I have found wikipedia useful on the basics, especially around form factor, chemistry, and protection circuitry (or not) in lithium. for example, 18650 lithium

I have found wikipedia useful on the basics, especially around form factor, chemistry, and protection circuitry (or not) in lithium. for example, 18650 lithium cell now popular in flashlights, computers and cars that can be very confusing when it is referenced with protection circuitry and 18650 does not have protection officially. http://en.m.wikipedia.org/wiki/List_of_battery_sizes http://en.m.wikipedia.org/wiki/List_of_battery_sizes