FYI, I am now running my Jolla on a modified Galaxy S3 battery. The cell has exactly the same size and nominal capacity. From the comparison, and being an electronics engineer who has designed lithium-polymer power supplies and also a battery seller on eBay, I can say that the original Jolla battery sucks big time. If anybody is interested in knowing what should be done to adapt an S3 battery to the Jolla, let me know and I will describe the process (which requires a good deal of manual skill).