I'm having few issues with chargers, current delivered to a device etc... just need to connect the dots I guess.
When I connect a phone to a charger for example IPhone which is rated at (5v,1A max), to a charger rated at (5v/2A) The phone will only draw 1A correct? what is limiting the current here? is it a resistor in series built inside the phone?
If I'm Building a PowerSupply that has a charging USB port, do I need a resistor before it? or would it cause a short circuit? For example (Voltage source) ---> (LM317 as voltage source) ---> (USB Port) -----> (Phone) do i need a resistor before the USB port or will the phone handle it?
Also, charging a lipo, let us say 1cell at 4.2v maximum, if i set the LM317 to 4.2v and plug the lipo, am i forced to put a current limiting resistor or will the lipo draw as much as it needs as the voltage is appropriate? wouldn't the charger stops automatically when the voltage off the battery be equal to the voltage of the lipo? 4.2v ---- 4.2v so no current will flaw?
Long Question short, is the current limiting resistor built in the batteries or do I need to place one? wouldn’t the charging stops automatically due to Vin = V of battery?