Mavic Crash Battery Overcharge

grizzard · Jan 28, 2017

jackgarner said:
Didn't mention this but I'd advise at least one full battery to hover with! It took a few minutes to happen last time so give it a chance to happen again.. It wouldn't be fun if it fell out of the sky later :/

I will and I'll be sure to use the same battery! I still am wondering if DJi has ever mentioned anything about "prop icing" as a potential concern? If it is a concern with real planes then small RC drones and airplanes would have similar consequences. The weatherman listed the current weather for the last couple of days with the word "MIST" and "FOG" and I flew the preceding day without troubles. This day though ... it was heaver. When I recovered the crashed drone the props did have ice on the leading edges which would disrupt the lift and gave thought that the engines/motors were racing in order to maintain stability and consequently overheat the battery. To the best of my memory most or all of the ice was on the front props and extended the full length (except the front left that had broken off about an inch) and I could break off with my fingers, probably about 1/8". Looking at the video again it appeared to bounce hard once, recover, land and spin. Maybe in the spin the prop was broken at that time? I'll provide a link for more analytical eyes as soon as I get it uploaded to Google Drive.

grizzard · Jan 28, 2017

ATXdrone said:
On the DJI Go App itself, before you enter the bird, you can choose Flight Record (on IOS it's that 3-bar thing in the upper right).
View attachment 5158 View attachment 5157
Find the flight from the flight list at the bottom. Tap it.
View attachment 5160
On the bottom you'll see an icon that looks like a controller. Tap it.
View attachment 5161

That worked great, thanks. It did confirm that I did not yaw hard with the stick after landing ... that was done by the Mavic itself. Possibly because it had just broken about an inch off the left front prop on impact disabling any yaw control. I did hit hard enough to knock off the rear leg? extension and one of the front ones. Now that may have cushioned the impact.

Now I need to see if I can find an app for my Galaxy Tab S2 that will record the screen when I play back the screen with the stick input. Suggestions anyone?

jackgarner · Jan 28, 2017

This is the stick input that the drone received

jackgarner · Jan 28, 2017

Probably didn't make sense without context...

To me, it looks like the drone received yaw control at the same time it hit the ground - however, a few seconds later when it was trying to land on its own no input was given and it did spin... Not sure if this answers any questions

grizzard · Jan 28, 2017

I appreciate the response ... thank you. It appeared to accelerate the last few feet before hitting the ground and then recover before landing, at which time it started to spin. Here is the actual video it was recording.

grizzard · Jan 28, 2017

m0j0 said:
Temp?

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About 24º

grizzard · Jan 28, 2017

Here is the GPS Flight path showing Home Point Recording, Battery Error, RTH (which never happened and in immediate rapid descent began and continued right into the ground). It bounced up, I pulled the stick down for landing. Two landing extensions flew off and one broken prop. Has to be icing it seems to me.

f3honda4me · Jan 28, 2017

This looks like it was caused by icing on the props. Pretty cut and dry case I think given all that we know now.

grizzard · Jan 28, 2017

I agree.

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ksull72487 · Jan 28, 2017

Run your batts dry first time or below 10%. They don't need to for maintenance but for accurate battery gauge etc they should. Similar to a phone. You may charge your phone all day everyday then one day it shuts off at 8%. You need to run them dry so the drone can learn the curve of the battery. Volts can drop before watts etc. Just good practice to do ever once in a great while.

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grizzard · Jan 28, 2017

Good point .... I had forgotten the importance of doing that. It is now on my To-Do list ....

f3honda4me · Jan 29, 2017

ksull72487 said:
Run your batts dry first time or below 10%. They don't need to for maintenance but for accurate battery gauge etc they should. Similar to a phone. You may charge your phone all day everyday then one day it shuts off at 8%. You need to run them dry so the drone can learn the curve of the battery. Volts can drop before watts etc. Just good practice to do ever once in a great while.

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I'm not sure I follow... Battery % is determined by the voltage. You're not teaching the drone anything.

jackgarner · Jan 29, 2017

f3honda4me said:
I'm not sure I follow... Battery % is determined by the voltage. You're not teaching the drone anything.

It's not exactly that simple...
(screenshot from - How does a smart phone measure the battery power?)

m0j0 · Jan 29, 2017

ksull72487 said:
Run your batts dry first time or below 10%. They don't need to for maintenance but for accurate battery gauge etc they should. Similar to a phone. You may charge your phone all day everyday then one day it shuts off at 8%. You need to run them dry so the drone can learn the curve of the battery. Volts can drop before watts etc. Just good practice to do ever once in a great while.

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I would refer to the manual on the batteries. Be very careful. If you run them dry they could actually be damaged.

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ksull72487 · Jan 30, 2017

f3honda4me said:
I'm not sure I follow... Battery % is determined by the voltage. You're not teaching the drone anything.

Not exactly true. Works the same way in a cell phone. Battery percentage can be determined by a number of things. In the case of a phone or battery like the Mavic. It can be determined by voltage, watts, amps etc. the low quality cheap stuff will just go off voltage to get an accurate reading. The battery should go below 10% every once in awhile. Those batteries have chips in them to learn. Lithium Ion is better you don't have the memory issues you would have with nimh but over time they loose their accuracy in interpreting the percentage not by much but if your on the gas light you'll want to be sure it's accurate. I work in electrical it's all about how it's built and what's put in to interpret. The Mavic and phones have a lot of things attached to that battery to interpret the data. Have you ever used an iPhone for months on end and seen a battery go from 5% to shut off. Then charge it back up and it works fine. Well yeah that's because during its drain it didn't take in account the extra power draw it may have received or lost track of zero.

Short story is % doesn't factor only voltage in 1999 it did, hardly anything today. They use a number of things.

You won't use your Mavic enough to experience it, odds are but as good practice. I'd bring them low once every year or so.

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ksull72487 · Jan 30, 2017

m0j0 said:
I would refer to the manual on the batteries. Be very careful. If you run them dry they could actually be damaged.

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10% isn't dry. And I Guarantee zero isn't dry either but I wouldn't push it. There's always a fail safe. The battery will read zero before it's depleted. If you run it to 30% and never go less than 30% I'll gurantee if you use your Mavic for a long time it will develop an issue sooner than if you let it get low say around 10% every so often as far as a battery is concerned. Has nothing to do with the Mavic and everything to do with the chip in that battery and Lithium Ion Polymer technology.

In the case of my earlier post low voltage cut off is 0 lol not depleted.

The point is these Mavics like phones have chips built into their batteries to give you the best possible reading. The chips assume all sorts of variables, watts, amps, mah, etc. In today's world they have to to be accurate. In 1999 or on a Nokia cell phone it was mainly voltage. Your Mavic can tell you the serial number of a battery and display it's 3 cells in which it attempts to drain equally. I'm some what of a guru in this field so you can take me seriously. To get the best possible life and insure it's charged equally and that the Mavic is predicting the percentage the accurately over time, not all the time around 6 months or so depending on usage it's good practice to hover it or leave it on the floor discharging to around 10%. This way it can see how the battery reads on the lower end of the curve. The Mavic isn't learning anything. The battery in a round about way does. Lithium Ion Polymer (Polymer cuz it's cheaper). Doesn't have as many issues. But on occasion it can hiccup as the battery ages and is used. Just like on a cell phone. Have you ever seen your iPhone go from 5% to 0. Yes. It's because it didn't anticipate the extra draw from an App you may have opened. The next time you charge it do the same thing again and notice it doesn't jump. Since the phone has somewhat figured it out. It predicts 0 slightly earlier now.

They are sUAVs. The manufacturer isn't go to tell you to fly to 10%. But in the case of the battery and its technology it's good practice to discharge them on the floor to around there every so often.

Never deplete your battery. This is true too. For the life of me I still can't figure out why they still put that in the manuals. Even on a phone. You can't deplete it you'd have to run it to zero and not charge it for a year. There will be a low voltage cut off before you run that battery anywhere near dry or what we call flat.

And as long as we are on the subject. The cold will affect the battery and its capacity. Keep that in mind as well. Charging a battery generates heat once that battery cools down again it maybe at 99% lol since heat tends to raise it and that's without any usage just heat from a charge. This is typical and exactly why devices go from 100% - 99% fairly quick. So be extra careful in the cold.

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f3honda4me · Jan 30, 2017

jackgarner said:
It's not exactly that simple...
(screenshot from - How does a smart phone measure the battery power?)
View attachment 5333

But does this same function take place in RC vehicles? I've never heard of this being in RC before. As far as I know with LIPO and RC, it's a simple table that equates a certain voltage being read directly from the battery into a % of fuel remaining.

ksull72487 said:
10% isn't dry. And I Guarantee zero isn't dry either but I wouldn't push it. There's always a fail safe. The battery will read zero before it's depleted. If you run it to 30% and never go less than 30% I'll gurantee if you use your Mavic for a long time it will develop an issue sooner than if you let it get low say around 10% every so often as far as a battery is concerned. Has nothing to do with the Mavic and everything to do with the chip in that battery and Lithium Ion Polymer technology.

In the case of my earlier post low voltage cut off is 0 lol not depleted.

The point is these Mavics like phones have chips built into their batteries to give you the best possible reading. The chips assume all sorts of variables, watts, amps, mah, etc. In today's world they have to to be accurate. In 1999 or on a Nokia cell phone it was mainly voltage. Your Mavic can tell you the serial number of a battery and display it's 3 cells in which it attempts to drain equally. I'm some what of a guru in this field so you can take me seriously. To get the best possible life and insure it's charged equally and that the Mavic is predicting the percentage the accurately over time, not all the time around 6 months or so depending on usage it's good practice to hover it or leave it on the floor discharging to around 10%. This way it can see how the battery reads on the lower end of the curve. The Mavic isn't learning anything. The battery in a round about way does. Lithium Ion Polymer (Polymer cuz it's cheaper). Doesn't have as many issues. But on occasion it can hiccup as the battery ages and is used. Just like on a cell phone. Have you ever seen your iPhone go from 5% to 0. Yes. It's because it didn't anticipate the extra draw from an App you may have opened. The next time you charge it do the same thing again and notice it doesn't jump. Since the phone has somewhat figured it out. It predicts 0 slightly earlier now.

I've never had an issue with my RC batteries "cutting off early" because I never ran them below 30%. That includes my various drones I've had. I've also seen the inside of these LIPOS and there isn't a chip in there like the one you are referring to that I've ever seen. Have you personally seen this technology in our RC LIPOs? Or is there something from DJI showing this is the case?

Are you claiming that if I never take my battery below 30% that someday it will go from 30% to 0% and cause a forced landing?

ksull72487 · Jan 30, 2017

f3honda4me said:
But does this same function take place in RC vehicles? I've never heard of this being in RC before. As far as I know with LIPO and RC, it's a simple table that equates a certain voltage being read directly from the battery into a % of fuel remaining.

I've never had an issue with my RC batteries "cutting off early" because I never ran them below 30%. That includes my various drones I've had. I've also seen the inside of these LIPOS and there isn't a chip in there like the one you are referring to that I've ever seen. Have you personally seen this technology in our RC LIPOs? Or is there something from DJI showing this is the case?

Are you claiming that if I never take my battery below 30% that someday it will go from 30% to 0% and cause a forced landing?

No possibly 5-0. Point is you don't understand the technology behind a battery. And have a far understanding of drones than I probably do. There should be a chip. If it's not in the battery than DJI has placed it onboard the aircraft. I'm an engineer. If you never drain below 30% odds are you'll never get the hiccup. The percentage is only questionable when the voltage, amps, mah etc become questionable based on the ratings of the equipment in the aircraft. Aka the lower end of the bat.

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maikm · Jan 30, 2017

I'm not a battery engineer, but a friend of mine is, physics Ph.D., former lead engineer at Sanyo, and author of a book about batteries, and he keeps telling me the same stuff @ksull72487 is explaining here, so there you go.

f3honda4me · Jan 30, 2017

I just asked this question of one of the DJI reps who has direct access to the engineers. They said there is no need to drain the batteries to 10%. It will not "teach" anything about the lower end of the curve so to speak. Never taking them below 20-30% will not have any adverse effect nor create any kind of "false" bottom to the capacity. While these kinds of chips may be in smartphones, etc, they are not in the DJI batteries.

So I guess agree to disagree. I'll go by what DJI says since they know what tech is in their batteries.