I purchased a kit for my son for Christmas. Got the quadcopter built and my son plugged in the battery. Smoke immediately came out of the board and then it wouldn't work. Thought my son had plugged the battery in wrong (as we are warned not to in the instructions). Ordered a replacement board, $61 and a few months later it finally came. Built the quadcopter, updated the firmware and had about a half dozen flights. Plugged in the second battery to fly more, making sure it was plugged in correctly. Immediately smoke came out of the board and it died! I checked the second battery and found that the polarity was reversed. The positive wire was negative and the negative wire was positive. The bad battery had fried the flight boards twice. Emailed Flybrix again but it's been 10 days with no response. This is completely frustrating!