There are a variety of products on the market which provide a power supply for Android devices through the ubiquitous MicroUSB 2 port. These include adaptors for 12V "cigarette lighter" car DC power supplies, adaptors for AC (120-240V) domestic power supplies, solar power supplies, AA battery power supplies, and so on.
One consideration with all such products is the maximum current they can supply. This is generally 500mA at a minimum, but I have seen up to 2 A.
How can we know what current our device will draw, so as to select a power supply which will maximize its recharge rate? What is the maximum current that can be supplied via a MicroUSB connection? How can we know if our device is able to safely use a power supply which can supply more current than it draws?