Hey guys, I think this will be my first real post here so bear with me!
First here's what I'm flying
- tarot 680 CF frame (Hex)
- APM 2.6 with telemetry and external Ublox gps.
- flyfun 40 amp opto esc with rctimer 750 kv motors 1245 CF props
- Tarot Brushless gimbal (powered by a small 3s battery and signal coming direct from the receiver.)
- 2 5000 Mah 4s lipos in Parallel (only one lipo running through the Power module so amperage reading is half I think)
- Dx7s radio
I went for a test flight with the Gimbal installed and realized I had totally forgotten to charge the GoPro. So I just decided to fly around and test the flight time on the new 4s batteries. Long story short, I landed towards the end of my flight saw that the Voltage was 14.75 and figured I could check that everything was cool and go for one more lap before packing it in.
On the return leg of the final lap the Hex seemed to jerk and stopped responding. It started bucking in both pitch and roll and heading down. I threw the throttle wide open with no response and the only other option I could come up with as it dropped was flip it into loiter. The hex bucked its way to the ground crashing hard in the feild. Luckily it came down slower than a brick but much faster than a hex frame can handle.
I looked the the mission planner running on my laptop to see where it was and it had frozen with a small pop up window saying "mavlink failed to respond" or something similar (sorry I just looked at it and ran off towards the Hex, should have made a better note of the error). So I picked up the hex with broken landing gear and one broken arm and headed back to the car. By the time I got back the mission planner was up and running so I wobbled the hex around a bit to make sure the telemetry was responding correctly then headed home.
So here is the part I can't figure out, the Tlog is basically blank starting where I lost control. It freezes at 73% and and shows the Hex just sitting in the air leaning at 41 meters up. I have 69% signal and line of sight so it should have a solid connection.
Ok, so I expect the first comment is going to be "duh, dude look at your voltage, no wonder it dropped like a brick". I for one, would have to agree and to make that comment worse I think I have my Escs programmed at lipo med voltage protection. So at this voltage they should have been going into soft cut off.
So at the very end the Voltage drops dramatically, it goes from 14 to 12 really fast!
So once I realized this I wanted to check the Voltage of the APM to make sure I didn't have a brownout causing the telemetry glitch. (Also, bear with me because I just learned how to use the logs yesterday)
So if I'm correct the above chat shows no brownout?
And we can see here around line 6800 rollin/roll seems to say the apm was went to neutral and the copter went to CRAZY!
Same with pitch, crazy time leading to a crash.
So my basic question here is could this be a crash caused simply by my voltage problem. Would the voltage drop be explained by poorly broken in batteries and the Hex falling out of the sky due to the ESCs hitting soft cut-off? Would any of this cause the Telemetry to cut out and the Tlog to be frozen or blank or whatever it is. Also If it were the ESCs cutting out wouldn't the APM still be trying to level itself out, not just throwing everything into neutral? I checked at the beginning of the flight and I still had the Voltage protection on parameters set for 3s so the Apm shouldn't have gone into voltage protection till 10.5v.
So I have the parts ordered to fix the frame and I'm going to power everything up shortly and check the settings of my ESCs (because I'm not positive what I set them to although I'm fairly sure I was reading the APM instruction while I did it). I don't think I'm going to make any immediate changes because I want to get everything back together and tether the Hex to a couple of cinder blocks to see if I can repeat the problem.
So if anyone has any input or see's a glaring problem that I didn't, I love some comments.
, Thanks -Ian
Replies
LiPo batteries do not have a breaking in period. I wouldn't trust a new battery without a thorough check on a balancing charger before and after a flight. Follow the rules mentioned by S.K. and you will be OK.
Regarding the '5 VDC' recorded in the log.. it is a software trick previously discussed weeks ago. It wasn't working properly at all for a while with one build of the code but looks to be functional, at least, on yours. The power module supplies the values used by the CPU to calculate the Vcc value.
In your case, with two LiPos in parallel but PM only on one...this is odd. Is the below diagram how you are connected?
The PM can handle a 4S battery, two in parallel is still only a 4S voltage but 2 x the amperage if evenly matched/balanced.
Two in series would be 8S and definitely exceed the rating of the PM, probably making smoke exit from parts of it.
Please clarify your wiring.
-=Doug
Hi,
A copter can't fly with its ESCs going into soft cutoff. They most probably don't all do that at the same time either (that would require some super precise everything).
14.8 volts is too low a voltage to (re)start with on 4S. It is where the battery is almost empty and you only have a few emergency reserves.
Sorry to hear about the damage.
Regards
Soren
I think I Forgot to mention that I was flying in Stabilize at the time of the crash, I switched to Loiter after it was out of control and halfway down.