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Which cell keeps your hearing aids running?

Which cell keeps your hearing aids running?

Hearing aids are an essential tool that helps many people with hearing loss reintegrate into society. These tiny devices amplify sound, allowing individuals to participate in conversations, enjoy music, and navigate their daily lives more quickly. But have you ever wondered what tiny powerhouse keeps these devices ticking?
The answer might surprise you. Unlike the rechargeable batteries found in many of our everyday gadgets &apos traditional hearing aids rely on a specific type of non-rechargeable cell: the mercury cell.

Why Mercury Cells?

Despite the environmental concerns surrounding mercury, mercury cells have been a popular choice for powering hearing aid due to several key advantages:

  • Long Lifespan: Mercury cells boast an impressive lifespan, with a typical lifespan of one to three years; this extended life is a significant benefit, especially for users with dexterity issues who might find frequent battery changes difficult.
  • Stable Voltage: Hearing aids require a consistent voltage output to function correctly. Unlike some batteries that weaken as they discharge, mercury cells deliver a stable voltage throughout their lifespan. This ensures optimal performance for your hearing device without worrying about fluctuations in sound quality.
  • Eardrum perforation: A hole in the eardrum can impede sound transmission.
  • Compact Size: Small and lightweight, mercury cells are ideally suited for the discreet design of modern hearing aids. Their compact size allows manufacturers to create comfortable and aesthetically pleasing devices that blend seamlessly into your daily life.
  • Low Current Drain: Hearing aids operate on a shallow current draw. Mercury cells are designed to deliver efficient power at this level, providing long-lasting performance without wasting energy.

Inside the Mercury Cell: A Look at the Chemistry

Mercury cells, also known as zinc-mercury oxide cells, generate electricity through a chemical reaction. Here's a breakdown of the critical components:

  • Anode: Made from a zinc-mercury amalgam (a mixture of zinc metal and mercury). Zinc atoms lose electrons during operation and become positively charged ions (oxidation).
  • Cathode: Composed of mercuric oxide (HgO) mixed with graphite or carbon powder. The mercuric oxide accepts electrons (reduction), transforming into elemental mercury (Hg).
  • Electrolyte: A paste containing potassium hydroxide (KOH) and zinc hydroxide (ZnOH). This medium allows the flow of ions between the anode and cathode, facilitating the electrical current.

The following equation can represent the chemical reaction within the cell:
Zn(Hg) + 2HgO + 2KOH → 2Zn(OH)2 + 2Hg + 2e- As the reaction progresses, the zinc anode gradually dissolves, while the mercuric oxide at the cathode is converted to mercury metal. This flow of electrons creates the electrical current that powers your hearing aid.

Environmental Considerations and the Rise of Alternatives

While mercury cells offer undeniable advantages for powering hearing aids, their environmental impact cannot be ignored. Mercury, a hazardous heavy metal, is discharged into the environment, where it can seriously harm the health of humans and animals. When mercury cells are disposed of improperly, soil and water sources may become contaminated, which poses a serious risk to ecosystems.

Recognizing these concerns, many countries have taken action. Regulations restricting the use of mercury in products like batteries have been implemented in various regions. As a result, the manufacturing of mercury cells for hearing aids has been phased out in many areas. However, existing stock may still be available in specific markets.

Thankfully, advancements in battery technology have paved the way for more environmentally friendly alternatives.

  • Zinc-air Batteries: These rechargeable batteries offer a sustainable solution. They utilize zinc as an anode and readily available air (oxygen) as the cathode. This eliminates the presence of mercury and reduces the environmental footprint associated with battery disposal. However, zinc-air batteries require regular charging, which might be inconvenient for some users.
  • Lithium-ion Batteries: Similar to the lithium-ion batteries powering our smartphones, these options are gaining popularity in the hearing aid world. They boast a long lifespan, often comparable to mercury cells, and are rechargeable, eliminating the need for frequent battery replacements. Additionally, lithium-ion batteries offer a stable voltage output, ensuring consistent performance for your hearing aid. The initial cost of hearing aids with lithium-ion batteries might be slightly higher than those with traditional options. However, the long-term savings on replacement batteries and the environmental benefits can be significant factors to consider.

The choice between mercury cells and alternative options depends on individual needs and priorities. While mercury cells offer convenience with their extended lifespan, their environmental impact is a significant concern. As technological advancements continue, we can expect even more sustainable and user-friendly power sources to emerge, empowering users to enjoy the benefits of hearing aids while minimizing their environmental footprint.

Choosing the Right Power Source for Your Hearing Aid

Selecting a hearing aid is crucial to regaining control over your hearing health. Beyond the device, another important decision involves the power source—the tiny battery that keeps your hearing aid functioning. Your audiologist will guide you through the available battery options, but understanding the factors at play empowers you to make an informed choice.

  • Lifestyle: Consider your daily routine and hearing aid usage patterns. If you prioritize a long battery life with minimal changes, a mercury cell (where still available) might be tempting. These boast a 1-3 year lifespan, minimizing the need for frequent replacements. However, if environmental concerns weigh heavily on your mind or you're comfortable with a charging routine, rechargeable options like zinc-air or lithium-ion batteries offer a greener solution.
  • Dexterity: For some users, talent can be a limiting factor. Handling tiny batteries can be challenging, particularly for individuals with arthritis or limited hand mobility. In such cases, the extended life of a mercury or lithium-ion cell becomes a significant advantage. These options require fewer frequent changes than zinc-air batteries, which typically need charging every few days to a week, depending on usage.
  • Hearing Needs: The severity of your hearing loss and the features of your chosen hearing aid also play a role. More sophisticated hearing aids with advanced functionalities might consume battery power more quickly. Discussing your hearing needs with your audiologist can help determine if a particular battery type can meet the demands of your chosen device.
  • Budget: While the initial cost of hearing aids with lithium-ion batteries might be slightly higher than those with traditional options, consider the long-term perspective. Lithium-ion batteries offer a lifespan comparable to mercury cells, eliminating the need for frequent replacements. Over time, this can result in significant savings. Additionally, some rechargeable options come with charging cases that double as portable power banks, offering added convenience.
  • Environmental Considerations: Mercury cells can be hazardous to the environment if they are disposed of incorrectly. While their convenience is undeniable, responsible hearing aid users should be aware of the ecological impact. Rechargeable options like zinc-air or lithium-ion batteries offer a more sustainable approach.
  • Beyond the Basics: During your consultation, your audiologist might introduce additional factors to consider. For example, some users slightly prefer sound quality with certain battery types. While these differences might be subtle, your audiologist can help you discern potential variations during a trial period.

Ultimately, the best power source for your hearing aid is the one that best aligns with your individual needs and preferences.

By considering your lifestyle, dexterity, hearing requirements, budget, and environmental concerns, you can make a choice that empowers you to experience the full benefits of your hearing aid. Remember, your audiologist is a valuable resource throughout this process. Feel free to inquire and share your priorities to ensure you find the perfect power source to keep your hearing aid running smoothly.


While the future of hearing aid batteries undoubtedly lies with environmentally friendly alternatives like zinc-air and lithium-ion options, we shouldn't diminish mercury cells' role. Their long lifespan and compact size revolutionized hearing aids, allowing people with hearing loss to experience a newfound connection with the world around them.

However, mercury's environmental impact necessitates a shift towards sustainable solutions. Thankfully, advancements in battery technology have paved the way for powerful and eco-friendly options. As these technologies evolve, we can expect even more user-friendly and environmentally responsible power sources to emerge, empowering individuals with hearing loss to enjoy the benefits of clear sound while minimizing their environmental footprint.

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Dr Harshi

Dr. Harshi, is an accomplished Audiologist with extensive expertise in treating individuals with hearing impairments.
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Frequently Asked Questions

Traditional hearing aids typically rely on mercury cells, which are non-rechargeable batteries known for their numerous advantages. One significant benefit is their long lifespan, lasting between one to three years, which minimizes the need for frequent battery changes. Additionally, mercury cells provide a stable voltage, ensuring consistent performance of the hearing aids. Their compact size allows them to fit seamlessly into discreet hearing aid designs, and their low current drain ensures efficient power delivery for the devices.
While convenient, mercury cells pose a significant environmental concern due to the hazardous nature of mercury. Many countries have implemented regulations restricting their use, leading to a phase-out in some regions.
Zinc-air batteries are a rechargeable option that utilizes zinc and air (oxygen), making them a more sustainable choice, though they require regular charging. On the other hand, lithium-ion batteries, which are similar to those used in smartphones, offer a long life and are also rechargeable, albeit with a slightly higher initial cost.
When selecting batteries, consider several factors. Lifestyle is important; long-life options like mercury (if available) or lithium-ion batteries might be ideal for those who prefer minimal changes, while rechargeable batteries provide an eco-friendly choice for those who are comfortable with a charging routine. Dexterity is another consideration; users with limited hand mobility might benefit from longer-lasting batteries such as mercury or lithium-ion. Hearing needs should also be taken into account, as more sophisticated hearing aids may drain batteries faster. It's essential to discuss your specific needs with your audiologist to ensure compatibility. Budget plays a role as well; although lithium-ion batteries might have a higher upfront cost, they can offer significant long-term savings due to fewer replacements. Finally, for environmental considerations, rechargeable options like zinc-air or lithium-ion are greener choices.
Your audiologist is a valuable resource. Discuss your needs and preferences to find the power source that best suits your hearing aid and lifestyle. They can guide you through the available options and address any questions.