An influence of the open-circuit standing time after oxidation of the lead electrode was investigated for understanding charge acceptance of the negative electrode of a lead-acid battery. It was confirmed by a potentiostatic transient experiment that charge acceptance of the lead electrode heavily depended on the standing time before charging, and charge acceptance decreased if the standing time was longer. This tendency was conspicuous at the initial period of the reduction process in particular. When the behavior of the lead electrode surface during the open-circuit standing after oxidation was observed by in situ electrochemical atomic force microscope (EC-AFM), it was found that some lead sulfate crystals gradually grow with time to bigger crystals having a smooth surface, retaining basically its morphology of previous one. We have concluded that the standing time dependence of the charge acceptance is caused by this behavior of the crystals. Also, it was confirmed that charge acceptance of a valve regulated lead-acid (VRLA) battery with different standing times can be explained by result of the potentiostatic transient test and the EC-AFM observation.