Loss of Power, but No Loss of Voltage... WHAT???!!

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Yep, I know it sounds crazy, but here's what happened. I built a new F550 around the NAZA-M V2 and the E305 propulsion system. I've had about a dozen or so flights with different settings on level one and two warnings, and finally settled on one that gave me a little over 24 minutes flight time, and that's with about 70% aggressive flying. So I finally got all my FPV gear added and wanted to fly again, to see how much my additional 229 grams of gear reduced the flight time.

Everything was going normally, with a crisp OSD readout of voltage. About 10 minutes into the flight, I just happened to turn the nose toward home point (thankfully), and glanced at the voltage from my 4s 8000 mAh battery, and noticed it was at 15.9v. Plenty of juice left, right? So as I watched the monitor, I noticed I was heading straight for the tops of some 120-150' pines and wondered when I descended that low. I had just enough time to navigate away from them to the side into a clearing and tried to accelerate toward home.

Here's where the trouble started. I noticed the distance to home was NOT decreasing and the altitude was. Try as I might, I could not gain altitude, navigate in any direction, or maintain any control over the unit whatsoever. Another glance at the monitor showed that I still had 15.9v and was descending smoothly toward the ground. I had a soft landing, very similar to an RTH landing, except the mode on the OSD said GPS. The distance from home showed 225 meters with the nose pointed about five to ten degrees off dead center. I jumped on the four wheeler and found the bird on the ground in perfect shape with the props still spinning at idle speed, as if I had just armed the motors or just landed.

Now it gets really weird. Again the voltage is steady at 15.9v so I increased the throttle to take off again. I had very little if any response from the props. You could detect a slight RPM increase, but certainly not enough to take off or even tip over if one motor was weak. The video transmitter continued to transmit. The camera continued to record. It just sat there idling. So I shut her down and brought her home, no worse for wear and very happy it happened close enough to recover.

When I charged the battery back to full, I noticed it took 4819 mA to finish it off. So it appears I had used maybe 60% or so of the capacity. Since this happened with the first flight after adding all the FPV gear, I examined all the connections closely. The only thing I found that could remotely have caused a current drain, would be that one of the 5v solder pads (the + side) had some flux that had run over and onto the ground side of the 12v solder pad. It didn't appear that any solder was touching between these two, but I'm wondering if the flux could have created enough of a high resistance connection to drain the current and not the voltage. I know that sounds weird, but this whole event was weird.

So, in a nutshell, a bird that flew perfectly before adding FPV gear, now had a loss of power, but no corresponding loss of voltage. It couldn't maintain enough lift to hover, so it softly landed but would not take off again. I'm at a loss for what could possibly be going on here, but it's critical to isolate the cause before flying again. Or at least, fly very close to home in case this event repeats itself about 10 minutes into the next flight. I've just about ruled out interference, because I live in a rural area surrounded by swamp on three sides. That's another reason I was so relieved that it happened in a clearing and not over Smokey the Bear's den.

Please offer suggestions or theories as to what I might check or isolate to discover the problem. I've always received great assistance on this forum and am once again in need of your expertise. Thanks in advance...
 
I'm not in the habit of replying to my own posts, but c'mon guys, I really need help with this. Can't someone offer a suggestion as to what to check?
 
First off, I'm no expert but I'll propose a theory. You didn't indicate whether you got any error messages, but you did indicate you had increased the weight. Possibly, increased motor load caused a temperature increase of the motors and /or ESC components, resulting in reduced output to the motors. This could have caused a forced landing for safety. Can you examine your flight logs?
 
Again, I am no expert but I would check the temperature of the battery as well, is it warm to the touch after a flight with the extra weight? Also (if you haven't already checked) have you adjusted the voltage warnings in flight assistant? There are many variables and when it comes to batteries I use an Imax charger which gives me a cell readout so I do get advance warning if a cell starts to go down in a particular pack. Sorry to be a bit vague but I think it's probably a battery pack issue rather then anything to do with the P1
 
I'm no expert but I'll propose a theory.

Hey drm, I really appreciate your taking the time. I'm not looking experts here, just support from the community, so thanks for trying.

You didn't indicate whether you got any error messages

No error messages of any kind on the monitor from iOSD-mini. Keep in mind, this is just a bird with FPV and a controller. No cell phone or tablet involved.

increased motor load caused a temperature increase of the motors and /or ESC components, resulting in reduced output to the motors.

If this had been a large weight increase, I would agree with you. But it's only 229 grams, less than a 2 axis gimbal. My battery alone weighs over 800 and I'm still under DJI's suggested total weight for takeoff.

Can you examine your flight logs?

There are no flight logs. This is just like a P1 with two extra motors and a different frame.

So as I mentioned earlier, thanks a lot for offering your theories. They are helping me isolate causes, one at a time.
 
I am no expert but I would check the temperature of the battery as well, is it warm to the touch after a flight with the extra weight?

Hey mouse, thanks to you as well for taking the time to try and help. Battery is barely warm to the touch at all, and that's after a twenty-four minute flight. It did however, take me about 10-15 minutes of panic to get to the bird's location, so I guess it could have cooled off a bit by then. But the extra weight of the FPV equipment and wiring is only 229 grams, very insignificant.

have you adjusted the voltage warnings in flight assistant?

Second level warning is still set at 12.8v, which is where it was before adding this equipment. Since this anomaly occurred about 10 minutes into the flight and at 15.9v, it would not have triggered an AutoLand.

I use an Imax charger which gives me a cell readout

I use an Imax as well, which is how I knew it took 4819 mA to top off the 8000 mAh battery. I always do a balance charge, but I am adding a buzzer to the bird to monitor individual cells.

I think it's probably a battery pack issue rather then anything to do with the P1

This is a new battery with only 12 previous charge cycles on it, which of course doesn't mean it couldn't go bad. Since it's not getting hot during a 24 minute flight, I'm hoping it's not the battery. BTW, this isn't a P1 but a hand built F550 Flame Wheel. Still very similar as far as the NAZA and controller go.

So thanks again for offering your suggestions. I've got to keep at it until I figure it out. If nothing else, I'll disconnect all the new equipment electrically and have a test flight to see if I return to the 24 minute flights or if the problem happens again.
 
OK guys, I couldn't stand it any longer. I had to do another test flight. Fortunately, this one went well. Rather than disconnect every piece of equipment I added, I left the iOSD-mini, vTx, and camera powered on. It was very windy at altitude, which I knew before going out, but I had to try it anyway. I got 23 minutes 2 seconds from spin up to touchdown. That's just over a minute of decreased flight time and the wind had some effect on that. Electrically, I did two things differently. I had the camera on, but this time not recording, and I did not connect the 5v charge lead from the BEC to the Trackimo. So now I'm wondering which of those two may have caused the original event, if either. The battery was only mildly warm, just like it was on all the flights before adding FPV equipment.

So I feel a lot better now, that something isn't seriously wrong. I'm going to continue to experiment with camera recording, though I may decommission the Trackimo altogether. I got my State Farm Personal Articles Policy today with $1000.00 coverage at a cost of $60.00 per year. That's with no deductible and no depreciation due to age. All I had to do is e-mail all my receipts and a few pics and they were happy. So now I don't need the Trackimo if it goes down in the swamp. I don't need to try to find it, fighting off bears and coyotes, just make a claim and get a new bird. I learned about the State Farm policy on this site, so I'm grateful to all those who shared their info on how to get it.

Again, thanks for your time and your input. Fly safe/fly happy :cool:
 

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