ZTW 25a Polaris ESC (BLHeli_S)


A new generation of BLHeli ESCs are here!  Designed to bring high performance through hardware PWM and the SiLabs BusyBee line of micro-processors.  The result is silent motor operation and a throttle response that is smooth as silk. Additional benefits are more throttle resolution, higher RPM ability and automatic detection of multiple input protocols: OneShot 125, OneShot 42 and Multishot. This ESC is equipped with the BusyBee 2 48MHz MCU!

The Polaris line is a more economical entry level BLHeli_S ESC.

Motor leads left off for easy solder of motor wires to pads.
Heatshrink and label packaged separately so you can do the solder first. 


  • 48MHz BusyBee2 MCU (EFM8BB21F16).
  • Continuous Current: 25A
  • Burst Current (10s): 35A
  • Battery: 5-12NC/2-4Lipo
  • Width: 14mm
  • Length: 27mm
  • Height: 5mm
  • Weight: 7g

BLHeli_S FIRMWARE target:
use A_H_25_<rev>.HEX which is for the BB2 MCU (48MHz)


  • BLHeli_S has motor PWM that is synchronous to the MCU master clock, as it is generated by hardware. This makes the motor silent and throttle response that is smooth as silk. 
  • BLHeli_S has very small throttle steps of resolution up to 2048 steps
  • BLHeli_S will have the same good Sync holding properties as base BLHeli. Maybe even better.
  • BLHeli_S generally spin-up better than base BLHeli.
  • BLHeli_S does damped light, only.
  • BLHeli_S supports very high motor Speeds. A BB1 MCU will support 350k erpm, and the limit of the BB2 is not yet known, so the code is set to limit at 500k erpm.
  • BLHeli_S supports regular 1-2ms input signal, as well as Oneshot125, Oneshot42 and Multishot. Autodetected when the ESC sees an input signal.
  • Last and by no means least, is simplicity. If you have a regular setup, just install and go fly (calibrate if your throttle range does not match BLHeli_S default). Or if you need to configure or update, just do so with the simplicity offered by connecting to your ESCs through the FlightController, using BLHeliSuite and a USB cable.

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