The capacity and energy output of a power bank can differ significantly depending on the device being charged. This variation is influenced by several factors:
 

• Voltage and Requirements: Different devices have different needs. For instance, laptops generally require a higher charging voltage than mobile phones. The greater the voltage boost needed from the power bank, the less efficient the energy conversion, resulting in less energy being delivered.
• Battery Cell Characteristics: The efficiency of a power bank's battery cells can vary at different output powers. Typically, higher output powers decrease energy efficiency due to the inherent characteristics of the battery cells.
• Circuit Design of the Charged Devices: The efficiency of the circuit design within the device being charged also affects how much energy is effectively used. Devices with more efficient circuits will experience lower energy losses, thus utilizing a greater portion of the power bank's output.

In summary, the variability in the capacity and energy a power bank can provide is primarily due to the differing voltage requirements and power needs of each device, along with the efficiency of the device's internal circuitry.
 

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