Im bought a second hand apple watch series 7 45mm it has 88% battery health like of i charge it to full and then i go to bed after charging it to full whenever i wake up the next morning the battery is around 68-70% is it normal? Or should i turn my watch off while going to bed also i dont overcharge it!
You can’t overcharge a lithium battery, there are many mechanisms in place to make sure that doesn’t happen as an overcharged lithium battery is dangerous (common misconception that leaving a device on charge after it’s at 100% will “overcharge it”). Yes it is normal for a device in standby to lose charge as it is still using power to connect to the phone, WiFi, and cellular (if a cellular model). Also 88% battery health is somewhat low and is usually the point at which I sell my watch for a new model to improve battery life.