ESC Cooling Concept- Theory and Practice

[questtek]

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!

No, Just the Blue Ice pac with attached copper sink went in the freezer. The ESC is added just before a run.

The ESC in the pics is one of many 100 and 200 amp ESC's that I fried. I am waiting on 4 new ones to actually test. I used it to determine the correct dimensions of the copper heat sink.

The ESC MUST be sealed. I do this by spraying on numerous coats of Silicon coating. SOme guys brush it on, others dip it....so there is a variety of methods but the ESC MUST be conformal coated. You are correct about the condensation also. This is the main reason to insure the ESC is coated.

I will mount the ESC after the copper plate comes out of the freezer. The new T-Clad Bond Ply 450 that I mentioned in a previous entry shows great potential here. I will have a simple mounting system that secures the ESC to the copper heat sink so proper contact and maximum heat transfer is obtained. This way I just reach into my ice chest, get a new cooling unit and strap it to the same ESC.

[questtek]

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.

Congrats.......you really have put on your thinking cap! This is a unit I built yesterday out of an Altoid breath mint box. (Pictures attached) You can play with your FE's and have kissing-sweet breath now at the same time!

The pictures show it all. First the unit is smaller and lighter than the standard Blue Ice Plastic Pac. I weighs a mere 4.4 oz or 146 grams without the Blue Ice and 7.8 ounces or 222 grams filled with the frozen Blue Ice. This is a bit less than the 9 ounces or 256 grams from the Plastic Blue Ice system.

The new system has many advantages. First the metal Altoid tin transfers the cold much better than the plastic Blue Ice pac. This also applies to the Tupperware-type containers you mention. In addition, it is easy to solder the twin heat conducting tubes to the Altoid tin and copper heat sink for maximum cooling. This greatly helps the water outflow directed to cooling the motor.

I think the pictures tell it all. There are a few more refinements to be made but this concept looks potentially very feasible.

[Jeff Wohlt]

Hey there you go!

Now I am thinking smaller yet or even and old asprin tin or others that fit the ESC.... Just put the tin on the thermo tape to use and water cooling on sides of the tin to run to the motor (the cooling lines will be in contact with more cold on the sides... Why try to cool the plate and then ESC? Direct contact and cooling lines could actually be inside that will go to the motor only.


Got to be an easy way...KISS.

We know the motor needs cooling and water passing in the lines will certainly help but not the best...unless the coils can be put inside the can and sealed,

[Jeff Wohlt]

Here is just one place

http://www.customtins.biz/standard_sizes.html

[Jeff Wohlt]

Another...I think these will be a perfect set up with the right size. Even cold gel is very cold and stays cold.

http://www.specialtybottle.com/index.asp?PageAction=VIEWPROD&ProdID=331

[questtek]

Hey there you go!

Now I am thinking smaller yet or even and old asprin tin or others that fit the ESC.... Just put the tin on the thermo tape to use and water cooling on sides of the tin to run to the motor (the cooling lines will be in contact with more cold on the sides... Why try to cool the plate and then ESC? Direct contact and cooling lines could actually be inside that will go to the motor only.


Got to be an easy way...KISS.

We know the motor needs cooling and water passing in the lines will certainly help but not the best...unless the coils can be put inside the can and sealed,

Word of caution...do not try to go too small. I think an asprin tin may be good for a 30 amp ESC. For the big boys you need to pull out lots of heat. I only deal with the 100 to 200 amp ESC's.

It is not the water cooling that is helping the ESC to any great extent....it is the massive cold sink with the copper contacting the FET's In turn, it is the Blue Ice in the Altoid tin that is keeping the copper sink cold. The amount of Blue Ice needed, thus the size of the contaner, depends on just how much heat must be pulled out. In my opinion you can never get a big ESC too cold!

I should do some math.........Possibly we could get away with a giant copper heat sink that is put into the freezer before use. We could "store" a lot of cold in this highly conductive hunk of metal.....maybe enough to cool a big ESC on a 5 minute run? Where is that old slide rule? The downside to this is that we do not take advantage of the latent heat of melting, (some times called the latent heat of fusion), as ice changes state into water or the Blue Ice goes from a solid to a gel

The term latent heat refers to the amount of energy absorbed by a chemical substance, such as water, during a change of state (ice to liquid) that occurs without changing its temperatue. For water, 144 BTU's per poundare absorbed in the ice to water. This is why you can put your beer in a cold water stream but it never gets really cold. You need to put it into an ice chest so the menting ice can "pull" the heat out of your Bud.

Lots to consider..........and experiment with!

[questtek]

Another...I think these will be a perfect set up with the right size. Even cold gel is very cold and stays cold.


http://www.specialtybottle.com/index...ROD&ProdID=331

Great find...I think they will be perfect.

[Drag Boat Bob]

I am curious about the benefit of pickup water circulation through the ESC at all.

Won't the water, being at a higher temperature than the frozen material actually increase the speed of defrosting? This may be different if you are staying with a closed loop water circulation system and not using pond water at all.

I think I am leaning toward your solid frozen block without circulation idea. Just swap them out before each run. I guess they will need to be of sufficient size however.

[questtek]

I am curious about the benefit of pickup water circulation through the ESC at all.

Won't the water, being at a higher temperature than the frozen material actually increase the speed of defrosting? This may be different if you are staying with a closed loop water circulation system and not using pond water at all.

I think I am leaning toward your solid frozen block without circulation idea. Just swap them out before each run. I guess they will need to be of sufficient size however.

You are ABSOLUTELY correct! I had to build all the hardware and do all the tests but that is the conclusion I arrived at.....and the data shows it!

Now that you have the punchline, I can show you just how I went about it.

First, my package of Mystery controllers arrive after a bit over 3 weeks. Packageg in a plain brown wrapper, I got 2 of the 100 Amps ESC's and 2 of the 200 Amp ESC's. (picture shows differences) I put on all the appropriate connectors and much to my surprise they all worked! I knew I was off to a good start. With the controllers working, I established temperature baseline conditions on the "stock" Mystery ESC's. I used three thermistors tied into my Eagle Tree data logger. One thermistor on the heatsink under the Mystery label, one inside the controller from the Power lead side and the last one into the controller from the 3-wire motor side.

I wanted to do lots of testing on these ESC'a and did not want to burn them up in the first few hours so I am limiting my initial testing to a 2S 40C 5000mAhr pac and limiting the current to 10 amps for about 70 watts delivered to a 540 XL mounted in my water bath test stand (see previous post for details of the test setup)

Even at low amps the temperature of the two thermisters shoved inside the shrink wrap of the ESC's got above 102 degrees. Measurements taken on the outside of the heat sink under the Mystery label were always about 8 degrees cooler. (all temps in degrees F) Amazing, with only 70 watts supplied to the ESC's the temps were around 102 degrees and that was measured NOT on the FET's but just inside the shrink wrap!

It was clear to me I would have to mount thermistors inside the ESC directly next to the FET's to really find out the temperatures they are exposed to.

I also designed some copper heat sinks with cooling tubes and even ones that integrated a small 12 VDC high velocity computer fan and heat sink. More on the testing and the results in the next post. You will be amazed at the actual test results!

[FE Wannabe]

Great informative thread.
Since we are speculating on cooling methods, I thought I would throw my idea in the mix.

I noticed you mentioned that one of your heat sinks had heat pipes in it. I was wondering if you had given any thought to using heat pipes by themselves to transfer heat from the heat sink or Peltier plate to the exterior of the hull? On the outside of the hull the heat pipes could attach to another heat sink or plate that would either contact cool air or water.
I hear that they are actually making flexible heat pipes now, which would make installation and day to day use a little more practical.
Also the one of the biggest benefits, if it works efficient enough, would be no water condensation to worry about.
Just my 2 cents.
Brad

[pescador]

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.

If your still looking for pumps check out bilge pumps, there are some pretty small ones and they are 12 volt.
If you want to throttle it down with a small valve always put it on the output of the pump.

[questtek]

Heat Sink Effectiveness using they Mystery 100 Amp ESC

Data from all tests are based on using a 2S, 40C, 5000 mAhr pac, Thermistor adjacent to the FET’s, with 540 XL motor running at 10 amps or about 75 watts in my water bath ESC torture test chamber. Ambient temperature about 80 degrees F. All temperatures in degrees F.

ESC testing configuration FET Temperature at: 1 min 2 min 4 min

“Stock” mystery 100 amp ESC with aluminum heat sink 94.2 100 109.5

I then used a large 5” diameter Sony Model SFF22C
centrifugal blower drawing .5 amps at 12 VDC to simulate
conditions of the ESC in the prop wash of an RC plane
(a small CPU fan is 2: dia and pulls only 0.05 amps) to see how
the 109.5 temperature would be lowered. With this fan ……. 94.6 90.8 88.6
(Great cooling but way too big to be practical)

My Copper sink with 12 VDC small CPU fan (fan off) 84.4 88.1 89.4

Above but with the small 2” dia CPU fan on 83.3 86.4 87.2
(From this you can see the small CPU fan is almost worthless)

And now I saved the best for last………

My Copper sink mated to a frozen Blue Ice Plastic Gel pac 63.2 68.3 76.7
(and even after 10 minutes of continual running the temperature
was only 92.6 degrees!)

The Blue Ice pac proved more effective than I anticipated. Even after 10 minutes only about 20% of the pac was melted. That indicated that the Blue Ice container could be potentially smaller BUT remember this 540 XL was only pulling 75 watts!

THE NET RESULT IS THAT AT THE 4 MINUTE RUN PERIOD THE BLUE ICE COOLING PROVIDED A FET TEMPERATURE THAT WAS 32.8 DEGREES COLDER THAN THE STOCK MYSTERY ALUMINUM HEAT SINK. (109.9 - 76.7)

Pictures show various configurations and Blue Ice test set up.

Recommendations and Suggestions?

[questtek]

Great informative thread.
Since we are speculating on cooling methods, I thought I would throw my idea in the mix.

I noticed you mentioned that one of your heat sinks had heat pipes in it. I was wondering if you had given any thought to using heat pipes by themselves to transfer heat from the heat sink or Peltier plate to the exterior of the hull? On the outside of the hull the heat pipes could attach to another heat sink or plate that would either contact cool air or water.
I hear that they are actually making flexible heat pipes now, which would make installation and day to day use a little more practical.
Also the one of the biggest benefits, if it works efficient enough, would be no water condensation to worry about.
Just my 2 cents.
Brad

All good ideas, Brad. I have two different heat pipe setups that I have been playing with. They are made from 1/4" copper tubing and have an incredible fin arrangement. From the experiments I did I was not impressed with the amount of cooling the heat pipes gave me.......even with a big finned radiator on the heat pipes. There is a degree of complexity with this system so I put it on the shelf for the time being.

If you see my latest thread, I am tending to favor a passive system that uses the Blue Ice gel and NO water cooling. The test results were very promising and I have a few ideas to considerable improve its effectiveness and practicality. The new system will fit perfectly in my Mean Machines and provide incredible passive cooling. I just may be able to keep the inexpensive Mystery ESC's operating for a reasonable time.

Details to follow in a later post. I need to go to my local industrial metal supply store and buy some more 1/4" thick copper plate. I am so glad I have a solution that does not require soldering the copper cooling tubes to the thick copper heat sink. That was a REAL pain.

[crabstick]

found a windscreen washer pump that might work as a pump for the closed loop system, anyone else got any ideas for a small pump?

[Drag Boat Bob]

Like me, I think there are some computer builders out there...

I have cooled a cpu with a frozen padlock (3 in succession) in order to complete a diagnosis and repair.

Keep up this amazing work. I for one (and most likely others) believe this is valuable stuff for the future of FE!!!