How to Get 48KHz on BLHeli_S ESC (More Flight Time on Tiny Whoops!)

sThe latest BLHeli_S firmware allows 48KHz and it reportedly gives you up to 50% more flight time on micro quads without downside! Interested? This post explains what 48KHz is and how to enable it.

What’s 48KHz?

48KHz is the ESC PWM Frequency, we’ve explained what it is and its benefits in this post. In a nutshell, it’s how often the ESC drives the motor.

I use 48KHz on all of my BLHeli_32 ESC’s, because it makes my quad fly smoother, and the motors run cooler.

It wasn’t possible to to do 48KHz on BLHeli_S ESC (only 24KHz max), until now. Our tiny whoops and toothpicks can finally enjoy this great feature! (And any quads that run BLHeli_S ESC’s)

Apart from cooler motors, 48KHz PWM Frequency also improves efficiency (mainly on micro quads, more noticeable on the tiny whoops and toothpicks). The increase of flight time varies from setup to setup, but from what I’ve gathered so far, it’s between 10% to 30%. Some even claims to have gained 50% longer flight time!

By increasing PWM frequency, it reduces the braking force on the motors. It resolves issues with excessive motor braking that sometimes occurs on tiny motors, such as 06XX and 08XX, and lowers current draw. Bigger motors generally don’t have this problem that’s why we don’t see the same level of efficiency improvement on larger quadcopters. And that’s probably why we might see diminishing improvement on larger micro motors, such as 11XX and 12XX.

As far as I know, even higher PWM frequency is being experimented, i.e. 96KHz. But your quad might perform worse if it gets too high, so it’s definitely not “higher is better”. For now 48KHz is a safer option.

There is concern if 48KHz will affect damping effectiveness (active braking), let us know if you notice any difference in performance after enabling 48KHz.

How to Flash BLHeli_S 48KHz Firmware?

The steps are exactly the same as flashing the bi-directional DShot firmware (for RPM filter), but this time you are going to download the latest firmware marked “48KHz”. I am not going to repeat it here :) Let me know if you have any questions!

12 thoughts on “How to Get 48KHz on BLHeli_S ESC (More Flight Time on Tiny Whoops!)

  1. Mark Miller

    A pick nit comment about the notation used to identify 48kHz
    The ‘k’ used here is for kilo, meaning 1000, an indication the frequency here is 48,000 Hz or 48,000 hertz.
    The ‘k’ should be lower case for kilo since an upper case ‘K’ means Kelvin in the metric system, a unit used in temperature measurement.
    Hz or hertz are used to show cycles per second in honor of Heinrich Hertz, a German physicist (1857-1894).
    When a unit is named for a person, such as hertz, (cycles per second), the abbreviation for the unit is show in upper case, but when the unit name is written in text lower case is used. By using upper case on the person’s name and lower case on the unit name it is clear whether the person or the unit is being referenced in the text. But the unit when abbreviated is shown in upper case to show it has been named for a person.

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  2. Don Strasser

    I tried this with my Eachine Trashcan that I run on 2s 300m Ah batteries. Before, for casual indoor flying I would typically get 3 to 3.5 min flight times. With 48 kHz I am getting 4.5 to 5 min flight times. There is significantly lower amp draw in a hover.

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  3. MartinW

    I tried this on the Mobula6, but it didn’t feel as agile anymore and whenever I hit the throttle to do a small punch out or catch a fall, it would just fall out of the air and reboot. Brownout?

    Reply

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