Hearing Aid Batteries
Hearing aid batteries come in 4 sizes, from smallest to largest: size 10, 312, 13 and 675. The smallest, the size 10, measures about 3 mm thick by 5 mm in diameter. The largest, size 675, is about 5 mm thick by 11 mm in diameter.
Batteries of this size could power your watch a year or so, but hearing aids use a lot more power than watches. Hearing aid batteries are not like watch batteries in materials or voltage, and they are less expensive than watch batteries.
How quickly the battery is used depends on a number of factors, including the size of the battery. The largest battery, the 675, might, MIGHT, last 2 or more weeks. The smallest battery will generally last between 2 and 6 days. Other factors that affect battery life include how much electrical current your hearing aid draws and how fresh the battery is. If you wear your hearing aid 24 hours a day (not recommended), your battery will not last as many days as someone with the same hearing aid but who wears the hearing aid 10 hours a day.
Modern hearing aid batteries are zinc-air and have a voltage of 1.35 to 1.4 volts. Batteries of years past were mercury and silver oxide and had a much smaller capacity (they didn’t last as long) than current batteries. Most hearing aid batteries stop working when the battery voltage drops below 1.2 volts. Making a digital amplifier of a hearing aid work on these small voltages was one of the hearing aid industry’s shining moments.
Hearing aid batteries are called zinc-air because air is an active ingredient in making the battery work. The colored tab, or sticker, on the battery is designed to keep air out of the hearing aid. This tab prevents air from entering the cell and activating it before it is ready to be used. Removing the tab activates the battery and makes it ready to use in your hearing aid.
Size 10 batteries have a yellow sticker; 312 a brown tab; 13 an orange tab; and 675 a blue tab. Do not take the sticker off until you are ready to use the battery. The tab (sticker) extends the shelf-life of the battery.
Changing the battery is not a big deal, but there are hearing aids designed to be placed and worn in your ear for months before having the aid removed and replaced. In other words, the battery in these extended wear hearing aids lasts several months, and the aids (and batteries) are not designed to be removed by the wearer. There is a trade-off between this convenience of not having to change the battery, but having to keep the hearing aid in your ear 24 hours a day.
Many hearing aids can use rechargeable batteries. Rechargeable batteries have been around for over 30 years and have improved over the years in ease of use and hours of use per charge. However, rechargeable batteries have not become as commonly used as standard zinc-air batteries.
If you want a rechargeable battery, keep in mind that you still need to have a few conventional zinc-air batteries around in case you don’t get your rechargeable batteries charged for some reason, for example if the electricity goes out over night. Rechargeable batteries also need to be replaced occasionally, sometimes every year.