A: the possible reasons are as below:
1.Inner polarization is big;
2.The pole sheet absorbed water and react with electrolyte, which cause battery buldge;
3.Quality and property problem of the electrolyte itself;
4.The volume of injecting liquid is not enough;
5.The sealing property of the laser soldering is bad, which may cause air leakage;
6.Dust, especially the dust on electrolyte will easily cause short circuit;
7.Anode and cathode sheets are too thick and very hard to put them into the outer shell;
8.Inject sealing problem, the steal ball sealing property is not good, which may cause gas expansion;
9.The outer shell is too thick, and the shell deformation causes the final thickness.