Trex 550L dominator Talon 90 problem

[Nigel Armstrong]

Went out flying today with the Trex 550 Dominator. After a few minutes of nice F3C style aerobatics it felt like the ESC shut down for 2 or 3 seconds. I clicked it out of idle up 1 back into normal mode and regained power. I had full control of the model during the power loss. The model was landed and the battery checked. It was showing 61% charge and the ESC was barley warm. I then fitted a fresh battery into the model to fly it again. With the throttle hold applied to safely carry the model to the strip, the motor tried to energise in very small bursts! only just enough for you to notice it.
The model was brought home and the end points in the Gpro checked as this sets the control input to the ESC, all looks to be OK. SO! does anybody have any idea what has gone on? I will fly the model again but keep it nice and close.....just in case I have to auto it.

[Grumpy]

What are the settings in the ESC for low voltage cutoff and for current limiting? The 'trying to energise' might have been the ESC sending 'beep' signals to the motor, the beeps make the motor twitch, that's normal.

Also, how good are your batteries, age, C rating sand have they been stored fully charged for any time.

[Nigel Armstrong]

Sorry for the slow reply. The settings are as it came from Align. The Talon 90 comes set up ready for use in the 550 kits. The motor was not making the normal "beep" noise and was trying to energise and turn very slowly. The lipos are Zippt compact 5000mAh 40C. they were charges about 48 hours before they were used so I am quite happy there not to blame.
Looking on various other forums this is not an isolated event. The "fix" seems to be mess about till it goes away!!! I have ordered a castle link so I can check the settings and be 100% sure of what they are. I have also checked the motor to ESC connections and they are ok. My final check of the model was the drive system. The gear mesh is spot on and everything feels free and smooth.

[Granpappy]

Is this a new build/first flight, or has it been running fine previously and then had the glitch on the last flight?

[Grumpy]

A bad connection or poor solder joint between one of the three wires between ESC and motor would be my next guess, I know you said you checked but sometimes even factory solder jobs aren't good or the bullets are contaminated with flux. Shorting of the motor/ESC wires on a sharp corner of the frame is another one to check for.

Other than that get the Castle Link and update the ESC firmware.

[Nigel Armstrong]

Hi Graham. To date the model has had about 15 flights without any problems with the ESC. I had thought of increasing the BEC voltage. It is still at 6 volts. If I turn this up it will reduce the current draw on this part of the ESC. The servos and RX are all high voltage so that wont be a problem. Its clutching at straws but anything is worth a try. I see that other pilots have swapped out the Talon 90 for the Talon 120 or Hobbywing 100A ESC.

[Grumpy]

Increasing voltage of the BEC will if anything increase current drawn by the servos, but yes, if they are HV servos it makes no sense not to run them at 7.4-8V (not that it could realistically be anything to do with the problem you have).

[Granpappy]

I had problems with an ICE 2 recently from new and a replacement ESC resolved the problem but it did give me the opportunity to do a bit of research on CC ESC's.

One thing I picked up on is that CC ESC's have no active freewheel which means that running under load with throttle at say 65% will stress out the ESC and cause problems. It was recommended that you optimise the gearing and Kv of the motor as much as possible so that you are running at least 75% - 80% minimum on the throttle to get the head speed that you want. I don't know how yours is set up but it might be worth looking at.

[Grumpy]

Relatively few ESC's have active freewheeling, the ones that do that i can think of are Kontronik and YGE (and the 'YEP' YGE clones). The only down side of not having active freewheel is a bit more heat generated in the ESC at part throttle. Not an issue if your ESC is suitable rated in my experience. Castle claim they rate their ESC's with enough headroom to fully cover for part throttle operation. As the original post said that the ESC was barely warm then it doesn't really sound like any sort of ESC overloading was the issue.

PS... Granpappy... so i take it the new ESC has sorted out your issues.. that's great!

[Nigel Armstrong]

Thanks for the replys Gents. My model was flying in idle up 1 which is set at a flat line 80%. At this setting it loops and rolls with ease and gives the lipo a sporting chance of making it into next year!