Momentary Power Surge HC1100

[Giovanni59]

This is a build that I have been flying for about a year but recently have been having issues with.
My last job the copter started spinning when landing and crashed into a tree. I had WKM V2 on it and thought it might be the culprit so I decided to get A2 and that is installed now but I am still having issues.
I have bench tested it and even put a vibration meter on each arm but there is no indication of motor failure.

These are Tiger U7 motors with T-Motor 80A ESCs.
The ESC wires are soldered to the motor wires.
Power distribution is a thick copper bus bar
In the video I start it up and idle and give a little bit of throttle but do not take off.
At timeline 00:9 seconds there is a pop.Then again at 00:54 and 59 and 60 seconds, and then at 1:06.

I then take off and hover and at 1:44, 1:48 - 49 you will see the copter lurch and the pop again.
It seems to increase power for a second.
It happens again at 1:55 and then at 2:07 - 11

Motor, ESC or what? It has been suggested I might have a bad solder connection somewhere.

Please let me know what you think.

Thanks

John

 

[fltundra]

John,
I would look at wiring between batts and pdb. All esc's are cutting out at the same time, so I would rule out any single one.
Have you checked the IR on those multistars? Maybe have a cell going bad. Did you see voltage drops on telemetry or A2 log files? Are the lipo's tied together, or each separately to the pdb?

 

[Giovanni59]

fltundra, thanks for the help. I checked the Multistars and all the cells are good and within .5 v of each other, I use an icharger 406 Duo.
I have some Gens Ace and I can do another test with them. The battery connection wires go directly to the pdb. I have a new iosd Mark II but cant get the green light on in assistant to check the log. I did not notice or was watching the voltage when it happened. I will do another flight and watch the voltage. I will also check my connections to the pdb. Thanks

 

[Old Man]

Might take a magnifying glass and look for burn marks around solder joints and connectors. A "pop" implies an arc occurred.

 

[Giovanni59]

I examined the FC power connections and it does involve a series of XT connectors. First the IOSD and FC are connected to a Y-XT connector and then that goes to an extension with two XTs on each end. That extension is then plugged to an XT connector attached to a wire that is then soldered to the bus bar. I made another extension with XT connectors and replaced the one I had. Also I have another power lead coming out of the bus bar that powers: video TX and FPV camera. I switched that power with the FC, thinking if the issue is there it is better to have a power failure with the FPV rather than FC.

I did a flight with a set of Gens Ace Tattu batteries and I still get the pops and surges but not as frequent. I flew for 17 minutes and I noticed slight pops and surges only about 6-8 times.

I did not see any burn marks or discolorations on any of the wires or connections.
Tonight when it is dark I will power it up in the house with no props on and look for arc flashes.
Other that that I do not see any resolution to this other than a complete break down and rewiring.
That way I can also have to separate leads coming off the bus bar for the batteries. I will also then have a wire
long enough so I don't need an extension for the FC power.

If there is anything else anyone can think of please let me know.

John

 

[Old Man]

I share some commonality with your set up in using extensions and additional XT connectors on a hex. It's a condition I intend to clean up one of these days through re-wiring and elimination of some of the connectors. Every one of them I can eliminate will reduce resistance losses.

 

[Giovanni59]

Kloner suggested a possible bearing failure as opposed to an electrical one. He asked to see if there was any play while pulling up on the motors and here are the results:

One motor, #2, does have some very slight play up and down. All the rest are very tight, no play at all.
The motor that does have the movement is so small I can't even see the gap change as I pull on it but there is a slight movement and when released there is a small click as if a spring is pushing it back into position. I would say the amount of play is .2 or .3 mm. Can that little amount be causing this? Is there another test or way to check it?

I do have another U7 motor perhaps I should replace it to see if that is the problem?

Others have pointed toward an electrical problem due to a loose connection or solder joint. It is curious that right at the "pop" the crafts surges and actually rises in spots.

Anyone have any more insight on the possibility of a bearing problem?

Thanks
John

 

[Old Man]

Interesting thought.

 

[fltundra]

It is curious that right at the "pop" the crafts surges and actually rises in spots.

That's because the FC is throttling up for a sec in response to the motors shutting off.


Check and make sure there is no intermittent connection loss at the FC and the receiver. You do have the FC connected directly to the buss bar now? You would be able to feel a bearing going bad, spin all the motors by hand and see if any have a mechanical roughness.

 

[Giovanni59]

Yes, FC is wired directly from buss bar to the PMU but going through a series of XT connectors.
Since the problem I hot glued those connections, just in case they are lose.
Of course if there are any problems along those solder joints I would have to rewire.

I have two power leads coming off the buss bar for power other than the battery leads, the other powers
the FPV system and goes through a voltage regulator and noise filter.
I switched those power leads (before the regulator and filter)and I get the same results although the XT connecters remain. Where there is the connection to the PMU and IOSD MII, there is a Y connector that comes installed by DJI to connect those two components together.

All the motors spin nicely with no grinding but one does has some play when I pull up on it, but very slight, as I have already described:

One motor, #2, does have some very slight play up and down. All the rest are very tight, no play at all.
The motor that does have the movement is so small I can't even see the gap change as I pull on it but there is a slight movement and when released there is a small click as if a spring is pushing it back into position. I would say the amount of play is .2 or .3 mm.

 

[fltundra]

How often to you clean the bullets in the xt connectors? They get oxidation over time with just current flowing through them. Your in the same climate as me and I have been cleaning mine every 5 hours or so and am always amazed at how dirty they are. Qtips with electronics cleaner.

 

[Giovanni59]

Hmm, never had that problem, I did examine the inside of the connectors and they seem to be crystal clear, no residue on them whatsoever.
It wouldn't hurt to give them a once over with cleaner though.

On connections that are used all the time like the batteries I use PRC6 6mm connectors from Progressive RC. I use a grease like paste that is a conductor and also makes the joining and pulling apart a lot easier. Don't know the name of the stuff but I got it at Ace Hardware.
I don't suppose that could be the culprit, I would have thought that the stuff would only help.
Just exploring different options.

BTW, just did a motorcycle trip to Key west and of course passed through Largo.
Do you exclusively do aerial or all types of photography/video?

 

[fltundra]

I use a grease like paste that is a conductor and also makes the joining and pulling apart a lot easier. Don't know the name of the stuff but I got it at Ace Hardware.

I would definitely remove it. Dielectric grease?

Do you exclusively do aerial or all types of photography/video?

Neither, looking at flir and other uses and waiting for the regs to be finalized. I hold a land/sea single engine ticket and thought about filing for the 333. But have to many other pressing issues like getting our house sold, and getting out of S FL. Now, I'm just flying as many hours as possible, and enjoying every second.

 

[Old Man]

On connections that are used all the time like the batteries I use PRC6 6mm connectors from Progressive RC. I use a grease like paste that is a conductor and also makes the joining and pulling apart a lot easier. Don't know the name of the stuff but I got it at Ace Hardware.
I don't suppose that could be the culprit, I would have thought that the stuff would only help.
Just exploring different options.

BTW, just did a motorcycle trip to Key west and of course passed through Largo.
Do you exclusively do aerial or all types of photography/video?

If that grease is a "dielectric grease" stop using it on connections. It's designed to inhibit electrical contact, not assist. Learned that the hard way with some military stuff. Took a while to figure out why we were having a lot if current issues.

 

[fltundra]

If that grease is a "dielectric grease" stop using it on connections. It's designed to inhibit electrical contact, not assist. Learned that the hard way with some military stuff. Took a while to figure out why we were having a lot if current issues.

I would imagine it can't be good at all coating the connector surface. I've only used the stuff on spark plug boots.

 

[Old Man]

Had some work instructions a long time ago that said to place a quantity of the stuff in the top of a spark plug cap before installing the cap on the plug. Whoever had written that instruction had clearly never run a spark ignition engine before...

 

[fltundra]

Had some work instructions a long time ago that said to place a quantity of the stuff in the top of a spark plug cap before installing the cap on the plug. Whoever had written that instruction had clearly never run a spark ignition engine before...

Never used it on the conductor. just a little around the insulator so the plug boots wouldn't stick to the plugs.

 

[Giovanni59]

It's called Anti-Oxidant Compound made by Ox-gard
First 3 bullet points:
-Guards against oxidation
-Improves conductivity
-Produces a cooler connection

I'm pretty sure it can only help

 

[violetwolf]

I think you guys are on the right track. It sounds like intermittent connection on the battery side of the PDB to me as well.

Or possibly the PDB itself

 

[violetwolf]

I posted above without watching the video. Upon watching it I think I wouldn't rule out a binding motor either. It sounds suspiciously like a bearing seizing too..

Tough one.. I'd maybe swap out each motor one at a time with your known good one and test that too