THE FIRST ROUND of input regarding the "From the Ground Up" series ended with "Advanced RC Systems," which was published in the February 2004 Model Aviation. During the almost-one-year period of this series, Bob Hunt and I have received many letters from readers that contain detailed follow-up questions and concerns.

The volume of these letters makes it impossible to answer every one personally. I try to respond to as many as I can, but there is never enough time in the day. The alternative is to sort through and select the more important questions and then, as I am about to do, provide an article addressing the most frequently asked questions (or FAQs, as I'll call them!).

This will be my first time doing this, and as a result the questions have been edited to save a great deal of space. Many of you write pages and pages to ask one question. I won't identify any readers by name or location (my choice).

The subject matter will be random; questions could be about Radio Control (RC) equipment, electric power, model building, model flying, etc. In this first FAQ article, most of the questions involve batteries, battery testing, and battery charging. It is the major source of concern and causes the most problems for the average RC flier.

I'm going to number each question sequentially. It is hoped to eventually expand on this FAQ concept and provide a search capability on the AMA Web site so you can seek out specific subject matter. Here we go!

Q1: In my "Battery Basics" article (in the October 2003 Model Aviation) I wrote the following: "The advantage of trickle charging is that the batteries are available the moment you want to fly. However, you can only maintain a charge level at trickle; you can't recharge a battery that has been used at the trickle charge rate."

A reader was confused by the words "that has been used." He went on to point out that after reading this, he assumed that after returning from flying he should only put the battery on trickle charge!

A1: I have to admit that including those four words was an error on my part and most unfortunately changed the sentence's entire meaning. It is no wonder my reader friend was confused. The sentence should have read: "You can't recharge a battery at the trickle charge rate."

You only use trickle charge (which is a low level) to maintain the charge in a battery that has already been fully charged at C/10 overnight or at a fast charge rate (2C or 3C), but fast charging is generally only used at the flying field between flights. You can't charge a battery at the trickle rate.

Click on photo to view large image with caption

Q2: "Several years ago I saw an article that gave tips on how to rejuvenate old Ni-Cd cells," recalled one reader. "I can't find that article today. Is there a technique that you are aware of that would bring old batteries back to functionality?"

A2: I recall the article but didn't bother trying to look it up. The following answer reflects my thinking on this subject. When a pack goes down (indicates lower-than-normal rated capacity), it is usually because one or two cells in a multiple-cell pack is/are starting to go bad. So the first problem is to identify the bad cells. To open a pack and search for the bad cells is a time-consuming process. After they are finally identified, you either substitute new cells or, as you suggested, try a technique to rejuvenate them.

There might be some tricks to revitalize those cells, but I wonder how long the process will last. When you are finished with any such process, you may still have a battery pack with a variety of cell characteristics.

The bottom line: Do you really think it is worth spending the time? When a pack starts to lose capacity noticeably, I prefer to discard it in favor of a new pack. When I consider the cost of a new one compared to the time it takes to repair an old one, I'd rather be out flying with that new pack.

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