All of a sudden, my quadcopter started having a very short flight time. It used to be up to 12 minutes or so, but now it is only 5 minutes at the most. It is small, so it uses a 3.7 volt 650 mAh lipo battery. Is there something wrong with how I'm charging it? There is a charger that has normal and fast rates, and I normally use fast charging. Normal takes about 1 hour and 15 minutes, and fast takes only 40 minutes.