typically used for cooling CPUs that have been over clocked. I decided to try using a single radiator that was sized for 120mm fans. I didn’t want the fan because I was worried about the noise. I knew I could locate the radiator right up in the front of the car with good airflow, like a normal car radiator. I can always add the fan later if I want to. Since I was going to use only one radiator I choose one made of brass and copper. I knew this type of construction would give me the best cooling.

 Radiator mounted under the front 8 cells

For the pump I decided to go with a Phobya DC12-220. It was quiet, had a flow rate of 1.5 gallons/minute, and used ceramic ball bearings. I felt if they were using ceramic ball bearings, then the rest of the pump construction couldn’t be too bad. It also made me feel that the claim for a life of 50,000 hrs might actually be true.

Water Pump Location

Most water-cooling systems that I found used in EVs had some sort of reservoir for water. I couldn’t find a reservoir small enough to fit where I wanted it. The Midget was very tight for space after I had placed all of the other components. I decided to go without a reservoir. I used clear ¼ id tubing for my hoses. I’m running a 50% antifreeze solution to protect any metal parts in the controller, and I do drive in the winter time so I needed antifreeze for that. The routing has the controller exit water going to the radiator, then the pump, then back to the inlet of controller. I have a tee joint in the tubing where my fill tube goes off. Not using the reservoir made it tough to fill the system and get all of the air out. I had to dismount the radiator and move it around while the pump was running before I could get all of the air out. Not having a radiator does simplify the system, but getting all of the air out of the system was a pain. So if others are considering this approach, be warned about purging the system.

Inlet and outlet water hoses for Soliton Jr controller

The air temperature hit 80 degrees F this weekend and I was logging my energy use while driving at 60 mph. The temperature being recorded was 6o degC. Evnetics has changed their hot warning temperature to 80 degC for the Soliton Jr. in the last code release. This was a good thing because my warning light would have been going off during these test runs.