Second Level Protection stupid stop motor time

[Mihnea de Vries]

Yet another WKM stupid problem.

When WKM hits second level protection it lands, which is nice.
The problem is that does not stop motors after landing, even when Cut Off Type is in Intelligent mode, and they say it has landing judgment.

So, yesterday the WKM hit first level protection, when i made an orientation mistake while the copter was about 300 meters away, and instead flying in my direction it was actually flying away. I know, it was stupid. When i realized that I fly in the wrong direction i hit the fail-safe switch and copter entered in GH and start coming back to me. On the way back it entered in the second level protection and landed nicely about 200 meters away from me. I start running and when i was closer i noticed there is a 2 meters water ditch between me and the copter. So i start running to find a place to cross it. Total time 3 minutes to late and and the almost new 8000 mAh LIPO puffed. By the time I arrived near the copter, the motors were stopped, but when i was checked my recorded video i noticed the WKM stopped the motors by itself only about 2 minutes after landing and i heard the battery puffing about 1:30 minutes after landing.

Now, I don't understand why WKM does not stop motors immediately after landing in second level protection? What sense make to stop the motors after 2 minutes when landing on second level protection? How stupid is that?

 

[kloner]

you'd think it should, but i bet depending where you have the voltage cutoff set to that pack was already damaged when it landed. to seriously take care of flight packs, you gotta use a timer and you gotta make it early enough that you know damage can't happen. seriously, 1 second to long and the damage is immense, puffed or not. IR leaves single digits and hits double digits in single digit seconds past 80%. if you fly a pack and see more than 80% put back in, garunteed the pack is on it's way to failure sooner than later. you run a minute too long, not only is it gonna land early next flight, it's IR damage is into triple digits and is junk

when IR get's high, the pack doesn't have the same voltage output throughout. it'll make that voltage watch thing land you early cause of the voltage not being normal. I disabled that thing all together and strickly go by timer on the throttle via JR

 

[Dewster]

That's interesting. I've always wondered what happens when I hit the second level of protection if I'm too far out on return. As soon as I hit my first level of protection I'll start heading home without delay. Have you tried using Course Lock Mode? I tried it yesterday for the first time and it's so much easier when flying at great distance. You won't have to worry about losing orientation of the craft. The only thing you will have to worry about is the battery state.

 

[Mihnea de Vries]

@kloner. Negative, the battery was just fine when it landed. It was not the first time I landed in Second level protection. Second level protection is set at 15% of capacity and the Lipo never exceeded 35 degrees Celsius at this state. I use 8000 mAh 5S and i usually discharge them 6500-7000 mAh without heating the pack over 35 degrees Celsius. The battery had 23 Cycles and the last line loss calibration was 3 Cycles before. I also have countdown set on 7 minutes on my TX.

Also, LIPO's IR measured after repeated discharge up to 90% was 2,2,1,2,1 in my logs. Maybe older generation LIPOs needed the 80% rule but I found by testing a lot that i can go even to 90% without damaging pack's IR.

Anyway, the post was about DJI WKM stop motor time way to long (stupid 2 minutes) after landing in Second Level protection, not about abusing LIPOs intentionally.

 

[Mihnea de Vries]

@ Dewster, Yes i use Home Lock Mode, but it applies only if the pilot does not move from home location. In my case, I was shooting a car chase about 5 km and it was not possible to rely on Home Lock since i moved from home location. Also, in thie case, you have to be lucky to be in the right direction when you use fail-safe return to home.