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We work in a supercharged industry of digital hearing aid technology that changes monthly. Each year, hundreds of pages are devoted in HR to the challenges related to new fitting technologies, the advances in directionality, the new world of wireless aids, and the science behind algorithms that are allowing people to hear better. However, this article is about the one tiny device that makes all of these things work: the hearing aid battery. The truth is that, without the zinc air battery, our smorgasbord of advanced digital innovations would not be worth one lick. Hearing aid batteries have played a major role in the evolution of hearing instruments and, in turn, evolved with their needs. In view of this fact, HR asked Serge Traylor of Energizer Battery Company, St Louis; Tom Begley and Ann Rule of Rayovac/Spectrum Brands, Madison, Wis; Frank Wang of ZeniPower, Guang Dong, China; and Elliott Alexander of Varta-Micropower Battery Company, Miami, to provide information via interviews and written answers on the latest technology and marketing trends influencing their industry. Part 1, presented here, examines the technical aspects of the hearing aid batteries in 2008. Power, Capacity, and Quality. There will always be three primary technical attributes on which consumers and dispensing professionals judge batteries: The battery’s performance within the hearing device (ie, retaining the appropriate power level without “motor-boating” or cutting out); Service life (battery capacity); and. Dependability or consistency. Serge Traylor, Energizer Performance and dependability are two aspects that go hand in hand. “People pay a lot for hearing aids, and consumers and hearing care professionals expect the hearing aid to work consistently, battery to battery, package to package,” says Tom Begley of Rayovac/Spectrum Brands. He points out that experiencing a quality problem with a hearing aid battery—which costs a tiny fraction of the hearing instrument—is something that no one wants to see. Battery service life is also important to consumers; people naturally want a battery that provides appropriate power and long life at a fair price. Battery size constraints limit the amount of material—and hence energy—packed into the metal “can” of the battery cell. The challenge for battery manufacturers is what to do with that space to maximize performance and get more active ingredients inside the can without risking product failure. “In general, all hearing aid batteries are very similar,” notes Serge Traylor of Energizer Battery Company. “But there are some obvious distinguishing features between brands, such as the number of air holes and tab sizes. Internally, there are also some differences in chemical formulation, materials used, and physical design of the parts.” All electronic features consume energy. As more features are added to a hearing aid, more energy is consumed. Therefore, battery life and hearing aid features have a kind of yin-yang relationship. The goal of most hearing instrument R&D departments is to engineer their devices for a battery life of about 1 week. However, when battery manufacturers come up with new strategies and technologies for extending battery life, it’s more likely the device manufacturers will opt for the addition of more features to their aids before opting for increased battery life. The net result is that battery service life has remained relatively constant. Tom Begley, Rayovac Tom Begley recounts a letter from a consumer whose concerns—aimed at the entire hearing aid battery industry—are reflective of many consumers: Why can’t hearing aids last as long as watch batteries? and. Is there a conspiracy among the battery manufacturers to produce batteries with shorter battery life? The answer to the first question centers on the energy drain characteristics and battery chemistries involved in watches and watch batteries. “[The second question] is a bit like the conspiracies related to lightbulb manufacturers, General Motors, etc,” says Begley smiling. “One of the points in my response was that the Size 10 battery that Rayovac introduced in 1986 had 50 milliAmp hours (mAh). Today, the Size 10 battery that Rayovac makes has 105 mAh. What that means to the consumer is that, if the battery lasted 1 week in 1986, it would last 2 weeks today in that same hearing aid. We’ve literally doubled the battery life in 20 years. However, [this added capacity] has also enabled hearing aid manufacturers to add more features to their devices. In other words, partly due to the increased battery performance, today’s hearing aids offer a lot more benefit and hopefully provide consumers with a better quality of life.” The Mini-BTE Revolution and New Power Requirements. The hearing aid market has changed dramatically in the last 4 years. In 2004, only a quarter (25%) of all hearing aids dispensed were behind-the-ear (BTE) type aids, whereas today more than half (51%) are BTEs, as a result of the smaller open-fit, thin-tube, and receiver-in-canal (RIC) BTEs. Relative to the battery market, it has meant a similar shift to Size 312, 13, and 10 batteries. “These new BTEs use more Size 13 and 312 batteries, [rather] than the smaller A10,” says Frank Wang of ZeniPower. “Our company has seen this change in battery sizes during the last 2 years.” Frank Wang, ZeniPower High power applications. Several new hearing instrument product lines—including offerings from Siemens, Starkey, Phonak, and Oticon—have been introduced with wireless features that connect the hearing aids to each other for binaural processing and/or to peripheral devices. And that requires power. In some cases, lots of it. “Several hearing instrument manufacturers have launched Bluetooth hearing aids, which require a minimum of 6 mA of current drain,” Wang says. “Service life at such high drain levels can be maintained only with the best high-performance batteries. The new class of wireless/Bluetooth products do need higher drain and working voltage, and dispensers can take advantage of ZeniPower batteries, which have a top performance rating due to its patented cathode technology.” Rayovac has also recently developed, in partnership with Phonak, a new high-power battery that was introduced to work where there is a requirement for greater than 130 dB output and/or greater than a 4 mA drain. The new battery line, Rayovac Extreme, was launched at the American Academy of Audiology (AAA) convention in April. “Essentially, the device was designed on the same platform as a cochlear battery,” explains Ann Rule of Rayovac/Spectrum Brands. “It satisfies the high-drain requirements of this new class of hearing instruments.” “Both Rayovac and Varta-Microbattery (XGen) introduced new batteries for Sizes 312 and 13 for this year,” says Elliott Alexander of Varta-Micropower Battery Company. “These batteries have higher power discharge capabilities and are designed to support the new wireless/Bluetooth-compatible hearing aids. If more demand comes to the market [in response to these high-power applications], other battery manufacturers will easily be able to tweak their battery formulations to offer cells with higher power capabilities.” “Over the past 5 years,” says Traylor, “hearing aids have incorporated more features, as the industry tries to make aids more user-friendly. These features—like Bluetooth compatibility—demand higher current from the battery. A few years ago, the IEC added two new tests to the [test regimen], recognizing this shift toward higher-drain digital aids. So, today, there are four tests in the [test regimen], but discussions are under way to remove the two older tests. In addition, there is some consideration to adding a test to represent cochlear aids.” Keeping it simple. Although high-power batteries are vital for some applications, they often confuse people. Some consumers have the mistaken belief that a high-power battery will always be better; however, in hearing aids with standard power requirements, the only difference the consumer will see in a high-power battery is a shorter service life. “It’s important to use the correct battery for the application,” Begley says. “Unless a high-power battery is absolutely required by the hearing aid manufacturer, the dispensing professional or consumer should try a standard battery in the device. If they find poor sound quality, intermittency, or low battery warnings, then they might want to try one of the new high-powered batteries.” Zinc Air: An Almost Perfect Technology. Elliott Alexander, Varta-Microbattery The zinc air battery is a technological marvel. Simply put, if it were not for the pesky holes necessary to drive the chemical reaction inside the battery can, zinc air would be the favorite battery chemistry of the world. However, the holes—which are opened when the tab is removed and allow oxygen to power the chemical reaction inside the battery cell—make the batteries more susceptible to drying out or being affected by moisture. Rust and corrosion. In extremely humid environments, as well as some BTE fittings where perspiration or outdoor activities become an issue, water can be absorbed into the zinc air cell. In some cases, this can lead to the battery shutting off or, in worse-case scenarios, corrosion, bulging, or rusting of the cell. While usually not a problem, several companies have tweaked or are tweaking their designs to be more tolerant of humid environments. “Rust is a very important issue, as it is a leading cause of damage and costly repairs in a hearing aid,” says Traylor. “In addition to corroding the components in the aid, it can result in difficulty removing the battery from the aid and, in turn, damaging the door on the aid. In order to reduce the occurrence of rust in a hearing aid, it is important to use a battery that is less prone to rusting.” The trend toward mini-BTEs has also increased the exposure of batteries to the environment. “The mini-BTEs, because they’re...

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