A new approach to the qualification of lithium-based battery systems

Lithium-based battery systems, including lithium ion, lithium ion polymer and lithium metal polymer, offer considerable promise in telecom systems and have generated a high level of interest in the user community. In a previous paper the authors highlighted the benefits of these technologies and pointed out the criticality of electronic subsystems in realizing those benefits and achieving safe operation. It was also suggested that the introduction of these electronic charge controls brings with it the requirement for a new approach to qualifying such batteries, particularly since they will be widely deployed in conjunction with existing charging systems that lack the advanced communication features that are quite standard in the portable battery field. This paper will discuss the typical features of electronic controls for lithium-based batteries. Additionally, it will suggest a systematic approach to their qualification, and to the qualification of the battery as a whole. Qualification begins with the identification of all possible failure modes and their potential effects on operating safety. It requires an evaluation of each element, such as hardware components, battery management algorithms, the software for implementing those algorithms, and the battery cells. Each of these elements must be separately qualified, then the system as a whole should be evaluated to ensure that all of these elements are working together effectively. Such a systematic approach is vital, but unfortunately the typical approach is to field a few demonstration systems and to approve a technology if nothing bad happens. Rather than leaving these requirements up to individual users, the authors suggest that a standards document is required. This could be produced under the auspices of T1E1, IEC or IEEE. The document should not describe specific tests, but rather a methodology for determining what tests are required, bearing in mind the differences between the technologies offered for telecom use, such as their sensitivity to overcharge or whether they require heating for proper operation. Historically, the introduction of new battery technologies has been accompanied by problems when existing charging methods and equipment have not been adapted accordingly. When properly implemented, the charge control electronics of lithium-based battery systems have the capability to avoid such problems. However, a proper approach to qualification is vital and will allow the full potential of these technologies to be realized.