Dell Alienware M15x Owner's Manual page 70

Battery
Type and dimensions
6-cell "smart" lithium ion (57 Whr)
Depth 53.8 mm (2.12 inches)
Height 21.3 mm (0.84 inches)
Width 213 mm (8.39 inches)
Weight 0.33 kg (0.72 lb)
9-cell "smart" lithium ion (86 Whr) (optional)
Depth 53.8 mm (2.12 inches)
Height 36.9 mm (1.45 inches)
Width 330 mm (12.99 inches)
Weight 0.5 kg (1.1 lb)
Voltage 12.6 VDC
Operating time Battery operating time varies depending on
operating conditions and can be significantly
reduced under certain power-intensive
conditions.
Life span (approximate) 300 discharge/charge cycles
70 CHAPTER 8: BASIC SPECIFICATIONS
Battery
Temperature range
Operating 0° to 50°C (32° to 122°F)
Storage –20° to 60°C (–4° to 140°F)
Coin-cell battery CR-2032