Electronics/maximum number of Smartphones charged by Power Bank.
Is 4 the maximum number of Smartphones charged by a Single Power Bank?.
If yes, Is it possible to charge Smartphones by a Power Bank greater than 4?.
It depends on the charging power required of the smartphone and the capacity of the power bank.
Most power bank chargers are around 2200 mah of charge which is really only good for one phone. Commercial grade or professional grade power banks can have much greater charge.
Ipads and tablets take much more charge power than smartphones.
So, there are power bank chargers that could handle greater then 4 phones but they are bulky and expensive compared with the nominal charger.
Check the google search for this question and you will find more details and recommendations.
Hope this helps.
PS: Most Power Banks do not fully charge a smartphone because of the tapering off of the charge rate as the phone approaches full charge conditions.