I have a Coolpix 2100 I bought a couple years ago. It's totally fine for most of my purposes. However, for a couple months now it requires extremely new batteries or else it shuts off saying the batteries are dead. However, I have a battery tester and they're still strongly in the "good" category. It shows my rechargeables as dead no matter what. It seems to be getting worse, too. In other peoples cameras these batteries still give people hours of use.

Anyone have any ideas? Do I need to just get a new camera?

Unfortunately, it sounds like your camera is done for. I can't think of any reason why batteries that have a good charge wouldn't work. Have you tried another set of batteries? That would help you decide absolutely that the camera, and not the batteries, are the problem.