Zinc-air batteries are the most popular battery system for hearing aids.
These batteries are not rechargeable and are electro-chemical batteries powered by oxidizing zinc with oxygen in the air. These batteries have high energy densities. Sizes range from very small button cells for hearing aids and mid-size batteries used in film cameras, to very large batteries used to power electric cars.
The four popular sizes of hearing aid batteries are size 10, 13, 312 and 675. The vast majority of hearing aids are designed to use one of these four sizes.
These batteries pack considerably more power into a small space compared to mercury, silver-oxide or alkaline batteries because they use oxygen as a source of power. The disadvantage is that they have a limited life once the air activates the battery.
Battery chemistries are interchangeable provided you use the correct size battery. For example it is possible to use the equivalent size silver-oxide battery in a hearing aid, however, the sound quality and battery life will not be as good as with zinc-air batteries.