15 inch above usually have shorter battery life, it depend on what you do with your notebook, if you use it to online only, try to shift to power saver mode <on battery>, i.e. when you use battery it will automatically change to power saver, it will reduce CPU clock and reduces power used, many application do not required <high performance> setting. If still have problem, please return it to me, I always recommended full testing on each battery, but customer usually want fast, try to save petrol and time perhaps.

You can download batteryMon from passmark, it will indicated how much power your laptop drawing, power draw by laptop in <performance mode> is quite dynamic, can draw 20Watt at one moment and 35Watt at next moment. Power Saver mode roughly draw 20W on notebook, 56Whr battery should give you roughly 56/20=2hours48minutes. At power jack plug in, a notebook can easily draw more than 50W if your notebook have good graphic chip and running game.

*A 10 inch netbook usually draw 8W average, 56Whr will have 56/8=7hours. It can also draw 15W at peak (screen brightness max, CPU stressed to full clock all the while), reduce to 56/15=3hours43minutes.