I very recently bought a new Samsung Galaxy watch and initially the battery power was decent but in the last week it has been overheating while charging, then not charging, then when it on occassion actually charges to 100% last only about 7hrs before its 0%. I dont use most of the apps that drain, I have optimised the battery usage, rebooted etc but its still the same. So frustrating and unreliable. Really starting to regret moving from a Garmin now.
Thank you for reaching out. I would be happy to look into this further for you. Can I please have your full model number and serial number/IMEI in a private message: http://bit.ly/2JH2rq2
For battery drain and charging issues, you can try a different charging cable. You can also try doing a complete backup and reset of the watch.
If the issue persists, service is recommended. For service options, you can send the full model code and the serial number or IMEI number in a private message. http://bit.ly/2XERsky