title_body: In what situations do puffy batteries pose a risk of ignition? In this Drones and Model Aircraft SE question, Is it safe to fly LiPo batteries after they get &quot;puffy&quot;?, David O. asked if it is safe to use puffy LiPo batteries.
  Gparyani provided an excellent answer, which was upvoted and accepted.
  To further understand the issues and risks involved, I would like to ask:
  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?
upvoted_answer: The risk of a puffy battery exploding during storage is still comparatively low, you shouldn't underestimate it however.
  During charging the risk of explosion is at its peak. This is also the reason why you charge your batteries slower than you discharge them (i.e. to lower the risk of puffing and explosions, as well as to keep wear and tear low).
  During use, the risk is quite high as well, though I'd say it's lower than while charging.
  Always, always get rid of them as quickly as you can. Exploding LiPos are not a joke. Besides, a puffy LiPo has a far lower total capacity, rendering it basically useless for flying anyway (though don't be fooled - the explosion is still more than dangerous).