Battery bulge?

[Ris Liam]

I am wondering if this battery's slight bulge is just part of this wired battery or an actual issue. It seemed to charge fine and had a no load voltage just over 4 volts after a full charge. Let me know what you think. 1816118160 Battery is a TCSS Panasonic 18650 3400 mAh

[RavenXp]

Hmmm... that looks to me like the cell is deforming and pushing the protection PCB out. You said this cell was from 2015? How was it stored? Was it stored at half charge, fully charged, or completely drained?

[Ris Liam]

Stored in various states. I usually had this charged and used slightly, then put away. I don't think I've used this cell for at least 1 year before charging it recently.