Power Conversion & Efficiency Calculated

Mobile power supply capacity is directly related to battery capacity of mobile device. Assume you  have a 5000mAh battery pack to charge an iPhone 5 (1440mAh). Using the mathematical sum of  5000/1440 to identify how many times a device can be charged, figures indicate it can be charged  3.47 times, but the actual use is 2.36 times. Why is this?

The reason for this is because the battery cell voltage is 3.7 – 4.2V, whilst the mobile device is  charged at 5V. This results in power transfer loss. Battery capacity conversion calculations:

§ Mobile power capacity x Product conversion efficiency (75~90%) = Actual discharge of  capacity

§ Actual discharge capacity x Conversion efficiency (85~90%) = actual charge capacity  into apparatus

§ Actual charge capacity / unit build battery capacity = actual charging time

Power Bank Charging Times

Power bank charging times will vary with the external power supply used. For instance, the majority of desktop and laptops use a USB2.0 (5V/500mAh) or USB3.0 (5V/900mAh) output, whilst a standard wall charger may use a (5V/1A) or (5V/2A) output. In these examples, the (5V/2A) output  will charge fastest. Action under 5000mAh Power as an example:

§ 5000mAh / 500mAh (USB2.0) / 0.85(Energy conversion efficiency) = 11.76 hours

§ 5000mAh / 900mAh (USB3.0) / 0.85 = 6.53 hours

§ 5000mAh / 1000mAh (AC) / 0.85 = 5.88 hours

§ 5000mAh / 2000mAh (AC) / 0.85 = 2.94 hours *Above is based on theoretical calculations as due to battery energy losses