3000mAh Battery for Sony PlayStation Dualsense Edge Controller, New Upgrade High Capacity Replacement Battery for Sony PS5 Dualsense Edge Wireless Controller with Repair Tool Kit

It was pretty simple - ifixit has good instructions. I think I flubbed it once and the USB port didn't match up with the shell. Reseated the battery more carefully and it was a perfect match. Sony OEM battery says it's 1050v mAh. Replacement is 3000 mAh. So it's a decent upgrade if you're willing to crack open your controller.