Some of my LiPo batteries got "puffy" after a few months. Is it still safe to fly them, or should I safely dispose of them?
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$\begingroup$ Defining "safely" is a really hard challenge. I'd fly that battery so long as I could quickly extinguish a fire. Charging it, though, is a different question of safety. Those things can spontaneously combust and LiPo bags don't do a lot of good. $\endgroup$– Kenn SebestaJul 31, 2020 at 20:19
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2 Answers
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You should dispose of them.
A LiPo battery has three parts: the anode (negative plate), the cathode (positive plate), and electrolyte (sandwiched in between the two plates). Electricity is formed by electrons moving from the cathode to the anode through the electrolyte (which helps the electrons flow).
The electrolyte decomposes over time, which results in the formation of elemental lithium and oxygen. Some of it combines into lithium oxide and sticks to the anode and cathode, but some of the oxygen remains a gas. This gas is what causes the puffiness you see.
Oxygen likes to burn, so if you use a puffy battery, the likelihood that the moving electrons will ignite the oxygen is much higher, so once it becomes puffy, you should stop using it and dispose of it.
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2$\begingroup$ Great answer. Does the potential for ignition exist during storage, charging, or use (or more than one of those)? Is it more prevalent in one of those conditions? $\endgroup$ Apr 15, 2020 at 6:23
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1$\begingroup$ @RockPaperLz- Mask it or Casket; I'm interested in the answer to this as well. You should post it as a question $\endgroup$– GalaxyJul 19, 2020 at 1:09
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1$\begingroup$ @Galaxy Your wish is my command: drones.stackexchange.com/questions/1457/… $\endgroup$ Jul 19, 2020 at 8:19
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Puffed batteries aren't going to fly well anyway. Usually, they will suffer from pretty bad voltage sag which will most likely trigger your copter's low voltage alarm and possibly auto-shutdown early. So, ultimately flight time will suffer and on these tiny packs, flight time is already low anyway. There's also a risk of bursting or catching fire if they rupture. Not really worth it as these tiny lipos are kind of cheap and expendable.
Not sure if this applies to your problem or not but... If you want them to last longer, don't store them charged. Most small quads will shut down right around the battery's storage voltage so just leave them until you want to fly again, then charge them just before use. Charged lipos deteriorate much more quickly if they are stored fully charged.
