Hearing instrument batteries work different than your normal every day battery (AA, AAA, C and D batteries). These batteries come with a little sticker over the back of the battery.
Before you place the battery in the hearing instrument, make sure it is fully active by leaving it out of the hearing instrument for 1 to 2 minutes after the sticker has been removed.
There are four types of batteries: 10 (yellow), 13 (orange), 312 (brown), 675 (blue). These four colors represent each size of batteries and the colors will not change (example: 675 batteries will always have blue on the packaging somewhere). Hearing instrument batteries charge can be affected by your environment. Different environments can cause the battery to lose some of it’s charge. Batteries kept in change purses with coins, a pocket with keys or other metal objects could short out a battery. Humidity also affects the life of a battery, you do not want to store them in a bathroom (shower) or kitchen (cooking) where the humidity is higher. The best place to keep them is in a night stand in a bedroom. Here is a video by Rayovac that will answer some of your questions and concerns on hearing instrument batteries: