You can use both 4S and 6S LiPo on the same motors

by Oscar
Published: Last Updated on

Even if your motors KV are for 4S LiPo (for example 2208 2500KV), you can still put a 6S LiPo on your quad. This is a new feature in Betaflight that auto adjust motor output to compensate for the voltage difference.

The Risk

Make sure your hardware support 6S voltage before trying this! Otherwise you could fry your ESC and FC. (as well as VTX and other components if you power them from LiPo)

You will probably lose some efficiency and get shorter flight time compared to running lower KV motors.

The main risk is when you crash and the motors are obstructed, ESC’s and motors are more likely to burn out.

How to do that?

Go to PID Tuning tab, and select PID Profile 1.

Under Motor Output Limit, set the Scale Factor to 100% and Cell Count to 4. Press the Save button.

This is the PID Profile for your 4S battery.

Now select PID Profile 2.

Under Motor Output Limit, set the Scale Factor to 66% and Cell Count to 6. Press the Save button.

This is the PID Profile for your 6S battery.

Now when you plug in your 6S battery, Betaflight will automatically scale motor output down to 66%. You can think of it as “Betaflight automatically reducing the motor KV for you”, although it doesn’t really quite work that way.

Note that Betaflight would select the PID profile based on the battery you plug in, so if you make changes to PID or any other settings in the profile, you might want to copy them across profile 1 and 2.

Also note that if you have a 6S setup, you can’t scale up motor output to 150% and hope it would work the same on 4S LiPo. You can only reduce motor output but you can’t increase it.

When scaling down motor output in Betaflight, we are basically putting a limit on the output of the ESC, more specifically, the signal duty cycle to the FET’s (how long the pulses stays high).

Alternative Method – CLI Commands

Entering these CLI commands basically achieve the same thing as what I have shown you above.

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

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16 comments

anz 7th August 2021 - 3:07 pm

When you mention “main risk is when you crash and the motors are obstructed”, does that apply if I am scaling down 1880kv to 1750kv on a 6s motor using 6s lipo for a bit more control and confidence? Thanks

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Joshua Kadash 28th July 2021 - 10:27 am

What are the downfalls of running 6s on 4s motors using motor output limit? My fc and esc can handle 6s but I have 2207 2750 kv

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jaysauce 6th July 2021 - 9:24 pm

What is the reason/calculation to go to a 67 value output limit from a 6s batt to 4s?

Is there a calc to go from 4s batts to a 3s max level output on 1103 8000kv motors?

Any recommendations?

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Oscar 6th July 2021 - 9:31 pm

calculation is based on the voltage difference.
4 divided by 6 is around 0.67.
To go from 3S to 4S, it would be 3/4 which is 0.75.

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Adrian Thomas 14th June 2021 - 12:24 am

follow up on my previous question… my aim on using 4s is to keep weight low as well as the cost buying 6s batteries

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Adrian Thomas 14th June 2021 - 12:19 am

Hi Oscar, i have apex3, fettec esc and fettec kiss fc, caddx vista, planning to use t motor f1507 2700kv 6s, and i plan to use 4s battery on it, can the 4s battery cope? will i get less performance? Initially i was using f1404 it felt under performing. My aim is to increase torque and power.
Thank you.

Reply
Oscar 14th June 2021 - 12:51 am

If that build is designed for 6S, using 4S battery should be fine. But you will get less performance from 4S as voltage is lower, and so RPM will be lower too.

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John 26th April 2021 - 11:02 am

Hi Oscar, If I also want to run 5S on e.g. 2500KV motors, can this be done on another PID profile, and if so is there are recommended Scale Factor % for this?

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Oscar 26th April 2021 - 6:26 pm

80% is a good number for 5S, please make sure your hardware can take 5S before plugging in or you will fry your quad.

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Kirk Charlot 25th April 2021 - 4:52 pm

can I use 4s on a quad with 3s motors just the same here?

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Oscar 26th April 2021 - 6:19 pm

Yes it works the same way. But make sure the electronics support 4S or you will burn it!

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Mike H. 25th April 2021 - 3:32 pm

I just want to say THANKS Oscar, your tips and reviews have helped me immensely.👍👍

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alan mccluskey 25th April 2021 - 12:24 am

ah, thanks i didnt know this, i’m still on 4s, i need to get some new packs so now i can crossover to 6s without wholesale clear out. i wonder if the quad will fly longer or have less sag near the end.

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Jack Teversham 9th April 2021 - 10:15 pm

Could you expect better performance with a ‘scaled’ 6S on a 4S build, or would the performance be similar to a 4S?

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ShortBus 31st March 2021 - 1:03 pm

Do you need to scale the PIDs down in the 7s profile of does that automatically happen?

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Oscar 31st March 2021 - 1:56 pm

Betaflight will switch profile automatically, but you need to set PID yourself in those profiles.

Reply