An aerator pump is a specialized water pump used on fishing boats.

Part of a livewell system, in which a fisherman keeps his catch alive, the aerator (or livewell) pump helps to “aerate” the water and put oxygen into it. This is most often done by re-circulating the water in the livewell through the pump and back to the well via a sprayer that agitates the water and induces oxygen. These are typically known as “recirc” pumps.

Another use for this pump can be as a “pickup”, where it draws in the outside water to fill the livewell or refresh it. The pumps come in a variety of pumping capacities and are powered by 12V DC.

Aerator pumps are manufactured by several well know companies, including Attwood Marine. The Attwood Tsunami Series features innovative engineering and compact design, that delivers high output from a small package.

Attwood aerator pumps are famous for using the most advanced material available, including the best quality bearings and state-of-the-art brushes, alloys and magnets.

They offer three high-efficiency aerator pumps that move water at output capacities of 500 gph, 800 gph and 1200 gph.

An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Batteries are a common power source for many household, industrial and transportation applications.

There are two types of batteries: primary batteries (disposable batteries), which are designed to be used once and discarded, and secondary batteries (rechargeable batteries), which are designed to be recharged and used multiple times.

Rechargeable batteries are what are used in automotive and marine applications. They can be recharged by applying electric current. Devices to supply the appropriate current are engine alternators or chargers.

The most common form of rechargeable battery is the lead-acid battery. This battery is notable in that it contains a liquid in an unsealed container, requiring that the battery be kept upright and the area be well ventilated to ensure safe dispersal of the hydrogen gas produced by these batteries during overcharging.

Battery boxes are used to secure the batteries on a boat against the extreme movement of the craft on water – a marine industry standard and a Coast Guard rule.

While batteries may sometimes be mounted on trays, they are more often stored and held in marine electrical battery boxes, which, besides keeping the battery in place, also protects it from exposure to outside elements like moisture while also containing the corrosive acids of the battery.

Battery boxes also make moving and transporting the battery safe and easy. Battery boxes normally include a box with molded handles, a lid, a strap to hold down the lid and mounting hardware.

Battery boxes are available from several marine manufacturers, although the most well-known are built by Attwood Marine.

Battery cables are one of the most crucial parts of any boat wiring system.

The foundation of the entire 12 volt marine electrical system is the batteries – both for energy and grounding, which are equally important. For each, the battery cable is a pivotal link.

Because of the nature of DC power and the easy potential for current loss over distance, battery cables are constructed of thick heavy duty copper and highly insulated. This makes them not only bulky, but expensive.

Good marine electrical design will use the optimal thickness (gauge) of the cables to provide the most current, while attempting to limit the distance they run, as longer runs necessitate increasing the gauge. Typically the cables will be terminated with either battery lugs (for the battery connection) or ring terminals, or most commonly a combination of the two.

Battery cables are available from many sources, although several websites now offer completely custom battery cables. The flexibility of these configurations allows boaters to get precisely the length, color, gauge and end-fittings that their boat wiring project requires.

Battery management is the efficient monitor and control the outflow of power from your boat’s batteries.

The “prime directive” of marine electrical battery management to to avoid the overuse of this finite power supply, which may eventually compromise an important function, like starting your engine.

Marine electrical battery management can be as simple as monitoring a voltmeter to determine battery voltage; to the use of switches to turn on certain batteries, while isolating others from use ; to having sophisticated voltage sensitive relays that will do the job of monitoring levels and switching batteries on and off automatically – often called a Smart Battery Switch.

Any boater that will be spending time at anchor running electrical accessories, like stereos, will need to maintain some awareness of the condition and level of their battery supply and life. The inability to restart an engine (which is a key source of recharge for the batteries), or to lose the use of a boat’s navigation lighting, boat horns or bilge pumps because of dead batteries is a situation to be avoided. Thus the importance of battery management.

Words of caution:

Lead-acid batteries contain a diluted sulfuric acid electrolyte, which is a highly corrosive poison and will produce flammable and toxic gasses when recharged and explode if ignited. According to PREVENT BLINDNESS AMERICA, in 2003 nearly 6,000 motorists suffered serious eye injuries from working around car batteries. The U.S. Eye Injury Registry reports that it is the third leading cause of eye injuries at home. When working with batteries, you need to wear glasses (or preferably Z-87 rated safety goggles), have plenty of ventilation, remove your jewelry, and exercise caution. Do NOT allow battery electrolyte to mix with salt water. Even small quantities of this combination will produce chlorine gas that can KILL you! If available, please always follow the manufacturer's instructions for testing, jumping, installing, discharging, charging, equalizing and maintaining batteries.

See Also

CAR AND DEEP CYCLE BATTERY
FREQUENTLY ASKED QUESTIONS 7.1

Bill Darden

An critical component on most boats, the bilge pump is a commonly used mechanical method for pumping out the water that invariably gathers in the bilge of most watercraft.

These inexpensive but often powerful pumps are expected to perform in often varying (and occasionally severe) conditions. Not only are they required to function while a boat is cutting through heavy waves, but also in the middle of the night after a rain storm when the boat is docked and the owner is gone.

The pumps come in a variety of pumping capacities, stated in gallon per hour (GPH), and are usually powered by 12V DC. The methods of wiring them for switching on can be for manual or automatic operation, and most often is for both. Manual switching typically uses a switch on the dashboard. Automatic operation involves the use of a float switch that senses the water level in the bilge. Once a level is reached that can be pumped out, the switch turns the pump on.

Bilge pumps are manufactured by several well know companies, including Attwood Marine. The Attwood Tsunami Series features innovative engineering and compact design, that delivers high output from a small package. Attwood bilge pumps are famous for using the most advanced material available, including the best quality bearings and state-of-the-art brushes, alloys and magnets.

They offer three high-efficiency pumps that move water at output capacities of 500 gph, 800 gph and 1200 gph.

The ability to audibly signal the presence of your craft on the water is a legal requirement. The most common way this is done is with a horn.

Most boat horns run off of 12 VDC. The sounding mechanisms they employ are an electrical diaphragm (like a car horn), a piezo (like an emergency buzzer) or an air diaphragm with a compressor (like a truck or ship horn).

A horn is a crucial safety feature when a sudden warning needs to be given, to signal trouble, or when underway with low visibility such as in fog.

Boat horns are available from several well known suppliers, the most famous in marine being the AFI division of Marinco. As the say on their website, they are

…the leading supplier of horns to the marine industry, with over fifty years of experience in designing and manufacturing sound devices specifically for use in harsh marine environments. Stainless steel is used for all critical components such as trumpets, motor cover, diaphragms, and assembly and mounting hardware. In the case of the XLP trumpet horns, the horn is given extra protection through the complete over-molding of the internal motor cover housing. It is this extra process that provides the added protection needed to back up the five-year warranty. AFI offers a complete line of marine horn products designed to meet almost any need, including electric and air trumpet horns, compact horns, electric and air below deck horns, and a comprehensive line of drop-in horns with a wide assortment of grill options.

The electrons of different types of atoms have different degrees of freedom to move around. With some types of materials, such as metals, the outermost electrons in the atoms are so loosely bound that they chaotically move in the space between the atoms of that material by nothing more than the influence of room-temperature heat energy. Because these virtually unbound electrons are free to leave their respective atoms and float around in the space between adjacent atoms, they are often called free electrons.

In other types of materials such as glass, the atoms' electrons have very little freedom to move around. While external forces such as physical rubbing can force some of these electrons to leave their respective atoms and transfer to the atoms of another material, they do not move between atoms within that material very easily.

This relative mobility of electrons within a material is known as electric conductivity. Conductivity is determined by the types of atoms in a material (the number of protons in each atom's nucleus, determining its chemical identity) and how the atoms are linked together with one another. Materials with high electron mobility (many free electrons) are called conductors, while materials with low electron mobility (few or no free electrons) are called insulators.

Here are a few common examples of conductors and insulators:

• silver
• copper
• gold
• aluminum
• iron
• steel
• brass
• bronze
• mercury
• graphite
• dirty water
• concrete

• glass
• rubber
• oil
• asphalt
• fiberglass
• porcelain
• ceramic
• quartz
• (dry) cotton
• (dry) paper
• (dry) wood
• plastic
• air
• diamond
• pure water

It must be understood that not all conductive materials have the same level of conductivity, and not all insulators are equally resistant to electron motion. Electrical conductivity is analogous to the transparency of certain materials to light: materials that easily "conduct" light are called "transparent," while those that don't are called "opaque." However, not all transparent materials are equally conductive to light. Window glass is better than most plastics, and certainly better than "clear" fiberglass. So it is with electrical conductors, some being better than others.

For instance, silver is the best conductor in the "conductors" list, offering easier passage for electrons than any other material cited. Dirty water and concrete are also listed as conductors, but these materials are substantially less conductive than any metal.

Physical dimension also impacts conductivity. For instance, if we take two strips of the same conductive material -- one thin and the other thick -- the thick strip will prove to be a better conductor than the thin for the same length. If we take another pair of strips -- this time both with the same thickness but one shorter than the other -- the shorter one will offer easier passage to electrons than the long one. This is analogous to water flow in a pipe: a fat pipe offers easier passage than a skinny pipe, and a short pipe is easier for water to move through than a long pipe, all other dimensions being equal.

It should also be understood that some materials experience changes in their electrical properties under different conditions. Glass, for instance, is a very good insulator at room temperature, but becomes a conductor when heated to a very high temperature. Gases such as air, normally insulating materials, also become conductive if heated to very high temperatures. Most metals become poorer conductors when heated, and better conductors when cooled. Many conductive materials become perfectly conductive (this is called superconductivity) at extremely low temperatures.

While the normal motion of "free" electrons in a conductor is random, with no particular direction or speed, electrons can be influenced to move in a coordinated fashion through a conductive material. This uniform motion of electrons is what we call electricity, or electric current. To be more precise, it could be called dynamic electricity in contrast to static electricity, which is an unmoving accumulation of electric charge. Just like water flowing through the emptiness of a pipe, electrons are able to move within the empty space within and between the atoms of a conductor. The conductor may appear to be solid to our eyes, but any material composed of atoms is mostly empty space! The liquid-flow analogy is so fitting that the motion of electrons through a conductor is often referred to as a "flow."

A noteworthy observation may be made here. As each electron moves uniformly through a conductor, it pushes on the one ahead of it, such that all the electrons move together as a group. The starting and stopping of electron flow through the length of a conductive path is virtually instantaneous from one end of a conductor to the other, even though the motion of each electron may be very slow. An approximate analogy is that of a tube filled end-to-end with marbles:

The tube is full of marbles, just as a conductor is full of free electrons ready to be moved by an outside influence. If a single marble is suddenly inserted into this full tube on the left-hand side, another marble will immediately try to exit the tube on the right. Even though each marble only traveled a short distance, the transfer of motion through the tube is virtually instantaneous from the left end to the right end, no matter how long the tube is. With electricity, the overall effect from one end of a conductor to the other happens at the speed of light: a swift 186,000 miles per second!!! Each individual electron, though, travels through the conductor at a much slower pace.

If we want electrons to flow in a certain direction to a certain place, we must provide the proper path for them to move, just as a plumber must install piping to get water to flow where he or she wants it to flow. To facilitate this, wires are made of highly conductive metals such as copper or aluminum in a wide variety of sizes.

Remember that electrons can flow only when they have the opportunity to move in the space between the atoms of a material. This means that there can be electric current only where there exists a continuous path of conductive material providing a conduit for electrons to travel through. In the marble analogy, marbles can flow into the left-hand side of the tube (and, consequently, through the tube) if and only if the tube is open on the right-hand side for marbles to flow out. If the tube is blocked on the right-hand side, the marbles will just "pile up" inside the tube, and marble "flow" will not occur. The same holds true for electric current: the continuous flow of electrons requires there be an unbroken path to permit that flow. Let's look at a diagram to illustrate how this works:

A thin, solid line (as shown above) is the conventional symbol for a continuous piece of wire. Since the wire is made of a conductive material, such as copper, its constituent atoms have many free electrons which can easily move through the wire. However, there will never be a continuous or uniform flow of electrons within this wire unless they have a place to come from and a place to go. Let's add an hypothetical electron "Source" and "Destination:"

Now, with the Electron Source pushing new electrons into the wire on the left-hand side, electron flow through the wire can occur (as indicated by the arrows pointing from left to right). However, the flow will be interrupted if the conductive path formed by the wire is broken:

Since air is an insulating material, and an air gap separates the two pieces of wire, the once-continuous path has now been broken, and electrons cannot flow from Source to Destination. This is like cutting a water pipe in two and capping off the broken ends of the pipe: water can't flow if there's no exit out of the pipe. In electrical terms, we had a condition of electrical continuity when the wire was in one piece, and now that continuity is broken with the wire cut and separated.

If we were to take another piece of wire leading to the Destination and simply make physical contact with the wire leading to the Source, we would once again have a continuous path for electrons to flow. The two dots in the diagram indicate physical (metal-to-metal) contact between the wire pieces:

Now, we have continuity from the Source, to the newly-made connection, down, to the right, and up to the Destination. This is analogous to putting a "tee" fitting in one of the capped-off pipes and directing water through a new segment of pipe to its destination. Please take note that the broken segment of wire on the right hand side has no electrons flowing through it, because it is no longer part of a complete path from Source to Destination.

It is interesting to note that no "wear" occurs within wires due to this electric current, unlike water-carrying pipes which are eventually corroded and worn by prolonged flows. Electrons do encounter some degree of friction as they move, however, and this friction can generate heat in a conductor. This is a topic we'll explore in much greater detail later.

• In conductive materials, the outer electrons in each atom can easily come or go, and are called free electrons.
• In insulating materials, the outer electrons are not so free to move.
• All metals are electrically conductive.
• Dynamic electricity, or electric current, is the uniform motion of electrons through a conductor. Static electricity is an unmoving, accumulated charge formed by either an excess or deficiency of electrons in an object.
• For electrons to flow continuously (indefinitely) through a conductor, there must be a complete, unbroken path for them to move both into and out of that conductor.

Published under the terms and conditions of the Design Science License
Disclaimer

You might have been wondering how electrons can continuously flow in a uniform direction through wires without the benefit of these hypothetical electron Sources and Destinations. In order for the Source-and-Destination scheme to work, both would have to have an infinite capacity for electrons in order to sustain a continuous flow! Using the marble-and-tube analogy, the marble source and marble destination buckets would have to be infinitely large to contain enough marble capacity for a "flow" of marbles to be sustained.

The answer to this paradox is found in the concept of a circuit: a never-ending looped pathway for electrons. If we take a wire, or many wires joined end-to-end, and loop it around so that it forms a continuous pathway, we have the means to support a uniform flow of electrons without having to resort to infinite Sources and Destinations:

Each electron advancing clockwise in this circuit pushes on the one in front of it, which pushes on the one in front of it, and so on, and so on, just like a hula-hoop filled with marbles. Now, we have the capability of supporting a continuous flow of electrons indefinitely without the need for infinite electron supplies and dumps. All we need to maintain this flow is a continuous means of motivation for those electrons, which we'll address in the next section of this chapter.

It must be realized that continuity is just as important in a circuit as it is in a straight piece of wire. Just as in the example with the straight piece of wire between the electron Source and Destination, any break in this circuit will prevent electrons from flowing through it:

An important principle to realize here is that it doesn't matter where the break occurs. Any discontinuity in the circuit will prevent electron flow throughout the entire circuit. Unless there is a continuous, unbroken loop of conductive material for electrons to flow through, a sustained flow simply cannot be maintained.

• REVIEW:
• A circuit is an unbroken loop of conductive material that allows electrons to flow through continuously without beginning or end.
• If a circuit is "broken," that means it's conductive elements no longer form a complete path, and continuous electron flow cannot occur in it.
• The location of a break in a circuit is irrelevant to its inability to sustain continuous electron flow. Any break, anywhere in a circuit prevents electron flow throughout the circuit.

Published under the terms and conditions of the Design Science License

Disclaimer