One stupid mistake I made was using my 12v charger on my 1/8 starter box for input voltage. It has a gel pack 12 volt battery. It does charge my batteries, to a point. I forgot to check the battery voltage and started to charge my lipos. It was telling all my batteries were charged, but the heli wouldn't lift. After some testing, if found I ran my 12v battery down to 4.7 volts. The charger was telling me they were charged. Make sure you use a good 12 volt source. Most car batteries are 12.6 NEW. If they are good, they will have higher surface charges above this. If I charge from a car, I try to charge from a running car so I wil have above 13 volts of input for the charger that constant. Since I have the Thunder Power 2100 LiPo, I run a 2 amp charge rate.