Can you run 4s on a 3s motor?

[danskis]

Apologies as I'm sure this has been asked many times. I want to know if a motor is listed as running on 3s battery if you can run it on 4s even if its not listed. Lets take this motor as an example. If it can run on 4s how would you know?

https://store.flitetest.com/emax-gt2215-09-1180kv-brushless-motor-emx-mt-0409/p694266

 

[Aireal Anarchist]

I want to know if a motor is listed as running on 3s battery if you can run it on 4s even if its not listed.

NO dont do it you will waste your money, it will blow at some point

 

[shadeyB]

Apologies as I'm sure this has been asked many times. I want to know if a motor is listed as running on 3s battery if you can run it on 4s even if its not listed. Lets take this motor as an example. If it can run on 4s how would you know?

https://store.flitetest.com/emax-gt2215-09-1180kv-brushless-motor-emx-mt-0409/p694266

You can and after 2-3 mins you get a little trail of smoke before the plane starts to make its own descent 🤪🎮💫✈️💫💥🔥

 

[LitterBug]

I have run 3S motors on 6S with no issue using a bit of science. It will depend on several factors. The key is to know how many watts the motor can handle safely and not exceed that rating. If you exceed it's rating, you will let the smoke out. The unfortunate thing is that motors are not rated by their Watt capability and are rated by the more arbitrary KV. If you dig into the spec sheets, you can get a better idea.

E=IR is your friend. Watts = Amps * Volts. More "S" = More volts. The more volts you run, the less amps you need to reach the same watts. If you limit max throttle below the smoke point, you will be fine.

If you are planning on running full throttle on 6S, you will most likely see the smoke monster!

The 3S motors I ran on 6S (Sunnysky x2212 kv980) ran fine at 4S rating without much heat.

Cheers!
LitterBug

 

[danskis]

@LitterBug - sorry to pick on you but your answer was the one I"m interested in (although the short answers are definitely valid). I'm not real proud of my electronics knowledge so I'm going to ask a few more questions. If you want to point me to something to read that's fine too. Hopefully this will help other folks.
E=IR
E=?, I=?, R=?

Amps is what your motor draws depending on how much work its doing i.e. size of prop and you can measure it with a meter.
Watt rating - only the manufacturer knows that and sometimes they supply it.

You said "The more volts you run, the less amps you need to reach the same watts (got it). If you limit max throttle below the smoke point, you will be fine."

So in the real world do you limit throttle or prop size or both?

I guess the simplest answer it to buy a motor rated for 4s or just go to a more powerful, heavier motor.

 

[Wildthing]

@LitterBug - sorry to pick on you but your answer was the one I"m interested in (although the short answers are definitely valid). I'm not real proud of my electronics knowledge so I'm going to ask a few more questions. If you want to point me to something to read that's fine too. Hopefully this will help other folks.
E=IR
E=?, I=?, R=?

Amps is what your motor draws depending on how much work its doing i.e. size of prop and you can measure it with a meter.
Watt rating - only the manufacturer knows that and sometimes they supply it.

You said "The more volts you run, the less amps you need to reach the same watts (got it). If you limit max throttle below the smoke point, you will be fine."

So in the real world do you limit throttle or prop size or both?

I guess the simplest answer it to buy a motor rated for 4s or just go to a more powerful, heavier motor.

Safest way is to limit the prop. Bench test with a watt meter attached , also good to have a heat gun to watch the motor temp and start with a very small prop and slowly work your way up.

 

[LitterBug]

@LitterBug - sorry to pick on you but your answer was the one I"m interested in (although the short answers are definitely valid). I'm not real proud of my electronics knowledge so I'm going to ask a few more questions. If you want to point me to something to read that's fine too. Hopefully this will help other folks.
E=IR
E=?, I=?, R=?

Amps is what your motor draws depending on how much work its doing i.e. size of prop and you can measure it with a meter.
Watt rating - only the manufacturer knows that and sometimes they supply it.

You said "The more volts you run, the less amps you need to reach the same watts (got it). If you limit max throttle below the smoke point, you will be fine."

So in the real world do you limit throttle or prop size or both?

I guess the simplest answer it to buy a motor rated for 4s or just go to a more powerful, heavier motor.

My short answer is, if the motor is getting hot on 3S, don't bother with 4S. It's mostly about the heat. If your motor is cool(ish) after running full throttle in the air, you can probably push it a little harder.

The longish story:
My testing was done on multirotors where the motors are out in the open air and have plenty of cooling. I also had power monitoring (current and voltage) on my OSD to keep tabs on the results. It was also very easy for me to limit the max PWM to the motors on the flight controller, thus limiting the max power. You could in theory do the same thing by limiting the max PWM in your transmitter by lowering the max PWM "AFTER" you calibrate the ESC(s). The idea we were testing was to have "dial-a-KV" on race drones rather than having to have different KV motors on different drones to tune for max power based on the course. Run high KV motors all the time, but then limit the max PWM to tune power. Kind of like setting up different rates for servos. Running Higher voltage has an added benefit of lower current for the same watts. Lower current = lower heat = lower loss due to heat. If you are tuning for endurance, Lower current lets you use smaller / lighter wires. And lighter is usually a good thing when it comes to endurance.

Watts = Volts * Amps
1S nominal voltage = 3.7V, 3S = 11.1, 4S = 14.8
So if you are pulling 20Amps at 11.1 volts, you are using 222 watts. 20A x 11.1V = 222
if you want to stay at or below 222 watts on 4S you will need to stay below 222W/14.8V = 15A
If you pull 20 Amps on 4S you will be using 20A*14.8V = 296 Watts

So that's the short long answer....

Cheers!
LitterBug

 

[danskis]

@LitterBug - just used your formula for a 200 watt motor - thanks for the education

 

[The Hangar]

@danskis what motor is it? I’ve run my emax c pack on 4s with a 9x6 prop with no issues.

 

[danskis]

@The Hangar - well its this motor. http://www.valuehobby.com/power-sys...runner-airplane/gforce-e450-1200kv-motor.html

So if you go to the chart at the bottom of the page you'll see that it can handle 327 watts on a 3s running a 11X4.7 prop. So if I wanted to run 4s I just have to stay under 327 watts by putting a smaller prop on. I think. As it turns out this motor has plenty of power for my bloody baron which has almost unlimited vertical on 3s. I would recommend it.

LitterBug did answer my question which was how do you really know without guessing or doing the how hot is the motor test. Unfortunately very few motors list their max watt output. On the other hand its just another piece in the puzzle of how to set up the power system in your plane.

And thanks for the Simple Stick!!!! Not built yet but its on the list.

 

[The Hangar]

@The Hangar - well its this motor. http://www.valuehobby.com/power-sys...runner-airplane/gforce-e450-1200kv-motor.html

So if you go to the chart at the bottom of the page you'll see that it can handle 327 watts on a 3s running a 11X4.7 prop. So if I wanted to run 4s I just have to stay under 327 watts by putting a smaller prop on. I think. As it turns out this motor has plenty of power for my bloody baron which has almost unlimited vertical on 3s. I would recommend it.

LitterBug did answer my question which was how do you really know without guessing or doing the how hot is the motor test. Unfortunately very few motors list their max watt output. On the other hand its just another piece in the puzzle of how to set up the power system in your plane.

And thanks for the Simple Stick!!!! Not built yet but its on the list.

Looks like a great motor for a great price! I can’t wait to se show you like the Simple Stick!

 

["Corpse"]

The only thing that will smoke a motor is melting the enamel off of the windings, thus shorting it out. You can't have excessive heat in the motor, or it will poof, and your plane will plop. If you increase voltage, you will have to decrease amperage to keep the same wattage.

 

[Brett_N]

I have about 7 of those motors on currently flying planes. It is fine on 4S, just don't run higher than a 9" prop, but as others have mentioned, you need to use a wattmeter to get into the correct range. I use 8x6 on a small 4S powered wing and it's fine.

 

[CorsaiRC]

DON'T IF YOU DON'T WANT TO BLOW THE MOTOR

 

[Merv]

I want to know if a motor is listed as running on 3s battery if you can run it on 4s even if its not listed.

The short answer is yes you can. BUT you will likely need to use a smaller prop.
Don't try this with ESC's, they need to be rated for the voltage you are using..

I agree with @LitterBug, knowing the watts a new setup is using is a great benefit. A watt meter is a very useful tool.

Even with a watt meter, I always bench test with a new setup. Start with a 10 second run at full throttle. Then stop, check the temperature of the motor, ESC & battery by touching them. Warm is OK but if they are so hot you can't hold them, stop, that's too hot. If it passed, try a 30 second run, then a 60 second run. If the setup passes, you can try a larger prop. If it fails try a smaller prop.

It's always a good practice to check the temperature of you components after a flight. A setup that worked when it's nice out (70's) may over heat when it get's hot (95+).

 

[varg]

A Wattmeter/Ammeter is an essential tool for the electric RC hobbyist. Get one. As discussed above the limiting factor we encounter with our RC model motors is the Wattage and thus heat dissipation, not the breakdown voltage of the insulation, so 4S on a 3S motor will be fine as long as you don't overprop it and exceed the maximum amount of heat it can dissipate. Yes, it is stupid that manufacturers don't give you a maximum Wattage rating, a decent substitute is to take their test results and figure the maximum Wattage based on that yourself. Throttle limiting is one way to do it, but not a good way. Testing props with a test rig that measures thrust and power is the right way, a close second is just testing the static amp draw with a Wattmeter. OK during static testing generally means OK to fly. I've had motors get hotter than I'd like during a static test and land cool to the touch after flying hard just because there is so much more airflow when flying. Depending on the prop you might also draw more current static than while flying because the prop is stalling with no forward speed.