[dsnow33]

So I'm making my first quadcopter and have run into a recurring problem. Basically, when I run the motors through LibrePilot some of my ESCs keep heating up and unexpectedly burning the shrinkwrap and burning. After, I bought a new set of ESCs and the same happened.

Notes:
- LiPo battery is 3S 2200mAh 11.1v (this was suggested in product Q and A)
- MT2204 2300 kv brushless motors
- 12A simonK ESCs

The full set is here:
https://www.amazon.co.uk/LHI-Quadcopter-Racing-Controller-propeller-x/dp/B010FMGUS8/ref=sr_1_2_sspa?s=kids&ie=UTF8&qid=1546894645&sr=1-2-spons&keywords=lhi&psc=1

Any help or advice welcome, I want to know if I'm just getting unlucky or if I'm consistently messing up somewhere. 

[TheOtherCliff]

Is it only one ESC or do they all burn?

When do they get hot?  Any time the battery is plugged in?  Only when you try to run the motors?

Do the motors start smoothly and run or do they jerk back and forth?  Jerking on one motor is a sign of a burned out motor.  Jerking on all motors is a sign of incompatibility between ESC brand and motor brand.

Measure the current draw of the whole system from the battery and quickly disconnect before it gets hot.  How much current?

These are likely if one or two get hot:
- one or more motors are shorted out internally (but only for the shorted out motors)
- you connect battery power to ESCs backwards (but only for the ESCs connected backwards)
- the three wires from ESC to motor are allowed to touch (but only for the ones touching)

These are likely if all get hot:
- your battery has more voltage than the ESC allows
- you run high voltage battery (3S or higher) and draw a lot of current through FC (something there is shorted out, or do you have servos connected?).

Related to the last thing in the list, unplug all extra components (OSD, GPS, mag, RC receiver).  Does it still heat up?  Measure current for each component.  What current does each one draw?

[dsnow33]

When all the ESCs were in place, it was one of them. After replacing that one (and an ESC that didn't work) one of the originally working ones burnt.
Yes, the affected motors did jerk around a bit just before the disaster.
The battery is the right way round, they link correctly to the PDB.
The ESC wires aren't touching either, I had them exposed during testing.

If the motors are jerking (shorted out) I can't fix them, right?
So new motors and new ESCs are needed?

[TheOtherCliff]

When do they get hot?  Any time the battery is plugged in?  Only when you try to run the motors?

Some small jerking is OK if they can all start up and they run smoothly once they are started.  I had a quad like that once.  The problem went away when I updated the ESC firmware.

If they burn only when you try to run the motors, then realize that the worst thing you can do is use more throttle to try to start a jerking motor.  That will make the ESC burn up and smoke.  When smoke comes out it is always destroyed.  Instead you try with just a little throttle and if some jerk, then you must stop the throttle and try to start the throttle just a little again ... and again.  If it is always the same 1 or 2 motors then there is a hardware problem.  If it is random or if it is always the "lowest" motor, then it is an incompatibility between ESC and motor.  Best solution is to update the ESC firmware to latest version.

Lowest motor is when it is sitting on the ground a little banked (unlevel) (even a such a small bank that you can't see it) and the lowest motor (downhill side) will be asked to start the hardest/fastest because it needs to come up to make the quad level.  If you suspect this, just bank it the other way and see if the problem motor has moved to the new lowest motor.  If you fine this is the only problem, then you can reconfigure Flight Mode Switch to use Rate mode (not self leveling) but that is hard for beginners.  Or you can just see which motor jerks and make it just a little higher and try again.  When you get it very carefully level, all 4 motors will start and you can fly it.

Any part that has ever smoked is probably damaged and should be tested or replaced.

You can test motors with an Ohm meter.  Any lead to any other lead should look like 0 ohms.  Any that read open (meter does not change when you connect leads) are burned out.

A very important thing you can do to avoid further damage is to insert an automotive light bulb in series with the battery.  Then it is impossible to burn motors or ESC and you should be able to test motors spinning slowly.  If you try to test motors faster, it will reset and you will have to rearm.
https://forum.librepilot.org/index.php?topic=2152.msg17429;topicseen#msg17429

The most common burned up thing for me is a motor winding is burned open, not shorted.  Acts like there is no connection to anything.  Motors like that must be replaced.  Motors like that will burn out ESCs if you try high throttle.
https://forum.librepilot.org/index.php?topic=3434.msg23481;topicseen#msg23481

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https://forum.librepilot.org/index.php?topic=3795.0
https://forum.librepilot.org/index.php?topic=3060.msg21284;topicseen#msg21284