When using a power bank, energy loss occurs mainly during two stages of the charging process, which affects how many times you can charge your device:

• Conversion within the Power Bank

The voltage from the power bank's battery cells must be converted to match the output voltage required by your device. This conversion through the power bank’s internal circuitry typically has an efficiency of about 82%.

• Conversion within the Device: After the power bank outputs the voltage, your device also converts this voltage to match its own battery cells. This conversion process generally has a similar efficiency rate of about 82%.

Combined Conversion Efficiency

The overall efficiency in transferring energy from the power bank's battery cells to your device's battery cells involves two conversion steps. Therefore, the combined conversion efficiency can be approximated as:

0.82 × 0.82 ≈ 67%

Estimating the Number of Charges

To estimate the number of times your device can be charged using the power bank, use the following formula: 

(Battery capacity of the power bank × Combined efficiency) / Device battery capacity

For example, if the power bank has a battery capacity of 10,000mAh and your phone has a battery capacity of 3,200mAh, the estimated number of charges is calculated as:

(10,000mAh × 0.67) / 3,200mAh ≈ 2.1 times