Choose the Right Charger and Power Your Gadgets Properly
YOU ACCIDENTALLY LEFT your micro USB charger back at the hotel... 500 miles away. Now it's time to buy a new one. You pick up a cheapie from your nearest electronics retailer and hey, what gives? What used to take 3 hours to charge now takes 12.
Turns out not all chargers are created equal, even if they look similar. Here are some quick buying guidelines that'll save you time and ensure you're using a charger that's optimized for your device's power requirements.
First, some background. Charging power is based on three things: power (P, measured in Watts), current (I, measured in amps or milliamps), and voltage (V, measured in volts). The amount of power is determined by the equation P = IV. In other words, power is the product of current multiplied by voltage. Because larger devices like tablets have substantially bigger batteries than smartphones, chargers designed for the former tend to deliver energy at a higher rate (a higher current).
For example, consider these charging scenarios for the Retina iPad mini. You could use a Lightning connector plugged into a computer (via USB), an iPhone charger connected to a wall socket, or an iPad charger connected to a wall socket. A PC USB charger delivers 2.5 Watts of power (5 volts at 500 mA). An iPhone charger delivers 5 Watts (5 volts at 1000 mA). A Retina iPad mini charger delivers 10 watts (5.1 volts at 2100 mA).
While all of these will charge your iPad, using the USB connected to a PC will charge your Retina mini four times slower than if you used the iPad charger it came with. Conversely, if you use a tablet charger for your smartphone, it'd charge up faster than normal (Note: Some devices like the iPhone will only draw up to 1A of current no matter the charger). If you play mix-and-match with these types of chargers like this, don't worry – you're not going to blow up your phone or anything crazy like that. And the myth that charging your device at a faster rate will reduce the life of your device's battery is false. For some older devices, the higher speeded charger just won't work at all, while newer devices will just charge faster.