Well, I finally got my quadcopter w/ APM 2.0 built and flying, and crashing. I was so happy to be flying that the I think I ran below voltage threshold on ESC, and lost power. I still need to confirm in logs. In any case I need a new frame. Here's some photos (before crash) and video (crash at end). Any advice would be appreciated, I made a lot of educated guesses on components.
Specs:
Frame: HobbyKing quadcopter frame V1 (3 arms broke on crash)
Motors: NTM 28-30A 750kv
ESC: Turnigy Plush 25A
Props: Slow Fly 12x45
Controller: APM 2.0 with Arducopter 2.8.1
Radio: Turnigy 9x, flashed with er9x
Battery: 2200mAh 3S 25C
Power distribution: 3DR power distribution board
Video: GoPro Hero
Comments
hey everyone, I got away from the drone world for the holiday. The advice on the battery C rating makes sense now that I've done a little research . I'm going to order some more batteries with a higher rating. Telemetry is something I'm also going to look into. When I get home next week I should have Turnigy Talon v2 frame waiting for me, and I came begin next build. I'm excited to get flying again.
Thanks again for all the help.
Brett
David, thats a good point. As many warnings about the battery the better probably. I have the FrSky module in my Turnigy 9x, so I have telemetry reporting my battery voltage, but that still screwed me. I need something else that also screams at me! Haha
I noticed the battery but I also wanted to point out his prop size and that he's hauling a GoPro. If I'm not mistaken that GoPro weight is going to drive your motors harder which is going to bring you to that MAX faster. So if all motors were running at their max you would be using 60A, and that's just the motors. This is on a 55A max battery.
Just something I would take into consideration is all, not necessarily the problem.
Right on Lars, his battery does seem a little weak I know I run a 4000 MAH 25-50 C 3s for that specific reason. Now of course I've never had his problem, mainly because I'm fairly new at the entire thing myself and getting above 20 or 30 feet really hasn't been my priority yet. As for my set up I have 21 amp Max motors, 30 amp ESC's and the 4000 MAH 25-50 C so like you it pretty much covers the motors at max which hopefully I'll never have to constantly push.
As for the setting of the ESC, again absolutely set it to NIMH, use a two dollar LiPo alarm plugged into the balance plug. Because at this stage in the game I would much rather fry a $25 battery then bust up the entire quadrotor. Of course I'm not really into that stage yet, after about 5 or 7 min. I'm ready to land and take in what I've learned LOL
Also ....
To answer your question about the battery, why NiMh doesn't have a low voltage cut off and LiPo does: This is because you can discharge a NiMh battery to empty (preferred if I'm not mistaken) and recharge without issue, but a LiPo batter: once you go lower than 3V a cell it will ruin the battery, which is why the cut-off.
Hey Brett,
One thing that I noticed that stood out to me was the rating on your battery. 25C seems a bit low for 20A max motors. That works out to 55A max output from your battery ...
I am a newb though, so take this with a grain of salt. I would run a higher rated battery myself, since that doesn't give you much room for AMP draw.
BTW, I had almost the same issue over the weekend. I was spending too much time enjoying the flight time and not my battery and I took it too low. Mine didn't drop out of the sky though, more of a drift to the ground thankfully. Which logs to you look at to see what happened? Is this function logged by default or do you have to have the battery monitor enabled? I assume the latter ...
Anyways, looking forward to your response and findings.
God speed,
Lars
Guys thanks for the tip on the ESC setting, I'll try setting it to NiMh. I see in the ESC instructions that you can disable cut-off threshold in for NiMh, but not LiPo. I wonder why that is? I guess I can assume everything else will work fine with the NiMh setting?
This was the quote I was referring to. Since I made the change, not 1 incident!
“For multicopters we typically all use lipos. The ESCs must be set for NiMh and no or soft cut-off because this makes the ESC low voltage cutoff lower so one or more of them does not decide to shut down in-flight which is always predictably bad ju-ju for multicopters. A throttle surge can be enough to momentarily put an ESC in shutdown mode if the ESC lipo setting is selected.”
Looks like you were descending fast into your own vortex, then you got hit by the cutoff. In the old days it would spin out of control, but now the opposite motor cuts quickly to ensure it lands on it's feet. Even so it doesn't take long to accelerate down. This happens to me occasionally as well after 2+ years of flying.
never heard of setting it to ni-xx.. I believe I can turn off the soft cut-off on mine.
Also,....switch setting on esc from "lipo" to "ni-xx", like above comment, I would rather lose a battery to low voltage than the aircraft. If (even 1 esc) at "lipo" setting, and esc detects low voltage, then it could fall out of the sky. Just determine flight time doing the math based on a bottom threshold of 3.2V per cell.
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