Hi,
Since it is getting older it is more likely to lose more power!
Firstly check your battery health! If it is below 80 percent than condsider a new Apple Watch!
If not try this:
- Turn off as many notifications as possible
- Turn off background app refresh except for the extremely necessary one!
- Turn off data (if you have it) and WiFi
- Turn on optimised battery charging
- Try deleting some apps
Also if none of these helps don’t wear it overnight just charge it and then it will last you the whole day!
As a last option you can see if you can get your battery replaced!
All of these helped my battery life a lot!
The series 4 is only meant to last a day and a half (18 hours)
If this helped please say so and mark this post as helpful!