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.
Table of Contents
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.
It Feels Differently
As explained in my motor buyer’s guide, the KV of a motor affects torque constant. A higher KV motor would require more current to generate the same amount of torque as a lower KV motor.
For example, indeed you could use a 2400KV motors (for 5″ on 4S) and run 6S on them. If you limit maximum throttle in the flight controller, it will work and not burn out. Besides the lower efficiency, it would also feel very differently when it comes to handling than using a 1800KV motor that’s designed for 5″ and 6S.
Using Betaflight for Automatic Profile Switching
Go to PID Tuning tab, and select PID Profile 1.
After navigating to the PID tuning tab, scroll all the way down to the bottom of the interface, find Cell count for auto profile switching.
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.
Then click on the ‘Copy Profile’ option and copied all values from Profile 1 to Profile 2, which essentially made the two profiles identical.
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.
Using 4S battery on 6S Drone?
If you have a 6S quad, you can’t scale up motor output to 150% and hope it would performance the same on 4S LiPo. You can only reduce motor output, 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
25 comments
Is it possible to do the same thing on mission planner?
Hello OScar, one thing is not clear to me, how long the drone will fly. In this case should i go for the amps of the battery or the total WH?
Example: 4s 650mah and a 6s 650mah, both on the same 4s motors drone, using motor_output_limit for the 6s.
Now the 6s should ideally last 50% longer than the 4s having 50% more WH.
Thanks !
Total WH is what determines the flight time, it’s the amount of energy stored in that battery.
So in your example, 6S 650mah will have longer flight time than the 4S 650mah.
I have recently bought xing 2 1755kv 6s motors, the unlucky I am I didn’t check if it’s for 4s too or not, now is there any way to use it on 4s setup and still it being punchy? Thanks brother
It’s going to feel less powerful, but it should fly.
Hi Oscar, so reducing the high time on the esc is effectively reducing the motor KV so this will apply across the whole throttle range. I have a 6” quad running 4s and obsolete 2306 2150kv motors that need replacing. I have a spare set of 2407’s 2500kv which is a bit too high for 6” props, they tend to flatten out. I could use this to effectively drop the kv to 2000ish by setting it to 80% still running 4s
Hey Oscar, I use 6s with 1800 kv motors, last week I used a 5s and I really liked the throttle feeling, I had so much more control. My question is could I put a motor output limit using 6s to match that 5s feel? Or should I use a throttle limit and/or throttle curve to get the feel I want?
Thank you so much for your content, it makes my life a lot easier a lot of times!
I’d use Motor Output Limit if you want to simulate the feeling of using 5S instead of 6S battery. throttle limit only affects user input but the drone can still output full power.
Love your content Oscar! Thank you for all the hard work and passion you pour into the hobby by helping those less experienced such as myself.
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
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
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?
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.
follow up on my previous question… my aim on using 4s is to keep weight low as well as the cost buying 6s batteries
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.
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.
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?
80% is a good number for 5S, please make sure your hardware can take 5S before plugging in or you will fry your quad.
can I use 4s on a quad with 3s motors just the same here?
Yes it works the same way. But make sure the electronics support 4S or you will burn it!
I just want to say THANKS Oscar, your tips and reviews have helped me immensely.??
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.
Could you expect better performance with a ‘scaled’ 6S on a 4S build, or would the performance be similar to a 4S?
Do you need to scale the PIDs down in the 7s profile of does that automatically happen?
Betaflight will switch profile automatically, but you need to set PID yourself in those profiles.