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Why would one cell in a lipo just sudden die?

Rasterize

Maker of skins for foam board RC planes
Mentor
#1
I have a 4S 6600 35C battery that I use on occasion. Maybe 5 flights on it. I discharged it after flying to 3.8 volts and store in separate bag.
Around the beginning of each month I check all batteries used or not for voltage. A month ago all cells read 3.8 volts. During this month's "Volt Check" The first cell reads 0.00. The other three 3.8 volts. I double checked with 3 different voltage checkers. Same on all.
What could have happened?
What should I do now? It makes me nervous. It's outside in a battery bag now.
 

The Hangar

Well-known member
#2
Wow - weird... Do you have a charger that shows the individual voltage of each cell? My Venom pro duo shows the voltage of each cell, so what I would do is outside with the battery in your batsafe or cinder block turn on the charger and see what it says. Could it be possible that one balance wire came undone from one of the terminals?
 

sprzout

Knower of useless information
Mentor
#3
I had a 3S battery like that - it was in a crash. No swelling or anything, just started saying it had a cell fault and the charger wouldn't charge it anymore. I just discharged it, ran it down dead while connected to a motor and doing servo testing; once that was done, I took it to the local Home Depot and put it in their lipo battery disposal box.
 

PsyBorg

Wake up! Time to fly!
Mentor
#4
There are many reasons for that happening. But the chances of it blowing up or catching fire are near nil. Its when they get hot or are over charged or punctured they be come dangerous.

It could have been damaged the last time you flew on it and you didnt know. It could be simply sitting in the sun heating that one cell while you were out doing things. It could be it had a bad cell or had high internal resistance from the factory. Depending on the cell placement in the pack it can be removed from the equasion and used as a 3 cell if done carefully. Depending on the other cells internal resistance it could still be a flight pack or a really nice pack to run a ground station or charge other smaller packs from with a field charger..

I ripped on a brand new graphene pack a year or so ago and like its third use one of the cells gave up the ghost. You could see when it happened in the flight video. Its like it would work as a low current draw battery but any high current use swamped it because the C rating changed so drastically.

If you are not comfortable with it being around here is a video how I dispose of lipos.

 

Rasterize

Maker of skins for foam board RC planes
Mentor
#5
Wow - weird... Do you have a charger that shows the individual voltage of each cell? My Venom pro duo shows the voltage of each cell, so what I would do is outside with the battery in your batsafe or cinder block turn on the charger and see what it says. Could it be possible that one balance wire came undone from one of the terminals?
I have the Venom pro duo as well and checked it. Says the same thing as my cheap checkers 0.00 3.8 3.8 3.8 Balance wires were the first thing I checked.

I had a 3S battery like that - it was in a crash. No swelling or anything, just started saying it had a cell fault and the charger wouldn't charge it anymore. I just discharged it, ran it down dead while connected to a motor and doing servo testing; once that was done, I took it to the local Home Depot and put it in their lipo battery disposal box.
I may end up going this route as well. The pyro mad scientist in me still wants to try charging it. :oops: My luck. I get Dr. Jekyll Mr. Dumb A$$. :LOL:

There are many reasons for that happening. But the chances of it blowing up or catching fire are near nil. Its when they get hot or are over charged or punctured they be come dangerous.

It could have been damaged the last time you flew on it and you didnt know. It could be simply sitting in the sun heating that one cell while you were out doing things. It could be it had a bad cell or had high internal resistance from the factory. Depending on the cell placement in the pack it can be removed from the equasion and used as a 3 cell if done carefully. Depending on the other cells internal resistance it could still be a flight pack or a really nice pack to run a ground station or charge other smaller packs from with a field charger..

I ripped on a brand new graphene pack a year or so ago and like its third use one of the cells gave up the ghost. You could see when it happened in the flight video. Its like it would work as a low current draw battery but any high current use swamped it because the C rating changed so drastically.

If you are not comfortable with it being around here is a video how I dispose of lipos.

I wish I had the skill/knowledge to remove that one cell. At this point it will probably end up getting discharged and trashed.

Thanks for the advice guys!
 

CarolineTyler

Well-known member
#6
I had a GMB 4S battery do the same - had just two flights on it. I had noticed that the battery was taking longer than normal to balance charge (I ALWAYS balance charge) and then come the third charge it was only being recognised as a 3S battery by the charger - cell 1 was reading 1.2 volts. Oh well, the other GMB batteries I have are excellent, guess I just got a bad one.
Stuck a car bulb across it to completely discharge it and cut off the leads. Its now in my dead battery box ready to go to recycle.
 
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sprzout

Knower of useless information
Mentor
#7
If you're nervous about it (and I would be a bit nervous trying to charge it with a bad cell), just don't risk it. Better to get rid of it than take a chance. And trying to remove the cell, well..in theory it's possible, but it might be more trouble than it's worth, and the risks are much higher of causing a short/heating it up for an explosion. I personally wouldn't chance it, especially when there's always the thought in the back of my head of, "What if I didn't do it right? Do I have a ticking time bomb in my lipo bag?"
 
#8
Check continuity of the balance wires from the plugs all the way to the cells.
I had a new 4S pack for my 1/8th scale buggy do the same thing within hours of purchase. I checked each wire, and found one was broken near the cell. Solder, heavy heat shrink, and good as new. (Because, well, it was new. :rolleyes:)