I am fairly new to flying drones. My new 3DR Iris drone does not retain charge. I bough the drone and the batteries couple of months ago and I have flown them about 5 times so far. After I put the battery in within minutes the voltage as read in the handheld radio controller comes from 10+ volts to 6. This is before I have even started flying!! I have two batteries and the same happens for both of them. As this is happening for both batteries (both bought new) I am suspecting that the problem may be in the drone itself. Any ideas what the problem might be?