Nikon D90 charger faulty?

So I just picked up a Nikon D90. I went to charge the battery and the charger light is green. Indicating its fully charged. So when I put it back in my camera it says its low. Even after its been on the charger for a couple hours. I checked the battery meter on the camera and seems to be running fine other then being low. Anyone else run into this? I'm thinking bad charger.

Is the charger a Nikon (MH-18a Quick Charger) or a generic?

My Nikon battery chargers light flashes amber until the battery is fully charged and then the light becomes steady.

Probably charger. With my Nikon D90 came a Nikon charger MH-18A. On mine if it's not blinking and solid it's fully charged.

That indicates to me that it's the battery that may be past it's best. Your camera uses a similar battery to the one used in my D100, namely an EN-EL3e (the 'e' probably means an extended life battery to the previous EN-EL3) My camera will accept 2 of the EN-EL3's if I so wish, or it can run on 4 Ni-Cad's, or plain Duracell AA's.

Check out the link below.

More likely a bad battery. A D90 is at the age where battery problems can be common, and especially depends on how well the previous owner used the battery.