Engineering Corner #2
The Basics
All batteries are designed to store and release energy (electrical current) through an electrochemical process or chemical reaction. The workings of a battery are based upon a simple theory: Two dissimilar metals in contact with an electrolyte (acid) will produce a flow of electrons (electricity) between each other when all components are placed in relative contact with each other.
The cycle life and performance characteristics of a battery pack are directly related to the following factors:
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The quality of the cells used in the pack
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The individual cell construction and internal battery cell pack assembly
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Battery pack usage pattern
In all cases, the amount of energy a battery can store gradually decreases due to usage, storage, temperature and lack of proper maintenance.
At GTS, we design and build battery packs using primarily 5 different cell chemistries. These are:
Nickel Cadmium (Ni/Cd) — is a mature and well understood chemistry, but relatively low in energy density (a battery‟s “power-to-weight” ratio). The Ni/Cd is used where long life, high discharge rate and economical price are important. Main applications are two-way radios, biomedical equipment, professional video cameras and power tools. The Ni/Cd contains toxic metals and is environmentally unfriendly, which is why this cell chemistry is used less in our battery packs. Nickel Cadmium cells have a nominal voltage rating of 1.2V per cell.
Nickel-Metal Hydride (Ni/MH) — has a higher energy density compared to the Ni/Cd. Many improvements have been made to this chemistry to replace the use of Ni/Cd. Ni/MH contains no toxic metals. Applications include data collection, wireless communications and laptop computers. Nickel–Metal Hydride cells have a nominal voltage rating of 1.2V per cell.
Lead Acid — is most economical for larger power applications where weight is of little concern. The lead acid battery is the preferred choice for larger hospital equipment,

wheelchairs, emergency lighting and UPS systems. Lead Acid cells have a nominal voltage rating of 1.6V per cell
Lithium-ion (Li-ion) — is used where high energy density and lightweight is of prime importance. The technology is fragile and microprocessor protection circuits are required to assure safety. Applications include data collection, notebook computers and wireless communications. This is the mainstay of battery products that we design and manufacture at
GTS. Lithium Ion cells have a nominal voltage rating of 3.7V per cell
Lithium-ion Polymer (Li-P) — offers the attributes of the Li-ion in ultra-slim variable geometry and simplified packaging. It is newer battery chemistry. Our proprietary NEOCELL ® technology, which was specifically designed for high-rate discharge RF (radio frequency) applications, has shown longer cycle life and capacity performance in extreme temperatures when compared to other Li-P technologies on the market today. At GTS, the main applications are for wireless communications, data collection, and across the industry it‟s used for mobile phones and PDAs. Li-P cells have a nominal voltage rating of 3.7V per cell.
Nickel Cadmium o The positive electrode is called the „Anode‟ and in this case is comprised of a nickel hydroxide active material, pasted on to the current collector (wire mesh) that is sintered
(heated and pressed) to make a plate. o The negative electrode is called the „Cathode‟ and is comprised of a cadmium compound active material, pasted on to the current collector (wire mesh) that is sintered (heated and pressed) to make a plate.
Nickel Metal Hydride o The positive electrode is called the „Anode‟ and in this case is comprised of a nickel hydroxide active material, pasted on to the current collector (wire mesh) that is sintered
(heated and pressed) to make a plate. o The negative electrode is called the „Cathode‟ and is comprised of a Rare Earth Metal
Hydride compound active material, pasted on to the current collector (wire mesh) that is sintered (heated and pressed) to make a plate. o These plates are separated by a thin woven fabric called the „Separator‟ and then wound into a spiral configuration. o This roll is then placed into a metal can, welded, filled with an alkaline electrolyte (KOH) and sealed with the vented safety cap.
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Lithium-ion o The positive electrode is also called the „Anode‟ and in this case is comprised of a carbon or graphite active material, pasted on to the current collector (wire mesh) that is sintered
(heated and pressed) to make a plate. o The negative electrode is called the „Cathode‟ and is comprised of a Lithium metal alloy active material, pasted on to the solid current collector that is sintered (heated and pressed) in<2% humidity to make the plate. o These plates are separated by a thin woven fabric called the „Separator‟ and then wound into a spiral configuration, similar to the above. o This roll is then placed into a metal can, welded, filled with a non-aqueous solution containing lithium salts and sealed with the vented safety cap.
Lithium Polymer o Lithium Polymer (Li-P) battery cells are the next step towards increasing capacity while decreasing a battery pack‟s size and weight, and can be manufactured in various thicknesses and geometric shapes. o Li-P has five times the operating time of the same-sized Nickel Cadmium cell and can be recharged in 1 hour, plus they have excellent temperature properties. o The anode and cathode are layered or stacked upon each other, which allows rapid heat dissipation and gas release, and they are manufactured with environmentally-friendly materials. o Can be discharged at a high rate for short terms.
Thanks to David Rose for this month’s Engineering Corner!
Until next time, stay charged!
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