Help About charging

[Phone charging struggle]

Hi, I'm using Samsung Galaxy Note 3 and Galaxy Note 2 right now. It's original charger is at 5.3V and 2.0A. Few days before I left it at my friend house, and I decided to use my Galaxy Gear S charger which is at 5V and 0.7A. And I just took my charger back, charging and I realized my phone charge very very very slowly (I really mean that slow). Both my Note having the same problem. Even battery percent dropped when playing games.
That's my first problem.

And the second is, I'm using the Gear S charger to my Samsung Powerbank which is at 5.0V and 2.0A input, and 5.0V 1.8A output. Charged full and my powerbank having the same problem, it won't charge both of my phone.

So, is it because I'm using the lower A then my phone and powerbank damaged or something? Is there any way to fix? Like using other charger temporarily?

Thank you for helping. I'm so desperate right now huftt.

 

[girolez]

Hi

All USB chargers (qualcomm fast chargers excluded) charge at 5V (maybe 5.3) . The max rate they can charge a device depends upon the charger's maximum amp output. A note 2 will use,say, 2 amps to charge quickly. If its on and in use, about 1 amp is used to run the phone so it charges at half the speed. If it has only 0.7 amps available, it will discharge when in use and connected to the charger, as you found. (Using a 3amp charger would not help as the phone decides how much current it draws and it would still only use 2 amps max.)

If your powerbank has 1.8 amp output, it should charge one phone reasonably well, but of you connect both, they get 0.9 amps each - not enough to charge them both up when in use if they are using 1amp to run. If your powerbank cannot charge one device, it may be faulty.

The numbers I have given are made up approximations (but about right) just to try and explain, so please don't take them as definitive! As an analogy, think of voltage as water pressure (constant) and available amps as the size of the pipe (if it helps).