Critical Low Power. Aircraft Landing.

[robee683]

Went for a fly a couple of days ago with battery at 53% and in ideal conditions with no wind and about 15C. Took off and spent a little time in hover while I checked and adjusted settings.

After 96secs climbed to 24m, selected Sport and flew for approximately 17secs in a straight line at constant height when I received Critical Low Power. RC showed battery at 43%. MP started to land.

Bit panicky at this stage but used Full Throttle up which stopped descent at 8m, which surprised me.

Then still in Sport I flew back to the take off site taking approximately 19secs and landed without further issues.

I have uploaded the flight log to phantomhelp.com. My file name is DJIFlightRecord_2017_06_16[14-04-26].txt and the LogViewer reference is B7Y3806P7IRT7PQGSFF7.

I note that the log shows battery voltage at start of flight at 11.354, 9.842 at the warning and 10.867 upon return landing.

It would appear that the battery was under stress but the short amount of time it took to descend was sufficient to allow it to recover.

I have read on the forum that extended use ie multiple minutes of Sport Mode especially whilst flying both forward and up can place severe drain on the battery however I was flying level and only for a very short period.

Any advice would be appreciated.

 

[Pathogen]

To me it does seem the battery might have issues, I have read that DJI recommends to drain a battery down to its internal cutoff voltage (although they don't say how), and then fully recharge it, periodically (I don't recall when), to rejuvenate it. Also, I've read that a new battery needs several charge/drain cycles to become fully functional.

Or maybe the issue was some sort of overheat?

 

[Kilrah]

Check the individual cell voltages.

 

[4wd]

This sort of behaviour was quite common on Phantoms especially before P3 when they seemed to improve battery monitoring and management.
I'd not try anything too ambitious with that battery unless it behaves normally on several cycles.

It is generally inadvisable to take off with a part disharged battery especially if it's not been used for a while (e.g day or more)

 

[Explorer]

Went for a fly a couple of days ago with battery at 53% and in ideal conditions with no wind and about 15C. Took off and spent a little time in hover while I checked and adjusted settings.

After 96secs climbed to 24m, selected Sport and flew for approximately 17secs in a straight line at constant height when I received Critical Low Power. RC showed battery at 43%. MP started to land.

Bit panicky at this stage but used Full Throttle up which stopped descent at 8m, which surprised me.

Then still in Sport I flew back to the take off site taking approximately 19secs and landed without further issues.

I have uploaded the flight log to phantomhelp.com. My file name is DJIFlightRecord_2017_06_16[14-04-26].txt and the LogViewer reference is B7Y3806P7IRT7PQGSFF7.

I note that the log shows battery voltage at start of flight at 11.354, 9.842 at the warning and 10.867 upon return landing.

It would appear that the battery was under stress but the short amount of time it took to descend was sufficient to allow it to recover.

I have read on the forum that extended use ie multiple minutes of Sport Mode especially whilst flying both forward and up can place severe drain on the battery however I was flying level and only for a very short period.

Any advice would be appreciated.

Im still new with my Mavic. I like this picture. Is this native to the DJI app?

 

[robee683]

Check the individual cell voltages.

 

[Kilrah]

I meant from the log, during the flight.

 

[robee683]

This sort of behaviour was quite common on Phantoms especially before P3 when they seemed to improve battery monitoring and management.
I'd not try anything too ambitious with that battery unless it behaves normally on several cycles.

It is generally inadvisable to take off with a part disharged battery especially if it's not been used for a while (e.g day or more)

I have since recharged this battery to 100% and discharged to 9% and flew without issue but did not stress by flying in Sport Mode.

 

[robee683]

I meant from the log, during the flight.

Checked them in the log and it showed cell three occasionally 0.1 of a volt lower than the other two cells as in the image.

 

[robee683]

Explorer

To gain access to your Flight Records touch and hold the small icon in the top left corner of the main screen of the DJI app. You do not have to be connected to the Mavic, just run the app.

 

[Lake_Flyer]

Always begin you fly day with a freshly fully loaded battery. Never with a battery that you used yesterday and still has some juice left. I thought that was common best practice.
Many Inspires have plunged from the sky because people loaded them with a partially depleted battery. I recon with the MP it's not different.

 

[msinger]

Here's your flight log:
DJI Phantom & Mavic Flight Log Viewer - PhantomHelp.com

 

[CyberNate]

Here's your flight log:
DJI Phantom & Mavic Flight Log Viewer - PhantomHelp.com

According to the flight log, you were flying into the wind in sport mode. This is apparent as you were seeing speeds around 36. You probably had around a 10 mph headwind. When you fly into the wind with sport mode the motors are pushed to maximum RPM which has considerable current draw on the battery. This causes some sag in the voltage due to the internal resistance of the battery. The resistance will be worse if the temperature outside is on the cool side or perhaps battery has not warmed up yet. As the battery warms up, it's performance will improve as internal resistance drops. Perhaps if you had started with a full battery, the battery would have warmed up during the flight and you wouldn't have seen the large voltage sag which triggered the low battery detection. Starting with a battery at ambient temperature and running it hard like that immediately causes a lot of sag in voltage.

In general, I would avoid using maximum thrust into the wind with sport mode, especially with a partially charged battery. It puts quite a strain on the battery. Sport mode with no wind or tail wind works fine, as the motors are not pushed as hard.

 

[Pathogen]

According to the flight log...

Just a thank-you from a random noob to say this explanation makes sense, and helps me understand the craft better, cheers!

 

[sparky1111]

According to the flight log, you were flying into the wind in sport mode. This is apparent as you were seeing speeds around 36. You probably had around a 10 mph headwind. When you fly into the wind with sport mode the motors are pushed to maximum RPM which has considerable current draw on the battery. This causes some sag in the voltage due to the internal resistance of the battery. The resistance will be worse if the temperature outside is on the cool side or perhaps battery has not warmed up yet. As the battery warms up, it's performance will improve as internal resistance drops. Perhaps if you had started with a full battery, the battery would have warmed up during the flight and you wouldn't have seen the large voltage sag which triggered the low battery detection. Starting with a battery at ambient temperature and running it hard like that immediately causes a lot of sag in voltage.

In general, I would avoid using maximum thrust into the wind with sport mode, especially with a partially charged battery. It puts quite a strain on the battery. Sport mode with no wind or tail wind works fine, as the motors are not pushed as hard.

Doesn't make sense. The higher the temperature the higher the resistance. Fact. Vice versa. I.e super conductors at absolute zero have zero resistance.

 

[Kilrah]

Of course it does, we're talking of battery chemistry here, which slows down in the cold leading to higher internal resistance - but that has nothing to do with an actual resistor.

 

[CyberNate]

Doesn't make sense. The higher the temperature the higher the resistance. Fact. Vice versa. I.e super conductors at absolute zero have zero resistance.

Doesn't with that way with lipos and lihv. Try flying with batteries that are cooled to freezing temperatures and immediately fly with sport mode full throttle. The mavic will go straight into critically low battery landing mode.

 

[HFMan]

Doesn't make sense. The higher the temperature the higher the resistance. Fact. Vice versa. I.e super conductors at absolute zero have zero resistance.

Read up on LiPos and temperature factors. Lots of facts about how they interact.

 

[Oingo Boingo]

Quick question ... Ever stored your batteries at 100% charged for more than 7 days or drained your batteries below 10% ?

 

[Cyberpower678]

Quick question ... Ever stored your batteries at 100% charged for more than 7 days or drained your batteries below 10% ?

I have. They were set to discharge after 10 days. I never got a chance to fly because the weather was persistently bad, so they just sat there fully charged. When I did get a chance, they were discharged to 50%. As for draining below 10%, yes. I occasionally cycle the battery to recalibrate them, so I discharge to 3%. Also once doing a flight, I committed an oopsie during flight, and misjudged the wind speed so the drone fought its way back and I was keeping it up in the air until 6%.