The BLHeli developers have released the new code and added the S to set it apart from the base code, the S represents something special.. the next generation of ESC firmware. But what makes BLHeli__S firmware so special and is it worth upgrading yet? And will it actually make a difference to your multirotor flight performance?

Key features of BLHeli_S

  • Hardware PWM – smoother and more responsive motor response
  • Always use damped light (Regenerative Breaking) for better drone control
  • Code supports sync loss prevention – tune able parameters to make your ESC work well in the most demanding applications (not just FPV racing)
  • High resolution throttle steps
  • Supports Oneshot125 (125-250us), Oneshot42 (41.7-83.3us), Multishot (5-25us) protocols
  • Automatically detects input signal protocol on ESC power up
  • Beacon Function – your ESC will start beeping after a set time of zero throttle to help you find your drone.

Since the initial release of BLHeli, hardware has improved so the new code is designed to take advantage of the new hardware improvements with the most signification being hardware generated PWM which gives much better performance. This is the most noticeable improvement of BLHeli_S as your motors run smoother, quieter and are technically more responsive too.

Because the hardware generated PWM signal is synchronized with the micro controller clock on the ESC, the motors run more silently and efficiently (with less high pitch squeal). This also enables much more precise throttle steps depending on the ESC hardware (micro-controller and PWM driver type), however the range is between 512 steps and as much as 2048 steps with high end ESC’s.

The hardware PWM also allows you to control very high speed motors. With the older BLHeli firmware and software PWM, the maximum speed signals can be sent to the motor was 16Khz. With the hardware PWM, your ESC can send signals at about 36Khz which is rather insane. Because your motors are getting updates much faster the control is much more precise and smoother response.

Can I upgrade my BLHeli ESC to use BLHeli_S?

No, this is not currently possible as BLHeli_S is designed to run on new ESC hardware, to take advantage of the hardware PWM driver. Current ESC’s that run BLHeli use software PWM and do not have a dedicated hardware PWM driver so they cant use BLHeli S.

BlHeli_S ESCs on the Market

I have been waiting for LittleBee-priced BlHeli_S ESCs before I pulled the trigger. Not because I couldn’t afford a couple of extra bucks, but because I like to have all my quads run the same ESCs so I only have to buy one set of spares.


The earliest BlHeli_S ESCs were the Aikon SEFM and the EMax Lightning series, and cost $16-$18/pc. That was simply too much for me – I’m just too used to the fantastic performance of LittleBees at $11/pc.


Later on a new ESC popped up called the Sunrise Cicada. It sold from a couple of vendors on eBay and Amazon for $14-$15. We were getting closer. Then, just a few weeks ago, Banggood called the “Racerstar” at the fantastic price of $10 perpc. I immediately pulled the trigger on the 20a variants.

race20amp racestar-20amp

It turns out these Racerstar ESCs are identical to the Cicadas. This is awesome news as the Cicadas are the only BlHeli_S ESCs that seem to be immune to motor desync problems pilots are experiencing on the other ESC variants,but some suspect a capacitance issue. Whatever it is, EMax actually recalled their Lightning ESCs because of it.


So, as you know that at the start you will experience a smooth and better control on your drone well if you have already used little bees and blheli escs and are using them if you are thinking to upgrade to blheli_s well then there isnt a need to do so … juss for the sake of a little hype in performance not worth spending around $40 better spend it on something else which is essential, but incase of you building a new drone i would suggest to go with the  Racestar blheli_S these esc have been new to market and Banggood sells them well the links are below:

4 a pack : 4X Racerstar RS20A V2 New 20A Blheli_S OPTO 2-4S ESC

1 a pack :   Racerstar RS20A V2 New 20A Blheli_S OPTO 2-4S ESC

4 in 1 version : Racerstar RS20Ax4 20A 4 in 1 Blheli_S Opto ESC 2-4S

Note: The above links are affiliate links. It doesn’t cost you any extra money to use them, and gives us a few cents back when you do. Thanks for your support if you buy any of these items!

These escs worked great on 3s for me also these are one of the chepeast blheli_S release so grab them fast ….


New version naming convention

The new BLheli S firmware will have the naming convention of A_L_10_REV16_0.HEX

  • The first letter denotes the pinout of the Micro controller (MCU) on the ESC. Currently A,B,C,D,E,F,G
  • The second letter is the MCU clock speed. L for 24MHz, H for 48Mhz
  • The two numbers denote the MOSFET switching deadtime, if the FET has adaptive switching then 00 is used
  • The REV is the actual code version, the bigger the number the more recent the code is.



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