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Swollen but balanced battery

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Hi guys,

As some of you may know I have got a second hand TH with two swollen batteries. One of them is kind of puffed much more than the other and I am trying to discharge it using a DC motor. I tried to puncture it laying it in a metal fire pit from a distance but I could only pierce top black(plastic or paper). It leaked a bit of something.. really a tiny bit.. more like a drop. since nothing happened like a fire burst or anything I got read of the idea to puncture it and I am not using a DC motor from multitool to discharge it. I would expect it to discharge in 2-3 hours but it run that much yesterday and about 2 hours today but it still have about 11V.


The second one though is less puffed and after checking each cell voltage I am realising that the battery is actually seems to be ok and well balanced... 3 cells voltage is showing as 4.09V and only one shows 4.10V I guess we can call it balanced. Now I am thinking may be destroying one battery should be enough. The previous owner has warned me that one is puffed. However he did mention nothing about the second slightly puffed, he also said he used both batteries for flying.


am I risking much using a slightly swollen battery in my drone? Can gases escape for some reason and just puff the top layer but a battery can be good at the same time?
It is a bit harder to insert it into the drone comparing with a new battery I have as a battery hole side scratching that black layer a bit but on the other one both sides already have removed a lot of black colour from that layer. So it seems it has been used by the previous owner a lot.

I know about salt water disposal but first there is another opinion about this method and it does not present it as a save method to dispose it. However I am not using salt water now for the that battery because of that opinion. I simply trying to discharge it a much as possible before I put it in salt water.
 

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Do not do anything with either battery, before thoroughly reading the following thread (and some of the referenced links in that thread):

Lipo Battery Care

This will give you accurate information to decide how to proceed safely.
 
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I am still happy to use salt water method and in fact I am suing it now. I just did not want to drop almost fully charge battery in a bucket with it. I know that contact will corrode in salt water and it may stop discharging in the water.
So after I posted the first post the motor started to slow down and stop. When I measured 3 cells went to almost 0 and only one had 2V left. So I dropped it in the bucket hoping it will get to nothing before corrosion will start to happen.

The question is though still the same, is it safe to use slightly puffed one if it shows balanced cells? And can I say it is balanced if my multimeter shows 3 cells at 4.09V and one cell at 4.10V?
 
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Ok I have found and read this thread Swollen Battery Disposal Or Recovery?

I think I will try my luck with the puffed one that is still left. The other one that is currently in the bucket still produce a bit of hydrogen bubbles through punctured holes and contacts. However it is now much less of them than right after I put it in salt water.
 

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Do you have access to a digital meter that can show internal resistance on the individual cells of the slightly puffed one? That will give the information you need to decide if the battery is still flight worthy. However even if not, that battery still could be used for non-flight operations. Examples would be calibrations or sitting outside to update the GPS almanac.
 
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A reading of 0 would not be correct... even a new battery would be 3 - 5 mΩ on each cell as a minimum. You are ideally looking for all cells to be in the single digits, with no more than a 5 mΩ deviation across all cells. Any cells in double digits are suspect.


What kind of charger are you using for these batteries?
 
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Just a stock one for a single battery. I have found somewhere online that multimeters may not show any resistance on Lipo cells. That can be a reason why I am getting no resistance.
 
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If your meter is set to M-Ohms that is MegaOhms not milliOhms (with a small m m-Ohms). Set the meter to M-Ohms and pinch the leads, one in the left hand the other in the right your readings should be in the single to double digits. Now set to Ohms scale and repeat. You should get a reading in the hundreds of thousands or OL for beyond measurable range.
 
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I do not have any scale in mΩ and I just assumed it was milliohm because it switches to it next from kΩ Anyway no matter what range I use it is either 0 or OL. No numbers shown at all.

I have current measurement mode on my multimeter, not sure if I can get anything from it but I can try.
 

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Don’t try current! You could fry your multimeter.
 

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You need a charger that can measure the IR or a separate IR meter. You cannot measure IR directly with a multimeter
 
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Do you have access to a digital meter that can show internal resistance on the individual cells of the slightly puffed one? That will give the information you need to decide if the battery is still flight worthy. However even if not, that battery still could be used for non-flight operations. Examples would be calibrations or sitting outside to update the GPS almanac.
Hi have 2 batteries I alternate for that purpose only!
 
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Do you have access to a digital meter that can show internal resistance on the individual cells of the slightly puffed one? That will give the information you need to decide if the battery is still flight worthy. However even if not, that battery still could be used for non-flight operations. Examples would be calibrations or sitting outside to update the GPS almanac.
Don’t trust your batteries. They will discharge quickly if they look like what you described. I lost my h trusting a swollen battery that still charged to the correct voltage. It showed full, went out about 300 yard then dropped into the forest. Not enough juice to return to home. Never again.
 

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Don’t trust your batteries. They will discharge quickly if they look like what you described. I lost my h trusting a swollen battery that still charged to the correct voltage. It showed full, went out about 300 yard then dropped into the forest. Not enough juice to return to home. Never again.
Which is why you do not use them for flight operations. The only time this aircraft draws enough amperage to cause a potential power loss, is when the motors have spun up to full speed during takeoff and flight.

The laws of physics demonstrate clearly that there is little risk of falling to the ground, when the aircraft is currently sitting on the ground, gathering GPS almanac data. Also the only risk of falling during a compass calibration, is the pilot dropping the H, not battery failure. ;)
 
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A reading of 0 would not be correct... even a new battery would be 3 - 5 mΩ on each cell as a minimum. You are ideally looking for all cells to be in the single digits, with no more than a 5 mΩ deviation across all cells. Any cells in double digits are suspect.


What kind of charger are you using for these batteries?
When testing resistance, does the battery need to be Charged or Discharged. Great video.
 

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It will show the Internal Resistance in either fully charged or storage levels. However in terms of making a decision of flight suitability, I would say fully charged state would be most relevant... since you should never be flying from a starting point of storage voltage.

Also to be clear, I did not produce the video on YouTube... just found it.
 
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This why you should always hover before taking off. I always hover, look at my voltage and test all my flight controls.
If you see quick successive drops in voltage while hovering, most likely your battery is failing, recharge it, if it continuous then battery is most likely bad.
 
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