Start with plain distilled water and fill them up to just above the metal plates. You are also going to need a digital volt meter to take some readings from each individual battery. The "gas gauge" style meters aren't accurate enough to diagnose potential problems with the batteries. You may end up having to hook up two batteries at a time to a 12 volt charger (36 volt cart?) to get them charged up enough to even turn the big charger on. Let us know how it goes when you plug it in! Good luck!!
edit: make sure you fill them up before charging. also, probably a good idea to take readings from the pack and posting before plugging stuff in.
re-edit: nevermind. don't listen to me. just saw that it is an RXV. Someone else will chime in with some help!