Q-6: "I'm concerned about your statement that any Ni-Cd cell will have a nominal (average) voltage of 1.2," commented one reader. "Then you went on in the testing discussion to say that when a four-cell receiver pack gets down to roughly 4.8 volts, it's time to recharge. I question how could the cell have an average of 1.2 volts or 4.8 volts (for four cells) and still need recharging?"
A-6: That is a good and sensible question! Through the years the Ni-Cd battery cell's nominal voltage has been identified as 1.2. I guess it seemed easy way back. It just stuck, and today we refer to a four-cell pack as having 4.8 volts, an eight-cell pack as having 9.6 volts, and so on.
The fact is that a fully charged Ni-Cd cell can reach almost 1.4 volts, so a fully charged four-cell Ni-Cd pack might go as high as 5.6 volts. Considering that fact and depending on that pack's rated capacity, it might take one or two hours to get the voltage down to 4.8, at which time I recommend that you recharge it before continuing to fly. In this regard, the nominal voltage is the minimum voltage before the need to recharge.
This is strictly a point of identification that started years ago and carried through to today. I'm sorry, but I can't do anything to correct this somewhat confusing terminology.