RE: battery question
I would cycle the batteries a few times with a good digital charge/discharge charger. If you dont have one you can buy them starting around $100. If after a few cycles you are not getting charge readings within 10% of the pack capacity, say about 540 or better the batteries should be replaced. The BEC circuit in you speed control sensed that the batteries were low and cut off power to the motor to preserve enough power to power the servos. NMHD are good but in electrics Lipos are much better as you can get a lot more capacity for the same physical size. 600 is pretty small evey for a very small electric motor. I have a Funtana electric that I fly with 1100 lipos and I get a solid 15mins of flying time. If I just cruise around I have pushed that to 25 mins.
A warning though.. although new technolgy is making lips safer, for the most part they are still very subject to bursting into flames if they are not charged correctly or are damaged, say in a crash so be sure to charge in a safe place under supervision and only with a charger that clearly states it will charge Lipos.
Best regards,
Randy