Sudden loss of power

Obsidian Triniti · Dec 10, 2020

Hello,
I am having some issues with my Squirt V2.1. It has a DJI AU. I'm relatively new to this, so forgive me if this is a stupid question.

I have been flying it since April and things were going well. I began losing connection and power intermittently and it turned out the power cable was broken. Fixed it, all was good for a couple of months and then I would be flying and any tight banked turn I made, it would disconnect and fall from the sky - still had power though. It turned out there was a bad antenna - so it was fail-safing. I replaced them both and for two months all was fine (getting the pattern here

). Yesterday it started losing power and falling from the sky - I've checked the antennae and the connection to the AU and they seem secure. I've replaced the power cable - soldered in a new one and the capacitor. Instead of flying it, I picked it up, armed it, and started moving the bird in the air. The moment the props had to work hard, it stopped - again, sometimes losing connection, other times not.

I flew it and it was fine for about 10 seconds then rolls and falls from the sky. Sometimes it loses connection and other times it does not (btw, I'm using the DJI controller - the green indicator tells me if I still am connected to the quad). The goggles don't show me anything indicating a failsafe. Checked antennae and power, all look good. I believe I saw the green light on the FC go out a couple of times during these disconnections. Don't know what that means . . .

I'm not really sure what else to check - maybe my AU went bad? I'm not really sure what to check next. Any assistance would be greatly appreciated.

Regards

tevek · Dec 10, 2020

Is the AU wired direct to vbatt or through a voltage regulator? Unusual that you would still have OSD and lose control. Assuming that the yellow wire is wired to sbus on your FC for use with the DJI controller, maybe double check that it is a solid connection. I’ve slammed my DJI AU quads into all sorts of things so they’re pretty solid, only other thing would be either ribbon cable plug not seated properly in the AU or one of those wires is not seated correctly in the ribbon plug. Usually if the AU eats itself, it would be terminal. May even be the FC dying on you, you may be able to open up the quad and start tapping with a non conductive stick when it’s powered up to see if anything starts playing up.

Obsidian Triniti · Dec 12, 2020

Thanks for this information much appreciated. I will do some tinkering to see. I hope it is something simple. One thing I did notice today is that when it is connected to the remote and armed, once I turn the quad on its side, the motors stop. The once steady green light on the FC is now blinking until I disarm and rearm. Does that give any more hints as to what might be wrong? I've been looking for a "legend" to the green lights, I have an HGLRC F7 FC.

The AU is wired directly to vbatt.

Thanks again!

Obsidian Triniti · Dec 14, 2020

Update - so I started to break down the quad to test each component - mainly the AU and the FC - I have spares so will try each one. When I took off the FC, I found what looks like melted parts on the ESC. If anyone can identify what is melted and if it can possibly result in the sudden loss of power - typically when the props rev up high - and sometimes it doesn’t lose connection to the remote or goggles. Any help would be greatly appreciated. Thanks

tevek · Dec 15, 2020

Obsidian Triniti said:
Update - so I started to break down the quad to test each component - mainly the AU and the FC - I have spares so will try each one. When I took off the FC, I found what looks like melted parts on the ESC. If anyone can identify what is melted and if it can possibly result in the sudden loss of power - typically when the props rev up high - and sometimes it doesn’t lose connection to the remote or goggles. Any help would be greatly appreciated. Thanks

Could be mistaken but they look like the mosfets managing your current to your esc’s. That would explain loss of power and control of your drone. Had a similar board a while back that cooked both the mosfets and the BEC due to a voltage spike (I think) from a dud battery. Replaced that board and always run a cap on my quads.

Obsidian Triniti · Dec 15, 2020

I’m thinking that has to be it. Got a new ESC coming in and am replacing the cap.

thanks again!

tevek · Dec 15, 2020

Obsidian Triniti said:
I’m thinking that has to be it. Got a new ESC coming in and am replacing the cap.

thanks again!

No worries, blowing things up and repairing them is all part of the addiction!

droneguy · Dec 19, 2020

Obsidian Triniti said:
Update - so I started to break down the quad to test each component - mainly the AU and the FC - I have spares so will try each one. When I took off the FC, I found what looks like melted parts on the ESC. If anyone can identify what is melted and if it can possibly result in the sudden loss of power - typically when the props rev up high - and sometimes it doesn’t lose connection to the remote or goggles. Any help would be greatly appreciated. Thanks

The burned components are capacitors which could lead to unfiltered voltages and cause all sorts of problems. Without the cap values, it would be difficult to replace them with the exact match, but given the location and number of these, they might be for the signal coming if for the motor outputs.

droneguy · Dec 19, 2020

tevek said:
Could be mistaken but they look like the mosfets managing your current to your esc’s. That would explain loss of power and control of your drone. Had a similar board a while back that cooked both the mosfets and the BEC due to a voltage spike (I think) from a dud battery. Replaced that board and always run a cap on my quads.

Typical modern mosfets look different than these and typically when a mosfet goes boom, it opens and the motor stops working. Sometimes they don't completely open, but when high current is applied, it usually finishes the job. The burned item in the picture is a capacitor and could normally be replaced pretty easily as often, the values aren't as critical as other components since they often provide filtering or similar functions.

I often repair these type of problems when there is enough information to identify the part. People send me dead boards all the time and I manage to revive 50-60% of them with minor fixes. What usually helps in troubleshooting is a recollection of what led to the failure as it help identify where to stat the diagnostics without wasting time or causing more damage.

I recently did a mosfet transplant on a tinyhawk freestyle 2 AIO board, which was a real challenge. The mosfets on these are tiny ICs 2mm x 2mm wide. I replaced two of them and successfully revived the output. I've fixed dozens of ESC by replacing mosfets, but this was a first on such a tiny component.

tevek · Dec 19, 2020

droneguy said:
Typical modern mosfets look different than these and typically when a mosfet goes boom, it opens and the motor stops working. Sometimes they don't completely open, but when high current is applied, it usually finishes the job. The burned item in the picture is a capacitor and could normally be replaced pretty easily as often, the values aren't as critical as other components since they often provide filtering or similar functions.

I often repair these type of problems when there is enough information to identify the part. People send me dead boards all the time and I manage to revive 50-60% of them with minor fixes. What usually helps in troubleshooting is a recollection of what led to the failure as it help identify where to stat the diagnostics without wasting time or causing more damage.

I recently did a mosfet transplant on a tinyhawk freestyle 2 AIO board, which was a real challenge. The mosfets on these are tiny ICs 2mm x 2mm wide. I replaced two of them and successfully revived the output. I've fixed dozens of ESC by replacing mosfets, but this was a first on such a tiny component.

I stand corrected, only had a quick glance and should know the difference between them and capacitors. The number of caps is the giveaway and the fact they don’t look anything like transistors and since the board I replaced went up in flames, I didn’t bother diagnosing much further than changing out the board.
Thanks for that.

droneguy · Dec 19, 2020

Hopefully the root cause was a problem on the board itself. I'd hate to see another board go up in smoke. What were the circumstances that led to the board failing? Often the details of the moments prior to the failure coupled with the damage incurred, can help shed light on the root cause. When it fell out of the sky was it still powered on?

tevek · Dec 19, 2020

droneguy said:
Hopefully the root cause was a problem on the board itself. I'd hate to see another board go up in smoke. What were the circumstances that led to the board failing? Often the details of the moments prior to the failure coupled with the damage incurred, can help shed light on the root cause. When it fell out of the sky was it still powered on?

Actually from memory I had a huge crash with the motors spinning and up it went. Too slow to disarm it, also had a similar experience hitting a tree, took out both the motor and the esc board on a Diatone 339.
I’ve also set fire to a paddock with an esc going up on a wizard x220.

droneguy · Dec 20, 2020

tevek said:
Actually from memory I had a huge crash with the motors spinning and up it went. Too slow to disarm it, also had a similar experience hitting a tree, took out both the motor and the esc board on a Diatone 339.
I’ve also set fire to a paddock with an esc going up on a wizard x220.

That's an impressive resume. LOL!