Battery cell 3 failure caused my Mavic to power off in flight!

[marklyn]

I like that idea. It's driving me nuts thinking about my next flight and I don't know what to look for before/after the flight to know if I have a potential problem with this battery.
Maybe that is something DJI could cook into the firmware?

 

[Kilrah]

That wouldn't be done by the battery, but... yeah.
0.2V would probably be too strict a tolerance IMO though.

It's always a double edged sword, you don't want false alarms either and the thing doing forced landings in unsuitable areas when it wasn't needed. Especially given the rarity of cases like the OP's.

 

[RayOZ]

OP, sign up to AirData, and set litchi to auto upload your flight logs there. There’s a tab to view battery trends for deviations.
I have the habit of just checking my battery performance after each flight session.

 

[Cyberpower678]

That wouldn't be done by the battery, but... yeah.
0.2V would probably be too strict a tolerance IMO though.

It's always a double edged sword, you don't want false alarms either and the thing doing forced landings in unsuitable areas when it wasn't needed. Especially given the rarity of cases like the OP's.

There should NEVER EVER be a deviation that high as 0.2V. That seriously hurts the cells. If there is, the battery will likely die in a matter of minutes as the cells continue to deviate quicker and quicker and get hot. It can, and has, started LiPo fires. Just imagine a Mavic free falling while on fire and landing on someone’s roof.

 

[Kilrah]

You can get a 0.2V difference just becasue of pack imbalance, not becasue a cell is necessarily worse. In this case it doesn't heat up more nor is it such a big deal unless you get to the very bottom of the back capacity.

Then you could argue the opposite as in this case 0.2V would probably not be early enough to prevent the crash either...

 

[kidroc]

Thanks for the replies, I will try to keep an eye on my batteries before and during a flight.
Can I monitor them during a Litchi flight (since I don't use DJI Go that often)?

Yes you can just tap the batt icon up top right and it will drop down to show batt info..

 

[marklyn]

OP, sign up to AirData, and set litchi to auto upload your flight logs there. There’s a tab to view battery trends for deviations.
I have the habit of just checking my battery performance after each flight session.
View attachment 48310

I already have a subscription to Airdata but not the one that monitors battery usage. The jump from $2.99 to $6.99 per month is a bit rich for me.

 

[dewster]

I had that happen on a drone that I built. One bad cell caused a brown out and my craft drooped like a rock.

 

[RayOZ]

I already have a subscription to Airdata but not the one that monitors battery usage. The jump from $2.99 to $6.99 per month is a bit rich for me.

It does seem expensive, but on the bigger scheme of things, you should consider it the running cost of this hobby. $84 per year might have avoided you crashing a $1000 drone. I bought the 1 year subscription, as it was little cheaper. I think sometimes, they give a discount for upgrading. Wait for that.

 

[marklyn]

So would the higher subscription really have alerted me to a problem? If so, how?

 

[Goof]

So would the higher subscription really have alerted me to a problem? If so, how?

It keeps track of trends in cell variation over time and displays it for you (starting at gold tier I think). Whether or not this battery would've had indicators before this flight is speculation, but the many thousands of people running LiPo gear outside the DJI ecosystem would perhaps suggest yes...

 

[Keule]

If so, how?

As Goof already mentioned, Airdata keeps track of all the batteries you used.
You could track the batteries visually: (sample next)



next flight:



That means, keep an eye on that specific battery - cell #1.

In addition, you can create an alert which alerts the pilot if some (user defined) threshold is reached.

 

[marklyn]

That sounds very interesting. My hesitation in upgrading to the plan that includes this is my lack of knowledge in understanding what constitutes a problem battery. I've read that some variances do happen and are somewhat normal. I was hoping that there would be something more automated that would tell me that a particular battery should no longer be used. In looking at the chart above is it obvious that this battery shouldn't be used for flying? Thanks for the visual, it helps!

 

[Goof]

The key warning sign in the above battery is the wild variation (consistency in its inconsistency?). The other cells show occasional excursions away from the other cells, but they return to a sensible range in the next few measurements. Cell 1 however, is having a party it seems. Every second measurement is showing it at a lower voltage than the others.

Infrequent 0.15-ish volt variances are pretty normal, but if the same cell is pulling down like that, especially across multiple charges it's probably time to ground it. (not literally, lest you want fireworks ).

If a single cell drops any more than 0.2-025V in a flight I'd be doing some very careful flights over grass or carpet before thinking about using it seriously again. It is very possible that bigger drops like can be one offs, but there's really no such thing as over caution when you're talking about >1000 dollar "toy" aircraft here...

 

[Keule]

understanding what constitutes a problem battery.

Here is what i am doing:
If one or more cell(s) of a specific battery deviates at more than 0.07v over a period of more than 30 seconds while under normal load, i cycle that battery and watch again. If the deviation stays, the battery is no longer used for flying.

 

[Hayabusa]

This now has me concerned but would really like to better understand and learn to check/avoid.
For someone like me who is sitting here scratching my old bald head while I try to understand what you obviously way more experienced pilots etc.. are saying.
Can someone break this down into a language I can keep up with/understand? baby talk might be a good start for my old/no room available brain. Whats an easy way to check all my batteries and exactly what I’m checking?
Can I just fire up in my house or does it have to be in flight? What numbers am Inlooking at?
Sorry for all the questions. I’m just a paranoid type of pilot
Thank you
Mike

 

[marklyn]

Yeah, I'm now scratching my head too. I looked up the history on this battery up to several months ago. I found one other instance of 10 seconds of major deviation, all of the rest were listed as normal deviations and none more than either of my two other batteries. So from the Airdata subscription I have I sure wouldn't have caught this until this flight, which was too late. So unless the Airdata gold plan provides more insight into this I'm not sure if upgrading to a new sub would help in my situation.

 

[Goof]

I think the free accounts with Airdata will allow you to sync your flights and analyse the battery page on a flight by flight basis:
This page will show you if something is wrong, there are a couple of examples there to get a feel for what a bad battery condition looks like.

If you want to do a quick check as a new user, it'd be best to charge all batteries, perform a normal flight with each one and then upload each flight to Airdata and have a look at the battery cells page for each flight.

Note that I don't work for Airdata, just a customer of theirs and think their service is great. Saves a ton of time manually poring over data logs myself...

Yeah, I'm now scratching my head too. I looked up the history on this battery up to several months ago. I found one other instance of 10 seconds of major deviation, all of the rest were listed as normal deviations and none more than either of my two other batteries. So from the Airdata subscription I have I sure wouldn't have caught this until this flight, which was too late. So unless the Airdata gold plan provides more insight into this I'm not sure if upgrading to a new sub would help in my situation.

Gold just gives you a nice trend line, plus a graph of the major/minor deviations per battery over time.

10 seconds of major deviation is what I'd call abnormal though....

 

[Hayabusa]

I think the free accounts with Airdata will allow you to sync your flights and analyse the battery page on a flight by flight basis:
This page will show you if something is wrong, there are a couple of examples there to get a feel for what a bad battery condition looks like.

If you want to do a quick check as a new user, it'd be best to charge all batteries, perform a normal flight with each one and then upload each flight to Airdata and have a look at the battery cells page for each flight.

Note that I don't work for Airdata, just a customer of theirs and think their service is great. Saves a ton of time manually poring over data logs myself...



Gold just gives you a nice trend line, plus a graph of the major/minor deviations per battery over time.

10 seconds of major deviation is what I'd call abnormal though....

Thanks but still confused on what am I looking at in regards to deviation? What’s normal? What’s not?
New to this talk

 

[Goof]

Succinct version: If nothing's showing in red it's probably normal.