Rechargeable Battery AA & AAA

Rechargeable battery, pen and half-pen
As you can see, the size of these batteries is AA  and  AAA. The generating materials of these batteries are nickel cadmium and nickel metal hydride. The capacity of the battery is usually 900, 1100, 1800 and 2500 mAh, and half-pen batteries are 380, 600, 850, 900 and 1000 mAh.

Building of Nickel Cadmium Batteries
Nickel cadmium batteries are a subset of rechargeable batteries in which nickel (III) oxide and cadmium are used as metal in the electrode position.

Building of nickel metal hydride batteries
Nickel metal hydride batteries are also battery-protected, with its positive electrode nickel oxyhydroxide and its negative electrode of hydrogen adsorption alloy.

The difference between nickel cadmium and nickel metal hydride is in their capacity. Nickel metal hydride is two to three times more delicate than nickel cadmium.