1.What is battery case ?
-Battery case is a unique power bank,it has a rechargeable power bank built-in
with a protect case shape.So it is suitable for a certain single phone model.
2.How does battery case work ?
(1)It works similar as a power bank.
(2)If power bank has no power or little power,it can't charge a phone,same to a battery case.
(3)When battery case is little power, charge it firstly.
(4)Connect it to a DC 5V usb port (or your PC) by a compatible usb calbe, case can get charged.
(5)Then stop charging the case by removing the cable.
(6)Insert your phone into case properly and press the power button, case would charge your phone
(transfer power from case to your phone battery).
Note: For a few battery cases, you should press the power button CONSTANTLY for 3-5 seconds, case
can charge your phone.If you press and release the button soon, this way can't work case won't charge
(7)When phone is charged, phone battery would get warm in some degree,when you use case to charge
a phone, that is the same.So it is better you don't use your phone when you use case to charge a phone.
(8) charge a battery case
use a battery case to charge your phone
You should do the 2 things separately (one by one), you can't do them simutaneously !
(9)Battery case can't support data sync!
(10) Last but not least: When you browse a title " battery case for iphone 6 plus 5.5" then case is ONLY
ok for ORIGIONAL iphone 6 plus (NOT OK for fake/clone iphone 6 plus).
3.About battery case's power:
(1) If battery case is 4200mah, its true power is about 4000mah.
(2) Battery case can't transfer 100% power to phone battery ( case itself would consume part of power).
(3) Case can transfer about 70-75% power to phone.