I'm a pretty new drone user, had the  Spark for 1.5 month now, used a single battery for a few weeks since I  couldn't afford the Fly More Combo. Later bought 2 extra batteries.
Had my share of adventures with aftermarket propellers, some rougher on  the surface, some smoother, but I'm almost 100% sure the ones I have  now, black with golden line at the tip, are very good and balanced.
Unfortunately I crashed them at the first flight today, from 1m above only but it let a few minor scratches on the surface
I'm almost sure it was the batteries fault, I used the very first  batterie at that try, after that tried battery #2 and #3 and they very  stable again.
Gave me a little heart attack, but like I said, I'm content now cause I'm almost sure it's the first batteries fault.

I think it's easiest to recognize that it fails to maintain the altitude  if you quickly push it up all the way in sport mode, the battery can't  handle all the drain.
Switching it back to "normal" mode or going slowly with the stick  sometimes makes it stable, sometimes not... I think there's also the  charger you use. Using the original USB one that came with the drone  takes longer but makes the battery "charge better" if you know what I  mean.
Also have an aftermarket one that can charge 3 batteries at a time much  quicker, but I think it's not making a good job with my very first  battery that had too many cycles already...

Try doing a Test with the Battery in question when it is fully charged...  Do a Hover flight only and see if it's the same flight time as the others..   Then try in sport mode (being careeful), see how long you can fly.    In the App you can check Battery Voltages and Temperature while it's flying.   If the Battery is much different to the other two I would throw it out.   Better to buy a new battery than lose or crash your drone.

Hi Shoonay,

Can you please upload that flight's log so we can see what really happend?
https://www.phantomhelp.com/logviewer/Upload/

Cheers,
Wolferl
PS: I like your avatar :-)

Hi, thanks for reaching DJI Forum. We do apologize for the troubles you had with your DJI Spark. Kindly fill out the form below for us to investigate what happened on that flight. We want to help you with this by sending your aircraft to our repair center and check your flight logs. We're here to help you. Thank you.

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Thank you everyone for you responses and suggestion.
It's funny, but all seems to be ok now. I mean I only had the time to test it 2 times with the suspected battery #1, but recharging it on the DJI USB charger and recharging it with the Sunnylife one proved exactly nothing, both flights with no hiccups in normal gentle mode and super-speed flying in Sport mode.

Which is good news but also means it can happen again and I still don't know why.

I tried to look for the "bad" flight log from the 15th on my smartphone, but the recordings show nothing abnormal, when the left stick shows me pushing up it goes up, and goes down when I push down... while in reality it looked like when I pushed the left stick to the max it went full power on, skipped a beat, went full power and so on, thus making the drone actually go down instead of up, like 20cm down, slightly up and again 20cm which eventually lead to a crash.

I did get 2 extra batteries, got a total of 5 now, including the suspected #1 which seems to be the problem but I'm not exactly sure now.

Will keep posting in this thread when this happens again, maybe I'll try to record it with an external camera to show the strange behaviour.

Shoonay Posted at 2018-8-18 03:12
Thank you everyone for you responses and suggestion.
It's funny, but all seems to be ok now. I mean I only had the time to test it 2 times with the suspected battery #1, but recharging it on the DJI USB charger and recharging it with the Sunnylife one proved exactly nothing, both flights with no hiccups in normal gentle mode and super-speed flying in Sport mode.

Maybe the battery wasn't charged properly in the first place.   Good to see it's now working

Greg F Posted at 2018-8-18 03:30
Maybe the battery wasn't charged properly in the first place.   Good to see it's now working

Well, that would go well with my "aftermarket charger being not good" theory, cause I'm always paying attention to the lights on the back of the battery and percentage in the app. As soon as my smartphone connects to it that is, cause sometimes it takes a while so it's usually something between 93-98%.

So many variables to pay attention too... hobbies are fun ;)

Shoonay Posted at 2018-8-18 03:38
Well, that would go well with my "aftermarket charger being not good" theory, cause I'm always paying attention to the lights on the back of the battery and percentage in the app. As soon as my smartphone connects to it that is, cause sometimes it takes a while so it's usually something between 93-98%.

So many variables to pay attention too... hobbies are fun ;)

Better buy DJI charger...  aftermarket are cheaper but sometimes not reliable.

Shoonay Posted at 2018-8-18 03:12
Thank you everyone for you responses and suggestion.
It's funny, but all seems to be ok now. I mean I only had the time to test it 2 times with the suspected battery #1, but recharging it on the DJI USB charger and recharging it with the Sunnylife one proved exactly nothing, both flights with no hiccups in normal gentle mode and super-speed flying in Sport mode.

Hi, we're happy that it's all working now. If there's anything that we could help, don't hesitate to reach us. Have a safe flight always.