What's the DC voltage range typically tolerated by modern smartphones?
Think of a replica of Volta's first battery or a potato battery.


In theory: yes

In practice: no

The current required to charge a phone's battery usually exceeds what a Volta type or potato battery can provide. Unless you'd make the battery really large.

What voltage a phone can suffer without damage on its charging port depends on the design. The USB specification ( usb.org/documents ) says 5V +/- 5% but most phones are designed to take up to 5.5 V or higher in order not to be damaged by cheap chargers that output 6V.


  Current is not a big issue


It will be an issue, if the phone draws more current than the battery can deliver at 5 V, the voltage will drop and the phone will decide that its connected to a crappy charger and stop charging. For example, you will be unable to charge a phone with 5 V, 10 mA. It will not simply take longer, it will not charge at all!