Quark 125b thermaling

[BrianG]

Yeah, I like their cases because they are easy to mount, but after looking at the thickness of the aluminum, it is really too thin and doesn't have enough thermal mass. Plus, the fins that do exist are really too small. According to their specs of being able to run up to 6s/18cells (~22v nominal) and 125A continuous, that is 2750 watts. At 90% controller efficiency, that's still 275 watts being dissipated on the controller, which is WAYY too much for that little heatsink. To be honest, the heat sink needed for that kind of dissipation would be quite large, even with fan cooling. Like I said, adding more thermal mass would be nice to pull the heat from the ESC, and then adding more/taller fins to dissipate the heat. Don't forget to use thermal compoung between the ESC heatsink and whatever you add for efficient thermal conductivity. I actually lightly sanded the back of the ESC to get rid of a lot of the texture and then used thermal epoxy (Arctic Silver) to secure the ESC to the added heatsink.

[squeeforever]

Brian, do you have a picture of what you did?

[BrianG]

Originally Posted by squeeforever

Brian, do you have a picture of what you did?

Not yet. My camera was dropped and I have to fiddle with it to get it to work. :mad:1

I'll try to get a pic of it later. The thermal adhesive I used is this: http://www.arcticsilver.com/arctic_s...l_adhesive.htm

The version I used has traces of silver in it (hence the name) so it is advisable to make sure none squishes across connections when you compress the heatsinks together. They have totally non-conductive stuff, but I didn't have any of that. You can use thermal tape too, but it doesn't work quite as good.

Whatever heatsink is used, make sure that both surfaces (the ESC and the added one) are smooth and flat for best contact and thermal transfer. Like I said, I sanded the back of the ESC with fine paper, and then I almost polished the piece of aluminum I used for the added heatsink.

[BrianG]

OK, a couple pictures of the heatsink:



I'll probably replace those shallow PC memory heatsinks with something a little bigger, but for now, it all works quite well.

[smhertzog]

The flat bottom of the heat sink offers the best surface area for heat transfer and it looks like you nailed it, I'd give it a few runs before I change anything. At most you might need a fan.

Very clean I like it.

I was going to swiss cheese my heat sink but the only problem is I don't know how much I can drill out before it is too much and I start overheating.
I think I'm going to make a few runs in the heat before I start fixing things that aren't broke.

[BrianG]

Like I said, the way I currently have it reduced temps by 12 degrees after 15 minutes of bashing around the yard. I am going to remove those small PC memory heatsinks and replace them with two of these, again mounted with thermal epoxy. That should reduce temps even more. I hate using a fan because it adds wiring complexity (albeit small) and it's just one more thing to break or wear out, which is especially bad if you are counting on the fan to keep things cool. I'd rather keep it passive if at all possible and arrange the fins so airflow runs through them. Swiss-cheesing the sink should work as well too - I'd use holes no larger than 1/8" and have 1/8" spaces between them. The idea is to create as much exposed surface area as possible while keeping enough mass in between.

[squeeforever]

Cutting holes in the top and adding a fan over them would be a good option...

[Sylvester]

He just said he doesnt like fans squee:p Alot of people think a fan is a type of "bandaid"

[squeeforever]

Sylvester, I don't particularly like them either. I was just saying. Its a option for some people.

[sjcrss]

how is a fan a "bandaid"...just think...if your PC didn't have any fans to help keep it cool...you wouldn't be able to use your pc with out it overheating...let alone getting on this forum...I see fans an neccessity in some cases, but a personal preferance on others.....my thought is...a little extra airflow on the controller can't hurt it at all.

[Sylvester]

Yea, but like brian said, on an rc you'd have to replace them after a while, it can be just another thing to break, takes away some runtime, and adds complexity to the wiring, i dont like them too much, thats why people use bigger heatsinks.

Originally Posted by BrianG

Like I said, the way I currently have it reduced temps by 12 degrees after 15 minutes of bashing around the yard. I am going to remove those small PC memory heatsinks and replace them with two of these, again mounted with thermal epoxy. That should reduce temps even more. I hate using a fan because it adds wiring complexity (albeit small) and it's just one more thing to break or wear out, which is especially bad if you are counting on the fan to keep things cool. I'd rather keep it passive if at all possible and arrange the fins so airflow runs through them. Swiss-cheesing the sink should work as well too - I'd use holes no larger than 1/8" and have 1/8" spaces between them. The idea is to create as much exposed surface area as possible while keeping enough mass in between.

Great site. http://www.accelthermal.com/ Is there a minimum amount of heatsink material you have to order.

[BrianG]

Originally Posted by Cartwheels

Great site. http://www.accelthermal.com/ Is there a minimum amount of heatsink material you have to order.

I'm not sure. I sent them an email yesterday asking that exact thing. It's funny; there is a link for how to order, but it doesn't tell you how to actually order the stuff. I guess either send an email or call them? If/when I get a response, I'll let you know.

As to the fan thing. I agree that sometimes they are necessary like in a PC (although I had an idea where if the CPU was mounted on the reverse side of the motherboard, you could use the whole side/bottom panel for a heatsink). However, in an RC, you have movement which creates airflow. PCs generally don't move around. :dft012: I try to remove as many mechanical parts as possible since things with moving parts are the first things to go bad. Sometimes though, a fan will be necessary and I can accept that as long as it makes sense and is not used to compensate for a bad design or use.

Personally, I think all these ESC heatsinks are too small. But if I look at it from a manufacturers standpoint, I would want to create something small and light that will fit just about everywhere and let the end user decide how to cool it. If they create something with a big enough heatsink, it might reduce their target audience since some may use it in buggies where room is more of a premium - or maybe the dimensions of the bigger unit won't physically fit where the user wants it to go.

I applaud Quark for making a unit where adding a heatsink is possible without having to seriously mod the unit. And doing this really can't go against their warranty as long as the voltage and current limits are met. Nothing was cut or changed, just added to. Thermal epoxy is considered permanent, but it can be removed if you really try.

Here is the heatsink I'm using right now. http://www.dealsonic.com/thera1ddrsdr.html . It works but does not fit that well. I've got the two heat sinks side by side runing long ways on the quark controller. They are not quite long enough and a little wide. I might order one more set and run them the other direction and cut the extra off. That way it would be a cleaner fit.

[smhertzog]

Fans do have some good points.
I have a lipo setup in my mini lst and on a few occasions I forgot to unplug the battery. Once it drained the lipo battery to the point were I had to charge it as a NIMH battery till it got a charge in it because my charger wouldn't even charge it. I was waiting for it to go boom but it didn't, it also was never the same either and I have since pitched it. There is no misstaking wether or not my Emaxx is on, the little novak fans sound like a turbo spooling up which is kind of cool in itself. Just imagine ruining $280 worth of batteries just because you forgot to unplug your batteries.
As far as run time goes I havent noticed a difference, there is a difference it is using a fraction of an amp but its not noticable.
As far as wiring complexity one more pair of wires isnt that big of a deal.
Just my 2 cents, I never knew fans were taboo with so many people.
In the end to each his own i guess.