Car won't hold a charge.

[Lokei360]

Ok so my 90 accord was dying randomly for the last few weeks. Figured it was the alternator so went and got one from the junkyard. Put it in and car started right up, but the volts were dropping slowly starting at like 11.4V, over two minutes got down to 9 at 2000 rpms. Very annoyed with Thisbe car right now. Anyone have any ideas? Also car shut right off when I unplugged the negative on the battery.