Custom (very) Quark esc heatsink...

[zeropointbug]

Hmmm, well that green one looks like a great one to use! With a little fan if you want?

The Athlon heatsink is kinda tall, and too heavy, IMO. Although, would work very well!

You've gotta have a small screw driver that can do this!? :032: :005:

I assure you, the FET's are not well thermally coupled to the case at all! First, the thermal pads are crap, not for high output applications, and there are two of these to go through. Second, where it attaches to the case, it's only touching along the two outer edges, about 1/4 each side. It just can't escape.

BTW, how come you bent down the side of your Quark case?! :002:

haha prying.. it's straight again.. if I did it again though, it'd most likely snap off.

i'll take it with me to work tommorow, and get it apart.. the AMD HSF is pretty big.. but I'm thinking about securing it to the controller.. and then have the fan on the side of the HS... and mount the HS on it's side, behind the steering servo, in front of one of the battery packs.. we'll find out how well that works in a few days i spose.. if not, the green one's the best bet.. I really need to get/make a 12V mod, so my fans run at 12v.. if you notice the deans connector on the UBEC, i've got one of my 12v fans running on 6v right now.. but it still pushes more air than the fans on the novak units lol

[BrianG]

I'm running the Quark on 4s with a 2600kv Neu on my buggy and it runs cool with a simple small heatsink (no internal mods yet). The internal mod just makes it run that much cooler.

And just to clarify about the way the internal pads work and what needs to be done to replace the existing heat spreader:



The drawing above isn't exactly to scale, but you get the idea...

The stock heat spreader is 2mm thick and each pad is 0.5mm thick. This thickness is needed so the capacitors clear the case. Once you remove the pads, there isn't enough thickness for the caps since the epoxy is very thin (practically 0mm). So, a new spreader that is 1/8" thick works perfectly.

[zeropointbug]

NICE work Brian! Very easy to understand.

The thermal pads and the slab, I measured 2.85mm together with a digital caliper. But I suppose 3.175mm won't hurt...

Do you know of any angle copper or aluminum that could be used to connect the top and bottom FET's together?

I'm almost tempted to make a water block slabs for the thing! And put a rad out front of the vehicle, now that would be the ultimate! :027:

I am just trying to figure out a way to keep this 540 7Xl cool! I should have just got the smooth can version and made my own water jacket for it. Then the entire vehicle would be water cooled.

Does anyone know how I could make the fins on the 540C can into a water jacket?

[zeropointbug]

GriffinRU, I know all the limitations about heatpipes...

They really do have to be tuned to a specific operating temps, and ambient temps.

I know this first hand.... frozen CPU.... i've done this before in the winter when it's -35C outside, with the PC case in the window, the CPU will get to below O temps, by doing this, you can get VERY high overclocking levels! Last year I took a Pentium 4 3.2 Northwood (130nm) to a sky high 4.25ghz! That was with a solid copper heatsink though.

THIS year, with my new PC with a large tower heatsink (Noctua NH-120) I did a cold window test, although only -15C, and the initial temps went down to about 5C, after a few mins of running the temps started to go up and up, until it hit 55C... hotter than what it gets at room temp! So they are definately sensitive to ambient temps. My guess is that the vapor just froze up and physically BLOCKED the vapor chamber.

I guess it all depends on the pressure of the working fluid for a certain temp range. Diameter, and length have to do with energy transfer.

Every couple months, manufacturers come out with new heatsinks, most all the new ones are heatpipe ones. The new Thermalright Ultra-120, and their IFX-14. The IFX uses biggest 8mm heatpipes, and uses 4.

If you had the room, the more heatpipes you can fit at the heat source and lower vaporizing temps the better, and evenly spacing the pipes into a fin radiator.

It's all in the design!

[GriffinRU]

Originally Posted by zeropointbug

GriffinRU, I know all the limitations about heatpipes...

They really do have to be tuned to a specific operating temps, and ambient temps.

I know this first hand.... frozen CPU.... i've done this before in the winter when it's -35C outside, with the PC case in the window, the CPU will get to below O temps, by doing this, you can get VERY high overclocking levels! Last year I took a Pentium 4 3.2 Northwood (130nm) to a sky high 4.25ghz! That was with a solid copper heatsink though.

THIS year, with my new PC with a large tower heatsink (Noctua NH-120) I did a cold window test, although only -15C, and the initial temps went down to about 5C, after a few mins of running the temps started to go up and up, until it hit 55C... hotter than what it gets at room temp! So they are definately sensitive to ambient temps. My guess is that the vapor just froze up and physically BLOCKED the vapor chamber.

I guess it all depends on the pressure of the working fluid for a certain temp range. Diameter, and length have to do with energy transfer.

Every couple months, manufacturers come out with new heatsinks, most all the new ones are heatpipe ones. The new Thermalright Ultra-120, and their IFX-14. The IFX uses biggest 8mm heatpipes, and uses 4.

If you had the room, the more heatpipes you can fit at the heat source and lower vaporizing temps the better, and evenly spacing the pipes into a fin radiator.

It's all in the design!

Dude have you tried liquid nitrogen cheap and efficient, you will be surprised what you can do with logic in liquid nitrogen :)

The only problem what is good for CPU is not the same for buggy running at open, not in air-conditioning environment...

I am sorry but I think we done here. Information was for everyone do not take it personal.

[BrianG]

Thanks! I thought it would be easier to explain with pictures. Unfortunately, I didn't take pictures of the process when I did it. Mine measured just under 3mm (like 2.97 IIRC) - maybe the pads weren't as compressed on mine. Dunno. But 1/8" works well.

I didn't touch the middle FETs since I didn't even have any idea how I was going to couple that heatspreader to the case. I figure the better cooling on the other side would help leach the heat away from the whole board improving cooling all around.

For your water jacket, just wrap some copper tubing around the fins. :)

[BrianG]

LOL, it's in the design of the CPU! Make a more efficient CPU and you won't need those exotic cooling solution. ;)

[zeropointbug]

Originally Posted by BrianG

LOL, it's in the design of the CPU! Make a more efficient CPU and you won't need those exotic cooling solution. ;)

Exactly! The record so far was the Pentium D 840, this thing was a SPACE HEATER! :005: :026:

The new Core 2 Duo's are quite a reduction in heat output! And doubling performance at the same time.

But a better heatsink, means higher clock speeds, IF you overclock, but enough of that talk...


"I am sorry but I think we done here. Information was for everyone do not take it personal."

Who is taking anything personal?

[GriffinRU]

Looking on all this mighty heatsinks I am thinking how much power dissipates on Quark?

Lets say 7XL draws 50A continuously, so at 0.00036Ohms at 25C power loss should be 0.9W
Next say at 100C derating factors bring us to 3 times up, so 0.00036*3=0.00108 - power loss now 2.7W

To get even 10W requires Rdon to be at 0.004Ohm which is 11.1 times higher then at 25C.

So, is the ESC efficiency so low or there is something else?

[zeropointbug]

Originally Posted by GriffinRU

Looking on all this mighty heatsinks I am thinking how much power dissipates on Quark?

Lets say 7XL draws 50A continuously, so at 0.00036Ohms at 25C power loss should be 0.9W
Next say at 100C derating factors bring us to 3 times up, so 0.00036*3=0.00108 - power loss now 2.7W

To get even 10W requires Rdon to be at 0.004Ohm which is 11.1 times higher then at 25C.

So, is the ESC efficiency so low or there is something else?

LOL, okay now I know... are you sure you know what your saying?

The physical resistance is only PART of the heat output. Most of the power loss is the design of the motor, and how well it transforms the power input to it.

What is 2.7Watt? That would be barely warm to the touch....

The esc I am guessing is somewhere between 92 - 97% efficient. Couldn't tell you, it's probably about 10 - 25 watts of heat, which is alot for these little FET's to dissipate, that's why they can get so hot because of insufficient heatsinking. With a proper heatsink, 25 watts of heat is a piece of cake to keep the temps down (~15C Delta).

Is there a misunderstanding here about motor efficiency.

[BrianG]

Originally Posted by zeropointbug

LOL, okay now I know... are you sure you know what your saying?

The physical resistance is only PART of the heat output. Most of the power loss is the design of the motor, and how well it transforms the power input to it.

What is 2.7Watt? That would be barely warm to the touch....

The esc I am guessing is somewhere between 92 - 97% efficient. Couldn't tell you, it's probably about 10 - 25 watts of heat, which is alot for these little FET's to dissipate, that's why they can get so hot because of insufficient heatsinking. With a proper heatsink, 25 watts of heat is a piece of cake to keep the temps down (~15C Delta).

Is there a misunderstanding here about motor efficiency.

Let's start by saying that motor efficiency has very little to do with ESC heat. The only motor spec that might effect ESC efficiency is the inductance value due to the phase angles produced, which can be more difficult to drive.

Assuming an FET goes rail to rail, the only time an FET dissipates power is when there is a voltage drop across the device AND current flow. If the output of the ESC were perfect square waves (0 rise time), then the ESC would be 100% efficient no matter what the motor is doing with that power. At the 0 point of the square wave, there is full voltage across the FET but 0A (0 watts). At the max point of the square wave, there is 0v dropped but there is max current (0 watts). But during the ramp up (the total time it takes to do this is the slew rate), there is voltage dropped AND current flow, which creates the heat. The longer the ramp, the more power loss and more heat. Higher frequencies have more pulses per second and therefore more "ramp up and downs" which can make them an ESC heat up more. However, too low of a switching frequency will cause the motor to not act correctly.

[GriffinRU]

Originally Posted by zeropointbug

LOL, okay now I know... are you sure you know what your saying?

The physical resistance is only PART of the heat output. Most of the power loss is the design of the motor, and how well it transforms the power input to it.

What is 2.7Watt? That would be barely warm to the touch....

The esc I am guessing is somewhere between 92 - 97% efficient. Couldn't tell you, it's probably about 10 - 25 watts of heat, which is alot for these little FET's to dissipate, that's why they can get so hot because of insufficient heatsinking. With a proper heatsink, 25 watts of heat is a piece of cake to keep the temps down (~15C Delta).

Is there a misunderstanding here about motor efficiency.

Thanks, but I think you need to work harder before you can corner me :)

Well, FET dissipates heat during switching when it is in analog mode, defined by rise and fall time plus capacitance and inductance of load. Which means that load (motor) can influence and does on ESC efficiency as well. Well if you integrate over time then you can calculate power loss on ESC, would be difficult to do that over each individual FET. And yes ther are lots of them in parallel, so 10W over n-FET's with 23.4cm^2 (70mmx34mm) heatsink surface area would be great. Old rule of thumb 1cm^2 per 1W good for 50C.

Do not forget to drive those FET's you need some power too, FET's are field driven but speed cost power, current in this case. In addition do not forget about built-in diode and it's temp dependence, I am assuming you know what this diode does in pair with caps, right.

Brian, for motor to be sensitive to rise and fall of FET's switching motor system (motor and inertia of drive train) must have response time in microseconds at list if not nanoseconds. Our motors without load maybe have ms of response time.

For me it looks like Quark 125A controller might have problem with some component on board, based on Leroy's comment about his low temperature runs with 80A. Does anybody have a clear picture of 125A PCB with FET's control part?

[BrianG]

I've wondered that myself, but it may simply be the way the Quark operates. I made a thread a while back showing the differences on how the MM behaves vs the quark when the motor is forced to a stall condition. Basically, the MM simple increases the throttle until the motor finally moves (which is bad IMO and the root cause of a couple of them burning up) vs the Quark being MUCH more gentle about it. I know this is mostly firmware programming, but maybe the engineers at S&T decided to decrease the slew rate a little for control reasons? And if you decrease the slew rate, there is more time where there is an actual voltage drop AND current draw creating more power loss. I really don't think it's a matter of raw FET specs. But, even in your example, 10W is actually quite a lot of power to be dissipated on a small heatsink.

And, I've not found a reason to get crazy with heatsinking - just enough to pull the heat away from the case and dissipate it to the ambient air, which should have enough flow in a moving vehicle to do so effectively. I don't like heat - at all - so when I say the ESC isn't hot, it isn't. To me, 130*F is too much.

[coolhandcountry]

I don't run a heat sink on a quark 80b. I have great temps on my gmaxx.
That is one huge heat sink though.