Designing and Optimizing Battery Systems for Mission-Critical Portable Applications

Medical life-saving equipment, test and measurement tools, and field data collection devices are vital to the modern mobile world. These devices share many common characteristics—they are critical to the tasks involved, often shared by multiple users, and subject to unprecedented power demands. In addition, they are often used in harsh environments, and they are in use for long time periods. As organizations are increasingly reluctant to invest in new equipment, these devices are characterized by longer product life cycles as well. This means they must perform optimally for months, sometimes years. With device sizes shrinking, it is also becoming necessary to supply ever greater amounts of power to ever-smaller form factors.

These market issues mean that supplying battery power to today's portable devices poses design challenges that tax even the most experienced engineers. Portable defibrillators, mobile bar code scanners, complex scientific measuring equipment—all require a high level of technical sophistication from the engineers who design the battery systems.

Battery systems are no longer simply a collection of isolated components, but a complete electro-mechanical structure that plays an integral role in the function of a portable device. Yesterday's "dumb" battery system typically consisted of the battery cells, safety components, and a physical enclosure. However, today's "smart" battery systems offer the addition of a fuel gauge and battery management components that enable communication to the host device. Sometimes these systems also include on-board charging capabilities.

This paper is intended for engineers who may be familiar with designing power systems for plug-in devices, but who are now forced to broaden their expertise into the realm of mobile power supplies.

This primer discusses battery design basics as an integrated system, including cell selection, battery pack characteristics, operating requirements, "smart" battery management, design validation and charger issues.