New owner, new questions

Received to got an 08 Prius with 151k miles the dash read hybrid battery dying.
Well a lot of posts I read say it could be many problems like t
Just the 12volt needing replaced. The car runs great mostly but every now and again the engine revs really high and the acceleration is null. The electric motorr and batter stop relaying as well (according to the screen) was wondering what some experts here