Some batteries may last two weeks, others just two or three days
There are few things more annoying than the unexpected beep in your ear that means your hearing aid battery is about to go dead. This is especially true if you don't happen to have any spares.
Even in controlled studies, the life of a hearing aid battery has proven unpredictable. A 2013 report on wireless hearing aids in Audiology Online found that the real-life performance of most of the batteries tested deviated significantly from the standardized measurements reported by the manufacturers.
A battery for larger or non-wireless hearing aids may last two weeks, while another one for smaller or wireless hearing aids may last just two or three days. In some cases, the battery may be defective, but battery life also depends on the kind of hearing aid you have, how you use it, the kind of batteries you buy, and the assistive-listening devices you may use.