Q6: "I own a Hobbico Accu-Cycle which has output charge rates of 50 and 125 mA [milliamperes]," wrote a reader. "Recently I purchased an 1800 mAh [milliampere-hour]-capacity four-cell receiver battery. I read what you said about always charging at the C/10 rate (which would be 180 mA in this example) but wondered if I could charge this new pack at the 125 mA and just settle for less than the rated capacity?"

A6: You probably could get away with it, but I would be uncomfortable with that kind of charging in the long run. It would almost be like saying that the battery was never fully charged but is that all right?

I would prefer that you buy a variable output charger, such as the ACE DDVC, set it for 180 mA, and let it stay on charge overnight, or at least for 10 hours. Then you would have maximum battery capacity available, and the battery chemistry would be happy. The result would be a long-lasting battery pack.

I receive many questions similar to this one; they all involve making do with equipment (chargers) on hand. Many alternatives will probably work, but I recommend the technically correct approach.

Q7: "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?"

A7: 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.

This has been my first attempt at providing FAQs for the readers' benefit. This concept will become a regular monthly column appearing in Model Aviation. It will also be available on the AMA Web site along with the reprints of the entire "From the Ground Up" series.

Although this first set of question/answers was almost entirely about electric power and battery-related items, I welcome your questions on any aspect of our hobby. If I can't answer your inquiries, I'll find an expert who can! I also value your suggestions and criticism of what we are attempting to do in this series. Please share your thoughts!

Direct your questions and suggestions to Bob Hunt at robinhunt@rcn.com or Box 68, Stockertown PA 18083. MA

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