I've been through all the threads here regrading this issue and could find a solution :(
I bought the Attopilot current sensor from Sparkfun:
I added the 3.9Kohm resistor in AN0 (and only in AN0) and i can't get the reading right. I am getting 0.63V-0.64V (correlating to 12.5V in full battery) in the Mission Planner.
I check the voltage that comes out of the sensor and its somewhere around 7V.