I'm going to write a completre explanation about batteries for powering the control system in R/C planes, I promise I will.

But for now, let me summarize; Be aware that C stands for the capacity of the battery cells in milliamp-hours. 2C means 2 times capacity, 2/c means capacity divided by two.

NiCad; 4c to 10 c current capacity depends heavily on type of cell, some self discharge, 6.5-6.7 volts, reliable but very heavy.
Nimh; 2c current supply, some self discharge, 6.6-6.7 volts fully charged, reliable but heavy for the capacity.
Li-Ion; 2c-3c output, no self discharge, 8.4 volts charged requires regulator, light with rugged case
Li-Poly; 10c-20c output, no self discharge, 8.4 volts charged requires regulator, very light, easily damaged
LiFe (A123) up to 30C output, no self discharge, 7.2 volts drops quickly to 6.6, lighter than Nimh, rugged case, very safe

A123s have the best combination of properties for R/C to give you a dependable simple power source.

TF