The capacity of batteries is indicated as XXXX mAh (milliampere/hour). If you insert this battery into an appliance which consumes 100 milliampere current continuously, the operating time of the appliance will be around 20 hours mathematically.
Batteries in smart keys usually last between 1 to 2 years. Unusually short battery life may be caused by electromagnetic interference. Avoid keeping your smart key near other electronic devices such as phones, laptops and other screens.
Operating times may vary depending on the conditions in which you use your hearing aid. The most common cause is not letting it breathe after you take off the seal. Ensure at least 60 seconds of air flow before inserting it into the hearing aid.