help everyone whats wrong with my brother's gameboy color nintendo?

well maybe it wasn't like it before but when my brother bought it i think it works fine but it got shut off my itself once what does that mean oh and before that my brother tried to use it by using an adapter 3volt dc was written i thought it would be okay but its started few times and then it didn't worked when we used it with batteries it was working fine it occured a problem the power which is a redlight started blinking and when i installed the new batteries in it worked fine a while and then it started blinking again maybe the batteries aren't powerfull enough maybe it needs rechargable batteries guys any suggestion and no it isn't new its old used but it was working just fine before we used the adapter