Nickel-Cadmium or the Ni-Cd rechargeable batteries are a type of alkaline storage battery, classified as a secondary battery. As the name suggests, they are made from two chemical elements, nickel hydroxide, cadmium and an alkaline electrolyte, which is usually a solution of Potassium Hydroxide.
Invented in I899 by Waldemar Jungner of Sweden, their practical application was only made possible after 50 years, with the development of the sealed battery by Frenchman, Neumann.
The Ni-Cd batteries are used in a variety of applications all over the world. They comprise of a positive electrode plate that uses nickel hydroxide as the main material, and a negative electrode plate that uses cadmium compound as the main active material.
There are two varieties of Ni-Cd batteries: sealed and vented. The smaller sealed variety is used in toys and other portable electronics. Specialty Ni-Cd batteries are used in wireless and cordless telephones, old motherboards, laptops cell phones and other applications. These batteries can supply high surge currents making them perfect for use in remote-controlled cars, boats, airplanes, camera flash units etc.
When compared to other rechargeable batteries, Ni-Cd is beneficial in many ways. They are strong and cannot be damaged easily, with the ability to withstand deep discharges for longer periods. They also have more endurance to the charge and discharge cycles. These batteries are lightweight and smaller even when compared to the lead-acid battery, making them a preferred choice in aircrafts where size and weight are crucial factors.
However, there is one drawback, if you can call it that. Ni-Cd are known for their “memory effect.” Memory effect is when batteries “think” that they are fully charged even when they are not. If your battery is about 80% charged, it thinks it is 100% charged, and due to this thinking, does not charge any further even when placed on the charger. The problem is that when gadgets with Ni-Cd batteries are used, they last for a shorter time because of being charged less. This problem mostly affects older batteries and not the brand new ones. However, there is a solution to this memory effect – that of performing a “full recharge cycle,” which is to let the gadget discharge completely before recharging it again. For example, recharge only when your cell phone starts beeping.
Now that the memory effect has been taken care of, let us look at some more benefits of Ni-Cd rechargeable batteries. They can be used for as many as 500 full recharge cycles, which is on the higher side. The charge is also retained for a longer time when not in use. Losing only 1% of charge per day takes almost four months for the battery to be completely discharged.
In spite of the Ni-Cd batteries costing more, having slightly lower voltage and the memory effect; their demand has not diminished because they have a significantly longer total lifetime than alkaline cells, which is what consumers look for when buying batteries – a long lasting battery.