Electronic Design
Battery Options For Embedded Applications

Battery Options For Embedded Applications

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.

Q: What are the driving factors on selection of mobile power applications?

A: There are a variety of factors that influence the selection of the portable power solution. A few of the main considerations are the energy and power requirements of the device, how the end user will be using the device, the mechanical design objectives, and cost. For example, the amount of energy required over a given time period is an important consideration. If the energy required by the device is relatively high, then a larger battery that stores more energy would be a reasonable starting point. High energy requirements may also cause the primary battery to be replaced too often which may be unacceptable to the end user. There are similar considerations for power requirements. Some systems are better than others at delivering high power, and within the same chemical system larger batteries typically have better power capability.

Mechanical design constraints are another important consideration. Some devices lend themselves well to cylindrical batteries. For example, a power tool, where the batteries are typically in the handle. Other devices, like cellphones, favor thin, flat batteries.

Cost is another important consideration. Primary battery solutions, for example, are generally less expensive for the OEM than a secondary solution. The primary batteries are usually less expensive than rechargeable batteries and the designer also eliminates the need for a charging solution, which adds cost to the rechargeable solution.

Q: How do designers choose between primary and secondary battery solutions?

A: The main considerations are how and where the device is used, how much energy is required in the application, and product cost. Designers look to primary battery solutions to keep the cost of their device low to reach a broader market. As mentioned earlier, if the device requires relatively large amounts of energy in a short period of time, this can lead to having to replace a primary battery too often which may be unacceptable to the end user. For these types of applications, rechargeable batteries may be a better solution. It is also important to look at how and where the device is used, because for many applications, recharging is simply not convenient. An example of this is the handheld GPS device. Since this device can be pretty critical to an outdoorsman and there is no way to conveniently recharge the device in the sorts of places you tend to use it, many of these devices are powered by primary batteries.

Energizer's Product Technical Support team routinely works with OEM customers to help them select the right battery for the application. It is important to note that we are not only battery experts; we also design devices, like flashlights and chargers, so we also have experience in selecting batteries as a device designer.

For clarification or specifications on any technical aspect of Energizer products, designers can visit our website at: http://data.energizer.com, or they can e-mail our Product Technical Support team at [email protected]

Q: How can intelligent battery control affect choices?

A: Intelligent battery control can lead to longer battery life, a better performing device and the opportunity to provide more information about the battery to the user, such as fuel gauging. This is an area where Microchip Technology and Energizer are working together to develop better solutions for device designers.

Q: Can application analog requirements affect the power supply choice?

A: The voltages required in the application can often times influence the designer to pick particular battery systems. Li Ion rechargeable systems at 3.6V, for example, make it easier for designers to provide higher voltages to their device. Designers also use multiple battery solutions of AA, AAA or AAAA, for example, to achieve higher voltages as well. This need drove the development of Microchip Technology's's MCP1623/4 Single Cell Boost Converter (MCP16xx family of products). This These devices boosts the voltage from a single 1.5V battery to the higher voltages needed in many devicesapplications. Microchip and Energizer are jointly promoting this product with the Energizer MAX Alkaline AAAA, to provide a small solution for device designers that who need higher voltages in their deviceapplications.

Q: What about environmental considerations?

A: Energizer recently completed an LCA (Life Cycle Analysis) of both secondary and primary battery solutions. An LCA is the only way to truly understand the environmental impact of a product. The LCA looks at the total life cycle from raw materials, through manufacturing and distribution, to use and disposal. We used Environmental Resources Management, a global leader in environmental consulting, to conduct the study, and they looked at the various battery systems as they are used in devices by consumers.

The first conclusion of the study was that batteries have relatively little impact on the environment. The other important conclusion was that no single battery type when used in low, medium and high drain electronic devices, has the lowest environmental impact across a wide range of environmental impact categories. Alkaline, lithium, carbon zinc, Li-ion rechargeable, and NiMH rechargeable all offer environmental benefits and shortcomings.

The key to remember here is that if the primary battery would need to be replaced frequently in an application, rechargeable batteries may be a better choice. Generally, designers of battery powered devices are using these batteries appropriately in their devices today, so the perception that rechargeable batteries are somehow more environmentally acceptable has no basis in fact.

Q: What safety issues should designers be aware of?

A: The primary battery solutions that Energizer offers present very little in the way of safety concerns. For toy designs, there is a safety requirement that the battery compartment require a tool to open it. This is to prevent the swallowing of small batteries by children. It is also recommended to build reversal protection into your battery compartment and to limit the discharge of primary batteries below the recommended voltage cutoff. These recommendations greatly reduce the risk of batteries leaking in the device which is a safety concern for users of the device. Another area to pay attention to is battery compartment design. It is important to design the contacts to minimize the risk of cutting through the battery insulation and shorting the battery. Energizer's Product Technical Support team can provide design assistance.

Q: What new solutions are available to developers?

A: Energizer has introduced a number of new batteries that offer designers some unique benefits.

Several years ago, Energizer launched the Energizer MAX Alkaline AAAA. It offers a smaller, thinner and lighter alternative to the AAA and AA, with similar performance attributes and the same relatively low cost. It also offers significantly more energy and power capability that lithium coin solutions, so for designers who are currently using lithium coin, the AAAA may offer opportunities for improving performance or adding features. The Energizer MAX Alkaline AAAA, combined with the Microchip Technology's MCP 1640 Single Cell Boost Converter, is a solution that more and more designers are interested in for their new designs.

Another unique product that Energizer offers is the Ultimate Lithium AA and AAA. Compared to Alkaline AA and AAA, these 1.5V lithium cylindrical batteries are lighter, work better in high drain/ pulse applications, work better at extreme temperatures and have a 15 year shelf life.

TAGS: Mobile
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