The NiMH battery technology used in Sleepbuds II has a track record of more than 30 years in consumer and medical products. The particular cell we selected for Bose Sleepbuds II allows for the tiny bud size needed for side-sleeping comfort, the power needed for all-night playback and the reliability and safety Bose customers expect.The battery technology used in the original Sleepbuds offered high-energy capacity in a small, safe package; however, during the product’s time on the market, a number of customers experienced issues with their Sleepbuds not charging fully and/or powering down unexpectedly. As a result of researching the issue, we decided to discontinue the product. Electronics have become meaningfully more efficient in the past few years. This allowed us to achieve the battery life required for the all-night use case, with the less-energy-dense and proven reliability of an NiMH battery in Sleepbuds II.