NiCd batteries, also known as Nickel-Cadmium batteries, are a type of rechargeable battery that have been used for many years in a variety of devices. They are composed of two electrodes, one made from nickel and the other from cadmium. When these electrodes are immersed in an electrolyte solution, chemical reactions create a flow of electrons - this is what powers the device. NiCd batteries are known for their durability and reliability, with the ability to last for up to 1,000 charge/discharge cycles. This makes them ideal for use in a variety of applications, such as airsoft gun AEGs. Additionally, NiCd batteries are relatively inexpensive compared to other types of rechargeable batteries. They also have a low self-discharge rate which means they can retain their charge even when not in use. While NiCd batteries are not as environmentally friendly as other types of rechargeable batteries, they are still a popular choice due to their low cost and long-lasting performance.