iPad Air Turns off on its own, new battery installed and charging.

I work in IT and this ipad was given to me by my boss who had given up on it because he knows I’m not afraid to work on circuit boards. It was having this problem so he replaced the battery on it and it didn’t have any effect. It charges just fine, but when you unplug it the battery percentage jumps around randomly (ex. 99%>24%>75%>1%) when you plug it back in it usually will show what I assume the actual battery percentage is. It also (plugged in or not) will turn itself off every few minutes. Is the ipad dead? I know that replacing the logic board will be more than the ipad is worth so I’m probably not going to give that a try unless I somehow find a free or super cheap one.

TLDR;

-Ipad turns off every few minutes (charging or not).

-Charges fine, but battery percentage is erratic when unplugged.

-Battery was replaced with no change.