UPS APC BX1400UI - How to replace the batteries

Requirements:
1) APC UPS BX1400UI - Out of Warranty.
2) Flat-Head Screwdriver
3) Cross-Head Screwdriver
4) Double-Sided Tape
5) Two new batteries. APC replacement battery is "RBC113" (2-batteries kit) or "RBC17" (single battery).
Battery specification is : 12V - 7Ah. Sizes (single battery): 6.5x9.4x15.1 CM (2.56x3.72x5.95 inches).