Crash log, can someone tell me what happened?

[Farmer Rob]

Hi All,
Attached is the flight log from tonights flight. Son swears the drone had 8 minutes of flight time then it said low battery and crashed within 10 seconds.
Any help would be appreciated.

I hope this is the right file as it wont let me send the csv.

Rob

 

[msinger]

The log shows he flew for about 6 minutes, the battery reached the critically low level, and the drone auto landed at its current location. Tell your son to start with a fully charged battery and to return to the home point before the battery level reaches 30%.

 

[Meta4]

Hi All,
Attached is the flight log from tonights flight. Son swears the drone had 8 minutes of flight time then it said low battery and crashed within 10 seconds.
Any help would be appreciated.

Here's what your flight data looks like:
DJI Flight Log Viewer - PhantomHelp.com

With Lipo batteries, once you get down to 3.3 volts per cell, it's all over
Jump down to 13:38.7 and have a look at what the battery is telling you.
Sport mode is like driving at 180 km/h. It's not very economical.
Your battery isn't like fuel in your car.
The last 10% is not as strong as the first 10%.
When a battery is getting low, sport mode isn't a good idea.

 

[Farmer Rob]

Ok. The log says it was at 29% at 13.487 23% at 13.38 at 14.07 it dropped to 18% then at 14.17 it was 15%.

I dont think it has dropped this quick before, is the battery dying? He swears there was no warning before the auto landed turned on at 14.4 and it stopped at 14.132

 

[Meta4]

Ok. The log says it was at 29% at 13.487 23% at 13.38 at 14.07 it dropped to 18% then at 14.17 it was 15%.

I dont think it has dropped this quick before, is the battery dying? He swears there was no warning before the auto landed turned on at 14.4 and it stopped at 14.132

Because it was a second flight we can't see how the battery was at the start of flying.
A battery that has been sitting around or is only partly charged is not safe to fly with.
The % indicator is only accurate if you start with a fully charged battery.
What's important to the motors and battery is the voltage level rather than the % indicated.
The battery voltage tells the story pretty clearly.
Running in sport mode is sucking the remaining juice from a low battery very quickly.

 

[Kilrah]

The % indicator is EXTREMELY out of calibration, never seen anywhere near that bad on any DJI battery before. This battery must have been sitting unused and without a full cycle for ages.
At 3.3V it was still reporting 30% but it should have been about 0.
That's why you should be looking at the voltage figure as well as just the percentage.

This battery has been discharged so low it is likely best to consider it dead and discard it now.

 

[sar104]

It's not clear to me whether there is anything wrong with the battery or whether the smart battery system had simply lost track of capacity, which is rather a weak function of voltage for partially discharged cells:



The individual cell performance looks pretty good until it collapses at the end, which isn't particularly abnormal. I'd charge it fully and fly the aircraft in a low hover until it lands to see how it behaves.

 

[Kilrah]

whether the smart battery system had simply lost track of capacity

Yes that's what happened, but to an extreme level since the smart battery system is supposed to factor in lower than normal voltages and skew the % reading accordingly (causing the common sudden % reading drops) but that didn't happen there significantly until the very last moment.

He was also ripping it in sport mode at that moment which might have had an effect (voltage drop effects are taken less into account when draw is high for obvious reasons).

I was recommending ditching the battery since the cells have now been brought down to close to 1.5V under load, and they won't have liked that.

 

[sar104]

Yes that's what happened, but to an extreme level since the smart battery system is supposed to factor in lower than normal voltages and skew the % reading accordingly (causing the common sudden % reading drops) but that didn't happen there significantly until the very last moment.

He was also ripping it in sport mode at that moment which might have had an effect (voltage drop effects are taken less into account when draw is high for obvious reasons).

I was recommending ditching the battery since the cells have now been brought down to close to 1.5V under load, and they won't have liked that.

Yes - but notice that the initial voltage was pretty flat under load. I think the battery will likely be just fine once charged. It's simple to test, anyway.

 

[Rick W]

The Flight Record indicates Light Rain. Also noticed that there was a significant spike in temperature as the voltage dropped. Was wondering what the Flight Record would show if the battery got wet?

 

[Farmer Rob]

The Flight Record indicates Light Rain. Also noticed that there was a significant spike in temperature as the voltage dropped. Was wondering what the Flight Record would show if the battery got wet?

Wasnt raining at the time of flight, but the quad wasnt flown for about 3 weeks and not charged before the flight but it was all 4 lights on the first flight which pretty much copied by the second flight, but shorter, and the quad wasnt turned off between flights, just pilots changed this is why its wasnt expected. but ill take on board what you guys said about keeping it above 30% in future and maybe invest in a new battery anyway, worse case i need it best case i have 2.

But thanks for all you input, i learn something new everyday. and once i get a new front leg,4 new props, and a new gimbal and vibation plate ill be back in the air to test the battery.

 

[Meta4]

the quad wasnt flown for about 3 weeks and not charged before the flight but it was all 4 lights on the first flight

Flying with a battery that has been sitting for a few weeks, slowly discharging is a good way to have a battery failure just like this.
Only fly with a fully charged battery.

The Flight Record indicates Light Rain. Also noticed that there was a significant spike in temperature as the voltage dropped./QUOTE]
There's nowhere in the flight record that indicates rain and the Mavic has no sensor that could detect it.