Nickel Cadmium Batteries (NiCd)

“NiCd” or“NiCad” is the chemical abbreviation for the composition of Nickel-Cadmium batteries, which are a type of rechargeable batteries. NiCd batteries contain the chemicals Nickel (Ni) and Cadmium (Cd), in various forms and compositions. Typically the positive electrode is made of Nickel hydroxide (Ni (OH) 2) and the negative electrode is composed of Cadmium hydroxide (Cd (OH) 2), with the electrolyte itself being Potassium hydroxide (KOH). NiCd batteries are made in a wide range of sizes and capacities, from portable sealed types interchangeable with carbon-zinc dry cells, to large ventilated cells used for standby power and motive power.

What’s specific about NiCd Batteries?

NiCd batteries are different from typicalalkaline andlead-acid batteries in several key characteristics. One of the main key differences is in cell voltage. A typical alkaline or lead-acid battery has a cell voltage of approximately 2v, which then steadily drops off as it is depleted. NiCd batteries are unique in that they will maintain a steady voltage of 1.2v per cell up until it is almost completely depleted. This causes the NiCd batteries to have the ability to deliver full power output up until the end of its discharge cycle. So, while they have a lower voltage per cell, they have a more powerful delivery throughout the entirety of the application. However, some manufacturers make up the voltage difference by adding an extra cell to the battery pack. This allows for the voltage to be the same as the traditional type batteries, while still retaining the constant voltage that is so unique of NiCd Batteries. Another reason the NiCd batteries can deliver such high power output, is they have very low internal resistance and that’s why they are capable of discharging a lot of power very quickly, as well as accepting a lot of power very quickly.

Application:

Sealed NiCd cells were at one time widely used in portable power tools, photography equipment, flashlights, emergency lighting, hobby R/C, and portable electronic devices. The superior capacity of the Nickel-metal hydride batteries, and more recently their lower cost, has largely supplanted their use. Furthermore, the environmental impact of the disposal of the toxic metal cadmium has contributed considerably to the reduction in their use. Larger ventilated wet cell NiCd batteries are used in emergency lighting, standby power, and uninterruptible power supplies and other applications.

Charging instructions:

Run down fully once per month to avoid memory effect. Do not leave the battery in the charger. NEVER short circuit a NiCd to drain as this causes excessive heat and can cause hydrogen gas to be released

Storing tips:

Be sure to pick a dry, cool place, with temperature range between −20°C and 45°C.

Advantages:

• Rugged, high cycle count with proper maintenance
• Only battery that can be ultra-fast charged with little stress
• Good load performance; forgiving if abused
• Long shelf life; can be stored in a discharged state, needs priming before use
• Simple storage and transportation; not subject to regulatory control
• Good low-temperature performance
• Economically priced; NiCd is the lowest in terms of cost per cycle
• Available in a wide range of sizes and performance options

Shortcomings:

• Relatively low specific energy compared with newer systems
• Memory effect; needs periodic full discharges and can be rejuvenated
• Cadmium is a toxic metal. Cannot be disposed of in landfills
• High self-discharge; needs recharging after storage
• Low cell voltage of 1.20V requires many cells to achieve high voltage

The standard NiCd remains one of the most rugged and forgiving batteries but it needs proper care to attain longevity. NiCd have memory effect that causes a loss of capacity if not given a periodic full discharge cycle. The battery appears to remember the previous energy delivered and once a routine has been established, it does not want to give more.