Robin Tichy
Micro Power Electronics

Three cell chemistries currently dominate the growing portable application market: Nickel-Metal Hydride (NiMH), Lithium Ion (Li-Ion), and Lithium Polymer (Li-polymer). While all of these chemistries can address the high-power demands of portable applications — handheld scanners, medical life-saving equipment, and consumer electronic devices — each has unique characteristics that make it appropriate, or inappropriate, for a particular portable device. Choosing the optimal cell can contribute to the success or failure of a product in the field and requires extensive knowledge of the performance profile of cells under consideration, as well as an understanding of the 'real world usage profile' for the device. This profile includes temperature ranges, discharge profiles, charging regimens, expected shelf life, and transportation requirements. Knowing the specific characteristics of each cell chemistry in terms of voltage, cycles, load current, energy density, charge time, and discharge rates is the first step in selecting a cell for a portable application. This paper provides a short overview of the characteristics, strengths, and weaknesses of each of the three cell chemistries.