Hi fellows,

Mavic air (the first - with me since Jan/18).

Yesterday I took off with half battery… then out of nowhere it came from 39% to 0% instantly.

Maybe my fault since I was full throttle in sports mode…. with a half juiced battery

Did it happens to anyone ?

https://youtube.com/shorts/1lWH3wzWDs4?feature=share

https://youtube.com/shorts/1lWH3wzWDs4?feature=share

Was this a freshly charged battery that you flew from 100% down to 39% the same day?  Or was it down to 39% after being in storage?

KlooGee Posted at 7-26 04:05
Was this a freshly charged battery that you flew from 100% down to 39% the same day?  Or was it down to 39% after being in storage?

Man.... other day I was thinking of you... and how long I was away from this forum....

Well. I flew it to 42% the day before (saturday). On sunday morning I started the day with this half juiced battery.

Adriano Araujo Posted at 7-26 04:09
Man.... other day I was thinking of you... and how long I was away from this forum....

Well. I flew it to 42% the day before (saturday). On sunday morning I started the day with this half juiced battery.

Yeah, I've been away for a long time as well.  Funny how life happens like that!     I hope you are well!

I've seen sudden voltage drops in batteries that weren't re-charged after being in storage for a period of time.  Have you stuck the battery back in the drone once you got back home and looked at the battery screen in Go 4?

Also, do you have the flight record you could post?  Maybe we could see if one of the cells has gone bad in it...

Cheers!

As @KlooGee has stated, the sudden voltage drops in batteries is a common situation for batteries that was not re-charged after being used and then stored for a while.

Your smart battery's internal controller monitors the voltage and reports it to your drone. Due to the large current that the drone is using and low voltage in each cell, a sudden increasement in current can significantly drop the voltage below the discharging platform voltage.

Sometimes your drone can draw over two hundred watts of power from the battery. 20Amps of current is not a small amount so even a small amount of internal resistance would contribute to a large voltage drop.

This is not a problem for charged batteries, because when you're charging and discharging, your battery controller calibrates the battery capacity estimation.

Please always charge your battery before using it if it was stored more than 24 hours and is already below 80%!

This can significantly reduce the chance of sudden voltage drops.

From what I've learnt, after a certain time of not being used, the controller would measure an open circuit voltage as the initial sample for the calculation of remaining capacity.

However, this is highly inaccurate, especially when you've used the battery to somewhere like 60% or even lower in the previous flight. This is because that batteries have an effect called polarization.

Due to battery polarization, the voltage of your battery can be "recovered" after not being used a lot which can fool your battery controller.

Let's say that your initial battery voltage was 4.3V@100% and then you used it to 3.5V@10%.

After you pulled the battery out and stored it for a day, due to the polarization effect, the battery's open circuit voltage is now 3.6V. You see, the problem is, you didn't charge your battery, didn't feed it any energy, but due to the polarization effect, the battery magically gained 0.1 Volt.

Now the controller has lost its previous actual power usage calculation based on V/A meters, so now it can only rely on the open circuit voltage of your battery to calculate the remaining battery life.

So the controller reads a 3.6V, seems like 40% of remaining battery, then it reported this to the drone.

However, polarization is not free energy. The polarized voltage would drop immediately once the current returns. With a large amp, it would only get worse.

That's why never fly a battery lower than 80% after discharge and storage. Never. Always recharge your discharged and stored battery!

Made a graph for better understanding of this problem. So always remember to charge before use!

Here are the info about the flight.

https://app.airdata.com/flight/a ... ns&val=detailed

KlooGee and FriedChicken, the auto-landing triggered at 00m52.9s: "Not Enough Force/ESC Error. Mode changed to Confirm Landing" with 8.16 volts.

There was NO CELL UNBALANCING:

https://app.airdata.com/flight/a ... 20/POWERCells_Graph

FriedChicken_II Posted at 7-26 05:15
From what I've learnt, after a certain time of not being used, the controller would measure an open circuit voltage as the initial sample for the calculation of remaining capacity.

However, this is highly inaccurate, especially when you've used the battery to somewhere like 60% or even lower in the previous flight. This is because that batteries have an effect called polarization.

Thank you for your explanation!!! It is great.

Hello there Adriano Araujo. I am sorry for the trouble this has caused and thank you for reaching out. Kindly please try to fully charge you DJI Mavic Air's intelligent flight battery to see if the issue will still persist. Just a reminder that  the lifespan and condition of the battery will depend on the totality of how it was used and stored. Hoping for your kind understanding that every electronic product and batteries has a certain warranty period and lifespan. For safety purposes please store and maintain the said batteries properly for you to be able to maximize the use of the said DJI intelligent flight batteries. Thank you.

Adriano Araujo Posted at 7-26 09:45
Here are the info about the flight.

https://app.airdata.com/flight/a7d544274b0763f3c60a8d0edbc81520/GENERALNotifications&val=detailed

Your battery was not at 43% at takeoff.
The % indicator is only accurate when you start with a fully charged battery.
The cell voltage is what's important and if you look at your cell voltage, it was down below the critical low voltage level of 3.2v already during takeoff.
It should have been >4v.

Only launch with freshly charged batteries.

Labroides Posted at 7-26 21:19
Your battery was not at 43% at takeoff.
The % indicator is only accurate when you start with a fully charged battery.
The cell voltage is what's important and if you look at your cell voltage, it was down below the critical low voltage level of 3.2v already during takeoff.

Now then Labroides, I read your replies to people's problems with interest, and take note,
If you fly midmorning with a fresh 100% charged battery and say fly down 70%  then the rain starts, can you fly safely the rest of the battery in the afternoon, or just recharge to be safe.
Keep safe.

UKMoose Posted at 7-27 02:18
Now then Labroides, I read your replies to people's problems with interest, and take note,
If you fly midmorning with a fresh 100% charged battery and say fly down 70%  then the rain starts, can you fly safely the rest of the battery in the afternoon, or just recharge to be safe.
Keep safe.

If you fly a bit and land and take off again, that's no problem.
A break of an hour or two is probably OK, but leaving a partly run down battery overnight is asking for trouble.

Labroides Posted at 7-27 03:37
If you fly a bit and land and take off again, that's no problem.
A break of an hour or two is probably OK, but leaving a partly run down battery overnight is asking for trouble.

Life and learn. Thanks

Learning something new here. Thank you guys.

Sunday I also learned to climb some trees to recover the drone... LOL.....

Labroides Posted at 7-27 03:37
If you fly a bit and land and take off again, that's no problem.
A break of an hour or two is probably OK, but leaving a partly run down battery overnight is asking for trouble.

That'll do, thank you, I have to say I've never done it, I've fully recharged or used the partly discharged battery to charge my tablet/phone down to 55% till next needed. Keep safe.

Adriano Araujo Posted at 7-27 03:46
Learning something new here. Thank you guys.

Sunday I also learned to climb some trees to recover the drone... LOL.....

Haha, glad to hear there was no crash as a result of your new tree climbing skills!  

Just to add to this discussion, there is no way to measure the remaining charge in a rechargeable cell. The display of remaining charge is a calculated figure, obtained by measuring the amount of current discharged from the battery over a period of time. The reason that 'percentage charge remaining' is displayed is because it is a value that the average non-technical person can relate to, while in reality, the terminal voltage of each cell while it is under load is a much more reliable indicator. However cell voltage under load is not a figure that the average person can get their head around. The problem is, with a partially discharged battery, one or more cells can be closer to fully discharged and the percentage figure is therefore inaccurate, and should not be relied upon.

For this reason, the recommendation from experienced fliers and the manufacturer is to always start each flight with a freshly charged battery that was charged in the pervious 24 hour period.

Geebax Posted at 7-27 16:23
Just to add to this discussion, there is no way to measure the remaining charge in a rechargeable cell. The display of remaining charge is a calculated figure, obtained by measuring the amount of current discharged from the battery over a period of time. The reason that 'percentage charge remaining' is displayed is because it is a value that the average non-technical person can relate to, while in reality, the terminal voltage of each cell while it is under load is a much more reliable indicator. However cell voltage under load is not a figure that the average person can get their head around. The problem is, with a partially discharged battery, one or more cells can be closer to fully discharged and the percentage figure is therefore inaccurate, and should not be relied upon.

For this reason, the recommendation from experienced fliers and the manufacturer is to always start each flight with a freshly charged battery that was charged in the pervious 24 hour period.

Many thanks for explaining this and to reinstate how important it is to always start flying with a fully charged battery, both in the drone, the RC and the phone.

A very informative topic.
I didn't know about the rules described here. I was also flying on partially discharged batteries. I didn't know what the threat was.

The golden rule has always been that you only ever take off on a freshly fully charged battery “including when landing after any mission” BE SAFE JUST CHANGE IT”

Now I understand why sometimes a partially charged M2 battery shows like 50% remaining capacity when pushing the battery button and when hooking up to the charger it goes down to only 25% after a few seconds.

Great info!

Labroides Posted at 7-26 21:19
Your battery was not at 43% at takeoff.
The % indicator is only accurate when you start with a fully charged battery.
The cell voltage is what's important and if you look at your cell voltage, it was down below the critical low voltage level of 3.2v already during takeoff.

Lesson learned