Project Analog - February 2009 - (Page 10) When it comes to production, reliability, safety, lowcost and easy installation are the important elements while maintaining quality. Each battery chemistry has its advantage over another. This article is intended to assist portable electronic product designers and engineers in selecting the right chemistry for today’s low-cost portable applications with design simplicity. The solutions are ideal for use in space-limited and cost-sensitive applications that can also accelerate the products time-to-market. TaBlE 1 BaTTEry comParisoNs 1 Ion) has advantages in both energy density weight and energy density volume among other available battery technologies. aLKaLine Alkaline batteries are not rechargeable, but are commonly seen as a portable power source because of their low self-discharge rate and they are always ready to use off the shelf. Therefore, they are included in (Table 1 and Table 2) as reference against secondary (rechargeable) batteries. Rechargeable Alkaline batteries are available, but they are not very practical and reliable to use in a system due to their fast degradation after a few charge cycles. sLa (seaLed Lead acid) SLA batteries are mature and inexpensive battery solutions, and have an advantage in low self discharge rate. However, they are not an ideal candidate for portable applications due to their low energy density, low charge/discharge cycles and the fact that they are not environmentally friendly. Contents Viewpoint Selecting the Right dc/dc Converter Selecting the Right Battery System Understanding the Buck Switchmode Power Converter Analog news BaTTery chemisTries There are three key attributes in a battery. 1) Energy Density (Size & Weight) 2) Charge/Discharge Cycles (Life Cycle) 3) Capacity (Operational duration without AC Adapter presence) Like most engineering works, the key attributes do not exist in the same technology. There is always a trade-off between them. In today’s portable world, the product life cycle is very short. Thus, the battery life cycle is a minimal concern for customers and manufacturers. The operating duration, package size and overall system weight become the most important factors when selecting the battery chemistry for a portable application. Batteries usually occupy a considerable space and weight in today’s portable devices. The energy density for each chemistry dominates the size and weight for the battery pack. Table 1 indicates that Li-Ion (Lithium- TaBlE 2 BaTTEry comParisoNs 2 Microchip analog page Sample center microchipDIRECT Reference designs/ app notes Technical training 10 · PRojeCt ANAlog · VolUme 3 / NUmBeR 1 http://www.microchip.com http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=79&redirects=analog http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423
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