So I've just walked back from testing my new custom quad. This was the second quad that I'd built; I'm relatively new to multirotors, but have spent a number of years with fixed wing systems.

Anyway, the specs of this new quad:

Carbon fiber folding frame (this one; other frames share the same name).
2x 5000mAh Multistar 4S 10C LiPos
4x Multistar 4225 motors (610kV, max 330W)
4x Carbon 13" x 5.5" props
4x HK Red Brick 30A ESCs
Pixhawk with typical accessories

Here's a picture of it being built:


Note that the ESCs for all 4 motors are coexisting in the frame, under where the Pixhawk is sitting.

As I do with any multirotor, I tied it down to a heavy grate and then performed a low power motor & control test, keeping power at <20% power and just gently moving the controls around (this is all with the PID settings modified to have zero integral gain).

Unfortunately after about 15 seconds of running it at ~20% throttle and some gentle pitch / roll, it decided it'd had enough and with an eruption of smoke, a juttering of props and a very brief fire, the test came to a halt. I immediately cut power to the system and then physically removed the batteries (which requires the cutting of 4 zipties) from the quad to prevent them from getting any hotter.

Here's a picture of it after it's maiden ground test run:

3689624161?profile=originalAs you might be able to see, the red ESCs in the center there have burnt up.

Here's a closer look:


Now, I know that Hobby King equipment gets a bad rap by some people, and at first I had thought that perhaps the ESCs had underperformed, as even at max throttle they were only expected to run at about half their max sustained current rating. It was only when I got back to a computer and went to double check their specs / what eCalc theorised the current draw was when I realised that I'd screwed up. If you look up the store page for those red brick ESCs, you'll notice something that I didn't at the time; they're only rated for 2-3S batteries; and I was using 4S...

A small mistake, but with relatively big results.

Well, I haven't had the time to check my other components but from what I've seen so far:

 - Motors and props are fine. Some cables are singed but still appear sealed and intact.

 - Batteries need to be tested; one looks fine, the other has some slight discolouration which may be from the smoke, or it may be from heat damage. I'll probably run them both through a charge and discharge (hooked up to an appropriate ESC and motor) cycle to see if they heat up or swell at all. 

- Pixhawk status is unknown, but it was flashing lights normally as far as I can tell during the accident, so I think it's alright. Its 3DR power supply is a bit burnt, but I don't know if that was due to its proximity to the ESCs or not; either way I'll replace it.

 - Frame looks alright, but either I have some molten plastic on it or the resin partly melted from the heat. I think I should be fine to use it again.

With the ESCs, I'll obviously have to replace all 4, this time, with ones that are 4S compatible. As those ESCs only just fit in there, and because their proximity certainly didn't help keep them cool, I'll be mounting the next set of ESCs probably under the frame.

So there you have it; always double and triple check your components, because the smallest difference of a number can mean the biggest variation from safe flight.

E-mail me when people leave their comments –

You need to be a member of diydrones to add comments!

Join diydrones


  • reminds me I bought 4pcs of ESCs from a hobby shop in Hongkong for a multirotor but when I plug my esc on a 3s in overheated. then when i put it on a 2s its normal. funny thing is there are no label that shows what battery to run on. so everything is guess work. now im stuck with some 2s ESCs only good for small aircrafts.

  • Sorry to see/hear about your mishap. I appreciate the candor. This is another example of why I use an arming plug on all my multirotor or fixed wing systems. It provides a single point disconnect for the battery source.

    I discussed arming plugs in THIS blog post.

    Of course that won't fix an error of exceeding the ratings of the ESC, only give you one place to 'pull the plug' as it were.

    Build on!


  • @Sgt Ric - It's fine, you don't talk about how you screwed up without expecting some comments ;)

    @Ed Kirk - The ESCs, whilst packed tight, did have wriggle room / weren't under any compression (although as mentioned in my post and in several of the comments, it was a bad idea to stack them (at the time I thought they'd have a sufficient amount of ventilation through holes on every side). The batteries were parallel; if they had been in series I would have also fried my gimbal and a secondary BEC.

  • Two things get my attention,

    first, ESCs packed in very tight. it doesn't take much for the boards to cut through the shrink tubing and short out.   Contact with aluminum post and CF.

    second, two 4 cell batteries, were they parallel or in series?


  • Moderator
    I know you're getting a lot of preaching by us arm-chair quarterbacks with great hindsight, but in a community like this, we hate to see a fellow flyer with such a catastrophic failure, so everyone wants to help!
  • Unless your ESC supports "active freewheeling", throttle inputs of less than 80% will cause increased heat build up in your ESC. This is common knowledge for RC helicopter users. It it not recommended to have low throttle inputs to your ESC without additional air flow. It looks like your ESCs were stacked, meaning you had inadequate airflow, contributing further to heat build up.
  • Hi Joshua,

    Great of you to share your experience. If you're looking for 4ESCs for your 4S setup, I'd recommend the Afro 30A. I used the exact same motor/prop setup as you and they always perfermed (with the added benefit of not having to flash them). Recently I changed to 14" props. 


  • Other than the 3-cell, 4-cell issue, it's not a good idea to have 4 ESCs stacked close together between 2 plates with very little ventilation. Even with only a few watts dissipated per ESC the heat will build up. Even though it's a 30A ESC, it won't last long at a lower current without some air flow to remove the heat.


  • You should avoid mounting the ESC's directly against each other.

    The heat build up will definitely cause problems.

  • @Sgt Ric; it was about 20cm of wire from each battery; unfortunately I can't reduce it any further than that due to my lack of options when it comes to mounting the batteries. Specifically, each battery is mounted under the frame, one at the tail, one at the nose, both outside of the legs of the skids. Their leads then go directly to a Y harness which goes directly into the center of the frame, through the Pixhawk power supply and then into a custom bit of cabling which links up all the ESCs; I don't have / use a power distribution board. Nonetheless, on my last quad this was even worse, but I didn't run into any noticeable issues.

This reply was deleted.