Please bear with me. This one is a little complicated (at least for my limited experience).
Equipment:
3DR Iris w/legs, gimbal & GOPRO. Only modification is GPS Mast. Everything else is just like it came out of the box.
Batteries:
IRIS Stock 3500mah 3S
Thunderpro 3850mah 3S
Zippy 5000 3S
Charger = HiTech X1 MF
Charger cutoff voltage 10.6vdc
Symptoms:
very reduced flight times. With the Zippy 5000 or the Thunderpro 3850 less than 5 or 6 minutes then lose power. It will fall out of the sky in a perfect vertical drop if your not ready for it. This can happen at voltages as high as 10.7 hovering. Higher voltages when flying.
Logs only show that I’m using 1900ma of 5000 on the zippy and 2050ma of the Thunderpro 3850 before losing power.
I don’t know if it’s normal but my motors get VERY hot. You can only touch them for about 1 second. Infrared temp gun shows temps as high as 140 degF after a flight.
logs show that the RCOU Chan1 is always higher than the other 3 channels. Eventually it gets pegged out at the max and the other 3 channels have to cut back to maintain pitch and roll. It will then make an immediate drop at full throttle in stabilize. The logs I have posted are only with hovering. If you try to fly it the RCOU Chan1 can max out and the bird starts losing altitude fast. This has happened as high as 11.1 volts. I have a log for that as well if needed.
List of things I’ve done as part of the troubleshooting:
replaced the front right motor which I understand to be RCOU Chan1.
Performed ESC cal several times. All looks good.
Autotune with full payload (legs, gimbal, go pro)
Visually inspected solder joints on ESC board
I guess the only thing left is the ESC? Could it be an ESC firmware issue? Or just a bad one? I will take advice, I’m just out of stuff to try and this bird is BATF (barely able to fly). Everything else works fine except right now it’s only good for hovering close to the ground.
I flew over a hundred missions before I put the legs and gimbal on. This problem revealed itself when I added the gimbal and legs from 3DR. It seems to be getting worse. Last night I reverted back to stock zero payload and flight times are down there as well.
From what I can see, if the RCOU Chan1 output to the front right motor is at 100% and can’t get anymore speed out of the motor then the other 3 motors have to cut back (which they do) to maintain attitude therefore reducing the overall lifting power. Please let me know if I’m reading that right.
If that is correct and the motor has been changed then the only thing left is the ESC? I tried to order the Iris 4n1 ESC and power board this morning but can’t find it on the 3DR web site.
Any help would be appreciated. Hover logs from 2 different batteries are attached.
Don’t do this. Autotune is to be done with the copter at its minimum flying weight, with the entire copter rigid (no gimbals or other hanging or loose mass).
10.7v under load on 3s is very low. I would set the buzzer to go off at 11.1.
Center of gravity is most of your issue. I doubt you have a problem with the ESC. You could try adding some weight on the opposite arm, but all of your motors are pretty high. May be possible to prop it up or move to 4s.
IRIS is just about at its maximum capacity with the gimbal. Doesn’t take much to make it fail at that point.
I did the auto tune with full payload under the direction of help@3drobotics. When it didn’t help they sent me back to the forums.
According to other IRIS users they are getting much better results with the exact same setup. Maybe some of them are passing inaccurate information. Setting at 11.1 would give only about 3 or 4 minutes of flight.
I have tried everything I can to check for COG problems and can’t find anything. This RTF Iris is stock out of the box with only the mast added which only weighs a few grams. I will try putting the GPS back in it’s stock position but if I do that I can very seldom get less than 2 HDOP.
Based on your advice I have decided to scrap the IRIS. The mast was installed because of about 80 flights of pure misery caused by the GPS touching Pixhawk issue. Now I add the payload that was purchased with the IRIS RTF and it can’t handle it. I have spent countless hours of testing and troubleshooting to get normal flights from an RTF bird. I have had less issues with scratch builds.
Are you sure you are getting a full charge in the battery, if charging at a lower rate than 1C, the chargers will terminate on a capacity limit. Say you are using 2A, the charger may terminate at 2.2Ah. My multiplex charger does this, its quite annoying, but I trust the charge so havent changed.
I charge at a lower rate than 1C as it doesn’t support 8 amps for my 8Ah.
If that is the problem restart the charger until terminates due to low current.
Yes I am sure the battery is charging all the way. I have the mah limit set at 6500 just to get it out of the way. It is charging to a cutoff voltage of 10.6 vdc for 3 seconds. The charger is a Hi-Tec X1 MF
Without legs, gimbal and go pro I can run the battery down to a 10.2 failsafe which I don’t normally do. I just did it for testing. Without the payload the Iris still has enough power to stay aloft all the way down to 10.2 volts.
Sorry, my mistake. Yes, 12.6 3 cell. All cells within 20 millivolts of each other at the end of charge and still balanced pretty good after discharge. And yes I am using balance charge at 1C.
I have 5 different batteries and they are all in pretty good shape. No balancing issues.
3 x 3500mah stock Iris batteries
1 x 3850mah Thunderpro (I think 30c)
1 x 5000mah Zippy
They all perform very well without the payload. With no gimbal and camera I get stabilize and loiter time of:
9-10 minutes on the 3500mah
12 minutes on the 3850mah
16 minutes on the 5000mah
with the gimbal and camera I can’t even do normal flying below about 11.5 volts. hover throttle is up around 80% or more.
I really appreciate your input but I have given up on the Iris. All I used it for is practice stabilize fly and running autonomous missions with multiple way points which has gotten boring without the ability to add any payload other than the way it came out of the box. There are numerous other Iris owners having the exact same issues with the payload. I have spent probably in excess of 100 flights trying to figure it out. It’s just an underpowered bird. The motors get so hot I can even touch them. I have measure the motors at up to 140 degF with an infrared gun after a flight.
Btw - I have changed every single motor during the troubleshooting process.
I use RCTimer HP2814 810KV and they generate a lot of trust…
Total power consumption on 2.5kg RcTimer Spider around 25amp hovering with 10 x 4.7 carbon props.
No motor heat at all, so I am planning to upgrade to 11 x 4.7, to be able to lift a 8200ma 4S, instead of the 5100ma 35C 4S I have now ( 9-10 Min flight time)
Sorry, they were wrong. I’ll talk to my boss about it. Autotune should be done at minimum payload, because that is when the copter’s rotational moments of inertia are smallest and thus the response is most sensitive. Tuning with payload can cause the copter to be unstable if you were to fly it without the payload. Moreover, having a sprung mass like a camera gimbal on board is a nightmare for autotune.
I don’t personally have an IRIS, but I’ve heard other devs recommend 4s batteries. Also if your motors are getting hot, make sure all of your motor connections are secure.
I just took another look, with the goal of figuring out if you really have a motor problem, or just a CG problem.
I took a look at the average of the CCW motors minus the average of the CW motors. It should be near zero on a quad regardless of CG. There is a small offset of about 25 uS PWM. Perhaps enough to indicate that there’s an issue, but an offset that small could also be caused by subtle geometry things like twisted arms and tolerances in electrical components. Subtracting 2*25=50 from motor 1 brings it down to zero, but the copter is still imbalanced front-to-back, so you’re probably a little bit front heavy as well.
Still, I’d contact help@3drobotics.com and get a replacement ESC. Link them to this post.