RE: When is the power too low on the TX?
charcoaldabs,
I agree with Psikelly, to a point. Going to the last green light is okay if your fly, hovering or crashing, say within about 40 or 50 feet.
If you go beyond that range, you may be asking for trouble. Play it safe and keep fresh batteries in the TX.
You may consider rechargable batteries, most of the flyers do. It's less expensive in the long run.
I purchased an Energizer rechargable system, Inital cost 19 dollars, comes with charger and 4 double A, 2500 mAh batterys. Yep, not enough batteries. 10 bucks more for an addition 4 batteries. Pays for itself in just a few months.
See attached Picture,
Dave / Choppersrule