Race Drone: 6S Batteries and Crispy Motors
Modified by Amir on the 28. Sept 2018 at 15:58 in FPV | Permalink

I've upgraded my my Chameleon TI to 6S batteries. That's kind of crazy as nearly everybody switching to 6S will also reduce the kV of their motors. On this drone I normally fly Emax LS2207 motors with 2400kV, which means that they do 2400 rpm/Volt of the attached battery. Flying these motors with 4S LiPos (eg. 4.2V/cell and 4 cells) resulted in around ~40k rpm. When we upgraded to 5S batteries the higher voltage resulted in ~50k rpm. To make sure we don't get too high currents and we don't overstress the propellers, we reduced max throttle to 80%. This resulted in ~40k rpm with 5S too, which was fine.

When upgrading to 6S batteries, we did not further reduce max throttle. This resulted in around 48k rpm, which is a bit high, but with stiff enough propellers it works out fine without the propellers flattening out. The resulting power is very impressive! Some guys jokingly called this instant teleport and I can confirm, the feeling is similar! :)

Switching to such high power levels sadly also has it's pitfalls. 2 weeks ago I had a signal loss 15 seconds after starting. I was so perplexed that I just watched my drone fall to the grass, convinced that I can no longer influence the drone using my remote control. My Chameleon TI came down hard and upside down. Having had the feeling that I no longer control the drone I did not disarm the motors on my remote control.


You probably can imagine what cames next. My brother, watching my crash, saw my Chameleon plunge into the field and generate a big cloud of dust! When he saw that he called to me "Your motors still turn!" and then finally I disarmed my motors. That was way to late!

My Chameleon TI already had dug a hole into the ground on full throttle for 6 full seconds resulting in red-hot blistering motors! The motors were too hot to touch! And they smelled kind of crisp and burned. It was the last flight of the day, so daylight was sparse and when the motors were no longer too hot, we packed and went home. But not before plugging in the battery a last time, to check if everything is still in order. It seemed so...

Arriving at home, we inspected the motors under light. They all looked similar to this one:

The isolating enamel varnish was reduced to black coal. Touching the crispy windings of the motor, the black coal fell off and left the blank copper. Thinking back to the field where we plugged in the battery to check for failures, I horrified realized how much luck we had that the defect motors did not short circuit the motor phases and take the 4in1 brushless controller with it.

Lucky me! Right? ;)

In the end I bit the bullet and bought 4 new fresh and shiny Emax LS2207. I was able to buy and mount them within a week and was airborne again at the end of the next week.

I promise, next time I will disarm immediately!

Make sure to check out my articles on my Chameleon TI, my Chameleon and my X210 race drones.

- Amir

Amir Guindehi's Blog

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