Low-Power Design Techniques

Years from a small battery.

Spend most of the time asleep. Wake on a timer or pin event, do the work quickly, and go back to sleep. Lower the clock when full speed is not needed.

Turn off sensors and radios between uses with a transistor switch. Unused pins should be set to a defined state, since floating inputs waste current.

Measure real current with a meter in series, because datasheet figures depend on conditions.