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Betaflight motor output limit vs throttle limit: running 6S on 4S motors and switching profiles by cell count

Betaflight has two settings that sound like they do the same job: throttle limit and motor output limit. They don't. Throttle limit only changes what your throttle stick asks for. Motor output limit caps what the flight controller can send to the ESCs, whatever the PID loop wants. If the goal is to protect motors and ESCs, for example when you put a 6S pack on a drone with 4S motors, only motor output limit does the job.

Tue, 3 Nov 2026

Throttle limit: a stick setting

Throttle limit arrived in Betaflight with pull request #5608. It adds two parameters, throttle_limit_type and throttle_limit_percent, and they live in the rate profile. The type can be OFF, SCALE or CLIP:

  • SCALE stretches the limited throttle over the full stick travel, so full stick gives you the set percentage.
  • CLIP leaves the stick response alone below the limit and ignores anything above it.

The percentage can be set from 25 to 100. The pull request describes it as a replacement for limiting throttle in the radio, which pilots used on tight race courses or to save battery when they did not need the extra power.

The important line in the same description: there is no effect on the maximum throttle seen by the motors, so the mixer keeps full authority. When the drone hits something or needs a hard correction, the PID controller can still drive the motors to 100%. UmbrellaFPV puts it bluntly: a throttle limit in the radio or in Betaflight works until the drone touches an obstacle, and then Betaflight uses whatever is available to fight the impact, with a good chance of burning the motors.

Use throttle limit when you want a calmer throttle, for instance on a small course or for a beginner. Don't count on it to protect hardware.

Motor output limit: a cap on the ESC signal

motor_output_limit is set per PID profile, as a percentage. Oscar Liang explains that it limits the output of the ESC, more precisely the duty cycle of the signal to the FETs. In practice it behaves roughly like lower-KV motors. Oscar adds that it doesn't really work quite that way, but the comparison helps.

It only works downwards. You can't set 150% to make a 6S drone fly like it did before on 4S.

Working out the percentage

UmbrellaFPV gives two ways:

  • By cell count: the cells the motors were chosen for, divided by the cells of the new pack. 4S motors on 6S: 4/6, about 67%. 3S motors on 4S: 3/4, 75%.
  • By KV: target KV divided by actual KV. A 2750KV motor that should behave like 1800KV: 1800/2750, about 65%.

In the comments under his article Oscar suggests 80% as a good number for 5S on motors meant for 4S.

6S on a 4S drone, step by step

First check the hardware. Oscar's warning comes first: the ESC, the flight controller and anything else powered straight from the pack, such as the VTX, must be rated for 6S. Motor output limit does nothing for them.

Then set up two PID profiles that switch on their own. In the PID Tuning tab, at the bottom, there is the cell count for automatic profile switching, next to the Motor Output Limit settings:

  1. Select PID Profile 1. Set the scale factor to 100% and the cell count to 4. Save.
  2. Use "Copy Profile" to copy Profile 1 to Profile 2.
  3. Select PID Profile 2. Set the scale factor to 66% and the cell count to 6. Save.

The same in the CLI (profile numbering in the CLI starts at 0):

profile 0
set auto_profile_cell_count = 4
profile 1
set auto_profile_cell_count = 6
set motor_output_limit = 67
save

Betaflight now picks the profile from the pack you plug in. The catch: PID changes made in one profile stay in that profile. If you tune one, copy the changes to the other.

UmbrellaFPV goes one step further and keeps a third, identical profile as a fallback with auto_profile_cell_count = -1 for any other pack. They also suggest showing the profile name in the OSD, so you can see which profile is active before you arm. A quick check on the bench: plug in different packs and watch the active PID profile change in the configurator.

What you give up

Oscar lists the trade-offs. You will probably lose some efficiency and get shorter flights than with lower-KV motors built for 6S. The handling also feels different, because a higher-KV motor needs more current for the same torque. The biggest risk is a crash with a blocked motor: ESCs and motors are then more likely to burn out.

On the other hand, a limited motor draws less current. In the comments Oscar confirms that limiting motor output should reduce current draw, and suggests checking it in the OSD.