The Changing Landscape of Hearing Aid Batteries

Not since transistors replaced vacuum tubes, and the drastic reduction in battery size and current drains made headlines, has there been a time where so much has been written about batteries. But now, as we enter a new era of microbattery technology there is much to say – particularly when it comes to hearing aid batteries.

The hearing aid industry is moving “to more differentiated solutions such as rechargeable hearing aids…[R]echargeability was a focus at AAA [2017], with most manufacturers now offering the silver-zinc battery solution from ZPower, which enables the user to recharge their hearing aid every night, with the battery lasting for about 400 charges (ie, over a year). In the medium- to long-term, we believe it is likely that most hearing aids will be rechargeable.”

Understanding Hearing Aid Batteries: Chemistry, Voltage, and Capacity

Batteries are defined by three main characteristics: chemistry, voltage, and energy or capacity. The capacity of the battery represents its specific energy and is measured in Ampere hours (Ah), or for hearing aid batteries, mAh. This is the amount of discharge current used by the battery over time. In an automobile, fuel tank capacity is the number of gallons of gas the tank can hold when it is full (eg, 20 gallons). In a car, this partially determines how far you can drive on a single tank of gas. Similarly, in a hearing aid, the battery’s capacity (eg, 160-180mAh for a 312 zinc-air or 37mAh for a 312 silver-zinc rechargeable) partially determines how long the hearing aid will operate.

Additionally, driving distance is also determined by driving habits and the mileage performance of the automobile. These contribute to the miles per gallon (MPG) used by your vehicle. Some cars may get higher MPG than others, and some drivers may have driving habits that result in better MPG than others. Hearing aids work in the same manner. Batteries have defined capacities that may vary by the chemistry or the amount of energy placed in the cell by the manufacturer. 3-5 Even though battery packaging and size may look the same, the actual battery capacity could differ quite substantially depending on the amount of energy placed in the cell by the manufacturer. Similarly, hearing aids use different algorithms to manage their features, such as noise or feedback management. Some companies and products use different streaming strategies, such as Near-Field Magnetic Induction (NFMI) or 2.4 GHz, and hearing aid consumers have different operational or wearing habits. These all contribute to different battery drain rates.

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