The recombination process of the evolved oxygen during the sealed cells recharge is presented in the form of two interrelated mechanisms. The first one is accounted for by absorption of oxygen on the pore surface of the negative electrode, oxygen entering through the pores which are free from electrolyte. The other mechanism takes place due to forcing the electrolyte out of the electrode and a separating plate smaller pores and recombination of gas on the surface of the negative electrode pores freed of electrolyte. Based on solution of the equation system obtained, the analysis has been made of cell gas pressure and volume changes of electrolyte forced out of the pores, depending on geometrical and structural characteristics of the electrodes, separating plates, negative electrode surface activity, and other parameters. In particular, it is shown that the less is flooding of the negative electrode pores by the electrolyte forced out of the smaller pores (the better are the buffer properties of the system), the lower is the inside cell pressure. Gas pressure significantly decreases when the recombination process mainly occurs by the second mechanism.