cell phone charger wattage
cell phone charger wattage
What do the figures and symbols in a charger mean?
The input of the charger is 230V~±10%/50Hz/21mA/4.8VA…
While the output of the charger is 3.7V /355mA…
So what do these figures really mean?
How much power (watts) they produce to charge a cell phone battery with 3.7V?
How long does it take to charge a cell phone battery with 3.7V?
I know it must produce 1.3135W to charge the cell phone battery but is this wattage right? I’m still very confused because I only based my answer in its output power… Please help me.. I really need the answers… Thank you guyz and God bless…. 
The ~ means alternating current (AC). The plus or minus is the tolerance, meaning that it is okay if the power varies that much. So it can vary 10% or in this case 23 volts. So anywhere from 207 – 253 volts is acceptable. The 50Hz is the frequency of the alternating current; the number of times the polarity switches back and forth per second. The 21 mA is 21 milliamps, or 0.021 amps. VA means volts times amps or volt amps, so that is basically the input wattage (technically, there is a difference because of the sine waves of AC and RMS, but we don’t need to go there). The 4.8 VA part is the input wattage. They got the 4.8 figure from multiplying the 230 volts with the 0.021 amps (and rounding).
You are right that the output wattage is 1.3135 watts. That is obtained my multiplying 3.7 volts by the output current of .355 amps (355 mA, must convert the units).
Yes, it is correct to base your answer only on the output. How much the transformer requires is irrelevant to what the phone requires. The input parameters could have been for the US, 120V~±5%/60Hz/40mA/4.8VA. The output parameters could have been made the same as what you gave, even in that case.