Different batteries are based on different chemical reactions in order for them to provide power. Hearing aid batteries are most commonly Zinc-Air batteries. Advances in zinc-air chemistry and battery cell engineering make it possible to provide more consistent power in ever-shrinking cell sizes.
Rayovac, one of the largest manufacturers of zinc air batteries, recently stated that they believed zinc air batteries “would probably be the most widely used battery type in the world, surpassing even alkaline batteries in popularity, if not for one problem: “those pesky air holes”.
Zinc-air batteries rely on exposure to air in order to work. The cell design involves some small air holes on the positive surface of the battery, which allow air into the battery and commence the chemical reaction that makes the battery work. The paper sticker attached to the battery blocks these air holes, so that the battery is idle. The removal of the sticker exposes the air holes, and allows air into the cell so that it can now power up.
So what is the problem with those holes?
Having holes in the cell make zinc-air batteries more susceptible to external environmental factors, and, once that sticker is removed and the battery is activated, the clock starts ticking on the zinc-air battery; it has a defined life cycle that cannot be stopped.
Environmental factors that can affect Zinc-air battery performance include:
- Humidity: low humidity can dry out the cell and shorten battery life, and high humidity can increase moisture uptake in the cell, causing it to swell / leak, again shortening battery life.
- Temperature: as temperature is reduced, the voltage is lowered in the battery, and it can reach its functional end point sooner.
- Altitude: as altitude increases, the oxygen left in the air is reduced, thus lowering the battery voltage again, and reducing its life.
In addition to the environment, there are many features in today’s hearing aids that can substantially affect battery life. These can include:
- Noise reduction algorithms
- Multi-channel processing
- Wireless capabilities between the two hearing aids and / or between external microphones or devices like TVs, stereos, cell phones and MP3 players
- Power requirements (hearing loss dependent)
If you would like to read more about factors affecting hearing aid battery performance, check out this article from the hearing review which has a great handout, also available from our clinics:
http://www.hearingreview.com/practice-management/21731-hearing-aid-battery-consumption-issues-a-consumers-guide