Just replaced my Gear S3 battery (24$ + 10$ for tools). Excited to get 3+ days back. Links in comments, will report back with new battery life in a few days. : r/GearS3
High Quality Samsung GEAR S3 FRONTIER Battery | LaptopBatteryDirect.net
Battery For For Samsung Gear S3 Frontier Classic LTE SM-R760 SM-R765 SM-R770 - Walmart.com