Battery Behaviour

Battery is designed for a portable system (devices, NB, PC) to work normally without power source (AC-Adapter), which is related to the mobility of system.
Customers are concerning on how long the system can work only with battery? Battery can be fully charged or not with the full loading on the system? Any abnormal behavior occurred during charge / discharge?
Therefore, to simulate an actual using for battery with system is the way to observe and record the battery behavior (Charge / discharge time, progress of charge / discharge and the power consumption of charge / discharge).