Update power docs with info on how to calibrate

en/SetupView/Power.md

@@ -1,3 +1,43 @@
 # Power Setup
 
-![](../../images/setup/PX4Power.jpg)
+The *Power Setup* screen is used to configure battery parameters and also provide advanced settings for propellers.
+
+![Battery Calibration](../../images/setup/PX4Power.jpg)
+
+## Battery Voltage/Current Calibration
+
+Enter data for your battery/power module from its data sheet: number of cells, full voltage per cell, empty voltage per cell. If provided, also enter voltage divider and amps-per-volt information. 
+
+*QGroundControl* can be used to calculate appropriate voltage divider and amps-per-volt values from measurements:
+
+1. Measure the voltage from the battery using a multimeter.
+1. Click **Calculate** next to the *Voltage divider* field. On the prompt that appears:
+  1. Enter the measured voltage.
+  1. Click **Calculate** to generate a new voltage-divider value.
+  1. Click **Close** to save the value into the main form. 
+1. Measure the current from the battery.
+1. Click **Calculate** next to the *Amps per volt* field. On the prompt that appears:
+  1. Enter the measured current.
+  1. Click **Calculate** to generate a new *amps per volt* value.
+  1. Click **Close** to save the value into the main form. 
+
+## Advanced Power Settings
+
+Click the **Show Advanced Settings** checkbox to specify advanced power settings.
+
+### Voltage Drop on Full Load
+
+Batteries show less voltage at high throttle. Enter the difference in Volts between idle throttle and full throttle, divided by the number of battery cells. The default value should be used if unsure!
+
+> **Warning** If the value is too high the battery may be deep-discharged and damaged.
+
+## ESC PWM Minimum and Maximum Calibration
+
+To calibrate the ESC max/min PWM values:
+1. Connect the vehicle to QGC via USB (only). 
+1. Remove the propellers. 
+1. Click the **Calibrate** button.
+
+## Other Settings
+
+Select the **Show UAVCAN Settings** checkbox to access additional settings for UAVCAN Bus Configuration and motor index and direction assignment.