I have a Pixhawk installed in my 3DR X8 running 3.1.
Was testing my FPV setup, so perhaps not as aware as I should be of the time, and battery level.
I use two 4200 3S (the brand provided by 3DR) in parallel. They have been good batteries, and I usually get about 14 minutes with the two.
I have everything set up as I should for Battery failsafe. I had to change it at one time, I had the current trip set to how much I wanted to use, not the amount that should be left. And that was finally working.
Today, right near the end, I did a RTL to bring it back. It got down to about 1 meter, and then dropped out of the sky. No damage, at least to the X8, but I’m very worried about my batteries, They ran very low.
Looking at the logs, I see a LAND command, right where it should have been. (10.2 V) But I didn’t notice any landing. It seemed to be fine. Looking at the graph, it does appear that the “throttle out” droped a little, but not much, and I didn’t notice an attempt to land.
So maybe I didn’t notice, but it shouldn’t have let me do an RTL. I was lucky that I was only a meter up.
At best, shouldn’t it ONLY permit a change to stab?
Looks like the battery voltage dropped off a cliff at the same time as the copter came down. I think it’s just that the battery was on it’s last legs and these Lipos lose their voltage very rapidly right at the end. I don’t think it’s a firmware issue.
The copter was actually in AltHold in the final stages although as you say it did switch to LAND before that, as part of the battery failsafe.
[quote=“rmackay9”]Looks like the battery voltage dropped off a cliff at the same time as the copter came down. I think it’s just that the battery was on it’s last legs and these Lipos lose their voltage very rapidly right at the end. I don’t think it’s a firmware issue.
The copter was actually in AltHold in the final stages although as you say it did switch to LAND before that, as part of the battery failsafe.[/quote]
Well I guess, it sort of should let the pilot do what he deems necessary, even though it’s in failsafe. I can see that if it is landing on people or in a lake, the pilot should be able to try to rescue it. Therefore, in this case, it let me do the RTL.
But:
if I have land instead of RTL set as an option, perhaps it should reconsider letting me do RTL. If I were to elect RTL as an option, I would probably trigger it to FS at a slight higher voltage.
there’s always the option of right stick during a land command, as a means of avoiding trouble.
the LAND action was not noticeable. As you see, the altitude was flat the whole time and no adjustment of throttle on my part. Is there an adjustment to make the “Land” a little more obvious? A higher descent rate… (SOME descent rate)?
My batteries seemed to charge fine, they’re new… we’ll have to see how they last during following flights.
It seems to me like something went wrong with your batteries. They went from 10.2 to 7 volts much to fast. This is more than the typical Lipo dropoff. I’m guessing you have a bad cell and it dumped early. That’s what it looks like. When a bad cell dumps, the voltage comes down FAST, as it can drop to 0V very quickly.
As for the FS action… it did switch to land, and then started descending, but then almost immediately you switched to Alt_Hold and took it back up again?