Battery Options For Embedded Applications

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Primary and secondary batteries

Batteries are central to the success of mobile devices. I recently spoke with Jon Eager, Director of OEM Marketing for Energizer Battery Company, based in Westlake, Ohio. Jon will be hosting a session for Electronic Design's Embedded Designers Forum entitled How Does Your Design Fit Into Smart Energy?. Sign up now. In the meantime, Jon was good enough to fill me in on the challenges and options for powering embedded applications.

Q: What are the most common primary and secondary battery solutions?

A: Within the primary battery systems the most common are the 1.5V alkaline batteries (AA, AAA, AAAA, C, D, 9V). These are widely available at retail and are relatively inexpensive for the designer to use. Another type growing in popularity is the Energizer Ultimate Lithium AA and AAA. Energizer introduced these 1.5V lithium cylindrical batteries over 15 years ago. They are more expensive for the designer, but offer significant advantages versus the alkaline batteries. The Energizer Ultimate Lithium batteries are lighter, work better in high drain/ pulse applications, work better at extreme temperatures and have a 15 year shelf life. The 3.0V lithium coin batteries are another relatively common solution available to designers. These are thinner, smaller, and lighter than the alkaline and lithium cylindrical batteries and consequently have much lower energy and power capabilities, and are used in relatively small devices with lower energy and power requirements.

Within the rechargeable systems, Li-Ion Prismatic is the most common system. Prismatic refers to the thin, rectangular construction of the battery. Voltage of the system is typically 3.6V depending upon the chemistry of the system, and a variety of shapes and sizes are available for designers to choose from. Li-Polymer offers thinner form factors than Li-Ion Prismatic, with similar performance characteristics. There is also a cylindrical version of Li- Ion that offers much better rate capability; this type is used in notebook computers and power tools, for example. There are also 1.5V NiMH rechargeable batteries; these are available in both cylindrical and prismatic sizes. These batteries continue to be used in a wide variety of applications, but have lost share to Li-Ion systems over the last 15 years.

These are the most common types of primary and secondary batteries (Fig. 1) that are used in portable electronic devices.