You can roughly estimate the runtime using this formula:
Runtime (hours)=Battery Capacity (Wh)×0.8/Device Power Consumption (W)
Notes:
This is only an approximate calculation. Actual runtime may vary depending on usage and environmental conditions.
This method works best for devices with stable power consumption, such as laptops, fans, phone or tablet chargers, and small humidifiers.
It is not suitable for devices with variable or high startup power, like air conditioners, refrigerators, or freezers.