Generally, you need higher voltage going into a charge controller than the battery voltage you are trying to charge (unless you have a boost controller like Paul above). The OP has 48VOC panels, so a max voltage of 2 in series of 96, but when charging will probably fall to around 84V.
A "96V" battery will have a working voltage calculated at 102.4V with a 116.8V needed to top of the charge, so 2 panels will not work for the OP.
