Gabrielle Filips

Gabrielle Filips, AuD, is an educational specialist at Siemens Hearing Instruments, Piscataway, NJ.

Batteries are the lifeblood of many electronic devices; however, most people only think about batteries when it’s time to change them. And, unfortunately, hearing aid wearers think about batteries all too often. In fact, as many as 45% of the 2008 MarkeTrak VIII survey participants rated the battery life of their hearing aid to be less than satisfactory.

Today’s digital hearing aids offer greater technology and more features than previous generations. These improved capabilities also can drain battery life more quickly, forcing wearers to change batteries more regularly. To ensure the best experience with hearing aids, batteries need to be powerful, user friendly, and convenient. In essence, the less wearers think about their batteries, the better.

To meet these challenges, rechargeable batteries have undergone an extensive technology overhaul to become a convenient, affordable, and environmentally friendly alternative for hearing aids.

Evolving Technology

Rechargeable hearing aids have been around for more than 30 years, but an honest appraisal of this technology leads one to conclude that they have achieved nominal success. There are several reasons for this. Some of the charging stations used for rechargeable hearing devices were difficult to operate, as they would work only if the hearing aid was placed in a very specific position—a difficult task for wearers with dexterity issues. In the past, concerns and drawbacks for rechargeable batteries included their size, circuit limitations, and perceived reliability. With all of these restrictions, rechargeable batteries have been overlooked in favor of traditional zinc-air batteries.

In recent years, rechargeable batteries have undergone much technological advancement to improve the life of the battery. The two main options available for battery technology are the nickel-cadmium (NiCd) cell and the nickel-metal hydride (NiMH) cell.

The NiCd cell has been determined to be not as environmentally friendly and also has a “memory effect.” Memory effect refers to the fact that, with some rechargeable systems, performance time is based on “memory” of previous time durations prior to being recharged. With batteries that have a memory effect, over time, a battery typically recharged while still at half capacity could lose capacity and not last as long as an identical battery that is consistently exhausted before being recharged.

The NiMH battery has been deemed to be a better option for rechargeable hearing aids. NiMH provides approximately double the power per package as compared to NiCd. Additionally, NiMH batteries do not contain any dangerous heavy metals, such as mercury, lead, or cadmium, and are therefore more environmentally friendly.

Along with choosing the appropriate battery technology, battery size is considered when designing the optimum rechargeable solution. The size 675 cell has been used in prior rechargeable options; however, current cosmetic demands (eg, ITCs and mini-BTEs) dictate that a smaller cell size is required. As a result, NiMH battery technology provides improved power levels in smaller sizes, including 312 and 13 cells, that were not previously available.

Another advancement made in rechargeable battery design is the discharge behavior. Discharge behavior refers to the rate and transition from full battery capacity to the cutoff voltage where it ceases to supply power. The discharge with the NiMH rechargeable battery is very smooth and consistent, similar to the zinc-air battery. Additionally, as NiMH batteries have no memory effect, there is no negative impact on daily use by recharging a battery that is not fully discharged.

Benefits of Rechargeable Batteries Spur Increased Adoption

The new eCharger from Siemens supports 20 rechargeable BTEs from the Pure RIC & Motion families.

As a result of these advancements in battery technology, perceptions about rechargeable batteries are beginning to change, and their use is increasing at a more rapid pace. Consumers routinely use rechargeable batteries in nearly every portable device, including mobile phones, cameras, and other high-drain battery-powered devices. The cost savings and other benefits associated with rechargeable batteries have spurred their adoption in many industries—including hearing aids.

The long list of benefits associated with rechargeable batteries is guiding an increasing number of hearing care professionals and wearers to this option.

Greater comfort and ease of use. According to the American Speech Language Hearing Association (ASHA), hearing loss is the third most prevalent chronic condition in older Americans. Age-related health complications and diseases that numb the fingertips and decrease dexterity, such as arthritis, diabetic neuropathy, and Parkinson’s disease, can make opening battery packages, accessing the battery compartment, and guiding the battery into placement a very frustrating—and sometimes painful—experience.

For these wearers, rechargeable batteries can improve their quality of life, as there is no need to deal with small batteries on a regular basis. With rechargeable batteries, the hearing aids can simply be placed into a charger at night, and wearers wake up every morning with freshly charged batteries ready for their daily use.

Environmentally friendly. Rechargeable batteries are significantly friendlier to the environment than their disposable counterparts. Batteries expose our environment and water resources to lead and acid. Over a 3-year time span, two digital hearing aids will require, on average, the disposal of more than 300 hearing aid batteries. Conversely, within the same time span, two hearing aids will use an average of only six rechargeable batteries.

Cost-effective. A common misconception in the hearing care community is that rechargeable batteries are a cost-prohibitive solution. However, over time, traditional zinc-air batteries may cost more than batteries that are recharged over and over again. For example, a single zinc-air battery costs an average of $1. Assuming the typical binaural wearer changes both batteries once a week, costs can exceed $300 during a 3-year time period. In comparison, a 3-year supply of rechargeable batteries and one charging station can be purchased for under $200.

Peace of mind. For many hearing aid wearers, there is a persistent fear that their hearing aid battery could die at an inopportune time—creating a stressful, embarrassing experience. Because hearing aids with rechargeable batteries are charged every night, wearers don’t have to worry about whether their batteries are going to last throughout the day. Additionally, wearers who use rechargeable batteries do not need to remember to purchase new batteries or locate them when they are needed.

Flexibility. Since committing to the sole use of rechargeable batteries in hearing aids may be too restrictive for certain people, some hearing aids now allow for both rechargeable and zinc-air batteries. This flexibility is crucial as a backup for circumstances without power or if wearers forget to charge their batteries.

Long shelf life. Most of the rechargeable batteries on the shelves today are protected with a strong, high-quality seal that ensures that the battery does not dry or drain in a premature manner—a possibility with zinc-air batteries. Plus, according to tests, rechargeable batteries have a higher capability to withstand severe conditions and climates.

Chargers Designed for Ease-of-Use and Longevity

The eCharger’s Electronic Drying Function also protects hearing instruments from moisture damage.

Rechargeable batteries were designed to increase the ease-of-use of the hearing aid and create a better experience. The same special care must also be taken with the design of the charging station to ensure an effortless recharging process.

Recent rechargeable systems incorporate many advantages for the hearing aid wearer in an intelligent and efficient package. These state-of-the-art charging units have the dual functionality of recharging the hearing aids while dehumidifying them with an electronic drying function, which will prolong the life of the hearing aids. The aids are simply placed inside the charging cavities of the charging unit. The battery doors do not need to be opened, nor do the batteries need to be removed. When the hearing aids are detected, the charger will turn them off automatically to eliminate any risk of feedback while charging.

In addition to ease-of-handling, the optimum rechargeable solution must avoid overcharging and also maintain a high number of recharge cycles. In contrast to inexpensive pen chargers, current chargers use a microprocessor-controlled multistage procedure that varies the charging current as a function of the ongoing charge of the battery. In the beginning, a very high charging current is applied to ensure optimum charging speed. Approaching the complete charge of the battery, the charging current is reduced stepwise to avoid overcharging. Thus, both optimum speed and high safety are achieved.

Chargers for reusable batteries are also available with modular designs that include an outer case and an insert. The insert differs based on the battery size, allowing professionals to stock one base and a few inserts to accommodate any hearing aid they may be fitting.

Rechargeable Batteries Poised for Continued Success

Although the history of rechargeable batteries in hearing aids has been one of limited success, with recent technology advancements, rechargeable batteries now provide many advantages to hearing aid wearers. Rechargeable batteries are now capable of powering the industry’s most advanced hearing aids. Wearers enjoy the reliability and many other benefits offered by these eco-friendly power sources.

To keep pace with the latest hearing aid innovations, such as Bluetooth wireless technology, hearing aid manufacturers are tasked with developing products and accessories that have low power consumption. This would allow rechargeable batteries to last longer on a single charge and may reduce charging time. Likewise, to further meet the demands of consumers regarding size, convenience, and functionality, manufacturers of rechargeable batteries need to continue developing innovative solutions to power these tiny high-tech devices.

The future of rechargeability will focus on packing more power into smaller designs so that all hearing aids—including waterproof aids—can take advantage of this power option. Charging stations will also continue to evolve to accommodate greater energy efficiency and smaller battery designs.

Rechargeability is here to stay, and given time, exposure, and education, hearing care professionals and consumers alike will take greater notice of today’s rechargeable hearing solutions and all the advantages they offer.

Correspondence can be addressed to HR or Gabrielle Filips, AuD, at .