1. AC Question's Avatar
    Most power banks comes with li-ion or polymer cells with a rated voltage of 3.7V.
    The standard input voltage of smart devices is 5V so power banks need an output of 5V to charge smart devices.
    If I want to figure out how many times a 5000mAh rated power bank(lets assume that power bank really have that capacity) can charge my xiaomi mi4 (3080 mAh ) what calculation do I need to make?

    For example do I use the following calculation or i need to do something differently?
    5000mAh*3.7V=18.5Wh
    18.5Wh/5V=3.7Ah=3700mAh
    3700*0.9=3330mAh
    3330*0.9=2997mAh

    so 2997mAh/3080mAh=0.97 time

    in first time 0.9 means 10% loss from boost converter in the power bank and second 0.9 means 10% loss from smartphone circuitry.
    03-28-2016 04:42 PM
  2. H3aTeRzz's Avatar
    Hi & Welcome to the Android Central Forums!

    Hope this helps!

    https://www.quora.com/Power-Banks-1/...ge-an-iPhone-6

    Don't forget to register with us, its free & easy!!

    Chris
    03-28-2016 05:46 PM
  3. billthompson84's Avatar
    Hi, it really does depend on the size of the battery in your phone. And also keep in mind that the power ratings that manufacturers quote, is often not the ACTUAL power figure.

    I'd recommend checking out this online power bank / phone mAh calculator:
    Power Bank Phone mAh Calculator - Power Bank Expert

    Simply enter in your phone, and do the calculation to see how many times a 5000 mAH power bank will recharge your phone. For instance, it will recharge an iPhone 6 roughly 1.8 times
    08-12-2017 06:32 AM
  4. Rukbat's Avatar
    The page that Bill Thompson linked to seems to have taken account of it, but remember, never allow a lithium battery (of the type used in cellphones, anyway) to discharge to less than 40%. That includes the battery in the powerbank. Regular discharge until the phone shuts off can kill a lithium battery in a few months. Regularly using a powerbank to charge a phone until the powerbank is fully discharged can kill the battery in the powerbank in a few months.
    08-12-2017 12:47 PM

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