Even with the newest generation of batteries, the larger size batteries will last longer than the smaller batteries. Therefore, in the smallest hearing aids (the "In-the-canal" types), you would have to change your battery more often that the larger aids ("Behind-the-ear" types.)

Two numbers are necessary to estimate how long a battery will last in your particular hearing aid. First, the particular battery's capacity is taken from the manufacturer's information. The capacity is like the size of the gas tank on your car. Battery capacity is measured in milliamp hours.

The second number you need is the battery "drain" for your particular hearing aid. Every aid uses electrical power at a different rate because of its particular components. The drain can be compared to the amount of gas sent to the engine of your car as you step on the gas pedal. Battery drain is measured in milliamps per hour.

Your battery's life is then calculated by dividing the battery's capacity by its drain. This number gives you the total hours (approximate) that your battery should last.

To figure out the days it should last, the usual calculation is to divide the total hours by 16 -- the estimate of how many hours your hearing aid is on each day. This number is only an estimate, because your use of your hearing aid may vary. You will know after you begin using your instrument how long the battery will actually last under your conditions for wearing and use