Oasis 2 battery charge life was never great, especially if you read more than 1 session per day separated by 30 minutes or more, but anyone buying one should make sure it doesn't update to 5.13.x
https://www.mobileread.com/forums/sh...d.php?t=335150
It does have really good to great battery charge life if you frequently go days without turning it on, since it hibernates. It can go weeks or months with only a few percent loss. Hibernating and waking up use a significant amount of battery, but nothing compared to whatever nasty bug is in 5.13.x