# Cooling a Curtis Controller



## onegreenev (May 18, 2012)

A radiator is mandatory but you may not need one the size of the stock radiator. A good sized oil cooler. Something like this. 72 pass oil cooler. 

http://vwparts.aircooled.net/Bugpack-MESA-Oil-Cooler-KIT-72-Plate-3081-12-p/3081-12.htm


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## Caps18 (Jun 8, 2008)

Is there a reason I can't use the heater core as it is? Now, I haven't taken apart the dash yet to get at it, and it might not have the airflow (if the vent fan isn't running). I would think the big block of aluminum would absorb a lot of heat. And aren't these electric cars supposed to be efficient, what is all this heat being generated for in the controller. 

Has anyone produce a temperature/speed/outside temp graph of different setups? I thought some people don't cool them at all? I doubt it would need any cooling from December to March around here. And a lot of my driving will have long pauses at stop lights. It is the extreme 2% of my trips that make me concerned with this at all.


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## Woodsmith (Jun 5, 2008)

I would imagine that if you had four litres of antifreeze in a tank above the controller then it would thermo-syphon all on its own, especially if the plumbing is large bore.

You could add a small pump, say an electric ICE coolant pump, into the pipework, with a thermostat to control it. That would increase the flow rate when needed.

The mass of water should be sufficient to cool it if the tank is in free air. You could always duct cool air to it for when you are driving.

I would run it this way, and it is what I have planned for mine. Should you find the pump runs all the time and the tank of water is getting very warm then you can add a radiator later on.


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## dougingraham (Jul 26, 2011)

Caps18 said:


> I would think the big block of aluminum would absorb a lot of heat. And aren't these electric cars supposed to be efficient, what is all this heat being generated for in the controller. .


Aluminum conducts heat but is does not have much thermal mass. You need to get rid of the waste heat to keep the semiconductors happy. At elevated temperatures they age rapidly.

Electric cars are efficient compared to ICE. There is still some waste heat generated in the components. Let me give you an example of the waste heat generated in the controller. Lets assume that the controller is 95% efficient and that you are driving down the highway at 60 miles per hour. In my car this takes about 18kw. At 95% efficiency this means 900 watts of heat are being wasted in the motor controller. Almost all of that heat is concentrated in a piece of silicon with an area a little larger than your thumbnail. You have to get rid of it somehow or the controller will cut back power to keep you from melting the silicon switches. This can happen so gradually that you don't even realize it. The addition of a water cooling system could increase dramatically your driving experience if the controller is tapering back to protect itself.

A good ICE motor is perhaps 15 percent efficient. It is going to take that same 18kw to move the car at 60 mph. That means that 102000 watts are being wasted. In an ICE this is all heat that goes away through the radiator and out the exhaust pipe. It is very convenient in the winter for warming the passenger compartment.


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## evmetro (Apr 9, 2012)

I used my original heater core on the first conversion below in my signature, but I mounted it up front where the stock radiator was. My cooling circuit passes through my charger as well. The controller never gets much hotter than ambient temp, but the cooling fan on the heater core cycles when charging.


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## Caps18 (Jun 8, 2008)

Thanks, that makes sense now. I might do it the 'easy' way for now by hooking a 12V coolant pump to the heater core just to test what happens and get it on the road in a few weeks. Then in the Summer, I will be able to monitor the temp and see how it doe with the trips I take, and if modifications will need to be made.


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## frodus (Apr 12, 2008)

Here's a place with some decent and cheap stuff. I've bought meters from them.

Pumps:
http://www.lightobject.com/WaterOil-Pump-C43.aspx

Radiators:
http://www.lightobject.com/Cooling-C52.aspx


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## gmills (Feb 26, 2017)

I am also working on a cooling system for my Curtis 1239E controller. I cannot drive more than 10 miles without it heating up. I have installed a large heat sink but that is not enough. Our outside temps this summer are at 40C. I plan on adding a EV West cooling plate and using their temp switch. I still need a water pump, reservoir and radiator. Any suggestions on those parts? And any ideas for designing this system would be much appreciated.


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## 914e (Nov 22, 2020)

gmills said:


> I am also working on a cooling system for my Curtis 1239E controller. I cannot drive more than 10 miles without it heating up. I have installed a large heat sink but that is not enough. Our outside temps this summer are at 40C. I plan on adding a EV West cooling plate and using their temp switch. I still need a water pump, reservoir and radiator. Any suggestions on those parts? And any ideas for designing this system would be much appreciated.


Unless you have a heavy vehicle or racing you don't need much. I usually use a 1 liter reservoir and a small computer radiator 120mm by 240 mm with 120 mmx 120mm 12v fans. and a small pump. It hits 50C here and the controller will overheat after driving around the block a few times. In my 914 the radiator is only 120mm by 120mm and seems to run plenty cool. The main thing is the coolant can pull away the heat quickly. If I remember correctly water can absorb 800 time the heat that air can.


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## gmills (Feb 26, 2017)

I have not completed my cooling system due to the BMS system failing and I have not figured that out yet. But I have collected parts for the controller cooling system. I purchased the Curtis cooling plate from EV west and I fabricated a reservoir from aluminum tubing. I was donated a Mercedes Benz water pump, (small 12 volt centrifugal pump), for the heating system and I am planning on using my heater core heat ex changer removed from my interior heater. 
Will report on the success after figuring out my BMS and charging system.


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