I am having serious issues with my copter, in the way that it does fly for a short period and then just descends abruptly hitting the ground. As soon as I see it descending (usually i’m flying at 2~3m above ground because I’m trying to find the cause of this problem) I switch to stabilize and cut throttle to avoid major damage.
At first I thought this is was a temperature related issue, but now I dont think so.
I saw a log that contained barometer error in the exact moment the temperature rised to 70º degree inside the frame (it’s an waterproof one) but now logs dont even show any error, the copter just falls to the ground…
Would appreciate very much if someone is able to help me figure this out
I’m using 3.4 rc-1 now but this issue was happening with 3.2.1 too
With those logs it’s not easy to catch much. Please increase the logging level. Don’t be afraid to set it to high values. At the moment there are a few points that the dev team would really need everyone’s help and logs are the best way.
Look at setting up these parameters LOG_REPLAY, LOG_DISARMED and LOG_BITMASK to 655358
Yeah that’s what I thought… i looked for the usual things like motor/esc, gps problems but couldnt see anything related. There must be something else causing this I cant fly this way
I will do that tomorrow and report back with new logs
In the case of the shorter flight at least it looks like a weak battery. Maybe take-off happened when the battery was not fully charged? It starts at 15.5V (4S battery?) but it’s 12.5 by the end. There’s also a slight motor imbalance with motor 4 (back right).
I enabled all logging possible and did some more tests today and i think you’re right about the batterys.
Im flying with 4S and charge my batterys to 16.8v and only fly until I waste 75% of them (2 multistar packs of 5200mAh 10C = 10400 total) wasting about 7500mAh.
In today’s logs I see that on the flights with no crash that batterys never went below ~14V
but on the crash flight they went to 11.87V , that could explain it right ?
Could you please check all logs and see if it’s the battery that are causing this issue ?
Also the battery 10C x 5000mAh - would theoretically be able to provide 50A, and you are using around 25/30A, which might be very close to what the battery can really provide.
Also check the presence/absence of the barometer foam and the placement of the PixHawk, your baro values vary a lot.
There are some parameters to compensate to tension and max current to the system, but I would start to reverify the entire setup, and please, please don’t skip setting up properly the failsafes (battery)
Luis, the failsafe of BATT_MAH is set to 1000mAh which gives enough time to bring the copter back. I have set BATT_VOLTAGE to 0 because since this is a low C battery, its common for them to drop voltage more quickly and so if I had it set to 14V for instance, it is possible that i would have a lot of battery failsafe triggers even with the plenty of battery left.
Unless I am understanding it wrong…?!
Regarding the 10C, this are the same batteries I am using since one year ago and never had any problems till 1 month ago that it started doing this and I havent changed anything on the hardware!
I will have to check if there’s foam inside, thanks for reminding.
Cant understand what’s wrong with motor 4, what do you see in that graph that points to a problem with right motor ?
the constantly measure of the batteries by tension is one of the best ways to ensure batteries don’t cause problems. In this case I believe that your batteries might already be degraded/damaged. If you only use capacity as failsafe you might have problems like crashes, because, imagine for an instant a cell blows up right at the beginning of a flight and tension goes to 12V and from the capacity remaining you would still have plenty of battery left…try to check the battery Internal resistance.
If you always had failsafes at 14V is a good indication of overweight and/or incorrect choice of batteries (too low C rating)
The motor 4 output is always higher than any of the other motors, that’s what I meant with it doing overtime to keep things level
It can be the propeller too, it’s a little dented because of the consecutive crashes
You said that I was on the limit because of the 10C, but since i’m using 2 packs (4S 5200mAh 10C each) , the maximum discharge rate would be 104Amps right ? And I’m nowhere near that.
This batteries don’t have an year of operation, and dont have more than 50 charge/discharge cicles, so probably it could be related to the temperature inside the quadcopter case (yesterday I measured 72ºC for pixhawk / raspi, which seems HIGGGHHH ), but can’t do nothing since it’s a closed frame in order to be waterproof.
I’ll make that test. One thing i’m sure is that 4 packs are dead, and those were the ones were I had the crashes.
Regarding CoG, that’s a good candidate to check and easy? to correct. But the motor 4 output higher can be anything in that line. Prop, ESC, arm distortion…
The problem with the low C batteries is that the value they place on the package is overinflated…so a reported 10C can be a 5C at best, and with age and over discharge things get worse. So the report of false failsafes is that they are not false, but true, but people tend to justify the purchase of those batteries without accepting the limitations…
An easy test to see the behavior of a battery is to get 2 or 3 H4 light bulbs (car headlights) in series with an ammeter and voltmeter connected and just watch what happens to the tension and current. You’ll be surprised…Be careful the bulbs get real hot.
It can be the propeller too, it’s a little dented because of the consecutive crashes
You said that I was on the limit because of the 10C, but since i’m using 2 packs (4S 5200mAh 10C each) , the maximum discharge rate would be 104Amps right ? And I’m nowhere near that.This batteries don’t have an year of operation, and dont have more than 50 charge/discharge cicles, so probably it could be related to the temperature inside the quadcopter case (yesterday I measured 72ºC for pixhawk / raspi, which seems HIGGGHHH ), but can’t do nothing since it’s a closed frame in order to be waterproof.
I’ll make that test. One thing i’m sure is that 4 packs are dead, and those were the ones were I had the crashes.
Currently I dont have any smart device.
I didnt add the C’s, i just added the capacity 5.2Ah + 5.2Ah = 10.4Ah * 10C = 104Amps max discharge, is it wrong ?
Yeah indeed it is, but i’m not seeing any good solution since it’s a closed frame
Batteries are not equal and the one with the highest voltage will “charge” the lowest and your results are as good as the worst battery on the set. Also 10C is an optimistic estimate. Add to that the doubling of the battery weight and consequential increase in motor load. Try to use one battery only and check the results. Also find on the web the methods to measure batteries internal resistance and monitor that for each cell of the batteries.
This might help
Thanks for the tip, as I am running my hexa powered from two 10Ah turnigy batteries, the concern you raised has been hunting me for a while. I’m carefully inspecting the batteries every 5 flights to make sure that they match, however I know that it isn’t enough.
I’ll order the board you sent. Regarding running two batteries I’ve measured the performance of one, two and tree 10ah packs. With two packs I can get 32 min of hovering, with one , 19. With three 45min. So, by now, I’m sticking with two. I had have problems to import ( brazil ) an 20ah pack , so I’m waiting for my next travel to eur or usa to try to bring one or two in my luggage.
Thanks… I’ve read that you need to get previous approval for that. Will try do to this in Portugal since I have dual citizenship. Otherwise I don’t see any other way somehow.
The “independent” transmitter is small and survey all the time all the cells:
It connects to the balanced port of your Motors battery.
This telemetry is programmable with two audible alarms set to two different voltages. Much much better than a total voltage alarm which is often meaningless and won’t save you, in most of te cases.
I cant fly this way
