In this paper, a smart control circuit with breakdown and charging completion detection to implement a power-off function for a lithium-iron phosphate battery charger is proposed. The smart control circuit of the lithium-iron phosphate battery charger has a simple structure and its advantages are as follows. (1) When the lithium-iron phosphate battery is fully charged during charging, the control circuit can implement the power-off function of the lithium-iron phosphate battery charger. Therefore, it can effectively increase the life of the lithium-iron phosphate battery. (2) In the event of a short circuit or under a low voltage condition, the control circuit can rapidly turn off the power source of the lithium-iron phosphate battery. (3) By incorporating a simple sensing circuit, the fault conditions in the lithium-iron phosphate battery during charging can be easily detected. Therefore, it can effectively decrease the probability of electrical accidents. Additionally, the charging status of the lithium-iron phosphate battery is shown by LED indictors, which allow users to easily determine fault conditions. Finally, a 51.7 Vdc and 150 W prototype of the lithium-iron phosphate battery charger is built and implemented. Experimental results are presented to verify the performance and feasibility of the smart control circuit with breakdown and charging completion detection to implement the power-off function for the lithium-iron phosphate battery charger.