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Dji phantom 2 battery issue
461 9 2018-5-5
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Andynilsson
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Sweden
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Hi,

So I have this issue with one of my batteries for the phantom, when I use it on the drone, after 3 or 4 min and goes into fly home mode showing that I have low battery. But when taking the battery off it shows as fully charge. I have compared both of my batteries on the phantom assistent and both have over 95%battery life time and have been recharged maximum 13 times. What is also weird is that the battery that works normal have less battery life time.

Does anybody had any similar issue or probably knows what it can be and have a solution?

Best regards
2018-5-5
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Mark The Droner
Captain
Flight distance : 2917 ft
United States
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Personally, I don't pay attention to battery life.  I do pay attention to the cells and the mAh.  

Tell us what each cell voltage is reading at full charge.  

What is the total mAh?  

Thanks
2018-5-5
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Andynilsson
lvl.1

Sweden
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Mark The Droner Posted at 2018-5-5 11:25
Personally, I don't pay attention to battery life.  I do pay attention to the cells and the mAh.  

Tell us what each cell voltage is reading at full charge.  

Hi Mark,

Thank you for the fast reply. I have now charged the battery and is shows the following:

Cell 1: 4154 mV
Cell 2: 4148 mV
Cell 3: 4207 mV


2018-5-5
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KedDK
Captain
Flight distance : 1133038 ft
Denmark
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Have you tried a really deep discharge cycle?
Let it hover just above ground until it land and if possible let it stand with the motors running as long as possible, This is supposed to improve the balance of the cells.
Your pic above say discharge to less than 8% but old posts around here mention 5%, 3% or until it can no longer power on, also a cell voltage of 3.3V was said by one of the admins but i think it powers down before you see this anyway.
2018-5-6
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Andynilsson
lvl.1

Sweden
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Hi Ked,

Thank you for your reply, I really appreciate all the help!
I had the battery down to 6% yesterday by letting the drone stand on and I fully loaded it this morning, that's when I took the screenshot of the capacity. Should I let the battery go even lower and try again?

Thanks once again!
2018-5-6
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KedDK
Captain
Flight distance : 1133038 ft
Denmark
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Andynilsson Posted at 2018-5-6 02:55
Hi Ked,

Thank you for your reply, I really appreciate all the help!

I think it would do no harm trying it once more with discharge to 0%. As it is, the battery is no good anyway so it can even get better or given up on.
If less than ½ a year old you would still have warranty on it, but i guess that is not the case.
2018-5-6
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Mark The Droner
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Flight distance : 2917 ft
United States
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Andynilsson Posted at 2018-5-5 23:35
Hi Mark,

Thank you for the fast reply. I have now charged the battery and is shows the following:

Obviously you've lost at least 4,000 mAh and you'll never get it back.  That's about 10% of what the battery is able to hold, which means your flight is reduced by that much at the very least.  But that doesn't explain why it RTHs after 3-4 mins.  Are you sure it's a legit DJI battery?  I have an aftermarket that auto-lands at 29% for no particular reason but it also has reduced mAh about the same as yours.  

If you brought the battery down to 6% yesterday, then fully charged it, there's an even chance that might have solved an imbalanced cell problem, but probably only temporarily.  I would fly it right away, keep it low and close, and see if the situation has improved.

If it does RTH early again, could you show us the cells like you did above - before you charge it?  
2018-5-6
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Mark The Droner
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Flight distance : 2917 ft
United States
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KedDK Posted at 2018-5-6 01:14
Have you tried a really deep discharge cycle?
Let it hover just above ground until it land and if possible let it stand with the motors running as long as possible, This is supposed to improve the balance of the cells.
Your pic above say discharge to less than 8% but old posts around here mention 5%, 3% or until it can no longer power on, also a cell voltage of 3.3V was said by one of the admins but i think it powers down before you see this anyway.

Those posts regarding 5% and 3% are discussing P4 and P3 batteries.  The P4 batteries are gauged differently regarding percentage.  Why?  Because I believe DJI is trying to keep us from over-flying the battery and killing our drone.  They're trying to save us from our own recklessness.  I think 5% on a P3 is about equal to 8% on a P2 -voltage-wise.  That's my take on it.

What I mean is, 3% on a P2 battery is actually much lower than 3% on a P4 battery.   So you would need to be careful applying P4 battery techniques on a P2 battery because you may do permanent damage.  
2018-5-6
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KedDK
Captain
Flight distance : 1133038 ft
Denmark
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Mark The Droner Posted at 2018-5-6 03:45
Those posts regarding 5% and 3% are discussing P4 and P3 batteries.  The P4 batteries are gauged differently regarding percentage.  Why?  Because I believe DJI is trying to keep us from over-flying the battery and killing our drone.  They're trying to save us from our own recklessness.  I think 5% on a P3 is about equal to 8% on a P2 -voltage-wise.  That's my take on it.

What I mean is, 3% on a P2 battery is actually much lower than 3% on a P4 battery.   So you would need to be careful applying P4 battery techniques on a P2 battery because you may do permanent damage.

Thank you for correcting me if i am wrong, i don't like those percentages at all.
Even they measure the percent differently they have the heart in common, lipo cells and i would expect the board made so it shuts down when a cell voltage get too low no matter what percent this would translate to, am i wrong making assumptions like this?
Guess no matter what phantom is in target the cell voltages is a better measure and the 3.3V mentioned as the "sweet magic number" in one of the cells is where it shut down and after cooling should be recharged full or am i wrong here too?
2018-5-6
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Mark The Droner
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Flight distance : 2917 ft
United States
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KedDK Posted at 2018-5-6 21:45
Thank you for correcting me if i am wrong, i don't like those percentages at all.
Even they measure the percent differently they have the heat in common, lipo cells and i would expect the board made so it shuts down when a cell voltage get too low no matter what percent this would translate to, i am i wrong making assumptions like this?
Guess no matter what phantom is in target the cell voltages is a better measure and the 3.3V mentioned as the "sweet magic number" in one of the cells is where it shut down and after cooling should be recharged full or am i wrong here too?

From what I've read, the AC autolands when any cell hits 3.3 volts, and the battery shuts itself off when any cell hits 3.0 volts.  I believe that's the same on all the lipo batteries.  That's why it's wise to have balanced cells.  I don't know what the "sweet magic number" would be voltage-wise, when it comes to a deep discharge.  Many people believe a deep discharge doesn't work anyway.  <shrug>

DJISusan has posted recently that a modern Lipo should be taken all the way down until it shuts off, but that was if the battery was to be stored for an extended amount of time.  Would that also apply to a battery that has unbalanced cells?  I would assume so.  Would that also apply to a P2 battery?  Maybe.  Not sure.  Because I've also read that taking a P2 battery down until it turns off can damage it.  
2018-5-7
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