Battery grip D300

Just picked one up but it may be faulty.I have one battery for D300 and its barely registering as charged when I have it in grip.Do I need a battery in camera as well for it to function or is this a fault?If it is a fault is it easily fixable?
Thanks for your help.

Mine works fine with a single battery in the grip and no battery in the camera. Although, that might not be the case with all brands and depend on who made your grip. Mine is a Chinese grip off Amazon and is not a Nikon brand...

Thanks for your reply,not sure what make mine is,I sprayed all the connections with Servisol Super 10,scrubbed it with a toothbrush,left it soaking overnight in servisol and now it works..