Capacity (Wh) is the energy stored in a battery. Wh is Watt x hour.

Power (W) is the speed of drawing the stored energy. W is Watt.

Maximum Power (W) is specified in the battery's specifications. The combined power draw of all equipment powered from the battery should not exceed its maximum power limit.

For example:

The Globalmediapro Li160S-II V-Mount Battery has a capacity of 158Wh and a maximum power limit of 150W.

A camcorder draws 30W, and a camera light draws 20W. The combined system power draw is 30 + 20 = 50W. You can safely use the battery to power the camera and light since the combined system power draw of 50W is lower than the maximum power limit of 150W.

The 158Wh battery will last 158Wh / 50W = 3.16 hours

To power the 50W system for 5 hours, you would need a capacity of 50W x 5 hours = 250Wh

In general:

battery operation Time (hours) = battery Capacity (Wh) / system Power draw (W)
battery Capacity (Wh) = system Power draw (W) x battery operation Time (hours)

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