Expensive Mistake?

[-MavicMiniPilot]

I’ve been testing my Mavic air battery to see how much reserve it has left after 0%. It flew for around 2-3 more minutes with the prop guards in after going below zero. I left it on the charger for an hour and it is still blinking in the first dot in an abnormal way faster than usual. I probably damaged something. Any suggestions to save the battery?

 

[AMann]

Unfortunately it may not be recoverable. There’s a firmware hack to reset the lock that activates when lflight batteries go to zero voltage on the battery charge management system inside the battery called “DJI battery killer”, but it’s not easy to use and requires some additional hardware.

I am planning on using it for my M2P batteries if they ever do die, but so far so good.

 

[-MavicMiniPilot]

What is it called?

 

[-MavicMiniPilot]

I just bought that battery too.

 

[AMann]

DJI battery killer

But hold on - some other people here might have another idea to try out first.

 

[AMann]

What model drone is it for?

 

[Yorkshire_Pud]

I’ve been testing my Mavic air battery to see how much reserve it has left after 0%. It flew for around 2-3 more minutes with the prop guards in after going below zero. I left it on the charger for an hour and it is still blinking in the first dot in an abnormal way faster than usual. I probably damaged something. Any suggestions to save the battery?

Perhaps.... put the battery in the drone, switch the drone on and connect everything then check the numerical value of the voltage showing in the app, write it down or screen capture it. Charge the battery for another hour and recheck it?

 

[slup]

I’ve been testing my Mavic air battery to see how much reserve it has left after 0%...I probably damaged something.

I just bought that battery too.

Just as a friendly advice... a test like this is totally useless & will not guide you a bit, if the flight circumstances change slightly (some more wind or you flying a bit differently) those 2-3min after 0% will be something different. Furthermore all this will change to the worse (flight time considered) when the batteries gets older & have more charge cycles on them.

If you feel that it's crucial to know what's left after 0%, you push it to far on a regular basis when you fly, or plan your flights really bad... you should touch down around 15-25% to give some headroom for unforeseen happenings in the end of the flight.

Pure technical a LiPo battery can go down to 3V/cell, but then it will be permanently damaged... no one that don't want to trash their batteries & want them to be somewhat reliable go down that far, they stop when the cell voltage is between 3,3-3,5v/cell. A DJI battery have 3,5V/cell when the BMS says 0% so the wear shouldn't be severe there... but going even lower the voltage will drop very fast in the end & here the factory cell choice for the battery (how good or how similar they discharge) can come into play with one of the cells falling lower that the others & being pushed below 3V.

And here, at these low cell voltage levels the BMS chip can deactivate the battery... making it a dead brick. Which might be totally fair... as the battery have been permanently damaged anyhow & even if you unlock the BMS block, the battery have taken a severe beating & can't be fully trusted anymore.

 

[Jack in Dixie]

Newbie question: Where are you seeing the number of charging cycles on the battery(s)? Is it in the DJI FLY App? If so, where? TIA

 

[slup]

Newbie question: Where are you seeing the number of charging cycles on the battery(s)? Is it in the DJI FLY App? If so, where? TIA

Google is always your friend ...

 

[Jack in Dixie]

Thanks for that info SLUP! Much appreciated.

FYI... I don't use Google for many different reasons. Thank you for the YouTube link.

 

[Cafguy]

There are only a few good reasons to use a BMS unlocker and your case is a - Don't.
The blocker activated for a good reason. Replace the Battery and Follow the good advice given above in the other answers. You can try and put the Battery in the drone to charge. It may work BUT you drained it way to far so you most likely have a brick.

 

[shb]

I’ve been testing my Mavic air battery to see how much reserve it has left after 0%. It flew for around 2-3 more minutes with the prop guards in after going below zero. I left it on the charger for an hour and it is still blinking in the first dot in an abnormal way faster than usual. I probably damaged something. Any suggestions to save the battery?

Sorry to here that. Guess I won't try that. Guess that's why they say if your battery gets real low charge it right away. It's good you posted your story so the rest of us know.

 

[AMann]

It’s a good point that slip made regarding recovering a battery from the dead. I hadn’t thought it through like that and planned on using the program for rebuilding mine if they ever need new cells, not to try and reuse it with damaged ones.

 

[AMann]

Thanks for that info SLUP! Much appreciated.

FYI... I don't use Google for many different reasons. Thank you for the YouTube link.

But did you know that Google owns and operates YouTube?

 

[Jack in Dixie]

But did you know that Google owns and operates YouTube?

I did not. Thanks for the 4-1-1.

 

[AnzacJack]

Sorry for your hard mistake
One of the problems with smart batteries, is that generally users dont need to understand the basics of lipo care like the old schoolers had to learn from day on of rc flying

 

[BigAl07]

I’ve been testing my Mavic air battery to see how much reserve it has left after 0%. It flew for around 2-3 more minutes with the prop guards in after going below zero. I left it on the charger for an hour and it is still blinking in the first dot in an abnormal way faster than usual. I probably damaged something. Any suggestions to save the battery?

You've essentially outsmarted the SMART in the battery which is there to protect the BATTERY. Once a Lipo get down to a certain low charge state (~3V/cell) it causes irreparable chemical damage to the battery.

DO NOT Try to recover/recharge this now SUSPECT battery. Safely dispose of it and under NO circumstances try to recharge it. An overly discharged LIPO could potentially lead to FIRE during a recharge after an OVER discharge. Internal damage (invisible from the outside) is NOT something you want to play around with.

 

[shb]

How come things like mp3 players and flashlights can go down to 0 battery and aren't damaged?
I have a story somewhat somewhat related to this. I had a NVIDIA shield tablet that would no longer charge to 100%. Only maybe 90. So on the internet, I read NVIDIA said to fix it, I should discharge it all the way, let it sit around for a while, they discharge it all they way again. Then charge it. I did this, and it wouldn't charge anymore! So NVIDIA's instructions bricked my tablet!

 

[slup]

How come things like mp3 players and flashlights can go down to 0 battery and aren't damaged?

It depends on what you mean by "0 battery"... & how you know they haven't been damaged?

If you mean 0%, they most probably are governed by a BMS that deactivate further use of the battery to protect it... but if you let it lay around without charging it there, it will eventually self-discharge below the lowest cell voltage & there it's goodbye, the flashlight/MP3 player will not turn on anymore & will not take charge.

You also need to understand that most of the ordinary household gadgets which have smaller Lithium cells aren't required to provide similar high amp draw as for our drones, which can go up to around 20A for a photo drone & even up to 70-100A for racing quads. If a flashlight battery is worn & fails it will not be catastrophic... it will just not turn on anymore, not fall as a rock from 400ft.

Also, most smaller gadgets use Li-Ion batteries (usually cylindrical shaped) & that chemistry have it's lowest limit at 2,5V/cell... instead of 3V for a LiPo... this will give a Li-Ion a bit more headroom before getting permanently damaged, but once low enough they will also stop working.

Have had at least 2 remote controllers (with squarish LiPo cells) for my TV that have suffered from swelling batteries to a degree that I couldn't get them out of the remote anymore. Both of these remotes had a stand which charged them... & obviously the remote was always placed there every evening, so the batteries was never really discharged, instead fully charged all the time.

And as said earlier... a BMS in a DJI battery indicate 0% when the cell voltage is 3,5V, that's a good enough cut-off limit where no major damage occurs.

But after 3,5V the voltage drops very fast to damaging levels... that's why you shouldn't fly your batteries down to 0%