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): 6.5×9.4×15.1 CM (2.56×3.72×5.95 inches).