A:Answer Hello Kibria,
Thank you for your interest in our SlimLine 800W Power Inverter, in regards to your inquiry, we believe there might be some misunderstanding as to what this device does. This device is an inverter that will convert DC 12V power into 120V AC power and will operate and run for as long as the power provided can sustain. The Device needs to be connected to a 12V power Source such as your vehicle's Battery, and the amount of times that the inverter can charge your laptop will depend on the battery size and capacity that the inverter is connected to. (For a Layman's term perspective, it would be like asking how long a Flashlight [that requires batteries] will run. The answer would be: it depends on how long the batteries will last. This is the same for the inverter, the inverter will work always, but it will only power for as long as the battery it is connected to can supply power).