The text below comes from the APM copter first time setup, powering the pixhawk section. I believe the last sentence should have said rarely consume more than 90 amps at full throttle.
For most users powering the Pixhawk is as simple as connecting the 6-pin DF13 cable from the 3DR power module into the Pixhawk’s “Power” port as shown above. This will provide a steady 5V and allow the Pixhawk to measure the current and voltage of the main battery. The power module can be used with 3S or 4S batteries (i.e. up to 18V) and 90amps of power (most multicopters draw less than 20amps when hovering and rarely consume less than 90amps at full throttle).