This study aimed to develop the small-scale experiments involving electrochemistry and the galvanic cell model kit featuring the sub-microscopic level. The small-scale experiments in conjunction with the model kit were implemented based on the 5E inquiry learning approach to enhance students' conceptual understanding of electrochemistry. The research tools consisted of (1) four small-scale experiments involving electrochemistry, which were oxidation and reduction reactions, galvanic cells, cathodic protection of iron nails, and connecting batteries in series, and (2) the galvanic cell model kit with the ability to generate various galvanic cells. The data collecting tools included (1) a conceptual test of electrochemistry and (2) the mental model drawing of a galvanic cell. Thirty-four grade 12 students participated in the series of four 5E learning activities for a total of 10 hours. Paired samples T-test analysis revealed that the mean scores of the post-conceptual test (mean 36.63, SD 7.69) was statistically higher than that of the pre-conceptual test (mean 21.51, SD 6.83) at the significance level of 0.05. In addition, the mean scores of the post-mental models in both the macroscopic (mean 3.56, SD 1.30) and sub-microscopic features (mean 5.98, SD 2.93) were statistically higher than those of the pre-mental models (mean 1.85, SD 1.11 and mean 2.20, SD 2.45) at the significance level of 0.05. Prior to intervention, most students were in the categories of less correct conceptions, Partial Understanding with Specific Misunderstanding (PMU) to No Understanding (NU). However, after the intervention, they moved to the categories of more correct conceptions, Partial Understanding (PU) to Sound Understanding (SU). This indicated that this intervention can enhance students' conceptual understanding of electrochemistry and mental models of galvanic cells.