ESC Cooling Concept- Theory and Practice

[Jeff Wohlt]

I would love to see numbers pumping cold water thru that copper plate.

My idea is to have a small nitro tank and freeze about 1/2" water in the bottom so it makes a block. Then you put them in your cooler. The block of ice will last much longer than any pieces put in. Then you simply use a 4 cell pack and 6v pump and use the Tank with the orginal clunker draw tube to stay on the bottom as it will be colder than water coming in at the top.

[pescador]

I found a pretty small pump here and it's DC with a switch.
Used for model train sets. 2 1/2" x 1".
Who knows how much it puts out though.
I'm picturing an Eagletree temperature telemetry and 3rd channel control of the pump.

http://www3.towerhobbies.com/cgi-bin/WTI0001P?I=LX7194&P=8

[questtek]

Mystery 200 AMP ESC cooling comparison graph

I could not figure out how to post an excel graph so I just took a picture of my computer screen to show the ESC FET temperature using several different cooling techniques.

If the graph is a bit hard to read perhaps I can explain it a bit…….

The graph is intended to show FET temps VS time (up to 6 minutes) for a 540 XL motor run on my water test stand drawing 75 watts from a 2S 40C 5000 mAhr LiPo pac. I used an Eagle Tree Glass Bead thermistor to measure FET temp. The test indeed compares apples-to-apples.

The upper graph is the stock Mystic 200 AMP ESC run under the load conditions mentioned. After 4 minutes the FET temp is up to 109.5 degrees F

The graph below this is the same ESC with my 2-tube copper heat sink but there is NO water flow thru the tube. At the end of 4 minutes the FET temp was 96.7 degrees F. The mass of copper did help “absorb” some of the heat generated. But, at the end of 6 minutes the temp was up to 104.5 degrees F. That mass of copper is heating up since there is no air or water forced cooling.

The graph below that is the same as above BUT WITH WATER COOLING. This was supplied by a small external 12 VDC pump using ambient water temp around 78 degrees F. The water-cooling helped, even with just this 2-tube copper heat exchanger. At the end of 4 minutes the temp was 85.7 degrees F. This represents almost 15 degrees lower that the “stock” Mystery ESC and about 11 degrees cooler than the large copper sink that did not have water cooling. Water-cooling works.

In the lowest graph I show the effects of the same ESC, under the same operating conditions but this time with NO WATER FLOW but mounted on a small BLUE ICE pac in my 25-cent Tupperware container. At the end of 4 minutes the temperature is a cool 76.7 degrees F. Even at the end of 10 minutes the FET temp only gets to 92.6 degrees F.

The test results show that the use of the small Blue Ice pac reduced the FET temp by 9 degrees compared to water-cooling. Remember, these tests were only at 75 watts and the 540 XL can easily handle over 800 watts. I expect the temps to have a much higher performance spread at elevated power levels.

Suggestions and comments?

[bustitup]

I can make these cooling plates but was wondering are they as efficient as your solid copper block cooling plates or are these single plate ones good enough

do you have a build thread on the solid block ones?

thanks in advance

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!

[questtek]

I can make these cooling plates but was wondering are they as efficient as your solid copper block cooling plates or are these single plate ones good enough

do you have a build thread on the solid block ones?

thanks in advance

I have included a few pictures to guide you but it is really simple. The main parts, shown in the first picture are
1. 3/8" thick copper bar stock
2. 5/32 copper tubing
3. drill to make the tubing fit snug in the drilled copper block
4. 2-part thermal conductive epoxy

I measure and cut the copper bar stock to fit the FET are of the ESC to be cooled. I then drill 4 holes through the bar stock. The snug gitting copper tubing is cut in 2.5" lengths and tapped with a rubber mallet into the openings. I then coat the ends with the black conductive epoxy. Add the silicon water cooling tubes in any arrangement that best fits your installation.

This arrangement, as you can read in the previous post is excellent for cooling the ESC. The only better arrangement is to use the Blue Ice system in which the copper plate is in direct contact with the small Blue Ice pac and no water cooling is necessary.

Hope this helps.

[Jeff Wohlt]

So all you are missing and would really help is pumping cold water like ice chilled water thru and see what you get. Pretty sure you may find the cold water really knockes that plate temp down quickly.

Can you pump some ice cubed water thru.

[questtek]

So all you are missing and would really help is pumping cold water like ice chilled water thru and see what you get. Pretty sure you may find the cold water really knockes that plate temp down quickly.

Can you pump some ice cubed water thru.

It appears your idea was a good one. The FET temps under the identical load of the previous tests now went from 42.8 F (I ran the pump and circulated the ice water cooling for 4 minutes to pre cool the copper heat sink), to a maximum of only 50.8 F at the end of 6 minutes at the 75 watt load factor.

This means that with a good heat sink and proper cold water circulation the FET temp increase was less than 7 F after 6 minutes of light load running. This is pretty incredible when you consider that the FET temps were 109.5 degrees afer only 4 minutes under the identical load conditions for the "Stock" 20 AMP Mystery ESC.

Test Conditions / Time in minutes
0 0.5 1 2 3 4 5 6
Factory Stock
88.3 91.2 94.2 100 105 109.5
With Blue Ice on copper plate heat sink
57.8 61.6 63.2 68.3 73.2 76.7 80.1 83.5
With large 2-tube copper heat sink (NO water flow)
75.9 81.9 84.2 88.6 92.9 96.7 101 104.2
With large 2-tube copper heat sink (WITH water flow about 78 F)
80.5 82.4 83.1 84.9 85.7 87 88.1 89.1
With large 2-tube copper heat sind (WITH ice water flow at 37.3 F)
42.8 44.1 45.5 47.6 48.9 49.9 50.4 50.8
(pump ran for 4 minutes to pre-cool copper heat sink)

Pictures of the test set up attached.

[Jeff Wohlt]

Wow...super stuff! Thank you very much for your time on this!

AND THE REAL BONUS to a system like this is pre cooling both ESC block and motor with a flip of a switch even a couple minutes before a race or sport running will still drive temps down. The other issue is you can run the pump very slow for this and still have great cooling.

Any idea how the motor heat was doing? Can you have a line to it as well? I know it would be great to cool mags before they crank up. More mag power!

You da man!

[questtek]

Wow...super stuff! Thank you very much for your time on this!

AND THE REAL BONUS to a system like this is pre cooling both ESC block and motor with a flip of a switch even a couple minutes before a race or sport running will still drive temps down. The other issue is you can run the pump very slow for this and still have great cooling.

Any idea how the motor heat was doing? Can you have a line to it as well? I know it would be great to cool mags before they crank up. More mag power!

You da man!

Glad you found it interesting.......I certainly did!

Now that I have the test set up I want to put in more thermistors. In my testing I did not even have the water jacket on the 540 XL hooked up so NO water flo thru it. The next tests will do this so I can report motor temps, etc.

You are certainly correct on the pre-cooling.
Here is the actual data from the FET mounted thermistor with just the ice cooling water on and my small pump to circulate it:
Start temp 71.3 F
30 sec 57.8 F
1 min 50.1 F
2 min 46.9 F
4 min 44.3 F

The large copper heat sink is a REAl key component here because it can "Store" the cold very effectively.

[Jeff Wohlt]

You are on a roll man!

Okay okay...how about a temp test on the smaller two line one you did not using the block? So it would be like a cooling plate we buy or that comes on the 240, etc...even though they are alum. My point is some systems may see the benefit even as they are now...I am sure they would but do not know to what degree.

Something like an etti controller or even a CC240, etc.

My reasoning is CAN a person simply add a small pump and tank and expect super cooling...even from aluminum plate or brass plate WITH the cooling tubes on the edges.

These numbers almost go down too low :) love it!!

[AndyKunz]

We used to pre-cool like this in the 1990's. A bucket of cold water drained thru fuel line into the boat's water pickup, and from there drained either on the parking lot or into a cooler (depending on if you had ice or not).

What's different?

Andy

[Jeff Wohlt]

A bucket vs a pump. :) A closed loop system pumping water out of a small nitro tank thru the equip and then back in the tank to chill. No 85 degree lake water. No rudder hole to plug up.

Even water cooling for cornering when the rudder does not pick up.

I found good micro 6v pumps for 8.95 and a tank is $7.00.

No ice chips but put tank in freezer with 1/2" of water and freeze to a block. Last longer and plenty cool.

Of course your EScs hardly got warm so just sit back down :)

[questtek]

You are on a roll man!

Okay okay...how about a temp test on the smaller two line one you did not using the block? So it would be like a cooling plate we buy or that comes on the 240, etc...even though they are alum. My point is some systems may see the benefit even as they are now...I am sure they would but do not know to what degree.

Something like an etti controller or even a CC240, etc.

My reasoning is CAN a person simply add a small pump and tank and expect super cooling...even from aluminum plate or brass plate WITH the cooling tubes on the edges.

These numbers almost go down too low :) love it!!

Ask and you shall receive.

See attached pics of the smaller copper heat sink I made with the edge tubes soldered in place. You can see also how it mates to the FETS. Again, I put a thermistor in between before the heat sink is mated to the FETs

Here is the data. Look specifically at the last entry. I included the entire table for an easy visual comparison. You can see it is still very effictive.

Unfortunately I have no aluminum plates for comps, just the plain, finned but not water cooled aluminum heat sink that comes with the "stock" controller.

Test Conditions / Time in minutes
0 0.5 1 2 3 4 5 6

Factory Stock
88.3 91.2 94.2 100 105 109.5

With Blue Ice on copper plate heat sink
57.8 61.6 63.2 68.3 73.2 76.7 80.1 83.5

With large 2-tube copper heat sink (NO water flow)
75.9 81.9 84.2 88.6 92.9 96.7 101 104.2

With large 2-tube copper heat sink (WITH water flow about 78 F)
80.5 82.4 83.1 84.9 85.7 87 88.1 89.1

With large 2-tube copper heat sink (WITH ice water flow at 37.3 F)
(pump ran for 4 minutes to pre-cool copper heat sink)

42.8 44.1 45.5 47.6 48.9 49.9 50.4 50.8

With small 2-tube edge copper heat sink (WITH ice water flow at 38.5F)
(pump ran for 4 minutes to pre-cool copper heat sink)

48 51 52.2 53.6 55.1 56.3 56.7 56.9

[questtek]

A bucket vs a pump. :) A closed loop system pumping water out of a small nitro tank thru the equip and then back in the tank to chill. No 85 degree lake water. No rudder hole to plug up.

Even water cooling for cornering when the rudder does not pick up.

I found good micro 6v pumps for 8.95 and a tank is $7.00.

No ice chips but put tank in freezer with 1/2" of water and freeze to a block. Last longer and plenty cool.

Of course your EScs hardly got warm so just sit back down :)

My test system is closed loop BUT I have a quart pitcher of ice water as my "tank" It would be interesting to try it on a very small tank, cool the 540 Xl motor also and run it for a longer time at a much higher amp draw.........but that's for another day.

[Jeff Wohlt]

Dang I feel like the poster child getting anything I want!

You are doing a big service to us all...just so you know that. Anyone not following this thread would be silly!

Yes, A small tank would be a better testing ground...just a simple tupperware container where the water is going back in the tank. Then prop up and pull some power! :) Are you finding that the tank is at a continuous level with water coming back in? Of course priming the system then filling with water would be good in a boat if using a very small tank and lots of tubing.

Also, a chance at geting a motor temp would be great....even if just by your hand!

Thanks man!