I have two batteries 12V GEL 130Ah, each charged to 14.4V. After connecting them together in parallel, the voltage drops gradually and equalizes at 12.99V. (I use 10mm^2 short cables to connect them together so I wouldnt expect much of a drop at the cable.)
I would expect voltage to stay the same. Why does the voltage drop occur? Does it mean that the battery bank is somehow faulty?