Please allow your VESC to cool down!
I’m almost sure that a lot of fried VESC come from bad cooling.
Heatshrink tube is good to protect from water, but doesn’t allow Mosfet and DRV cooling.
VESC 6 and FOCBOX are well cooled.
Thierry
Normally the VESC decreases the current when a critical (adjustable in GUI) temperature is reached which is measured over a temperature sensor located nearly to the FETs. So it should not be possible to overheat when the temperature limits are set wisely. Can you back up your “almost sure” with something?
You are right about the protection if the temperature rise is slow, and that’s often the case with low to mid current motors.
But if it fast, and with high currents, the temperature of the die of the Mosfets will be much higher than the temperature of the sensor.
If you do a serious thermal analysis and take into account all the thermal resistances in your circuit model, you’ll see that I’m right.
That’s partly why the VESC 6 has been created.
Have a Nice Day.
Thierry
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I’m running two builds with dual Vescs They are covered with shrink tube and inside a sealed enclosures and I have no over heating issues. I’m 195 lbs and I charge steep hills. The catch is that they are equipped with heat sinks. That is the way to keep your Vescs cool. Ollinboards was first to offer Vescs with heat sinks. Then came the focbox and then Vesc 6
I dont think we are near the point that the temperature of the MOSFETs is far of the NTCs value. I have done a test with up to 120A motor current shooting the temperature in the temperature limit. You can read more about it here: VESC HW 4.12 temperature comparison - ESK8 Electronics - Electric Skateboard Builders Forum | Learn How to Build your own E-board
I dont think the temperature is off that much that it had destroyed a lot of VESCs as you stated. Let it be up to 5-10 °C difference max.
But feel free to make a serious thermal analysis and show us the results. 
Just equip them with heatsinks and then put them in heat shrink and inside a sealed enclosure isn’t useful at all. You have a slightly higher thermal capacity, but if your heatsink is hot ones it will also take longer to cool down. Look at the link I posted above.
All of my Vescs came with heat sinks and shrink tube. I neglected to mention that the shrink tube is cut to expose the heat sinks. I put them in a sealed enclosure to keep them dirt and moisture free. I also neglected to mention that they are not stacked or stuffed tightly in with other components but they have a decent amount of space around them to allow for some heat dissipation. I apologize for not being more specific and for being a little misleading.
That explains a lot. Couldn’t believe someone putting a heat sink on his VESC just to but a heat shrink over it afterwards.
What also explains why you don’t have a problem with heat is the observation that you are draining relatively low max currents of around 26.3A motor current when referring to this post: https://www.electric-skateboard.builders/t/6v-sag-too-much/32002/37?
When you are pulling over 60A you will see how important the airflow gets.
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How do you manage to pull 60a? I’ve tested 6s going steep uphill with dual motors and only pulled 36a total from the battery.
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I will do a more extensive post taking into account ambient temperature, current, voltage, switching frequency, and datashet of the Mosfet, because the problem is very complex.
And when someone blow-up a VESC, it’s often the result of many factors, not only temperature or current.
But it’s always better to keep electronic cool.
Have a Nice W-E.
Thierry
So do FOCboxes need external cooling, like an airscoop, over their heatsinks, or can I just put them in my enclosure and leave them like that?
I was talking about motor current, because that current flowing through the FETs is heating the VESC up. As you can see in the link I already posted above (VESC HW 4.12 temperature comparison - ESK8 Electronics - Electric Skateboard Builders Forum | Learn How to Build your own E-board) Im not just pulling 60A but 120A for a short time when accelerating. 60A was just a example where good cooling starts to become more important in my opinion.
It depends on the motor currents that you will reach and for how long. If you are pulling just 26A like @Namasaki does you shouldn’t have to much problems I think. The easiest way would be just log your temperature with something like the metr.at bluetooth module where you would see when you are hitting critical temperatures.
@ThierryGTLTS Looking forward to your post. Great that you will investigate more on that topic. 
I see, your talking about an E-bike pulling those high amps. My examples are with an E-board.
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It may take a few days.
Thierry
I am running one of my first VESC’s in heat shrink on a single motor build. I regularly hit the thermal cutoff on a really steep hill just before I reach the top. This VESC has been in service for over two years! I think you assume too much in regard to why a VESC will fail.
The biggest cause for failure by far is improper installation followed by poor manufacturing and cheap components. You could run a VESC at 80 degree Celsius all day and it would be fine.
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When you wanna have a very long lifetime (especially for electrolyic capacitors and semiconductors), you have to run them cool.
A well known engineering rule in the electronic industry says:
+10°C cut the lifetime by a factor of 2.
So you do what you want, but I don’t recommand using the VSC at those elevated temperatures.
Thierry
I thought you were blaming MOSFET failure on heat? Are we talking about capacitors now? I agree cooler is better but you are off the mark on your original assumption. If you are having trouble with heat I suggest you switch to a dual motor drive or a directfet design with heatsinks and actively cool with a fan.
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If you read my first post, I also include the DRV.
But I just wanna give advices after what I see here and elsewhere (industry and power electronic).
Some have troubles with Mosfets, others with DRV, others with capacitors.
Most of the resistors and MLCC capacitors are the only components that tolerate to work at high temperatures without premature failures.
As I said you can do what you want, no problem for me.
I know you have no issues with what I do but I do have issues with people spreading assumptions and stating them like facts without field testing on a skateboard. If a board is built with good specs and a proper gear ratio we actually do not see any issues with overheating or hitting the cutoff.
Some of us have been at this for a long time and have “real world” experience with the current state of eskate. It is disheartening to see new members join only to spread advise based on assumptions. If your VESC is getting as hot as you say you have a problem somewhere else in your build, gear ratio too tall, heavy rider paired with a single drive or something else?
The fact is there are many people still riding on 2 year old VESC’s who regularly push them to their limits. Are these people magicians, do the emit some protective force-field around them that protects electronics from failure or maybe it is because we are operating well withing the recommended temps for the components we use?
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My 2 ollin vescs from 2 years ago are still alive and well on my trampa in a UK water proof case. I might be a magician.
It seems I’m not welcome altough my advices are also based on more than 30 years of electronic engineering experience.
So I will shut off my mouth.
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