Today i charged mini 2 battery in the multi charger, when fully charged the 3 rd light was flashing fast .  when put in drone the cells showed 4.26 v and 4.38 v , i presume one cell is being over charged before the other gets fully charged .   i flew battery down to 10% and there was 0.05 v difference.   then  recharged ,  voltage difference was still the same as originally at 0.11 v between the two cells.   flew drone with no problem afterwards down to 46% with same difference in the cells.
is there a way to re balance?  is this difference  0.11 v of any concern do you think ?

Hello there goldenorfephoto. Thank you for reaching out and for the information you have provided. In general, the battery cell deviation should be lower than 0.05V at high power, and less than 0.1V at low power. May we know if you re you receiving any error messages on the DJI Fly application? Thank you and fly safe always.

DJI Stephen Posted at 2-17 19:41
Hello there goldenorfephoto. Thank you for reaching out and for the information you have provided. In general, the battery cell deviation should be lower than 0.05V at high power, and less than 0.1V at low power. May we know if you re you receiving any error messages on the DJI Fly application? Thank you and fly safe always.

No errors, flew the battery down to 40% without a problem.    going to try full discharge and re charge next

goldenorfephoto Posted at 2-18 04:50
No errors, flew the battery down to 40% without a problem.    going to try full discharge and re charge next

May I suggest you research the battery technology on Wiki or even leading manufacturers before draining the battery. It won't balance the cells, because the charge circuitry in the battery does this.
If a cell is faulty or developing a fault, draining it will hasten its end.
If the battery is otherwise normal and in good condition, normal use will sort things out.
You never mentioned how many charge cycles the battery had.
Has it been used like at least once or more times a week?
If infrequent use, what was the charge % when you recharged.
How old is it?
All these things have a marked effect on the battery life.
The battery is a bag of chemicals that are adversely affected by temperature, current demand and neglect.
The battery is degrading from the moment it was made and everything you do with it, or don't do with it like storage, hastens that end, by varying degrees.
Drone batteries are the key component that is most likely to fail, causing the drone to drop from the sky.
If in doubt, don't use it. You can always use it with an adaptor as a powerpack for your phone.
Phone and laptop batteries are better sized for the current demands on them and tend to last longer than drone batteries. They also don't fall out of the sky if they fail.

AlansDronePics Posted at 2-18 05:17
May I suggest you research the battery technology on Wiki or even leading manufacturers before draining the battery. It won't balance the cells, because the charge circuitry in the battery does this.
If a cell is faulty or developing a fault, draining it will hasten its end.
If the battery is otherwise normal and in good condition, normal use will sort things out.

it has been charged 4 times, from about 65 % each time     

Depending on how long it was in the suppliers store before selling, it should sort itself out.
I would fly at, say, head height in a large unpopulated open space for a few charges and evaluate from there.
It won't have far to fall.
Try practicing stick control around something on the ground.
Watch the battery cell voltage on the app as you fly using different power and compare with what DJI mentioned.
Good luck.

is this difference  0.11 v of any concern do you think ?
It's completely normal.
Don't worry about it.

goldenorfephoto Posted at 2-18 04:50
No errors, flew the battery down to 40% without a problem.    going to try full discharge and re charge next

Hi there goldenorfephoto. Thank you for the reply and for these information you have given. If you have any other concerns or inquiries with DJI. Please feel free to post it here at DJI Forum. We are all here to help and support you. Thank you and fly safe always.

Labroides Posted at 2-18 05:56
is this difference  0.11 v of any concern do you think ?
It's completely normal.
Don't worry about it.

On A mini 2 evidently it's not a problem. (At least not yet on DJI Fly.  DJI may change to be the same as DJI Go 4)  On a Mavic Pro and DJI Go 4 it will not take off and report a battery error. There is no way that I have found to balance it yet.... I am going to dismantle and use a Hybrid charger on it and see what happens.

A 0.11V difference means one of 2 things.

1) The cell is deteriorating and will fail early.
2) The balance cct of the charger system can not drain current from the high cell fast enough to allow the low cell to catch up. (Why Hybrid charging is so much better.)

Cheers

bjr981s Posted at 2-19 00:17
On A mini 2 evidently it's not a problem. (At least not yet on DJI Fly.  DJI may change to be the same as DJI Go 4)  On a Mavic Pro and DJI Go 4 it will not take off and report a battery error. There is no way that I have found to balance it yet.... I am going to dismantle and use a Hybrid charger on it and see what happens.

A 0.11V difference means one of 2 things.

What is hybrid charging?  
I also wonder if charging in the drone vs. in the 3 battery charge block is better or worse.

Astro Bob Posted at 2-19 07:55
What is hybrid charging?  
I also wonder if charging in the drone vs. in the 3 battery charge block is better or worse.

LiPo Balance Charging.

A LiPo balance charger charges the battery at the +ve and -ve Poles.

It uses a voltage that provides a constant current that you elect. Normal set at 1C. e.g. 2200mah battery charge rate at 2.2A.

The actual stored watt hours of each individual cell will be subtly different so they will charge at a subtler different rate.

This is why you use a balance charger. As the battery charges it will detect that one cell will be lower than the others. To balance, the charge will discharge the high cell while it also charges the total battery.

As long as the high cell does not reach max charge while this is happening all is OK and all cells will end up at the full charge per cell.

If one cell has too large a gap for the balance to complete it will end with a lower voltage than the other cells.

To continue to charge past the fully charge value of the high cell will overcharge and damage the battery.

Once this happens the low cell will will remain low. Once it reaches a specifically lower voltage the gap is too large for a balance charger to balance.

This is the issue with all LiPo balance chargers.

Hybrid Charging.

A hybrid charger will charge the same as a balance charger via the main -ve and +ve main leads.
But it will ignore the balance leads.

Once the first cell reaches its fully charged state the hybrid charger will stop charging from the -ve and +ve leads. And charge the remaining cells individually till they all reach full charge.

A Hybrid charger is more complex as it requires the ability to charge via the main leads and also individually over each cell.

So a 6S charge would require 7 individual charger circuits. The only downside of a hybrid charge is the max current that can be pushed through the balance leads.  So it can take more time to charge extremely large LiPos.

Cheers







   

I have absolutely the same problem. I bought DM2 and one of three batteries have an 'over charge' problem - after a full charge, I see that led3 is blinking 2 times.
App show 4.21v and 4.37v, so diff is 0.16v.
Is is a defect and i should go to service? Is this RMA or not?

kapu Posted at 4-18 11:07
I have absolutely the same problem. I bought DM2 and one of three batteries have an 'over charge' problem - after a full charge, I see that led3 is blinking 2 times.
App show 4.21v and 4.37v, so diff is 0.16v.
Is is a defect and i should go to service? Is this RMA or not?

mine died completely,  Dji service said under warranty and sent UPS pre paid courier details.  sent it off nearly 3 weeks ago and it still hasn't arrived at the service centre in holland,  bloody Brexit crap!