Have a look at our multimeter tutorial
. Scroll down to Example 1 (batteries) and Example 2 (wall-warts).
With a couple of alkaline AA's , the MintyBoost will give you about 1000mAh of charge at 5V. I don't know what the battery capacity of the Droid X is, but you should be able to divide 1000mAh by whatever the capacity is to get the expected percentage of Droid charge you can expect from the AA's. There's a really good discussion of MintyBoost batteries here
Finally, if you post some clear, detailed pictures of both sides of the circuit board, we'll have a look for any assembly problems.