That I'm not sure as I've a D700 with a Nikon MB-D10 - but when I had a ownuser grip for a D40 & that held two batteries but you had to swap them around as it only ran off of one battery...
So, I would imagine that you can have just the one inside as I can't see why not but than again you could always get a 3rd party battery if it needs two to operate (which sounds silly to me if thats the case) but ask the seller he would know more than me on that as its him thats selling the grip... You could bell them on 01158226152 & ask them..