Hi, my question is about battery in P3A.
Phantom was bought in december 2016 so probably the battery is just over a warranty. It was bought by my friend and I just bought it from him.
He used it only 1 time, then it was stored. So after few months I took it and turned on. It was charged at about 50% (I think it was automatic discharge which is set up at 14 days).
I turned Phantom on, everything was correct so I updated firmware. After updating I tried to charge the battery, but at the end LED3 started to blink twice (overcharge detected).
DJI App showed "cell error" and Cell number 2 was 0.20V lower than cells 1,3,4.
I tried to fly and discharge it to 5-8% few times but it does nothing. Fully loaded battery is 0.20V lower on cell2, when discharged the difference is about 0.07V.

The best thing is I have slept the warranty period. Is there anything I can do with that? I read a lot and I found some people had similar problems after firmware update (also with cell 2)! There were no error before upgrade.
Already bought a second battery but I'm very disappointed with that. I have also a hand-built 500mm drone and never had problems with LiPos.

Maximum Auto discharge setting I believe is 10 days ... far too long anyway !

Never heard about Cell2 with updates ... seems a bit 'iffy' ... but the problem is the board in the battery receives the balance plug voltages and then transmits with the telemetry data - so who knows.

Discharging in fact does very little as the weakest cell will always discharge more / faster than the others. You probably already know that from your DIY drone experience and 'normal' LiPo's.

Only way to balance a LiPo is in the top full charge area when a proper LiPo charger does its job ... unfortunately the DJI charger is purely a regulated power supply and the board in the battery case shuts off charge when it detects "full charge' regardless of balance state.

What can you do ?

Talk to DJI ... see what they do ?

Nigel

We feel sorry for the issue of your battery. Due to the warranty of battery is 6 months, I'm afraid that DJI may not be able to help you. Also, for the battery storage, please refer the battery guidelines for better understanding.

OK thanks for answers.
It was 10 days auto-discharge of course (just checked settings)
After auto-discharge and few months not used, the battery was 50% and cell voltages was perfectly balanced (about 0.02V difference) that's why I just started with firmware update and charged it after update. I was sure everything is OK.
So  I didn't follow 3rd step from the list (recharge to bring it out of hibernation). So it's probably my fault.
I suppose it's too big risk to use this battery, right?

There's no way it would have powered anything to do update if in Hibernation mode.

I would connect to charger and keep an eye on it ... leave it to see if anything 'wakes up' ....

IF it charges and then shuts off automatically as it should ... there is one little trick you can do to get the last bit into the pack ....

The battery has charged normally ... charging stopped.
Remove battery from charger and switch it on by the one-two press ...
Connect to charger again ... while still switched on ...

The act of switching on over-rides the board and makes it accept charge again til it hits 100% and switches off again.

Given the cost of these - I am loathe to just give up !!

If it still did not sort - then because its outside warranty - I would replace the cells with own LiHV cells ... but that is not something many can do as it needs tricking the board counter etc. Please do not ask ...

Nigel

atomic77 Posted at 2017-8-2 02:20
OK thanks for answers.
It was 10 days auto-discharge of course (just checked settings)
After auto-discharge and few months not used, the battery was 50% and cell voltages was perfectly balanced (about 0.02V difference) that's why I just started with firmware update and charged it after update. I was sure everything is OK.

Turn the battery on in the charger when charges sometimes help to balance it. It worked for me and the battery has been perfect for more than a year and 45 charges.

G_Sig Posted at 2017-8-2 02:34
Turn the battery on in the charger when charges sometimes help to balance it. It worked for me and the battery has been perfect for more than a year and 45 charges.

Thanks for answers. I tried to do those things but with no success.
I think I will get local help from someone with more experience than me.
One more question: is it safe to fla? What can happen if I fly with this battery?
I tried few times, log file shows that broken cell is as good as other cells, just 0.2V lower. It's 0.1V when discharged.

lipos are iffy no matter what they are in after storage i have taken care of all of my rc batteries i sit with them as they charge and of course the one time i leave a battery unattended for ten minuets after checking all 6cells and temps of both battery and charger my transformer shorted out and i had a lipo explosion in my basement cost insurance 16,000 for clean up THIS WAS (NOT) A DJI PRODUCT it was for a 100+mph rc car.

Moral of the story never leave a battery unattended especially after hibernation. not saying you did but the fact that you have a cell below the others that is when they go bad and fast, or a transformer/Charger failure. i now charge everything on a piece of wood and in lipo bags in the shade outside.

I also have an aftermarket battery that is pretty new (only about 8-9 charges on it) and I got the "Bad Battery" error. I have an Advanced. I tried the charging procedure without any luck. Still had the error. The #2 cell is down 0.20V too, just like yours. Just wanted to share with you what I tried, so you don't have a problem. I though I would try to run the aircraft with this battery down as far as I could and then attempt a full re-charge after it cooled off. It shows 98% battery charge when powered up, but I still have the "Bad-Cell" error. I opened the battery information in the app, and took off, closely watching the voltages. I put the phantom over a grassy spot on my yard and about 2-feet in the air and let it hover......after 15 minutes or so it is getting down to 30%, I get the "Low Battery" message, which I expected. Kept going with hand on throttle to bring it down if needed......let it go to around 20% and noticed the voltages on all the cell were around I think 3.4V, but the #2 was now right at 2.9V. I knew I  was in trouble at that point, and I was just getting ready to land and all motors just stopped instantly and it tumbled to the ground.....like I said with 20% battery. I have landed my Phantom with 6% (good battery) and not had it quit like this. I think when the voltage drop gets below a certain point the power is just cut off. I had no damage, but if I would have been in the air another few feet, pretty sure I would be replacing at least a shell. The battery also popped out. I then proceeded to throw that thing away! LOL

Long story sorry, but I wouldn't trust a pack with a bad cell. I learned a good lesson I think. I won't chance it again. Don't claim to know anything about LiPo batteries, but if after a couple attempts and the cells are still out of whack, I am going to discard them rather than lose my bird. I am fortunate that I do have 6-batteries, but like I said this one was fairly new, just didn't expect it from that one. Maybe one of the original that are over 2-years old with 150 charges, but nope had to be this one.

RicardoGray Posted at 2017-8-8 12:35
I also have an aftermarket battery that is pretty new (only about 8-9 charges on it) and I got the "Bad Battery" error. I have an Advanced. I tried the charging procedure without any luck. Still had the error. The #2 cell is down 0.20V too, just like yours. Just wanted to share with you what I tried, so you don't have a problem. I though I would try to run the aircraft with this battery down as far as I could and then attempt a full re-charge after it cooled off. It shows 98% battery charge when powered up, but I still have the "Bad-Cell" error. I opened the battery information in the app, and took off, closely watching the voltages. I put the phantom over a grassy spot on my yard and about 2-feet in the air and let it hover......after 15 minutes or so it is getting down to 30%, I get the "Low Battery" message, which I expected. Kept going with hand on throttle to bring it down if needed......let it go to around 20% and noticed the voltages on all the cell were around I think 3.4V, but the #2 was now right at 2.9V. I knew I  was in trouble at that point, and I was just getting ready to land and all motors just stopped instantly and it tumbled to the ground.....like I said with 20% battery. I have landed my Phantom with 6% (good battery) and not had it quit like this. I think when the voltage drop gets below a certain point the power is just cut off. I had no damage, but if I would have been in the air another few feet, pretty sure I would be replacing at least a shell. The battery also popped out. I then proceeded to throw that thing away! LOL

Long story sorry, but I wouldn't trust a pack with a bad cell. I learned a good lesson I think. I won't chance it again. Don't claim to know anything about LiPo batteries, but if after a couple attempts and the cells are still out of whack, I am going to discard them rather than lose my bird. I am fortunate that I do have 6-batteries, but like I said this one was fairly new, just didn't expect it from that one. Maybe one of the original that are over 2-years old with 150 charges, but nope had to be this one.

RicardoGray thank you for your story, now I'm sure I wont risk my P3A, even if battery is expensive it's not worth it. I already have a second one so  it's better to not use the broken one.
Again, thanks all of you for answers!