Solved FPV drone shut off mid flight

[Daniel98]

Hello
I have a problem with my new FPV drone. I am quite new to this hobby and haven't had the chance to fly mutch. The issue i have with the drone is that under flight, seemingly at random moments. Its like the drone "dissarm" itsself mid air without me flicking the lever. This diden't start at first but after like 6-8 trips it started. The drone does not go into safe mode. Because i can rearm the motors after the crash and fly like normal. But after some time the drone falls out of the sky. Right before the drone falls out of the sky for a brief moment i cant control the drone and it "disarms" istelf and crash. All the flying i have done is in a open feild with little to no obsticals. The "dissarm" seem to happen faster when the battery voltage decrease overtime.
I have tried to resolder all the motor wires to the ESC and to the RX for the taranis. I cant find any solution online with this kind of problem. At this point im starting to get frustrated. Do i need to buy a New FC/ESC stack?
I hope some bright minds can help me here.

Drone specs
FC: MAMBA F405 DJI
ESC: MAMBA F50
MOTOR: EMAX eco
CAMERA: Runcam Phoenix 2
VTX: TBS unify 5g8 v3
RX: frsky
Taranis: frsky taranis QX7
Battery: Cnhl 4s 1500mAh

 

[JasonK]

The "dissarm" seem to happen faster when the battery voltage decrease overtime.

what what is your battery's C rating?
What is the voltage when this is happening?
are you getting any warnings in your googles from your FC stack?
do you have a cap on the power input?

your quote makes it sound like your system might be browning out from voltage sag.

 

[Daniel98]

what what is your battery's C rating?
What is the voltage when this is happening?
are you getting any warnings in your googles from your FC stack?
do you have a cap on the power input?

your quote makes it sound like your system might be browning out from voltage sag.

Battery C rating is 100c and it starts at under 15v. I get no warnings in the goggles. I hav not changed any cap on the power input in betaflight . And it dont fall out og the sky when i give max throttle, when battery is fully charged.

 

[JasonK]

4.2*4 = 16.8... it should not _start_ under 15v unless you didn't correctly change the battery correctly or if something is wrong with the battery.

What voltage is the battery showing when your craft drops out of the sky?

 

[LitterBug]

How long has it been in the air before this happens? Sounds like classic case of battery sag

 

[Daniel98]

4.2*4 = 16.8... it should not _start_ under 15v unless you didn't correctly change the battery correctly or if something is wrong with the battery.

What voltage is the battery showing when your craft drops out of the sky?

Im not to shure what the voltage is exactly. And to me, it varies some times lower and some times higher than 15v. But isn't the recommended min voltage on lipo batteri 3.5v per cell? This apply to all my batteries and they ar under 2 month old.

 

[Daniel98]

How long has it been in the air before this happens? Sounds like classic case of battery sag

Maby 2-3 minutts

 

[JasonK]

Im not to shure what the voltage is exactly. And to me, it varies some times lower and some times higher than 15v. But isn't the recommended min voltage on lipo batteri 3.5v per cell? This apply to all my batteries and they are under 2 month old.

you said _starting_ voltage, not ending voltage. 3.5*4 = 14, if your at 15volts before putting load on the battery, ending up under 14v is very likely. Are you checking your batteries with a battery checker before/after charging.

Maby 2-3 minutts

many quads only get 2-3 minutes flight time - depending on how you fly.

 

[JasonK]

I get no warnings in the goggles.

Do you get anything like arm status in your OSD? if not, go into the OSD setting in betaflight and make sure your getting the status message line.

 

[Daniel98]

you said _starting_ voltage, not ending voltage. 3.5*4 = 14, if your at 15volts before putting load on the battery, ending up under 14v is very likely. Are you checking your batteries with a battery checker before/after charging.


many quads only get 2-3 minutes flight time - depending on how you fly.

But in the beginning i could fly almost down to 14v, then get battery warning in goggles and land. It never just cut off by itself without warning first.

 

[Daniel98]

you said _starting_ voltage, not ending voltage. 3.5*4 = 14, if your at 15volts before putting load on the battery, ending up under 14v is very likely. Are you checking your batteries with a battery checker before/after charging.


many quads only get 2-3 minutes flight time - depending on how you fly.

My battery starting voltage is around 16.4v?

 

[Daniel98]

Do you get anything like arm status in your OSD? if not, go into the OSD setting in betaflight and make sure your getting the status message line.

After the drone shut down, i get a "status" menu, Just like if i land and disarm the drone?

 

[JasonK]

My battery starting voltage is around 16.4v?

can you DVR your OSD for a full flight were this happens, make sure the status line and voltage are on the OSD, perhaps something useful will show that your missing.

 

[Daniel98]

can you DVR your OSD for a full flight were this happens, make sure the status line and voltage are on the OSD, perhaps something useful will show that your missing.

I can take a record of the flight. But my frsky RX antenna wire got broken of due to last crash. So i have to order a new one. I live in a remote place. Estimated delivery is thursday nexst week. But i will upload video as soon as i can.
Thank you for all the help so far

 

[JasonK]

I can take a record of the flight. But my frsky RX antenna wire got broken of due to last crash. So i have to order a new one. I live in a remote place. Estimated delivery is thursday nexst week. But i will upload video as soon as i can.
Thank you for all the help so far

add RSSI to the things to make sure are on the OSD

 

[Daniel98]

add RSSI to the things to make sure are on the OSD

Will do

 

[JasonK]

I will be at flite fest next week, so very unlikely that I will be on the forums until the week after, but still get it posted, there are plenty of people here that it is likely that someone will be able to evaluate it.

 

[LitterBug]

I FINALLY made it up to Edgewater a week or so ago. Had a few packs that I thought were good and quickly found out otherwise. They sagged out in less than a minute :-O Like JasonK said, typical fly time is 2-3 minutes depending on how hard you push. You may just be hitting severe sag. I'll have to see if the DVR caught any of those flights. Even if you have good voltage at the start, a sagging battery will drop you out of the air really quick.

 

[Daniel98]

Status report:
I got hold of a new RX for the drone. Before i whent out flying i updated the softwear on the FC (just to be sure). I charged up all my batteries and whent out. This time it flew like normal, with all my 6 batteries, and i could fly them down 14V. No issues no nothing. I even tried to max the trottle at 15v multipe times on diffrent batteries to se if sag wold knock it out of the sky. But to my supprise everything worked. One thing i forgot to mention in the first post is that i flew with a friend of mine. This time i was alone. I dont know if that was the problem or not. But i will go out and fly some more alone to see if the fault happens again.

 

[JasonK]

sounds like your RX might have been damaged and was causing signal loss -> fail safe.