To calculate Hours of Operation, the Nominal Capacity of the Battery (in Milliamps) is divided by the Total Current Consumption Rate of the items being powered by the battery. Example: An 800mA battery (.8Amp) is being used to power a black and white board camera that consumes 150mA per hour. Divide 800mA by 150mA to yield 5.33 hours of operational power use. Note: Peak battery performance diminishes as it reaches the end of the estimated opera- tional cycle. To ensure uninterrupted power performance, replace the battery 15-30 minutes prior to the end of cycle.