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Bad or not? Deviation of a cell by 0.071v
2233 9 2017-8-24
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Tealk
lvl.4
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Romania
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i need a little help ... i have a deviation of a cell on one MAvic Battery... what it means? ... i understand cose the voltage is not the same on those 3 cells, but this little deviation is afecting the battery ?

cell1.png
cell2.png
2017-8-24
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Tealk
lvl.4
Flight distance : 479613 ft
Romania
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it is a Mavic battery
2017-8-24
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Bekaru Tree
Second Officer
Flight distance : 15513100 ft
South Africa
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in the dji go4 app general settings go to battery icon and check yr battery stats there.
if they still worry you then use that information to support your concern about yr battery.
It might be that the dji app stats are differant to airdata stats - if there is a problem and you want dji to help then they will investigate their own data not that from a third party.
2017-8-24
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Tealk
lvl.4
Flight distance : 479613 ft
Romania
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now i see on djigo app -  36% - cell1 3,74v, cell2 3,78v, cell3 3,76v 1161mAh from 3830mAh ... it is ok ?

how about the diference between cells ? is big the diference ?
2017-8-24
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ImHereToCrash
Second Officer
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i dont know the normal for a mavic, yet... but all cell deviation is bad if not protected and controlled, specially on lithium based batteries..  that being said, i wouldn't worry too much about small amount of deviation.  try to recalibrate it charge it up.. run it flat, let it sit in aircraft turned on until it cuts completely out, as in wont even light up LEDs, then charge it up 100% dont touch it, and then see if the cell deviation still exists and how much better or worse it is..  in theory once you zero battery out and bring it back completely it shouldn't have any deviation cell to cell or should be much smaller.. if it has gotten larger or remained the same, i suggest exchanging or replacing the battery asap.. unless something else going on that makes this value normal..


the reason you dont want cell deviation is because of a few reasons:

the biggest reason is because for lithium especially, it means imbalance and once deviation gets too large, natural way lithium chemistry works is it will forcefully try to rebalance itself, if its a large deviation when that forceful rebalancing occurs that means a lot of heat and offgassing and larger potential of fire.   how this forceful event can occur depends on how batteries are engineered, weakest link isolating each battery from directly connecting each other will likely be the cause of a forceful rebalancing..aka puffing up, heat, possible fire..RIP

the other reason cell deviation is bad is because the battery and protection has to work a lot harder and it means that possibly issue with it properly reading how much remaining runtime is left correctly..  
2017-8-24
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Tealk
lvl.4
Flight distance : 479613 ft
Romania
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ImHereToCrash Posted at 2017-8-24 10:46
i dont know the normal for a mavic, yet... but all cell deviation is bad if not protected and controlled, specially on lithium based batteries..  that being said, i wouldn't worry too much about small amount of deviation.  try to recalibrate it charge it up.. run it flat, let it sit in aircraft turned on until it cuts completely out, as in wont even light up LEDs, then charge it up 100% dont touch it, and then see if the cell deviation still exists and how much better or worse it is..  in theory once you zero battery out and bring it back completely it shouldn't have any deviation cell to cell or should be much smaller.. if it has gotten larger or remained the same, i suggest exchanging or replacing the battery asap.. unless something else going on that makes this value normal..

i understand...i will do a 0 discharge than a 100% recharge ...i never discarged below 10%
2017-8-24
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ImHereToCrash
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Tealk Posted at 2017-8-24 11:10
i understand...i will do a 0 discharge than a 100% recharge ...i never discarged below 10%

make sure not just 0% reported by the app or the RC.. make sure power so low that battery completely cuts out.  then plug it in, dont disturb it until charges completely up, no blinking on the battery anymore.. then check to see if the issue cured itself..  

i suggest every so often to do a calibration, i plan on for each battery imma recalibrate it every 10 or 20 flights.  just so the smart circuit knows where 0% really is and where 100% really is at each stage of its life and can adjust accordingly.
2017-8-24
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Tealk
lvl.4
Flight distance : 479613 ft
Romania
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ok ...thank you bro
2017-8-24
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DJI Thor
Administrator
Flight distance : 13602 ft
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Please fly the drone and keep it for hovering, when the aircraft is hovering or the battery is fully charged, the difference between four battery cells shouldn't be larger than 0.1V. So if the deviation within 0.1V is regarded as normal. No worries.
2017-8-24
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Tealk
lvl.4
Flight distance : 479613 ft
Romania
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Thank you Thor...i will test today
2017-8-25
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