ESC Cooling Concept- Theory and Practice

[domwilson]

Utilizing Amonium Nitrate and water should cool things down a bit.

[Jeff Wohlt]

One reason I think a pump is key to consistant flow. Sometimes, depending on turning, the water is not picking up as well. Full flow seems like it would be better to cool prior to a run and then after as well.

If you can guide me to any pumps I can sure try it easy enough. That and a cheapo fuel tank for nitro. My wondering is about how long the water will stay under 60 degrees. 4 minutes? 10 minutes? If the motor stays cooler to begin with then it will keep water from getting hot longer. If that makes sense.

6v should be fine to slow it down. Most rc fuel pumps will run on both 6 and 12v and are $12.

[questtek]

Boat Components Water Test Fixture

After preliminary bench testing of various ESC cooling systems my plan was to evaluate performance for the various systems mounted in my Mean Machine with Eagle Tree data logging. However, I knew there would be lots and lots of testing with many environmental factors varying by a day to day. Any change or new system evaluation would take quite a bit of time to install in the Mean Machine, etc.

In an attempt to save testing time and make the evaluation boat and environmental conditions independent I developed a simple but effective water test stand. I wanted the ability to evaluate motors, props, ESC’s, data acquisition systems and even shaft drives using a convenient test bed fixture. Even the evaluation of the various ESC cooling systems could be evaluated under much more accurate and controllable conditions. This includes not being affected by daily ambient and water temperature changes. In addition, I could accurately monitor and control the water-cooling flow rate, something impossible to due using my Mean Machine since the water flow rate from the rudder pick up is speed dependent.

I have included a number of pictures of the test set up in my workshop. You can also see how the Eagle Tree data is displayed on the large monitor as well as recorded. I record all motor parameters plus three thernistors in-line with the water flow but not restricting the flow.

The motor is mounted to the top of the aluminum box section is a 540XL with a water-cooling jacket. It is coupled through a straight wire shaft that rotates inside a brass stuffing tube. This is sealed by two Hyco fittings so it can easily be removed and replaces with larger or smaller drive shafts. The props are also easy to change since the top waterproof lid is secured by four knobs. Attached to the motor is one of many different types of ESC’s to be evaluated. The large mass of wires are Eagle Tree sensors. To the right on the housing is my small water pump with inlet to by “Busty” water supply and output to the ESC and motor via the thermistor “T” fittings.

I have taken the lid off the test fixture and provided a close up picture of the motor and drive assembly. I built a bunch of different aluminum box sections so a wide variety of inrunner and outrunner motors could be evaluated.

You will notice in one of the final pictures that the liquid in the test tank is blue. Naturally you have to add a bit of “Tidy Bowl” to minimize cavitation bacteria, shaft fungus and propeller decay. (Just kidding, a few drops of blue food coloring added for show)

I have not put in a way to measure force or thrust at this time. There are a few ways to do it but that is Phase 2 of the project. Now it is time to start evaluating ways to best reduce ESC temperatures. Comments and suggestions welcomed.

[Meniscus]

Joe, I'm glad to see you testing this idea.

Here are a few comments I have while moving forward:

1. Keep in mind that it may be advantageous to consider instant ice pack materials used for military field medical care. I'm not 100% familiar of the process, but it may be that you could incorporate controlled agitation (via vibration) to start and sustain cooling.

2. There is a product out there called Burn Gel that the military uses for severe burns. If I remember correctly, they had some concerns due to the high conductivity of the gel. It may be that the material would be a good, stable medium to use in the final design. The company that manufactures this stuff is H&H Associates and they also market the Cinchtight product. I'll see what I can do about going through my contacts of years past as I've known the owners for some time now. If I manage to get my hands on some, I'll send it to you.

Last, I have a question. At what point is this going to turn into a full blown condenser and maybe complete with an evaporator? I've often thought about controlled release CO2 canisters, utilizing the cooling generated as the compressed air escapes.

Just some thoughts and ideas. I'm looking forward to seeing the progress as this moves along.

[questtek]

Peltier Cooling Device Test Results

Several current threads in this forum mention the potential use of Peltier devices for ESC cooling on FE boats. I thought it was time to investigate this a bit further with some actual lab testing and real numbers.

The pictures attached show the details of my Peltier testing set up. On the desk is the Peltier thermoelectric cooling unit and large aluminum heat sink. Nest to it is the control board. It is powered by a 3S LiPo pack providing about 12 vdc. A V-3 Eagle Tree data logger with three temperature probes round out the test configuration.

The real-time data on the LCD monitor shows the three thermocouple temperatures both in gauge and numeric digital formats. The temperatures are ambient, around 77 degrees F, cold temp from the top of the Peltier device, T1= 57.4 and the temperature of the large aluminum heat sink, T2=119.1 and ambient air temperature T3=78. The LiPo pack voltage was 12.51

System specifications;
The unit I tested was one I purchased over 10 years ago at surplus. It was designed for provide the transport of temperature sensitive medicines on aircraft during long flights. Ice melted and was unreliable, Dry ice was hard to get, but the Peltier with a good battery pack worked out just fine.

The aluminum unit shown in the close up photo weighs 1 lb 9 oz or 704 grams. It is about 5”x5”x3”. The circuit board next to it is 2 oz or 60 grams: about 2”x5”x0.5”. The circuit board permits cooling adjustment by a slide switch, ability to turn the unit on at a certain temperature and auto fan control to take spread the heat or cold around. I checked the respective voltages and think the unit can work at max cooling without the circuit board. The temp set features are not necessary for a FE application I believe. The unit does draw 4 amps at 12 vdc that represents around 50 watts of power.

The top Peltier cooling plate is the solid, almost cubic piece of aluminum on the top of the large aluminum heat sink. This is the “Meat” of the device and measures only about 3”x3”x1.5”. It absolutely does need a heat sink to work….BUT that heat sink could be a finned aluminum box section that holds your LiPo batteries and keeps them nice and warm for optimum performance. The ESC could then be mounted on the top of the Peltier block and snuggled down by the two bolts attached.

Does this have merit if a FE…………………. What do you think?

[questtek]

Joe, I'm glad to see you testing this idea.

Here are a few comments I have while moving forward:

1. Keep in mind that it may be advantageous to consider instant ice pack materials used for military field medical care. I'm not 100% familiar of the process, but it may be that you could incorporate controlled agitation (via vibration) to start and sustain cooling.

2. There is a product out there called Burn Gel that the military uses for severe burns. If I remember correctly, they had some concerns due to the high conductivity of the gel. It may be that the material would be a good, stable medium to use in the final design. The company that manufactures this stuff is H&H Associates and they also market the Cinchtight product. I'll see what I can do about going through my contacts of years past as I've known the owners for some time now. If I manage to get my hands on some, I'll send it to you.

Last, I have a question. At what point is this going to turn into a full blown condenser and maybe complete with an evaporator? I've often thought about controlled release CO2 canisters, utilizing the cooling generated as the compressed air escapes.

Just some thoughts and ideas. I'm looking forward to seeing the progress as this moves along.

All really great suggestions. First I want to make sure that the concept of using Blue Ice is feasible. It is certainly cheap enough, easy to get and will give me some basic data fast. It it does work out, you are correct, the next logical step is to use a Mil Spec or Medical version on this. Some how I think it might be a bit more athan 94 cents a pack!

Your CO2 idea is one that I have already been playing with. I would consider getting the CO2 from dry ice. If you ever tried to put water in a bottle then add a bit of dry ice and put on a cork? Fire in the Hole! It is dangerous to do but if you use caution you will be impressed with the temendous amount of pressure released.

The system I am considering adds a controlled amount of misting water to some dry ice in a copper container next to the ESC. The CO2 generated would provide good flow and eliminate the need for any additional pumps, batteries. Let the expending gas do the work including helping with the cooling. The system would have to be designed with a high degree of safety in mind. It is one thing to crash and sink a FE but quite another to have it blown up by a CO2 bomb!

Now, your mission is simply to come up with that safe, workable solution!

[Jeff Wohlt]

I would like to know if you cool the Peltier with our regular water cooliong if it indeed takes the coolness lower as well.

Also, I think the newer petiers may be a bit better but can't say for sure.

So how long would a 3S 1500 mah lipo last on that pletier?

Good stuff....I'm think you need to change your name to Dr FE!

I also found a pump that is small, I have not given up on the ice water idea but was impressed with the ice pack with so little in it to drop 20 degrees.

[wolf IV]

Great stuff joe!!

[questtek]

I would like to know if you cool the Peltier with our regular water cooliong if it indeed takes the coolness lower as well.

Also, I think the newer petiers may be a bit better but can't say for sure.

So how long would a 3S 1500 mah lipo last on that pletier?

Good stuff....I'm think you need to change your name to Dr FE!

I also found a pump that is small, I have not given up on the ice water idea but was impressed with the ice pack with so little in it to drop 20 degrees.

I would mount the FET side of the ESC direcly to the Peltier cold side plate. You could integrate a few copper tubes to pass thru cooling to the motor. At a constant 55 degrees F from the Peltier I cannot help but think those FETS would be quite happy.

Remember this used, surplus unit I have probably cost me less than $10 years ago. I have not done any research on current devices but that may be worthwhile. I certainly agree with you that there has probably been a terrific performance imporvement.

Also, I was thinking of removing the large aluminum heat sink on the unit I tested. I would replace it with a high capacity cooling plate and fan from some large quad-core computer processing chip. I bought a few of them for about $4 each.........but again they were surplus but new.

Your 3 cell Lipo is 1.5 amps and the unit I have runs at 4 amps. So, as a veryrough rule of thumb 1.5/4 = 0.375 hours or about 20 minutes.

As far as Dr. FE...........Thanks for the kind thought but there are probably at least several hundred guys on this forum that deserve it FAR more that me!

[Jeff Wohlt]

But the peltier begins cooling very quickly, yes?

20 minutes is good if a person can rotate the cells between heats. Just not sure it is worth it but for the big boats with room and long runtimes for racing. I would think anything would be better.

Keep up the good work. I am still on the cold water circulation idea but need something to work with in a real system . I have to stop by the hobby shop and get a fuel pump that works on 6v or 12 which draws next to nothing for power.

[questtek]

But the peltier begins cooling very quickly, yes?

20 minutes is good if a person can rotate the cells between heats. Just not sure it is worth it but for the big boats with room and long runtimes for racing. I would think anything would be better.

Keep up the good work. I am still on the cold water circulation idea but need something to work with in a real system . I have to stop by the hobby shop and get a fuel pump that works on 6v or 12 which draws next to nothing for power.

Yes, the Peltier begins cooling very fast. I found another Peltier unit I want to experiment with. It requires 6 VDC or two LiPos and pulls only 1.5 amps. It is very efficient and small. Even with the cooling heat sink is is about a 2" cube. The entire weight of the unit would be only a few ounces......compared to the 1 lb 9 oz unit I previously tested today!

[Meniscus]

Jeff, Why not a small fishtank pump? You can get very small ones fairly inexpensive and many of them run on 12v, very little power consumption.

Joe, regarding the blue ice, I was actually referring to a product the military uses where static, it is the same temperature as the environment. Then when agitated, a chemical reaction occurs where the pack safely drops temperature using biodegradable safe components that, even if exposed to a wound, are safe for contact and environment. => Instant ice pack. I'll see if I can find a link.

[Jeff Wohlt]

Most fish pumps I find were air not water but I will look. I found a very small round one that weighs nothing and only $12.

I also want a 6v for slow flow and then just a small pack of 2s would run it for a long time and actually bump it up a bit with flow.

My thought is why not be able to begin cooling prior to running. We used to do that with brushed and it made a big difference.

I remember people putting pumps in the cooler with water and hooking to the cooling system and circulating. Mags do much better at cool temps.

[Jeff Wohlt]

Found a lont of good info on cooling fluids and what the militarty uses, etc. Here was a pretty good one.

http://www.lytron.com/tools-technica...er-fluids.aspx

[Jeff Wohlt]

After reading so much this morning, I will now always use copper to make my ESC cooling plates. Also, there are many cooling fluids that can be used and much better than water. Now I might be able to use the little ice cubes Steven had so not to taint the fluid yet chill it.

PC fluid cooling CPUs is easy to find and good stuff.

[questtek]

After reading so much this morning, I will now always use copper to make my ESC cooling plates. Also, there are many cooling fluids that can be used and much better than water. Now I might be able to use the little ice cubes Steven had so not to taint the fluid yet chill it.

PC fluid cooling CPUs is easy to find and good stuff.

Glad all the stuff I wrote on thermal coefficients and heat conduction made a bit of sense to you. Since I mentioned CPU coolers let me give you a practical example. If you go to buy a normal CPU cooler with aluminum heatsink and 12 VDC brushless fan you will pay about $12 retail. You can pick the identical CPU cooler up in many surplus outlets for about $3 NEW. I have a good friend in the surplus business and this is what he sells them for at the local electronic swap meets.

However, if you do a search you will find that a COPPER heat sink CPU cooler will cost between $39 and $49. You can see this if you look at CPU coolers at www.frys.com (our local discount computer retail store in So California). Hummmmmmmmmmm.

If you put on your thinking cap there is a better, easier and cheaper way to cool your now copper heat sink that is mounted to the FETs oy your ESC that the Blue Ice methods I proposed. I even copied one forum members idea and tried to run 1/4" copper tubing inside the 94 cent Blue Ice pac. You can see the picture attached. I put thermistors on the inlet and outlet so I could monitor the output cooling temperature changes once per second for 5 minutes. I was really disappointed since in these tests I was seeing only a 9 degree F temperature difference at best! Not good enough so I had to come up with a new idea....and I did it by accident. This new idea shows real promice but you will have to wait a bit for me to build the system, instrument it then test it. Stay tuned for more unbearable excitment in the world of FE brushless ESC cooling technologies!

[Jeff Wohlt]

Interesting because I used 3 brass tubes and it took water down from 90 to 75. But when I put cooler water it did not bring it down as much.

Certainly when I slowed the flow by adding 3' of silcone tubing the water was cooler coming out. For this set up the coils are the key and flow in the coils and not fast. Easy enough to regulate flow with a small adjuster...like a drip garden inline that can slow the water down if needed...as in a pump method.

[Meniscus]

Most fish pumps I find were air not water but I will look. I found a very small round one that weighs nothing and only $12.

I also want a 6v for slow flow and then just a small pack of 2s would run it for a long time and actually bump it up a bit with flow...

My mistake, I meant a small fountain pump. They have real cheap ones that hardly flow any water, for instance a fountain that spills water over cut bamboo sticks or a rock.

Very cool find on the liquid cooling! If you were to go with a closed system, then there are many more options.

________________________________

I can see you scale guys now, incorporating motor mockups sticking up out of the hatch, tied to copper heat sinks inside. In my case, I'd be too tempted to generate Hydrogen and Oxygen out of water for the flamethrower out the back Or for that mater, to power a steam engine to depressurize and cool the air inside. This is just talk kids

[Jeff Wohlt]

I can find those pumps all day long but they are 120v.

Oh there is a way. I did not know there was a better cooling fluid. Distilled water is great but there is better...but then you do not want to use ice with it like you can with water. You have to use the cooling cubes...or maybe have a seperate place for water and just freeze the entire deal and let the water run around it or something. A block form of ice will last much longer as well.

We are really only talking about enough to stay cold for one heat or sporting around. At this point I can't say how long the cold water will last after removing heat so that is what I will try and test...not fair now with colder weather but worth it.

[domwilson]

I have one of those fountains. It has a "wall wart" that says 1t's output is 12v AC.

[questtek]

Interesting because I used 3 brass tubes and it took water down from 90 to 75. But when I put cooler water it did not bring it down as much.

Certainly when I slowed the flow by adding 3' of silcone tubing the water was cooler coming out. For this set up the coils are the key and flow in the coils and not fast. Easy enough to regulate flow with a small adjuster...like a drip garden inline that can slow the water down if needed...as in a pump method.

You are probably correct. My flow rate was pretty high. I should have measured it. The drip system miniture black plastic valve is a good one to try to control flow. I use those fittings a lot, especially the "T" fittings to put the thermistors in for my Eagle Tree monitorig.

I am off on a new approach. SOmehow I lost sight of the main objective which is to keep the FETS cold as efficienl as you can. Use of water cooling, while pretty good, may not be the only answer. I will post more of the new system I am currently testing.

[questtek]

I can see you scale guys now, incorporating motor mockups sticking up out of the hatch, tied to copper heat sinks inside. In my case, I'd be too tempted to generate Hydrogen and Oxygen out of water for the flamethrower out the back Or for that mater, to power a steam engine to depressurize and cool the air inside. This is just talk kids

Ok, OK, so you want to go James Bond on us! I included some pictures that probably fall into this category. It involved a 5" diameter finned COPPER sink twin heat pipes. You can see it on the back of my Mean Machine in the pictues attached.

The unit weighs 5.1 oz or 146 grams. If you do the calculations and set it up correctly with all the appropriate tricks, you will lower the temperature at ESC FET's by 50 to 60 degrees F! This means if your ESC peaks out at 140 degrees ,F ( just before smoking), you could potentially reduce the surface FET temperature to 80 to 80 degrees F. This special finned copper heat sink with heat tubes and some other tricks can pull out almost 90 watts of heat.

While incredibly efficient it is not practical for small FE's obviously. But, if you did have one of those big mother FE's that are only run by guys who wear Extra Large Speedos, this may be the James Bond toy for you...........to keep your cool.

[questtek]

I can find those pumps all day long but they are 120v.

Oh there is a way. I did not know there was a better cooling fluid. Distilled water is great but there is better...but then you do not want to use ice with it like you can with water. You have to use the cooling cubes...or maybe have a seperate place for water and just freeze the entire deal and let the water run around it or something. A block form of ice will last much longer as well.

We are really only talking about enough to stay cold for one heat or sporting around. At this point I can't say how long the cold water will last after removing heat so that is what I will try and test...not fair now with colder weather but worth it.

I am now experimenting with a VERY simple idea for ESC cooling. It is no way near the finished system but it is the start of a concept that involves bringing the FET's in direct contact via copper heat sink to one of the 94 cent plastic containers of Blue Ice. The attached pictures say it all.

I machined a 3/16" rectangle of pure copper plate. I carefully mounted it direcly on the indentation in the Blue Ice pac, (on the side that has the label..after removing it). The conduction through the copper plate is incredible, as you would imagine. I now place the speed controller, in this case a 100 AMP model, directly onto the copper plate via some thermal conducting white "grease".

It is in the freezer now so hopefully I will have a chance to test it tomorrow.

This represents probably one of the simplest ideas for DIRECT cooliong with out the need or electronics or pumps. But the idea can be greatly improved. With a little more work some copper tubing can be added and thus provide a cooler water flow to the motor.

[Ub Hauled]

how about some heat transfer paste to get the heat off the FETs faster to the copper plate?

I live in Lake Forest, Ca....

I know exactly where you live!!! Kyosho is just up the street from you, I have been there in a few occasions. There is a lot of water in that complex, very nice to see from the road...
are you allowed to swim in it?

[questtek]

how about some heat transfer paste to get the heat off the FETs faster to the copper plate?



I know exactly where you live!!! Kyosho is just up the street from you, I have been there in a few occasions. There is a lot of water in that complex, very nice to see from the road...
are you allowed to swim in it?

Yes, I always use the white heat transfer paste. I think I called it "grease" in a previous post but paste is more appropriate.

In term of the lake, you are probably thinking of Lake 2 which is called the Sun and Sail Club You can see it from Lake Forest Dr. I live on Lake 1, (called 1 beacuse it was the first of the three artifical lakes built in this area. I live on the lake at Lake Forest Beach and Tennis Club. If you have a chance, stop over some time. I have never been to Kyosho ...do they sell from their shop to the public?

[Ub Hauled]

I am not 100% sure they sell stuff at Kiosho, but they have the shop with the "thinkers there and they are always up to something... Kiosho in my opinion makes the most beautiful, RC cars, they are not the best out there but in finishing they take 1st place. I went there with something I both in one of the RCX shows and was having problems with, they were friendly and fixed it... maybe it's the kinda place you can walk in and talk to the people making the things happen... besides, straight across the street is a "little" place called "RED" one of the best HD cameras in the market (it's the pet project of the owner of Oakley), never been in there... don't have the money to afford their cameras.
Yes, I was thinking of Lake 2, I didn't wanna mention the name of the street going up since I dind't know if you wanted to give away your location, but yes, it is Lake Forest Dr. that takes me up to Kiosho.
If I ever come down there again, I'll get in touch with you and see if we can meet.

[questtek]

Blue Ice / Coppersink Cooling Tests

The purpose of this bench test is to monitor the temperature of the FET side of the copper plate integrated into the Blue Ice pack as described in a previous post.

Themistors were mounted on FET contact side of copper plate integrated into the 94 cent Blue Ice plastic container and another measuring ambient temperature.

Ambient temperature remained a constant 79 degrees F throughout the testing.

Copper cooling plate temperature decreased with time. These values represent the temps the FET’s would see, (ESC is not under load for this initial so it generated no temperature).

Time Temperature of Copper Plate Delta Temp (ambient-copper cooling plate)

1 minute 59.9 degrees F 19.1 degrees F
2 57.3 21.7
3 54.9 24.1
4 52.5 26.5
5 50.8 28.2
6 49.0 30.0
10 48.5 30.5

To me, this looks VERY promising. I was hoping for a 20 degreed drop and the tests show the actual temperature drip is closer to 30 degrees F. This impresses me.

I have been waiting 3wbeeks now for the 200 AMP Mystery ESC’s to be delivered for some real testing. Hopefully I will not have to wait much longer to publish some actual performance results.

[questtek]

Looks like a new, very promising het transfer materal was just developed and released. One of the technical magazines I receive monthly just had an article on it. I ordered some samples so hopefully it can live up to its claims. It is apeel and place thermal solutions that will even withstnd the heat of solder reflow. It will permit the adhearing of the FET sde of the ESC directly onto the copper cooling sink.

See:
http://www.bergquistcompany.com/ther...nd-ply-450.htm

[Drag Boat Bob]

Did you put the whole thing in the freezer after attaching the ESC via 'grease'?

If so, did you seal the ESC with anything?

Just wondering about the condensation as everything starts to thaw.

This is great stuff, keep up the good work!

[Jeff Wohlt]

There are virtually 1000's of small boxes with lids that could be filled with blue and frozen to actually fit on top of the ESC fets with the termo tape with very little weight if that is the idea. No need for larger. A small copper plate mounted on the box, even alum plate would be fine for that cold, then freeze it and you can even hold it on the ESC fets with two rubber bands. It would be very cold.

I do worry about condensation but at what point that would happen is undetermined yet. No matter if the gel begins to met as it would still have plenty of cold....maybe not frozen yet only left in the cooler of ice so it gel is still very cold....which should do plenty.