I was asked to expound on the subject of nicad batteries and the do and don'ts of this very critical piece of R/C equipment, so we'll explore the whys and come up with some "rules of thumb" that are an accumulation of the experiences of many experts in the R/C field.

I must make one point very clear: We could get into the technicalities of nicads and their inherent fickleness, and we could get into some pretty hairy controversy regarding how to take care of nicad batteries only because there seems to be no formula that we could consider as standard criteria for nicad longevity. At this very moment, you are going to learn the basics of nicad good health, and if you adhere closely to what you learn from this articles, you will have maximum success with your new and perhaps old nicads. Let's get to it right now:

First of all, there are nicads on the market that are better quality than others, but only in the fact that the "better ones" cost more, last longer after a thousand charges, and retain charge in between flights longer than the cheaper units. So, what to buy? SR Batteries seem to be enjoying the best reputation for the past several years. I have used them and have had no battery failures yet. G.J.'s sells some very good brands that you can rely on faithfully.

The biggest single cause of aircraft crashing is still due to battery failure... but is it really the fault of the battery? Let's explore this:

We mere mortals usually do not read instructions that manufacturers put with their products, instead we rely on the experiences of our peers to guide us to success from their success and failures. This is bad.

Far too many "peers" offer poor advice based on experiences directly related to improper battery maintenance and lack of technical knowledge. Therefore, let's take you in time from the moment that you purchase a brand new battery pak and tread through a year of battery use.

WHAT SIZE BATTERY PAK TO PURCHASE?
Never, never use a 500 MAH battery pak in any giant scale aircraft, no matter how small the model. Why? Aerobatic GS models receive much greater "G" forces on control surfaces creating a much larger demand from servos, which in turn create a much greater demand for DC current. Flying with a 500 MAH battery pak in a large model is like installing a Volkswagon motor in a full-size Oldsmobile station wagon and expecting the engine to hold up, be dependable and give reasonable performance. If you equate battery size to performance, then you will purchase batteries that will give performance.

Rule of Thumb #1:
Never purchase an on-board flight pak of less than 1200 MAH. Question: Should I buy a 4-cell pak or a 5-cell pak? Answer: 5-cell paks are used where extra current demand can happen due to the fact that an unusual amount of servos are being used. Example: Don Godfrey's B-25 is using 12 servos, and the large type that draw above average current on demand. Straight and level flight does not require much current draw. The 5th cell will expend 20% more current output preventing "current stall" as so often happens when too-small batteries are used and current demand is high. When this happens, you will quite often hear the outcry, "I ain't got it!!". So true, you do not have control and your on-board battery could not deliver the demand on demand.

For the average Giant Scale aircraft that is being flown today, a four-cell pak is adequate providing that your model is not using more than six or eight standard 48 inch-ounce servos. I am assuming that you do double your servos on ailerons and elevators, don't you? Redundancy is mandatory. SR Batteries do not make up 750 MAH paks, but rather only the 900 PAK to sub for the 750 MAH, so why is this? Answer: SR Battery paks are smaller in size than all other brands, therefore having a 900 Pak that is smaller and lighter is an accurate plus for you and your aircraft.

Okay, so what do you do the moment that you get home with your brand new battery pak? I'll tell you: You charge it fully. (Chart on rate charging follows this article). Once fully charged, you cycle the battery down to 4.3 volts to determine the capacity in minutes or hours that the new battery is capable of. If you have a 750 pak, it should have taken approx. 1 1/2 hours to cycle the pak down to 4.3 volts. If it took less time to cycle down, say only one hour, you may have a weak cell or the battery may need one more full charge and one more cycle down to bring up to specifications. Are you with me so far? Good!

You are now ready to fly and feel safe, at least for maybe a month or two of flying--maybe. Your flying habits may well determine how "human" your battery feels like being! If you are a creature of habit and fly approx. three or four times every time you go to the flying field, you will then have created a nicad "memory" that will crash your model even though your battery will check okay after the crash and continue to check good days later!! So what does this "memory" do? I'll tell you.

All nicad batteries will develop a memory if you constantly draw current at the same amount of time, every time you demand its use. Once memory sets in, the battery will drop below 4.3 volts after the 3rd redundant flight and the receiver will shut down for just long enough (usually 2-3 seconds) to lose the aircraft to mother earth. There are two basic methods to prevent nicad memory:

1. Fly at different amounts each time you fly. At times fly three times, then the next time out fly four times etc., etc.

2. Cycle your batteries, including your transmitter, every 60 days.

Rule of Thumb #2:

Cycle all nicads six time each year. So... your next question(s) to yourself are:

1. What battery cycler to purchase?

2. What is my airplane worth compared to the cost of a battery?

The most popular cycler is the L.R. Taylor, available in various models to suit your battery-transmitter size. The Taylor sells for approx $80. This unit has two clock motors that time the "down cycle" to 4.3 volts letting you know exactly how much flying or use time (capacity) the transmitter and airborne paks had. Once the unit reaches a bottom of 4.3, it automatically goes to "charge" and begins putting the removed charge back in. The unit will not automatically go to trickle when your batteries reach the 5.2 full charge. You have to know when to take the batteries off charge. Ace R/C has several cyclers and chargers, all very good, available as kits or fully assembled.

A simple method of cycling is to go to an electronics store and purchase a single volt meter. Add a 10 ohm, 1 watt resistor to the meter for cycling 5.2 (or 4.8 paks) and add a 20 ohm, 2 watt resistor for the eight cell paks, as found in transmitters.

By using this inexpensive cycling method, you achieve the same results as the Taylor unit, however, the Taylor unit will "babysit" your batteries and go to charge when the 4.3 bottom occurs. The voltmeter requires you as babysitter! You must write down the exact time that you begin cycling, then record the time that the voltmeter reaches the 4.3 bottom. The difference in time is the exact amount of time your batteries had stored in them. Easy? It sure is!

Most chargers nowadays are the Fast Type, the six-hour kind that charge at a 100 Mil rate. This type of unit will top off any battery in six hours or less.

Rule of Thumb #3:
Always charge your batteries the night before you go flying no matter when you charged them last. Over-charging damage cannot occur unless you charge beyond 24 hours on a slow rate, and 12 hours on a fast charge rate.

Some makes of batteries store charge longer than others. Sanyo batteries store longer than most others, but this does not necessarily mean that Sanyo's better. Cycling will always tell you how good your batteries are regardless of the brand.

In 1970-1971, a very intelligent electronic engineer by the name of Jim Fosgate designed and invented Pro-Line radios. His circuitry was so good that almost every well-known pattern flyer switched to Pro-Line. The unit that impressed me was his battery charger. This Pro-Line charger would charge at 50 Mils (slow rate) or by flicking a switch, 100 Mils, (fast rate). When the batteries would reach the maximum of 5.3 (not 5.2) voltage, the charger would automatically go to trickle charge, preventing battery damage in the event that you would forget to take your batteries off charge. I have three of these chargers and would not part with them for love or... ?

A Word of Caution:
Charge your batteries once every month whether or not you are using your system, and cycle every other month anyway. Dormancy without charging usually results in at least one cell going bad or weak. Keep a "log" on all batteries.

By the way, Ace R/C has a vari-charger that is a must for us guys. This unit allows charging batteries up to 1200 Mils, and will charge from "0" to 1200 Mils variably! It has a meter and a knob. You simply dial the charge rate you desire! With this unit, you can put any battery on trickle and leave it on indefinitely. Say... set the charger at 10 Mils and let the battery idle at full charge, ready to use. Look into this unit soon troops. 'Tis well worth the investment.

M.E.N. (Model Engineering of Norwalk, CN) has a nifty charger that will go to trickle once your batteries are full charged, allowing you to leave your system on charge all the time, ready to fly at any time you so desire. This is a duper charger!

NOW TO AN IMPORTANT POINT:
You cannot charge a 5-cell battery pak with a charger meant for 4-cell charging. The 5-cell battery will never reach its full capacity. This is where the M.E.N. charger will fail you as well as many others, however L.R. Taylor has a charger that will allow you to charge two transmitters, two 4 cell paks and two 5-cell paks all at the same time! Mr. Taylor is a man after our giant scale hearts! I would like to see a battery charger that offered a digital readout, charge any size nicad unit, show you on the read-out what voltage has been achieved, and go to standby or trickle when charging is complete. This same unit could have a cycler built in and the read-out would also slow down voltage. It should be possible.

Okay... you have learned a lot about the whys and hows of batteries, but what price can you put on your giant scale aircraft? Fact is, your model is priceless, only because you not only have a lot of hard-earned bucks invested, you have hours and hours of labor and shop time vested. Do you realize that your system is only as good as your battery system? Do you realize that the entire investment is hanging on whether or not your battery is going to fail or stay above 4.3 volts during flying? I have seen some absolutely beautiful models destroyed on account of bad batteries. On account of old batteries. On account of batteries that were not cycled at all. And on account of batteries too small for the intended use.

The use of redundant systems is on the rise. I'll explain the details of some of them now: The first redundant system to come out, using two on-board batteries, was the RAM system. It would switch, by relay, to the secondary battery if the main pak would fail for any reason, and at the same time a Buzzer or small Siren would go off letting you know that the switch was made. Problem. The relay was mechanical and too sensitive, often times switching for no reason, or creating intermittent noise in the system.

The next system to arrive on the scene was the George Steiner unit, and later sold to Ace R/C and called the G.P. 2x5 redundant system. To explain this unit easily, the two batteries, both having to be 5-cell paks, would be used at the same time, giving extra servo power. If one of the batteries failed, the G.P. unit would shut off the bad battery and use only the good battery. My 8-25 has this system. You can use any two batteries as long as both batteries are the same value. The G.P. unit by Ace is considered the finest overall redundant unit.

There is another very good one yet! JOMAR is owned by my good friend, and IMAA member, Joe Utasi of Cincinnati, OH. Joe's interest in Giant scale goes far beyond the norm and he has been a pioneer in electronic safeguards for RC for about 5 years. In addition to items such as engine sync systems, glitch busters etc., Joe designed an all-electronic fail safe for on-board batteries. Using two batteries of the same value, only one battery is being used to drive your system. If the main pak fails, the unit will switch, electronically, to the piggy-back battery. An LED will light up when the switch is made. I use this method also, and I know that Chris Dascano has several. By the way, both the G.P. and the Jomar units weigh in at less than 4 ounces.

Therefore, if you have a precious Giant Scale aircraft, or any aircraft that you cherish, you ought to have a two-battery redundant system onboard. This is very cheap insurance. If you elect to not use a redundant system of any kind, then you must cycle and monitor your batteries every 60-days. Get in the habit.

Finally, when your batteries get over two years old, throw them out. That's right! Put 'em in the garbage can. Buy new batteries and get a fresh start for your aircraft. I will not use a battery any longer than two years, mainly because I do not keep a log of how many flights that battery has given me, therefore by average, after two years, that battery should have had enough service time and enough cycling to be put to rest. A word to the wise? So what if it checks GOOD? Each battery has only so many charges and discharges. Why fly with a battery that is on the fringe of exhaustion? Batteries go bad (by one cell at a time) very quickly, and usually in the air. Does Murphy live in your basement?

Okay good friend, let us review the basic rules of thumb to forever remember for heavenly flying:

1. 1200 MAH, and no less than 900 MAH battery paks are recommended for GS aircraft ONLY. The more servos you use, the more battery performance you require.

2. Cycle all nicad batteries every two months or six times a year. You must keep nicad memories clear and open.

3. Always charge your batteries the night before flying, or top them off by fast charging a few hours before flying.

4. Charge batteries once every month whether you fly or not.

5. Get rid of batteries every two years regardless of usage.

6. Redundant systems are recommended for 100% elimination of onboard battery failure.

Now you have the basics... the "commandments" for battery maintenance, upkeep, and longevity.

One Last Thing:
Batteries do not like vibration. Pack them carefully in 1" or more of foam rubber, not foam plastic. Batteries do not like heat. If you are to fly in 90-100 degree temperature, cover your model with a blanket or keep model in the shade. Fuselage heat has been known to reach temps of over 150 degrees! Nicads hate heat and will rebel by dropping capacity by 50% on that day.

Epilog: Never install batteries with a taut wire, and always tape the battery connection leading to the switch harness. Batteries must be installed so that they cannot shift or come loose, pulling apart the battery connection. I have seen this happen 5 times in 8 years.