The small-scale vapor compression system based on a mini-channel heat sink was investigated in this work for battery thermal management. The single-factor experiment was carried out to determine the optimal refrigerant charge of the refrigerant cooling battery thermal management system. Based on the optimal refrigerant charge, the influence of different system parameters on thermal management performance was examined. Finally, the system problem was optimized, and the solution was proposed and verified by simulation software. Taking the coefficient of performance (COP) as the performance index, the optimum refrigerant charge of this system was 250 g, which was applied in the following experiments. Then the heating power of the battery module was fixed and the opening of the expansion valve (OEV) was adjusted to investigate the influence of OEV on cooling performance. The result showed that with the increase of OEV, the heat transfer coefficient of the mini-channel heat sink increased continuously, but the battery temperature decreased first and then increased. Thus, there was an optimal OEV to obtain the best cooling effect of the system. The heating power of the battery module was changed, and then the OEV was adjusted to make the temperature of the battery reach the minimum under different heating power conditions. The result indicated that with the increase of heating power of the battery module, the outlet dryness of the mini-channel heat sink continuously decreased, the heat transfer coefficient of the mini-channel increased, and the temperature of the battery also increased. The variation of ambient temperature was simulated by altering the indoor temperature with an air conditioner. The study showed that though the increase in ambient temperature had an impact on the cooling effect, the battery temperature can still achieve sub-ambient cooling even at the high ambient temperature of 35℃. A scheme of increasing condensation area to reduce compressor exhaust temperature was proposed, and the model was built based on AMEsim software for verification. The model analysis showed that the method of increasing the heat transfer area of the condenser can effectively reduce the exhaust temperature and improve the heat transfer effect.