AC/DC Battery Pump has a built in Lithium battery. Its plug and play. That means when the power goes out, it automatically switches over to battery power and remains operational. When the power swithes on again, the pump remains on and charges the battery. Very simple and easy to use. Even if you are multiple days without power. Voltage:AC 110V-240V/50Hz Battery: DC 3.7V 5200 mAh Power: 8W Air Flow: 2×4.5L/min Presure: 2×0.02Mpa Sound <30db The A-15D is more powerful than the A-12F. So it will work even when you use it for a pond. The A-12F has a larger battery and uses less power than the A-15D – this means its the best unit for very long power outages.