You want to know the secret? I'm cheap. I almost never buy expensive stuff. It's not that I can not afford it and buy cheapest stuff available. In my opinion, both ways are wrong. I buy things that position themselves somewhere in the middle. Not the cheapest, not "the best" and most expensive? Why not the cheapest? Because of very low quality. Why not the best? Because I have to pay a lot a little of additional quality or performance I do not really need. And things in a middle usually provide enough for reasonable price. For me it makes sense...

Thanks to GearBest I've received a set of EMAX SimonK Series 30A ESC for a review. They are not the cheapest 30A ESC for multirotors. You can easily buy some no-name for almost half a price. You can also but "the best" for almost twice as much. But are they worth the price? I will try to find out in the next couple of weeks while using them on my 600mm quadcopter.


EMAX SimonK Series 30A ESCs are packed in antistatic bags with a user's manual in Chinese and English.

EMAX ESC SimonK 30A boxed



Nothing fancy, but everything what needed is inside. Shrink wrap is thick and strong, servo leads are long enough, all connectors are described. Personally I would prefer a version without cables, but let's not expect too much. At this point the weakest point of those ESC is user's manual. Why? Because it says it's BLHeli version. Slight difference, but kind of makes one to doubt if all other data is correct.

According to EMAX, those ESC have following specs:

  • Software: SimonK (and I really do not mind lack of BLHeli, the way I see it, I have too much settings on FC to worry about ESCs too)
  • Battery: 2S-3S
  • Constant current: 30A
  • Burst current: 40A for 10s
  • BEC: linear 2A
  • Dimensions: 52x26x7mm
  • Weight: 28g with wires

Since I prefer to solder motor wires directly to ESC and decided for external UBEC, I've decided to remove shrink wrap and make few adjustments. Here is how they look inside:


EMAX ESC SimonK 30A bottom

As you can see, linear 2A BEC is indeed 2 LM7805 working in parallel. Quite popular solution. MOSFETs are LR7843. That makes 30A constant current fully correct, since maximum allowed current for LR7843 in exactly 30A. Good job! Both LM7805 and LR7843 are covered with single heat sink with thermopad. MCU driving EMAX SimonK Series 30A is SiLabs C8051F330 [F330].

One thing sure: it's not high tech, but PCB and placement is decent quality. Also soldering is fine. Nothing to worry about at this point.

During motor wires removal I discovered very nice feature of those ESCs. Used solder is very nice and easy to work with. Not this "eco" lead free gooey stuff is so commonly used everywhere now. For me it is regular 60/40 lead solder. And this is a HUGE plus those ESC that saved me a lot of work. Once again, good job EMAX!



During last weekend I successfully installed them in my "Sparrow Hawk" 600mm quadcopter and made few test flights with following conclusions:

  • after 10 minutes of flight with average current of 10A they were warm, but not overheating. My big quad has poor air circulation around ESCs so this is normal
  • all 4 ESC calibrated without any problems on first try
  • ESC settings menu is functional, it is quite easy to change motor direction or other settings with throttle
  • OneShot125 interface works out of the box

I will publish full review with final conclusions in a few weeks after at least few hours in the air with EMAX 30A SimonK Series ESC. Stay tuned!

ESC were provided by GearBest GearBest