Batts are probably for the -48V power plant. Line voltage is fed to the rectifier and then that sends voltage to batts, and equipment power is picked from batts and passed to the PDU for distribution to equipment.
Sort of in a round about way a UPS..... --
"Saying something in another language that you don't think the other person understands is just saying that you're a pussy and are too afraid to say it in English." --Harddrive