why charging time increase using computer USB port
1.your computer's USB port does not deliver a constant amount of power.The amount of power it generates out to your device all depends on several variables,such as the software and hardware on the computer, the amount of USB ports being used,and using your computer while simultaneously charging the device.
2.The other reason that you should charge your device via the wall charger is because these adapters are specifically designed to charge your device at its maximum level.The wall plugs all charge faster than the USB specification of 500mA at 5V (which are the specs for my MacBook; it differs in all computers).
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