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  1. #1
    RC Turnbuckle Jr. streetdemon's Avatar
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    WHY does a LiPo puff (scientifically)

    Okay before this gets deleted or put into a certain section let me preface this by saying this isn't a question about why MY LiPo puffed, just curious as to what happens that causes it if anyone knows.
    Yes I know using them in over-draw applications or running them overly low can cause it, but I am more interested in the science behind it. What chemical reaction takes place to cause the expansion and buildup of gases? Anyone know?
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  2. #2
    RC Turnbuckle Jr. streetdemon's Avatar
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    And PLEASE I DONT WANT ANY brand names mentioned in here. It is not my intention to have a thread get closed down, just want an answer. And no, I don't have a LiPo that puffed. I was talking to someone today and we were both wondering what the puffing was and the chemical reactions behind it.
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  3. #3
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    In a nutshell, the lithium batteries have 3 components which make them work. A cathode, made out of either lithium, manganese, and oxygen, or lithium, cobalt, and oxygen, an anode made out of lithium and carbon held in a semi-liquid state, and a separator between the two made of a special polymer soaked with a conductive electrolyte. A chemical reaction between the cathode, anode, and electrolyte causes electrons to flow, giving us electricity.
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  4. #4
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    The typical cause of puffiness is either age, or abuse (or a combo of the two.) As the cells are used, the anode naturally degrades, producing oxygen and leaving the Lithium and other element in a useless state. In addition, as usage goes along, the cathode slowly starts to produce metallic lithium. The oxygen produced by the anode bonds to the metallic lithium produced by the cathode, again limiting cell usability, and creating lithium "rust." However, the anode produces oxygen faster then the cathode produces metallic lithium for it to bond to. This means that the oxygen has nowhere to go, and pressurizes the cell, making it puff out. This is also one of the reasons an overcharged cell will ignite under water without the presence of oxygen and air. Also due to lithium being HIGHLY reactive with water.
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  5. #5
    RC Turnbuckle Jr. pavmentsurfer's Avatar
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    Super interesting... its like a comment out of "big bang theory"... over my head but interesting non the less.

  6. #6
    RC Turnbuckle Jr.
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    Quote Originally Posted by pavmentsurfer
    Super interesting... its like a comment out of "big bang theory"... over my head but interesting non the less.
    Nah, anyone who does what you do for a living could understand LiPo failure.

    Using vpr5703's explanation (which was very good) to help clarify:
    Quote Originally Posted by vpr5703
    The typical cause of puffiness is either age, or abuse (or a combo of the two.) As the cells are used, the anode (material that sacrifices ions) naturally degrades, producing oxygen and leaving the Lithium and other element in a useless state. In addition, as usage goes along, the cathode (material that receives ions) slowly starts to produce metallic lithium. The oxygen produced by the anode bonds to the metallic lithium produced by the cathode, again limiting cell usability (by reduced cathode surface area), and creating lithium "rust." (simple oxidation corrosion, similar to when your new aluminum ladder turns dull gray) However, the anode produces oxygen faster then the cathode produces metallic lithium for it to bond to. This means that the oxygen has nowhere to go, and pressurizes the cell, making it puff out.

  7. #7
    RC Turnbuckle Jr. pavmentsurfer's Avatar
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    New question, how come a cell that has puffed slightly, can de-puff (scientific term for sure) when its properly charged again. (to a point... I know thats not true under heightened circumstances)

  8. #8
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    Quote Originally Posted by pavmentsurfer
    Super interesting... its like a comment out of "big bang theory"... over my head but interesting non the less.
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    Quote Originally Posted by pavmentsurfer
    New question, how come a cell that has puffed slightly, can de-puff (scientific term for sure) when its properly charged again. (to a point... I know thats not true under heightened circumstances)
    This I have no idea, but possibly because the anode is recovering some of the oxygen and re-creating it's original chemical makeup. OR under the heat and load of charging, the cathode is absorbing more oxygen, turning into lithium oxide (rusted.) I think the former explanation is probably the better solution.
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  10. #10
    RC Turnbuckle Jr. streetdemon's Avatar
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    Thanks for the great answers, that helped a lot.
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  11. #11
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    Sure, not a problem. I work with Lithium Ion batteries at work every day (cellular telephone technician) so I've learned a lot about the chemistry behind these powerful little batteries.
    Last edited by vpr5703; 11-04-2010 at 07:11 PM.
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  12. #12
    RC Turnbuckle Jr. rag6's Avatar
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    does water make a lipo puff?
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  13. #13
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    Lithium is very reactive to water, but I think that is a different reaction than "puffing"

  14. #14
    RC Turnbuckle Jr. streetdemon's Avatar
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    Putting a LiPo in water doesn't cause any kind of Lithium to water contact, it would burn instantly if that happened. That's why they can catch fire when exposed to air. The chemicals with react with the oxygen I believe.
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  15. #15
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    Sort of. A Lipo WILL react with water because the water accelerates the reaction in the cells that I previously explained. However, a Lithium battery NORMALLY does not have any metallic lithium in the cell itself, it is held in solution by other chemicals. The only way you will get enough lithium metal is to short the cell out or over charge/ discharge it. So its half and half. The water accelerates the reaction, creating hydrogen, oxygen, and lithium metal. Once all this gets hot enough and reacts with what water remains in the cell, it explodes. and VIOLENTLY. I'm sure we've all seen what these things can do. However, most LiPo manufacturers prevent this well enough by sealing the actual contents of the cells in a sealed package. Otherwise, the electrolyte would leak out and you'd have a burning battery before you even got a chance to take it out of the box.
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  16. #16
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    But how many licks to the center of a tootsie pop? ; )

    Good info VPR.
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  17. #17
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    Quote Originally Posted by dtnel
    JUst sucks that it happened to two lipo batteries that I got the same week, same store and they were 5200 mah and 24c.

    One of the posters brings up a good question. If there such a thing as overdraw meaning if a battery don't have enough c's to power a car will it actually hurt the battery or will the car just not go.

    I'm not referring to running a battery below lvc though. my problems occurred with a vxl esc which traxxas sets at 3.2 from the factory so a dip to 3.0 would seem logical under a load from a objective point of view and it would then rest at 3.2 where the esc detected it when it made a draw on the battery before the esc shut it down. So why would perfectly good less than ten cycle lipo batteries puff. They were balanced and charged per mfrs specs and the owner of the hobby shop also got one that week and had twice as many cycles on his as I did and we both use the same chargers, settings and the charger has a built in balancer so those are the same and the same vehicles, motors and escs as well. Just stumped.......
    Unfortunately, because they are manufactured by humans. Remember the Dell/Sony/HP/Apple exploding laptop batteries a few years ago? All was due to some tiny metal flakes inside the battery causing them to short out. Every manufacturing run will have duds, and it's both financially and logistically impossible to test each item (this goes for everything.) WHY did they puff? Water, metal, faulty chemical makeup, faulty separator...It could be a thousand different things.
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  18. #18
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    Quote Originally Posted by dtnel
    YOu are so correct with your response but I give you kudos because you didn't go and blame the user (me) from the get go and see I don't know if your a battery mfr or not but we both didn't rush to judgement as some people (employees) are led to do whether it be as a measure to make themselves look good for their employer due to job performance or what their boss has instructed them to do knowing that he can pin it on his employee and try to make it right which didn't happen when I spoke with him prior to the battery even being shipped to them and it was a hardcase so they had to get it and take it apart which I have disassembled one to repair a balance wire that broke and then sealed it with regular wrap afterwards. I'll just take my dollar elsewhere as most of us do when scorned.

    This thread has been helpful because I had seen a manufacturing process for lipos but never understood the liquid portion of the process but I did see the big thick piece of raw aluminum as it was pressed and pressed and the other steps in making lipo batteries which would be a good watch for anyone interested in knowing how lipo batteries are made. JUst Google "how lipo batteries are made " in youtube.
    Thanks for the kudos. Im not an employee of any battery manufacturer, just a lowly cell phone repair tech who likes to know the workings of the things he works with. I think batteries in particular are very interesting.
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  19. #19
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    Very interesting thread. I have enjoyed reading this one. thanks guys.

  20. #20
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    Quote Originally Posted by pavmentsurfer
    New question, how come a cell that has puffed slightly, can de-puff (scientific term for sure) when its properly charged again. (to a point... I know thats not true under heightened circumstances)


    no, the Lithium Polymer batteries will not de-puff, the puffing generally indicates that charging (or overcharging) has caused a heat issue and damaged the cell (also worked as a Cellular Phone Technician, for Alltel Communications)
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  21. #21
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    Quote Originally Posted by livewire
    no, the Lithium Polymer batteries will not de-puff, the puffing generally indicates that charging (or overcharging) has caused a heat issue and damaged the cell (also worked as a Cellular Phone Technician, for Alltel Communications)
    The cell phone batteries are in hard shell cases. When they puff the metal is permanently distorted. Most of the R/C Lipos (even the hard shell cases) are in soft cases that can return to their shape, although the excess gas will never completely go away.
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  22. #22
    RC Turnbuckle Jr. NStampede Freak's Avatar
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    Quote Originally Posted by pavmentsurfer
    New question, how come a cell that has puffed slightly, can de-puff (scientific term for sure) when its properly charged again. (to a point... I know thats not true under heightened circumstances)
    Trying to de-puff a lipo is like trying to de-burn a piece of wood. Not possible.

    While I am not that familiar with the chemistry makeup of a lipo, it would be safe to assume that a solid compound reacts and produces a gas(oxygen?) when a lipo puffs.
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  23. #23
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    Quote Originally Posted by NStampede Freak
    Trying to de-puff a lipo is like trying to de-burn a piece of wood. Not possible.

    While I am not that familiar with the chemistry makeup of a lipo, it would be safe to assume that a solid compound reacts and produces a gas(oxygen?) when a lipo puffs.
    The third thing it could be other then the first two I posted is also outgassing. The excess oxygen leaks out of the cell from somewhere. I know that NiMH and NiCd batteries have valves in the to contain cell pressure up to a certain point, and then they vent the hydrogen gas out to prevent the cell from exploding.
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  24. #24
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    Quote Originally Posted by dtnel
    THe batteries aren't built with calves in them. THe building process can be watched on youtube. I've watched to process and It's rather neat.

    I have saw a video on youtube where someone put a really tiny hole in THe lipo and pushed the air out and then they superglued It. I thought this was intriguing as well.
    Yeah thats wierd! Personally, I wouldn't puncture one of those cells, but if he has the guts to do it, more power to him.
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    Wow that looks like a crazy project! Please keep us all posted on the progress you make to your truck! Looking very forward to seeing the end result!
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    Last edited by Double G; 02-28-2019 at 09:45 AM.

  26. #26
    RC Turnbuckle Jr. Greatscott's Avatar
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    Quote Originally Posted by Melyssa48 View Post
    Wow that looks like a crazy project! Please keep us all posted on the progress you make to your truck! Looking very forward to seeing the end result!
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    Not be a buzz-kill or anything, but the last post on this thread (before yours) was over eight years ago...
    Last edited by Double G; 02-28-2019 at 09:45 AM.
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  27. #27
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    Quote Originally Posted by Greatscott View Post
    Not be a buzz-kill or anything, but the last post on this thread (before yours) was over eight years ago...
    It was a spambot. He/she/it had changed the link color to the background of the page so it was hard to detect until you quoted it.
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