Here are some pics
Battery compartment on my ND. Not sure about how yours will come in but on mine the bus on the right (under the plastic cover) is a slight limitation.
Current batteries are approx 7 inches wide
Height of the current batteries is approx 10 inches
Width available for 2 batteries is approx 15.5 inches.
I'm limited to 4 pics so I'll post the length in the next reply.