Mobile phone adaptor

Hello friends,

Today I had a mobile phone adaptor for repair.
I replaced a fried resistor (2.2 ohm).
Now that I measure the voltage of the output of the adaptor there is 4.8V while there is a register on the adaptor that says the out put is 4.5V.
Since the mobile phones are using li-po and li-ion's so I want to know if the adaptor output is safe for mobile phone.
Is there any kind of regulator in the mobile phones to control the input voltage for the battery?

Thanks

Don't worry about 0.3V, that's pretty good for a mains adaptor. The off-load voltage is 50% higher than the rated value. This seems too good to be true but it's probably a small switch mode power supply.