HOW TO SIZE THE BATTERY BASIC INFORMATION AND TUTORIALS

You might get the idea that you can connect hundreds, or even thousands, of cells in series and obtain batteries with fantastically high EMFs. Why not put 1,000 zinc-carbon cells in series, for example, and get 1.5 kV?

Or put 2,500 solar cells in series and get 1.25 kV? Maybe it’s possible to put a billion solar cells in series, out in some vast sun-scorched desert wasteland, and use the resulting 500 MV (megavolts) to feed the greatest high-tension power line the world has ever seen.


There are several reasons why these schemes aren’t good ideas. First, high voltages for practical purposes can be generated cheaply and efficiently by power converters that work from 117-V or 234-V utility mains.

Second, it would be difficult to maintain a battery of thousands, millions or billions of cells in series. Imagine a cell holder with 1,000 sets of contacts. And not one of them can open up, lest the whole battery become useless, because all the cells must be in series. (Solar panels, at least, can be permanently wired together. Not so with batteries that must often be replaced.)

And finally, the internal resistances of the cells would add up and limit the current, as well as the output voltage, that could be derived by connecting so many cells in series. This is not so much of a problem with series-parallel combinations, as in solar panels, as long as the voltages are reasonable.

But it is a big factor if all the cells are in series, with the intent of getting a huge voltage. This effect will occur with any kind of cell, whether electrochemical or photovoltaic.

In the days of the Second World War, portable two-way radios were built using vacuum tubes. These were powered by batteries supplying 103.5 V. The batteries were several inches long and about an inch in diameter.

They were made by stacking many little zinc-carbon cells on top of each other, and enclosing the whole assembly in a single case. You could get a nasty jolt from one of those things. They were downright dangerous!

A fresh 103.5-V battery would light up a 15-W household incandescent bulb to almost full brilliance. But the 117-V outlet would work better, and for a lot longer.

Nowadays, handheld radio transceivers will work from NICAD battery packs or batteries of ordinary dry cells, providing 6 V, 9 V, or 12 V. Even the biggest power transistors rarely use higher voltages. Automotive or truck batteries can produce more than enough power for almost any mobile or portable communications system.

And if a really substantial setup is desired, gasoline-powered generators are available, and they will supply the needed energy at far less cost than batteries. There’s just no use for a mega battery if a thousand, a million, or a zillion volts.

NICKEL - CADMIUM CELLS AND BATTERIES BASIC INFORMATION

You’ve probably seen, or at least heard of, NICAD cells and batteries. They have become quite common in consumer devices such as those little radios and cassette players you can wear while doing aerobics or just sitting around. (These entertainment units are not too safe for walking or jogging in traffic.

And never wear them while riding a bicycle.) You can buy two sets of cells and switch them every couple of hours of use, charging one set while using the other. Plug-in charger units cost only a few dollars.

Types of NICAD cells
Nickel-cadmium cells are made in several types. Cylindrical cells are the standard cells; they look like dry cells. Button cells are those little things that are used in cameras, watches, memory backup applications, and other places where miniaturization is important.

Flooded cells are used in heavy-duty applications and can have a charge capacity of as much as 1,000 Ah. Spacecraft cells are made in packages that can withstand the vacuum and temperature changes of a spaceborne environment.

Uses of NICADs
There are other uses for NICADs besides in portable entertainment equipment. Most orbiting satellites are in darkness half the time, and in sunlight half the time. Solar panels can be used while the satellite is in sunlight, but during the times that the earth eclipses the sun, batteries are needed to power the electronic equipment on board the satellite.

The solar panels can charge a set of NICADs, in addition to powering the satellite, for half of each orbit. The NICADs can provide the power during the dark half of each orbit. Nickel-cadmium batteries are available in packs of cells.

These packs can be plugged into the equipment, and might even form part of the case for a device. An example of this is the battery pack for a handheld ham radio tranceiver. Two of these packs can be bought, and they can be used alternately, with one installed in the “handie-talkie” (HT) while the other is being charged.

NICAD neuroses
There are some things you need to know about NICAD cells and batteries, in order to get the most out of them. One rule, already mentioned, is that you should never discharge them all the way until they “die.” This can cause the polarity of a cell, or of one or more cells in a battery, to reverse.

Once this happens, the cell or battery is ruined. Another phenomenon, peculiar to this type of cell and battery, is called memory. If a NICAD is used over and over, and is discharged to exactly the same extent every time (say, two-thirds of the way), it might start to “go to sleep” at that point in its discharge cycle.

This is uncommon; lab scientists have trouble forcing it to occur so they can study it. But when it does happen, it can give the illusion that the cell or battery has lost some of its storage capacity. Memory problems can be solved. Use the cell or battery almost all the way up, and then fully charge it. Repeat the process, and the memory will be “erased.”

NICADS do best using wall chargers that take several hours to fully replenish the cells or batteries. There are high-rate or quick chargers available, but these can sometimes force too much current through a NICAD.

It’s best if the charger is made especially for the cell or battery type being charged. An electronics dealer, such as the manager at a Radio Shack store, should be able to tell you which chargers are best for which cells and batteries.

MINIATURE CELLS AND BATTERIES BASIC INFORMATION AND TUTORIALS

In recent years, cells and batteries—especially cells—have become available in many different sizes and shapes besides the old cylindrical cells, transistor batteries and lantern batteries. These are used in watches, cameras, and other microminiature electronic gizmos.

Silver-oxide types
Silver-oxide cells are usually made into button-like shapes, and can fit inside even a small wristwatch. They come in various sizes and thicknesses, all with similar appearances.

They supply 1.5 V, and offer excellent energy storage for the weight. They also have a flat discharge curve. The previously described zinc-carbon and alkaline cells and batteries have a current output that declines with time in a steady fashion


Silver-oxide cells can be stacked to make batteries. Several of these miniature cells, one on top of the other, might provide 6 V or 9 V for a transistor radio or other light-duty electronic device. The resulting battery is about the size of an AAA cylindrical cell.

Mercury types
Mercury cells, also called mercuric oxide cells, have advantages similar to silver-oxide cells. They are manufactured in the same general form. The main difference, often not of significance, is a somewhat lower voltage per cell: 1.35 V. If six of these cells are stacked to make a battery, the resulting voltage will be about 8.1 V rather than 9 V.

One additional cell can be added to the stack, yielding about 9.45 V. There has been some decrease in the popularity of mercury cells and batteries in recent years. This is because of the fact that mercury is highly toxic.

When mercury cells and batteries are dead, they must be discarded. Eventually the mercury, a chemical element, leaks into the soil and ground water. Mercury pollution has become a significant concern in places that might really surprise you.


Lithium types
Lithium cells have become popular since the early eighties. There are several variations in the chemical makeup of these cells; they all contain lithium, a light, highly reactive metal. Lithium cells can be made to supply 1.5 V to 3.5 V, depending on the particular chemistry used. These cells, like their silver-oxide cousins, can be stacked to make batteries.

The first applications of lithium batteries was in memory backup for electronic microcomputers. Lithium cells and batteries have superior shelf life, and they can last for years in very-low-current applications such as memory backup or the powering of a digital liquid-crystal-display (LCD) watch or clock.

These cells also provide energy capacity per unit volume that is vastly greater than other types of electrochemical cells.

Lithium cells and batteries are used in low-power devices that must operate for a long time without power source replacement. Heart pacemakers and security systems are two examples of such applications.

OHMMETERS USED IN ELECTRONICS BASIC INFORMATION AND TUTORIALS

You remember that the current through a circuit depends on the resistance. This principle can be used to manufacture a voltmeter using an ammeter and a resistor.

The larger the value of the resistance in series with the meter, the more voltage is needed to produce a reading of full scale. This has a converse, or a “flip side”: Given a constant voltage, the current through the meter will vary if the resistance varies. This provides a means for measuring resistances.

An ohmmeter is almost always constructed by means of a milliammeter or microammeter in series with a set of fixed, switchable resistances and a battery that provides a known, constant voltage. By selecting the resistances appropriately, the meter will give indications in ohms over any desired range.

Usually, zero on the meter is assigned the value of infinity ohms, meaning a perfect insulator. The full-scale value is set at a certain minimum, such as 1 Ω, 100 Ω, or 10 KΩ (10,000 Ω).

Ohmmeters must be precalibrated at the factory where they are made. A slight error in the values of the series resistors can cause gigantic errors in measured resistance.

Therefore, precise tolerances are needed for these resistors. It is also necessary that the battery be exactly the right kind, and that it be reasonably fresh so that it will provide the appropriate voltage. The smallest deviation from the required voltage can cause a big error in the meter indication.

The scale of an ohmmeter is nonlinear. That is, the graduations are not the same everywhere. Values tend to be squashed together towards the “infinity” end of the scale.


It can be difficult to interpolate for high values of resistance, unless the right scale is selected. Engineers and technicians usually connect an ohmmeter in a circuit with the meter set for the highest resistance range first; then they switch the range until the meter is in a part of the scale that is easy to read.

Finally, the reading is taken, and is multiplied (or divided) by the appropriate amount as indicated on the range switch.


Ohmmeters will give inaccurate readings if there is a voltage between the points where the meter is connected. This is because such a voltage either adds to, or subtracts from, the ohmmeter battery voltage.

This in effect changes the battery voltage, and the meter reading is thrown way off. Sometimes the meter might even read “more than infinity” ohms; the needle will hit the pin at the left end of the scale.

Therefore, when using an ohmmeter to measure resistance, you need to be sure that there is no voltage between the points under test. The best way to do this is to switch off the equipment in question.

SEMICONDUCTOR - HOW IT WORKS? BASIC INFORMATION

In a semiconductor, electrons flow, but not as well as they do in a conductor. You might imagine the people in the line being lazy and not too eager to pass the balls along.

Some semiconductors carry electrons almost as well as good electrical conductors like copper or aluminum; others are almost as bad as insulating materials. The people might be just  little sluggish, or they might be almost asleep.

Semiconductors are not exactly the same as resistors. In a semiconductor, the material is treated so that it has very special properties. The semiconductors include certain substances, such as silicon, selenium, or gallium, that have been “doped” by the addition of impurities like indium or antimony.

Perhaps you have heard of such things as gallium arsenide, metal oxides, or silicon rectifiers. Electrical conduction in these materials is always a result of the motion of electrons.

However, this can be a quite peculiar movement, and sometimes engineers speak of the movement of holes rather than electrons. A hole is a shortage of an electron—you might think of it as a positive ion—and it moves along in a direction opposite to the flow of electrons.


When most of the charge carriers are electrons, the semiconductor is called N-type, because electrons are negatively charged. When most of the charge carriers are holes, the semiconducting material is known as P type because holes have a positive electric charge.

But P-type material does pass some electrons, and N-type material carries some holes. In a semiconductor, the more abundant type of charge carrier is called the majority carrier. The less abundant kind is known as the minority carrier.

Semiconductors are used in diodes, transistors, and integrated circuits in almost limitless variety. These substances are what make it possible for you to have a computer in a briefcase.

That notebook computer, if it used vacuum tubes, would occupy a skyscraper, because it has billions of electronic components. It would also need its own power plant, and would cost thousands of dollars in electric bills every day.

But the circuits are etched microscopically onto semiconducting wafers, greatly reducing the size and power requirements.

Semiconductor is so little that we barely recognize it in our daily life. Share us your experience on a time wherein we recognized the existence  of semiconductors.