In general, it is about the charging problem between the mobile power supply and the device.
1. The voltage is currently a constant voltage source, using the usb interface, the voltage is all 5V. The 850ma marked on the mobile phone charger indicates the maximum current provided by the charger.
2. Small current, relatively long charging time, large current, relatively short charging time. Just like your mobile phone charging, you plug in the usb port of the computer, and you use the charger to charge, is two different times. Because the current they provide is not the same, the laptop usb port, the current is 500ma.
3. The two output currents on the mobile power supply are to take care of different devices. In fact, you can choose a large output current, set a small, should be to take care of a mobile phone a bad heat dissipation equipment, because with a large current will heat more obvious, faster. So the low current is also more appropriate to be careful with digital devices. 4 & 5. Let's answer them together. You don't have to consider these in China, because the indicators are always fixed. The problem of computer usb was mentioned earlier. ps. For desktop computers, many times the front panel usb port is often due to insufficient power supply, resulting in various devices can not be used. So just connect it to the usb on the back panel... Samsung S4 mobile phone charger specifications for voltage between 100-240 volts, 2 amp special charger with fast charging function, charging time is about 2 hours, the output voltage is 5V-0.7A, so