phone charging help please

[mitchdublin]

Hi, Im building a multiple mobile phone charging station using usb hubs. Most phones are 5v and draw 500ma to charge.
If i want to charge 500 phones at the same time, how much input would i need. We use 240v with 32 amps coming into office.
Would that mean that i could only charge 64 phones? or am i missing something here. I know the office supply can run lights, pcs, air con, heaters, microwaves all at the same time. I must be calculating the draw of a mobile incorrectly, i didnt think a mobile charger used much power?
Any help really appreciated.

[I_Daniel]

One phone at 500 milli-Amps x 5 volt is 2.5 watt.
Your input/available wattage is 240V x 32A = 7680 Watt

From this you could do some further calculations. i.e 2.5W x 500 = 1250 Watt.

Remember to take the transformer losses into account and add about 20% to 25% to the 1250 Watt.

The point you are missing is that it is the available input wattage (or K V A) and the output wattage used to charge the phones.
Think of a desktop computer with a 300 Watt power supply. The fuse is usually 2 amps and the 5 V output is rated at about 35 amp and the 12 Volt output at about 12 Amps.

Unless it is in a factory I doubt whether there is ever any need for 500 chargers.
Another thing to remember is if charged from a PC via the USB then the amps available is about 80 Milli-amps per USB Port. But check the specifications of the USB Port.

[mitchdublin]

Thanks for your help, im trying to build a mobile charging unit for outdoor festivals. Most phones will work on the 24 usb hubs that i have. only the iphone needs a computer connected to hub to power it. Trying to sort that now.