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How much heat is too much?

I couldnt figure out where else to post this so here it goes. I just got my first Bixler V1.1 I purchased the ARF and installed a HobbyKing HK 30A esc and a Turnigy 2200 3s. After the first flight I was supprised to feel alot of heat inside the plane, at first I attributed it to the fact that it was a foam plane and just retained the heat as there is no venting in the fuse itself. After the second flight I found the afore mentioned heat again and this time found the ESC had become hot enought to come loose from the adhesive on the velcro that I had attached it with, and was still quite hot to the touch, the battery and motor seemed about a normal temp. Both flights were at moderate throttle settings usually 1/4 to 1/2 with only a couple of short bursts to WOT lasting no more than a couple of seconds. Could the ESC have a problem, surely its big enough? I am reassonably new to electric flight and I am still learning so please share your knowledge with me on this matter. I am considering either moving the ESC outside the plane or adding some vent holes. I have a few other electric planes and have never had this problem before no matter how hard I flew them. Thanks for any advise you can give.


You probably want to consider cutting some ventilation holes in the nose and a bit aft of the canopy. I've seen escs get hot in these planes plenty of times. Another thing to consider doing is cutting the heat shrink from the metal heat sink on the esc. Really, I don't understand why manufacturers cover the heat sink with an insulator! Just silly. The heat sink will be on the "flat" face of the esc, probably where the label is affixed.


Active member
In rough terms the battery, ESC and motor all produce about the same amount of heat. They are after all handling the same amount of power.
Thermally the battery is big so it should not get too hot before it is exhausted and in a multi cell arrangement the amount of heat you can extract by air cooling is rather limited.
A brushless motor can tolerate quite high temperatures and an out runner has its moving parts directly in the open which provides a degree of forced air cooling particularly if the heated air can can be carried away.
The ESC has the biggest problem.
It is physically small, particularly the MOSFET chips that are doing all the work, so aluminium heat sinks are added to carry the heat away but even with them its thermal mass is small so it heats up quickly.

So of the 3 main items in an electric set up it the ESC that is likely to need some form of cooling.

Yes, you can cut away some of the heat shrink to expose the bare aluminium heat sink to improve the heat dissipation but be careful the heat shrink not only provide electrical insulation to the exposed parts of the circuit board but also holds the heat sink firmly in contact with the MOSFETs that need the cooling.

Try to arrange that there is a positive airflow over the ESC, preferably over both its surfaces.
It would also be useful to know exactly what current is actually flowing. If its getting close to 30A then a good cooling air stream over the ESC gets really important.

I hope this helps
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RC-Flyer I'm relatively new to the hobby but one of the first concerns I had was the overheating ESC's. I would cram everything into my power pod with little or no airflow. I have since moved the ESC's to the outside of most of my builds and they have performed as expected. If you can live with the looks, Id move it outside where it can breath and displace the heat. Good luck Brother.