The TV•Ears^® Battery Replacement is a small rechargeable battery found inside the TV•Ears^® Headset (Version 5.0). The batteries are expected to last up to 6 hours per use on a full charge. We recommend that you change the battery when you begin to experience a decrease in the typical operating time. The normal lifetime of our batteries is around 1 to 2 years before a replacement is needed. The TV•Ears^® Battery Replacement is only compatible with the TV•Ears^® Headset (Version 5.0). Please call us toll free at 888-883-3277 before you purchase this product so we can help you to make sure a battery replacement is needed.