Brain board must be powered from L2

Author: sedders123

kit/brain_board/index.md

@@ -22,6 +22,11 @@ The LEDs on the HAT display the current status of the robot and can be used to h
 
 ![brain board assembly diagram]({{ site.baseurl }}/images/content/kit/brain-diagram.png "The Brain Board Assembly")
 
+## Powering the Brain Board
+
+Your Brain Board will not power on unless it's connected to the "L2" port on the Power Board. 
+This is because the rest of the power outputs are disabled until the usercode runs. 
+
 ### Indicators
 
 | LED              | Meaning