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Hello and some questions about a 250 Racing Quad

#1
Hi everyone! This is my first post on this forum, and I wanted to ask a question regarding my Quadcopter.

I'm using a 250 frame with a 3 Cell 2250mAH Lumenier battery, and it has 12 Amp BLHeli ESCs, along with EMAX MT2204 KV2300 Motors.

As I have only flown this drone for roughly three months, and I'm just getting into FPV, I lack a certain amount of experience with how everything works and what works with what.

My issue is regarding the motors/ESCs, during set up, when I arm the drone, three of the four motors spin up. (occasionally two, but rarely) The fourth motor will (from what I know) try to unsuccessfully spin up, and ends up jittering and not spinning at all. I've kind of set up a rhythm of count to two, arm it, and on three, spin the nut on top in order to get the initial spin up going. After this tedious and repetitive process, once it gets spinning, the motor works perfectly, and the Quadcopter flies as one would expect. Obviously, this is still not only an inconvenience, but also a safety issue, and so I tried to figure out how to fix it. My father and I both have different theories on how to fix it. He says that we need to get a 2250mAH 4 Cell battery, and with its additional voltage, it will provide enough power to get the initial spin going. My idea is replace the 12 Amp ESCs with 20 Amp ESCs as I assume they are getting overloaded or something along that line (They don't heat up very much, but that may be from the cooling of the propellers spinning on top)

So, here I turn to you. I want to get an idea of what the problems might be since I know it isn't a bad soldering job or bad bullet connector connections as I've rigorously checked for this issue. I want to have an idea of what needs fixing before I go buying Willy Nilly, and I hope this is an easy answer. Thanks to everyone in advance!

IMG_5652.JPG IMG_5667.JPG

*Edit* I will note that I noticed the the heat-shrunk part where the wires connect to the motor, when facing down, make it jitter, but once moved to a horizontal position, the motor spins up, this happened both during arming and whilst armed and jittering.
 
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ElectriSean

Eternal Student
Mentor
#2
Sounds like your min_throttle is set too low. After removing the props, in the cleanflight/betaflight motors tab slowly spin up each motor and note the number at which it spins consistently. Take the highest number and add 10, and set min_throttle to this value in the configuration tab.
 
#3
Sounds like your min_throttle is set too low. After removing the props, in the cleanflight/betaflight motors tab slowly spin up each motor and note the number at which it spins consistently. Take the highest number and add 10, and set min_throttle to this value in the configuration tab.
Darn, unfortunately whilst I hadn't considered this, it appears that it doesn't fix the problem.

I will note that I noticed the the heat-shrunk part where the wires connect to the motor, when facing down, make it jitter, but once moved to a horizontal position, the motor spins up, this happened both during arming and whilst armed and jittering.
 
#5
It seems as if the issue does indeed involve the ESCs, yesterday it was acting up on full throttle where the left half would provide the burst I wanted for a quick upward ascent, but the right half didn't. I'm assuming I'm using the term brownout correctly for the situation. Some reviews of the 12amp ESCs also mention they don't provide the amperage required for the vehicle and brown out a lot. I'll consider buying some 20 Amp ESCs along with new motors.
 
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cranialrectosis

Well-Known Member
Mentor
#6
Jittery motors are most often caused by a poor connection between the ESC and the motor. One of the motor leads isn't soldered on well.

With 12A ESCs you are limited to 3S. With 24A ESCs you can go 4S and 3 or 4 blade props. :D
 

PsyBorg

Wake up! Time to fly!
#7
Take a step back and think thru your problem mate. You are describing two separate and very different issues.

The first issue is the motors spinning upon arming. That is either a improperly calibrated throttle and or too low min throttle setting. The second issue is at full power with things not having the umph you think it should have. This could again be due to a bad throttle calibration but is more then likely it is battery sag as you are only running 3s. I am willing to bet your batteries are 25 c or lower rating.

Before replacing parts or worse yet just randomly changing over to 4s take a step back and redo the basic set up. Go back and zero out all your radio trims. Then go into clean flight and make sure each channel is centered at 1500. Then make sure your end points are at 1000 min and 2000 max on all channels.

Once that is done start with everything turned off and un powered. Connect to the FC with Beta flight as normal (NO PROPS!!!) Go to the motor tab check the box to allow motors to spin then move the main slider to max. Connect the flight battery to the quad and the esc's will give some tones. As soon as they do slide the slider back down to zero. At this point your esc's will reboot and your throttle will be calibrated for all four motors. check that they do in fact start at the same time and very close to the same speed when you stop raising the throttle.

Leave the battery connected and high light the motor 1 slider with your mouse. Use the up arrow to advance the slider until the motor spins steady and is not twitchy. Write that number down. Repeat that with the other three motors. now since you are using 3s with six inch props and probably a 4.5 pitch I would add 15 - 20 points to the highest number to use as your min throttle setting.

That "Should" clean up your stuttering and start up issue. Keep in mind that even though the throttle is at the lowest setting the FC still thinks it is flying and will change the speed to adjust the longer the quad sits not changing its position. Try flying like that for a battery or two and see if that also helps the "unevenness" you perceive. Again remember you are flying a heavier quad on 3s power. I would suggest with the 12 a esc's to go down to a 5x4.5x3 prop. It will ease the load on the motors and esc's and make the quad a little more responsive although slightly lessen top speed which is not that impressive on 3s anyways. Better control will help you more then speed this early in the game as well.

IF all that does not help THEN start thinking of upgrading esc's then battery.