Battery technology for emergency lighting

The widespread consensus is that electricity, which has been in use since about the middle of the nineteenth century despite having been found much earlier, is one of the biggest discoveries that has had a substantial positive influence on the world's population.

Batteries are commonplace in the sense that they are used everywhere and power a wide range of devices, from little devices like computers and cell phones up to bigger ones like vehicles and vans.

While everyone refers to a chemical device with two or more cells as a "battery," the correct term is actually a "cell," as the word "battery" has military connotations and refers to weapons working together. This chemical device has the ability to store chemical energy, which is converted into direct current. The variety of batteries on the market today is almost limitless, ranging from tiny primary batteries used in watches to enormous secondary batteries with a megawatt capacity used as energy storage to power towns and cities when necessary.

There are basically two different types of batteries, and these can be categorized as either being a Primary Battery, which means it is not rechargeable and is considered to be a "use it and bin it" (but re-cycled, of course) type product, or being a Secondary Battery, which means it is rechargeable and falls into two areas of operation. Batteries of this type are used for electrical equipment, such as watches, clocks, and children's toys. First, there are batteries that can be used to charge and discharge devices like cell phones or laptops, or second, there are batteries that can be charged and then provide power when needed, such in electric cars. With this second type, which is used for emergency lighting, the battery is constantly charged and ready to provide electricity in the event that the building's main electrical system fails by discharging the necessary amount of energy.

For primary batteries, a variety of chemicals are often used, with Alkaline, Zinc/Carbon, and more recently Lithium. These chemicals are known as "dry cells" since they do not need a wet paste electrolyte to allow current to flow. When the technology for lead acid cells was first developed for secondary batteries, all other batteries were of the primary kind. Lead Acid batteries, also known as SLI Batteries (Starting/Lights/Ignition) Batteries, are referred to as "wet cells" because they contain a liquid electrolyte. They come in a variety of sizes, ranging from the smallest 1Ah up to 12,000Ah. This technology has been used to store energy centrally within buildings at a variety of various voltages, supplying power to run Central Battery Systems as necessary for emergency lights.

As battery technology advanced, nickel-cadmium batteries were introduced, followed by nickel metal hydride batteries and, even more recently, lithium ion batteries, which have now taken over as the standard. The voltage that battery cells typically produce ranges from very low voltage to around 3–4 Volts, with bigger voltages and greater current supply being attained by the installation of additional cells. The collective cells produced by the cells put in a parallel circuit provide more current, while the collective cells produced by the cells located in a series circuit produce more voltage, providing a solution for both higher current and increased voltage.

NI-Cd (Ni-Cad) = NICKEL CADMIUM This is one of the earliest battery technologies, and the advantages of these battery types include its excellent reliability, ability to withstand high discharge rates at a variety of temperatures, and extended shelf and operational lives. These batteries produce a voltage of about 1.2 volts using a cathode of nickel oxide (NiOOH) and an anode of the metal cadmium (Cd). The main disadvantage of partial discharge followed by charging is that the battery will lose its "memory," reducing its maximum charge capability over time. Additionally, they can be damaged by over-charging. The advantage of these Ni-Cd batteries is that they have the ability to perform high rate charge and discharge as well as operate within a wide temperature range.

Ni-MH, or nickel metal hydride, is a relatively new technology that makes use of nickel oxide (NiOOH) and a metal alloy. During the charging process, hydrogen is stored to produce metal hydride, which is then released during discharge. This technology has a 3000 cycle life expectancy. Nevertheless, it only has around 60% of the capacity of a lithium-ion cell of the same size. A nickel metal hydride cell can have two to three times the capacity of an equivalent-sized nickel-cadmium battery. As opposed to some of the more antiquated battery technologies, they are said to be ecologically benign because they don't contain cadmium, mercury, or lead.

LI-ION - lithium ion The first thing to note is that there are two types of batteries: lithium and lithium ion. The former is a main battery for one-time usage, while the latter is a secondary battery that can be recharged. In recent years, the industry has seen a revolution thanks to the emergence of the Lithium-Ion technology in the 1970s, which is now used in a wide range of devices, from mobile phones and laptops to all forms of transportation. The cathode, which defines a lithium-ion battery's capacity, the anode, which enables current to flow, the electrolyte, which is made up of salts, solvents, and additives, and lastly the separator, which functions as a barrier to keep the contacts apart. During the discharge process, lithium ions flow from the negative to the positive, then back again while the battery is being charged. It has a lifespan of 500–1,000 cycles since working in conditions with greater temperatures might cause the operation to become unstable.