I was flying my Phantom 3 Pro and coming in for a manual landing on P mode. I was aware the battery was low ish at 45% so i came in for a landing. I was 1 meter from the ground and almost landed when i heard an alarm. The phantom suddenly accelerated and wouldn't allow me to counter it. I could see it heading for the trees and couldn't stop it. It hit the tree came thundering down and accelerated again. Luckily i cought it but the only way i could stop it from flying away was to remove the battery. Looking at the log it was all fine and the low batery alarm came on at 42% even though its programmed to alarm at 30% which is the default.
Can anyone advise on what happened? I feel like this should be repaired under warrenty.

Hi Craig

Did you start with a freshly fully charged battery?

A while ago I wrote a post that attempted to explain this exact behaviour when a discrepancy may exist, whereby the voltage of a pack may drop dangerously low, whilst the Percentage indicator still shows sufficient capacity.

Battery:
http://forum.dji.com/thread-41951-1-1.html


RTH Behaviour and regaining control:
http://forum.dji.com/forum.php?mod=viewthread&tid=40587


Also upload your flight log to healthy drones and post a link here. It will greatly help to understand exactly what happened.

Yes I started with a fully charged battery. How do I upload my flight log?

craig.flash-pho Posted at 2016-3-23 06:03
Yes I started with a fully charged battery. How do I upload my flight log?

Healthy Drones website has instructions for both iOS and Android. Follow that.

https://healthydrones.com/main?a=upload

Thanks for all the info, here is the link http://healthydrones.com/main?share=MzA0OA

Take off battery shows 46%.
Not good.

Yes, i flew for a while, landed then took off again.  I then came in for the final landing at 44 % battery.

The Lancaster B Posted at 2016-3-23 22:11
Yes, i flew for a while, landed then took off again.  I then came in for the final landing at 44 % b ...

Maybe show your log from before too?

Notice cell 4 drops way down, well below the others.  Several times, the battery is limiting you.  It really sounds like  the battery dropped to critical and triggered RTH (shows RTH in your record).  It then, apparently, flew into the trees trying to get to home point.  If that battery were mine, I'd do a calibration discharge on it and then recharge it fully to see if you can restore full use of it.  It's looking flaky to me as it is now.

The Lancaster B Posted at 2016-3-23 10:11
Yes, i flew for a while, landed then took off again.  I then came in for the final landing at 44 % b ...

That's a no-no. fly, land, recharge to 100% ＝ no problems!!!

Here is the flight before i landed http://healthydrones.com/main?share=lYmcOY

I'm a little confused about the battery info.....the first healthy drones post  (2nd part of flight) says you took off with 46% battery power......it also shows the battery was charged 3 times.

The second healthy drones report ( 1st part of flight) indicates you took of with 95% battery power but shows the battery was charged 2 times.  It seems like they are 2 different batteries?

I'm confused by the data.

No it's the same battery. To be honest I don't recal turning the motors off. Just landed and minutes later took off again. I only have 1 battery so it's the same one.

Tmygun Posted at 2016-3-28 14:03
I'm a little confused about the battery info.....the first healthy drones post  (2nd part of flight) ...

I think it records the number of complete charge/discharge cycles, so fully discharging the battery would count as the next complete cycle...maybe.

The Lancaster B Posted at 2016-4-3 21:54
No it's the same battery. To be honest I don't recal turning the motors off. Just landed and minutes ...

You almost certainly would have switched the motors off but not necessarily the battery, which would start a new flight record.  If you don't switch off the motors it still thinks it's in the air & will try to maintain altitude & attitude, which often causes the aircraft to either take off or tip over.

Fw 1.5 ?   Battery shut off and bird falling from the sky was a fw 1.5 problem and battery fw problem

The Lancaster B Posted at 2016-3-23 12:44
Thanks for all the info, here is the link http://healthydrones.com/main?share=MzA0OA

It looks like the aircraft has no idea where it is or what it's doing.  The altitudes are negative down to nearly 85 meters below the home point, yet the aerial view doesn't look like that's even remotely possible.  There are loads of warnings saying the satellite positioning is off but that shouldn't affect the altitude reading.  It looks to me to be more than just a battery issue.

nigelw Posted at 2016-4-4 07:48
It looks like the aircraft has no idea where it is or what it's doing.  The altitudes are negative ...

All of that confusing data is crash related - it's crashed and not in flight.
Disregard GPS and altitude from there on.

labroides@yahoo Posted at 2016-4-3 23:40
All of that confusing data is crash related - it's crashed and not in flight.
Disregard GPS and al ...

Ah yes, I was distracted by the talk about battery charge which appears to be a red herring.

Ye your probably right. Motors dos probably get switched off. Anyhow I've sent it away to DJI and hopefully they are sympathetic or have decent warranty.

I had a look at weather in Hamburg region on March 22, 2016:
https://www.wunderground.com/his ... c=3&reqdb.wmo=10147

It was 7 degree Celsius in the morning, and wind about 19 km/h, at times a light rain. I would recommend on cool days to initialize motors and let motors to run idle for about a minute to warm up. And then to start flying at first slowly, - to let mechanics and electronics to warm up.

I had a problem with my trainer, a small quadcopter Blade QX 200, recently.  On a cold morning I started to pilot it a bit too aggressively right from the beginning and after two minutes in the air it started to drop from the sky without any apparent reason. I barely could avoid falling into a river. One leg of a landing gear was broken during the hard landing, nearly a crash. Fortunately, it was repairable.

Later, the same morning I could fly with the same battery still 4 minutes. So the battery was well charged, but probably I drew too much energy too fast from it.

So now I let the aircraft, including my P3A, to warm up a bit, first on the ground and then in the air, before starting to fly fast, and insert into a flight some calm moments to let the chemical reaction in the battery to replenish the energy.

I didn't think it was all that cold to be honest. I was about 40 miles from Hamburg and it was bright and sunny. Good tip for cold weather though. I've learnt a lot from all these posts and the good news is my drone returns tomorrow, repaired free of charge