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.
A Glossary of Battery Terms
|
See Also
CAR AND DEEP CYCLE
BATTERY
FREQUENTLY ASKED QUESTIONS 7.1
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.
Working inside a boat up on blocks is essentially the same as one in the water, if it is grounded through its three-wire power cord. If the vessel is not grounded and a fault develops in the hot lead, workers outside the boat on wet ground or contacting metal ladders or stands are in danger.
Extension cords, especially the household two-prong type, increase the risk; wearing rubber boots and rubber gloves can reduce the risk somewhat. Using an AC on the exterior of a floating boat is courting disaster. If a power drill or sander gets splashed or falls overboard, seawater will conduct current from the hot wire to the case, making the tool hot. If the grounding wire is not effective, any path to the sea via wet decks or a metal conductor makes the worker part of the circuit. Divers and swimmers in the water are susceptible to electrical shock, especially if there is a direct short such as would occur if a live power cord drops into the water.
Even a relatively low-voltage fault can establish an electrical field around the boat, which could cause a current flow through a swimmer’s body causing fibrillation. Current leakage into the water can also paralyze muscles and cause drowning with no visible evidence of electrocution.
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:
Conductors:- 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.
REVIEW:- 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
It was discovered centuries ago that certain types of materials would mysteriously attract one another after being rubbed together. For example: after rubbing a piece of silk against a piece of glass, the silk and glass would tend to stick together. Indeed, there was an attractive force that could be demonstrated even when the two materials were separated:
Glass and silk aren't the only materials known to behave like this. Anyone who has ever brushed up against a latex balloon only to find that it tries to stick to them has experienced this same phenomenon. Paraffin wax and wool cloth are another pair of materials early experimenters recognized as manifesting attractive forces after being rubbed together:
This phenomenon became even more interesting when it was discovered that identical materials, after having been rubbed with their respective cloths, always repelled each other:
It was also noted that when a piece of glass rubbed with silk was exposed to a piece of wax rubbed with wool, the two materials would attract one another:
Furthermore, it was found that any material demonstrating properties of attraction or repulsion after being rubbed could be classed into one of two distinct categories: attracted to glass and repelled by wax, or repelled by glass and attracted to wax. It was either one or the other: there were no materials found that would be attracted to or repelled by both glass and wax, or that reacted to one without reacting to the other.
More attention was directed toward the pieces of cloth used to do the rubbing. It was discovered that after rubbing two pieces of glass with two pieces of silk cloth, not only did the glass pieces repel each other, but so did the cloths. The same phenomenon held for the pieces of wool used to rub the wax:
Now, this was really strange to witness. After all, none of these objects were visibly altered by the rubbing, yet they definitely behaved differently than before they were rubbed. Whatever change took place to make these materials attract or repel one another was invisible.
Some experimenters speculated that invisible "fluids" were being transferred from one object to another during the process of rubbing, and that these "fluids" were able to effect a physical force over a distance. Charles Dufay was one the early experimenters who demonstrated that there were definitely two different types of changes wrought by rubbing certain pairs of objects together. The fact that there was more than one type of change manifested in these materials was evident by the fact that there were two types of forces produced: attraction and repulsion. The hypothetical fluid transfer became known as a charge.
One pioneering researcher, Benjamin Franklin, came to the conclusion that
there was only one fluid exchanged between rubbed objects, and that the two
different "charges" were nothing more than either an excess or a deficiency of
that one fluid. After experimenting with wax and wool, Franklin suggested that
the coarse wool removed some of this invisible fluid from the smooth wax,
causing an excess of fluid on the wool and a deficiency of fluid on the wax. The
resulting disparity in fluid content between the wool and wax would then cause
an attractive force, as the fluid tried to regain its former balance between the
two materials.
Postulating the existence of a single "fluid" that was either gained or lost through rubbing accounted best for the observed behavior: that all these materials fell neatly into one of two categories when rubbed, and most importantly, that the two active materials rubbed against each other always fell into opposing categories as evidenced by their invariable attraction to one another. In other words, there was never a time where two materials rubbed against each other both became either positive or negative.
Following Franklin's speculation of the wool rubbing something off of the wax, the type of charge that was associated with rubbed wax became known as "negative" (because it was supposed to have a deficiency of fluid) while the type of charge associated with the rubbing wool became known as "positive" (because it was supposed to have an excess of fluid). Little did he know that his innocent conjecture would cause much confusion for students of electricity in the future!
Precise measurements of electrical charge were carried out by the French physicist Charles Coulomb in the 1780's using a device called a torsional balance measuring the force generated between two electrically charged objects. The results of Coulomb's work led to the development of a unit of electrical charge named in his honor, the coulomb. If two "point" objects (hypothetical objects having no appreciable surface area) were equally charged to a measure of 1 coulomb, and placed 1 meter (approximately 1 yard) apart, they would generate a force of about 9 billion newtons (approximately 2 billion pounds), either attracting or repelling depending on the types of charges involved.
It was discovered much later that this "fluid" was actually composed of extremely small bits of matter called electrons, so named in honor of the ancient Greek word for amber: another material exhibiting charged properties when rubbed with cloth. Experimentation has since revealed that all objects are composed of extremely small "building-blocks" known as atoms, and that these atoms are in turn composed of smaller components known as particles. The three fundamental particles comprising atoms are called protons, neutrons, and electrons. Atoms are far too small to be seen, but if we could look at one, it might appear something like this:
Even though each atom in a piece of material tends to hold together as a unit, there's actually a lot of empty space between the electrons and the cluster of protons and neutrons residing in the middle.
This crude model is that of the element carbon, with six protons, six neutrons, and six electrons. In any atom, the protons and neutrons are very tightly bound together, which is an important quality. The tightly-bound clump of protons and neutrons in the center of the atom is called the nucleus, and the number of protons in an atom's nucleus determines its elemental identity: change the number of protons in an atom's nucleus, and you change the type of atom that it is. In fact, if you could remove three protons from the nucleus of an atom of lead, you will have achieved the old alchemists' dream of producing an atom of gold! The tight binding of protons in the nucleus is responsible for the stable identity of chemical elements, and the failure of alchemists to achieve their dream.
Neutrons are much less influential on the chemical character and identity of an atom than protons, although they are just as hard to add to or remove from the nucleus, being so tightly bound. If neutrons are added or gained, the atom will still retain the same chemical identity, but its mass will change slightly and it may acquire strange nuclear properties such as radioactivity.
However, electrons have significantly more freedom to move around in an atom than either protons or neutrons. In fact, they can be knocked out of their respective positions (even leaving the atom entirely!) by far less energy than what it takes to dislodge particles in the nucleus. If this happens, the atom still retains its chemical identity, but an important imbalance occurs. Electrons and protons are unique in the fact that they are attracted to one another over a distance. It is this attraction over distance which causes the attraction between rubbed objects, where electrons are moved away from their original atoms to reside around atoms of another object.
Electrons tend to repel other electrons over a distance, as do protons with other protons. The only reason protons bind together in the nucleus of an atom is because of a much stronger force called the strong nuclear force which has effect only under very short distances. Because of this attraction/repulsion behavior between individual particles, electrons and protons are said to have opposite electric charges. That is, each electron has a negative charge, and each proton a positive charge. In equal numbers within an atom, they counteract each other's presence so that the net charge within the atom is zero. This is why the picture of a carbon atom had six electrons: to balance out the electric charge of the six protons in the nucleus. If electrons leave or extra electrons arrive, the atom's net electric charge will be imbalanced, leaving the atom "charged" as a whole, causing it to interact with charged particles and other charged atoms nearby. Neutrons are neither attracted to or repelled by electrons, protons, or even other neutrons, and are consequently categorized as having no charge at all.
The process of electrons arriving or leaving is exactly what happens when certain combinations of materials are rubbed together: electrons from the atoms of one material are forced by the rubbing to leave their respective atoms and transfer over to the atoms of the other material. In other words, electrons comprise the "fluid" hypothesized by Benjamin Franklin. The operational definition of a coulomb as the unit of electrical charge (in terms of force generated between point charges) was found to be equal to an excess or deficiency of about 6,250,000,000,000,000,000 electrons. Or, stated in reverse terms, one electron has a charge of about 0.00000000000000000016 coulombs. Being that one electron is the smallest known carrier of electric charge, this last figure of charge for the electron is defined as the elementary charge.
The result of an imbalance of this "fluid" (electrons) between objects is called static electricity. It is called "static" because the displaced electrons tend to remain stationary after being moved from one material to another. In the case of wax and wool, it was determined through further experimentation that electrons in the wool actually transferred to the atoms in the wax, which is exactly opposite of Franklin's conjecture! In honor of Franklin's designation of the wax's charge being "negative" and the wool's charge being "positive," electrons are said to have a "negative" charging influence. Thus, an object whose atoms have received a surplus of electrons is said to be negatively charged, while an object whose atoms are lacking electrons is said to be positively charged, as confusing as these designations may seem. By the time the true nature of electric "fluid" was discovered, Franklin's nomenclature of electric charge was too well established to be easily changed, and so it remains to this day.
- REVIEW:
- All materials are made up of tiny "building blocks" known as atoms.
- All atoms contain particles called electrons, protons, and neutrons.
- Electrons have a negative (-) electric charge.
- Protons have a positive (+) electric charge.
- Neutrons have no electric charge.
- Electrons can be dislodged from atoms much easier than protons or neutrons.
- The number of protons in an atom's nucleus determines its identity as a unique element.
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
The boat (Hammer P) is a 1966 -35 ft. OWENS flagship. She is double plank mahogany on oak frames, Teak decks and fiberglass cabin shell and fly bridge.
Equipment when we got her included mismatched and somewhat tired For V8 engines, Borg-Warner Velvet Drive transmissions all fresh water-cooled. Also outfitted with a 6.5 KW Kohler Gen- Set.
By mid 2006, I had decided that re-powering was essential. Having toyed with the electric idea for a year or so, I finally decided- "Just Do it" and began the search for a supplier for all the components. After considerable browsing catalogs and online information, this is what I chose for our application: (This is basic electric stuff)
2-Advanced DC Motors-L91-4003-13hp-72Volt
2-Curtis-PMC Motor Controllers- 72Volt-400amp
2-Merritt Inline Joystick control
2 -Albright Main Contactors
2 -Albright Reversing Contactors
3 -400 amp Ferraz/S'mut Safety Fuses
1-Link 10 E Meter
1-Onboard Charger 48-108 volt
2-Deltec Amp meter shunts
2-Westberg Ammeters
180 Lin. feet 2/0 Welding cable
90 Cable Lugs
24 -L16H Trojan Batteries
That is pretty much the electrics of the system, plus misc. hook up wire, etc.
The Mechanics portion needs some thought: Motor to shaft reduction, belt tensioner and battery placement. As you will see by the photos, I had to lengthen the propeller shaft to accommodate the larger pulley for a reduction ratio. I chose a 4:1 reduction because the motors need to turn fast enough to run cool and I need 1000rpm at the shaft to match our previous cruising speed. The rest of the mounting hardware is like a big erector set. All bolted parts were pre-drilled except for bolting to the original engine bunks. These were bolted in place after shaft augment. Motor mounts are adjustable for belt tension and tracking.
There are two flange bearings each side, and opposed for thrust bearings. This all makes a fairly compact package and we can now decide on battery placement. In our case, we are designing a 72 Volt system. Battery placement is somewhat a balancing act. Original components, (fuel) was stored behind the drive train and of course, motors amid ship. Fuel weight (160 gallons) was about 1300 lbs. Motors and transmissions about 1500 lbs. New battery pack weight: about 3000 lbs. To best balance the boat, I put 8 batteries forward and four behind each motor. With motors, batteries and electrical equipment we have an approximate weight gain of 1000 lbs.
Now, looking at performance. First we need to consider the boat Shape and Hull design. As the professionals see it, this is the second poorest hull design for electric power. Only a barge with square ends is worse. The ideal craft would have a sharp entry, a long waterline length and the transom out of the water. Boat design is always subject to compromise and the ideal form is not always practical. In our case, we will work with what is at hand and improvise, compromise and succeed.
Operation of the boat has not really changed. Still have twin props, still a hull speed just short of 6 knots (6.9 mph). What has changed is the planning and navigation. Without regenerative power we have to plan with power consumption. With batteries one should not run them totally dead. Always plan for about a 20% 'no touch' area to protect the battery life. In our case, we have about 670 usable amps that are available. Our "E' meter tells us exactly what power we have used and how long it will last based upon the rate of discharge over the last 10-12 minutes. It's nice to have that information available at the touch of a button.
For our longer distance cruises, we have adapted a temporary generator that run our battery charger at about 10 amps at best. Hi tech. chargers and modified sine wave generators are not very compatible for high output.Even the 10 amps will help some to increase longer distances. Over a 6-hour cruise, those 10 amps will return 60amps. Ifwe are traveling at 60 amps this has gained an extra hour of travel time. Of course now that we have made the trip, if it was one way, we need to allow adequate time to recharge. If we have used 550 amps and the charger output is 20 amps, potentially it could take 30-36 hours to recharge. Discharge rate and your speed are directly related and the need for speed shortens the trip. Here are some discharge rates that will help:
40-amp draw will run about 12.5 hrs.
60-amp draw will run about 8.5 hrs.
80-amp draw will run about 6.25 hrs.
Needless to say, the faster you attempt to travel, the shorter your travel time will be. This is where hull speed, weight and power storageneed to be considered.
Modern cruising vessels have high electrical demands, where refrigeration, radar, laptop computers and even plasma TVs are the norm. Keeping batteries charged is a challenge, and fitting a second alternator, says Scott Fratcher, is an easy solution
Alternator II
More charge needs either a bigger alternator, or better yet, a second alternator which adds significantly more potential to the boat than only increasing the amperage of the original alternator.
The math is easy. Imagine a typical diesel with a 55 amp alternator. If the alternator is removed and replaced with a 100 amp model, we gain 45 amps. If you add a second 130 amp alternator to the original 55 amp system, you instantly send a battery-boosting 185 amps into the electrical system.
Higher charging also increases the vessel’s safety margin. Single alternators may fail due to overwork – the constant heavy load to recharge the boat’s electrical demand takes its toll. This could lead to discharged batteries, with all electrical systems shut down. I’ve encountered many boaties who’ve spent an uncomfortable night in the shipping lanes alternating the last of the battery power between radar and navigation lights…
Many consider the decision to fit a second alternator a no-brainer. The only question is: how do you install one easily? This article discusses a technique to mount a second alternator on almost any inboard engine. And it’s worth noting that the process can be used to belt drive more than just an alternator – a hydraulic pump, dewatering bilge pump or anything else you might need to turn are also possibilities.
SIX STEPS TO ALTERNATOR II
- Design and planning
- Mounting a second front pulley
- Making a base plate
- Building a bracket from the base plate
- Installing a belt tensioning device
- Bolting in the alternator
DESIGN AND PLANNING
Start the design process by taking an alternator in hand and holding it next to the engine with the pulleys aligned.
There should be 12 possible positions: starboard low, starboard high, port low, port high, and above or below the drive pulley.
Face the alternator aft and you have six more possible locations – for a total of 12.
Hold the alternator in all 12 positions. Pick the best two or three positions and compare the possibilities. Choose a mounting position with the alternator as close to the engine as possible. Look for access, wire runs, mounting bolt holes in the engine and cooling air.
MOUNTING A SECOND PULLEY
We need to spin the second alternator from a second drive pulley at the front of the engine. Your engine may already have one, but usually you’ll have to add one, bolting it to the front of your existing engine pulley.
First, choose a pulley size. For a typical 30 to 75hp engine with maximum rpm of around 3600, a good drive pulley diameter is about 175mm.
I’ve experimented with larger pulleys (up to 230mm) but it’s not effective as most engines begin to hunt at low rpm. Conversely, if the pulley diameter is less than 150mm I often have to run the engine up to 1200rpm to get a good charge.
If in doubt, duplicating the original pulley size is usually a good bet.
There are two easy methods to fit a spare pulley to the front of an engine:
- Have a machine shop make the new pulley; or,
- Modify an existing pulley.
METHOD 1
A machine shop makes the new pulley, the simplest but most expensive option.
The machine shop will need the bolt pattern and centering ring measurements from the existing drive pulley on your engine. If you can take the measurements from the manual, the machine shop should have an easy job. If you have to take the measurements yourself, use digital calipers. Be sure to scrape away any old paint so your measurement is metal to metal.
Note: If the alternator is to produce more than 80amps, you should use a dual belt drive. You’re pushing the limit with a single belt – it will often slip, leaving gobs of black, sticky dust in your engineroom.
METHOD 2
Buy an “off-the-shelf” pulley at your local hardware store and have a machine shop make a new centering ring that fits your engine. You can even use an old car’s sheetmetal “stamped” pulley. The machine shop will combine the pulley onto a centering ring and you’re ready to install.
This option has the advantage of knowing the pulley face angles are going to be correct and smooth. It does not take much angle error, a nick or lathe marks left in the pulley face to make the belt begin to “dust”. Belt dusting is the major problem in building a dual alternator system. Twist, misalignment, rough surfaces, and drawing too much load all add to the amount of the belt dust. Commercial pulleys help solve this issue.
MAKING THE BASE PLATE
The base plate is a steel plate that gets bolted to the engine, and it becomes the base which holds the soon-to-be fabricated alternator bracket. The bracket is typically welded to the base plate.
Look for flat areas on the side of the engine block near where you want to mount your alternator. You want the plate to cover a minimum of three bolt holes – five or six is better.
Cut a piece of steel to cover the bolt holes. Using 6mm plate is the minimum – 8mm is better. Test fit the piece of steel over the area of the engine block. If it all fits and covers the bolt holes, you’re ready to start marking and drilling the holes.
Marking where the holes are to be drilled can be challenging, especially if the plate is in a difficult to reach location. Here’s an easy trick – it’s what I call the “sneak and tap” approach, and involves using a sharpened bolt screwed into each of the engine bolt holes (one at a time) to serve as a “reverse punch”.
Leave just enough bolt thread (the sharpened point) showing so you can use a pair of pliers to remove the bolt. Lay the base plate in the exact final location. Now for the tricky part – strike the steel plate with a single sharp blow from a hammer directly over the punch. Once marked you are ready to drill the hole.
Remove the bolt/punch and shift it to a new hole. Fasten the base plate (with a bolt through the newly-drilled hole) in position. Another sharp tap, remove the plate and drill the new hole. Repeat this process until all holes are drilled. This method is fast and easy and leaves no sloppy holes. If you make the base plate perfect, the rest of the job becomes much easier.
BUILDING A BRACKET
The bracket is the metal frame that holds the alternator, allowing it to pivot for tensioning the belt. I like to use a 50mm piece of 6mm flat bar. Cut two ears and weld them on the flat bar at a 90º angle (see photo).You should now have a base plate and bracket all made up. They may need to be connected with a strut (depending on the position of the alternator) to get the two pulleys in alignment. It’s usually the simplest to weld the plate, strut and bracket together.
ALIGNMENT
To find the correct alignment for the alternator, lay a wooden dowel rod in the drive pulley of the engine. Let the rod find its natural centre. You can now simply lift the rod up and down to show where an exact straight line to the slave pulley will fall. Reverse the procedure until the slave pulley is pointed directly at the drive pulley.
Remove all parts and tack the strut into position.
Replace and see if it all fits. If it does it’s time to weld it up and paint. Use this dowel rod method anytime you want an easy check of belt alignment.
MAKING A BELT-TENSIONER
Turnbuckle tension arms are an easy solution for making an alternator adjusting arm, and you only need simple tools – a hacksaw, welder and a drill. If you were making a conventional car-type tensioning arm, you’d have to cut an arc in the flat bar with an oxy-acetylene torch. Many boaties fit this turnbuckle swing arm to their existing alternator just to solve adjustment problems.
Begin with a half-inch or larger open barrel turnbuckle, and remove the studs from the barrel.
Cut the centre out of the barrel, leaving leavening 120 to 150mm of turnbuckle barrel.
Weld the barrel back together. Put the studs back in place and cut them to the length you worked out for the project at hand. Weld a flat plate to the end of each stud, drill a hole in the plates and mount to the engine.
STOP ENGINE BEFORE TURNING “OFF”
Ever notice what battery switches have printed on their faces? We all know not to disconnect the batteries while the engine is running, but what would happen if we did?
An alternator diode would fail – and that’s not good.
The reason is buried in Ohm’s Law which lays out the relationship between volts, amps, and watts. An alternator’s total power output is measured in watts. A typical high-output alternator might be charging 100amps at 14V – 100 x 14 = 1400 watts. If we had a 24-volt system, the alternator would be producing 50amps at 28 volts to make 1400 watts.
So, when we have an alternator producing 1400 watts and someone turns off the battery switch, the 1400 watts is already in the pipeline, so to speak. But the load (or current or amp draw) just dropped to zero because of disconnection to the battery.
Ohm’s Law tells us 1400 watts divided by zero (our new amp load) equals infinity. In other words, the voltage inside the alternator will climb toward infinity till it finds an escape route (the path of least resistance). That’s the shortest path to ground and typically, that’s the thin film inside a diode. Pop! The diode shorts.
Quickly switching the batteries back on might save the situation, but usually the damage is done. The boat owner may see the output of the alternator suddenly drop by a third. A typical complaint from boaties is: “My 100amp alternator is now producing 66 amps on the meter.”
This is because the alternator stator is really three-phase, and has three separate windings combining to produce 100amps. Since only the diode was ruined, each phase of the stator is still producing 33amps. If all three phases of the alternator are still producing 33amps each, why is the boat’s electrical meter only showing 66amps?
The “lost” 33amps are still being produced, but they’re not being rectified because that is the diode’s job. And un-rectified means alternating current (AC) is entering your DC system.
This is bad. At the same time that we are charging at 14 volts DC, we are also sending a battery-destroying AC “charge” into the boat’s electrical system. And because the boat’s electrical charge meter does not read AC, the owner has no clue something has gone wrong.
Those 33 AC amps are destroying the boat’s battery bank, electrical boards, and maybe even the hull zincs.
DIODE TEST
To check whether your alternator has a shorted diode you can clamp the positive alternator output lead with an AC/DC “clamp amp” meter. Switch the meter to DC amp and read the charge rate. Switch the meter to AC and we should see three or four amps.
A reading half of the DC charge rate indicates a bad diode. For example, if we were to see 66amps DC and 33amps AC, this would tell the technician it’s time to pull the alternator and change the diode pack.
Although not as accurate, we might also take a high-quality digital volt meter and measure voltage at the back of the alternator. We should see around 14 volts, but switch to AC and we should see around seven volts. Reading 14 volts AC could also indicate a faulty diode.
Adapted from Scott Fratcher’s How To Make Money With Boats, available at www.yachtwork.com
AUTO TENSIONING ARM
An automatic tensioning arm is another easy solution for a DIY installed alternator.
You can buy a “rasta” or LoveJoy arm for automatic belt tensioning from a good bearing supply house. Check out http://www.lovejoy-inc.com/
The device costs about $100. Simply mount the roller inside the unloaded belt between the drive pulley and alternator. In the photo above, the pulleys turn clockwise. Adjust the tension and ignore it for the life of the belt.
The second advantage of using a “rasta” or LoveJoy tensioning arm is the alternator does not have to rotate away from the engine to adjust the belt. This may mean a lot if you have a tight space to work in. You simply mount the alternator as close to the engine as you can manage and let the tensioning arm take up the belt slack.
AUTHOR PROFILE
Scott Fratcher has designed and installed more than 100 dual alternator systems. More photos can be found at www.yachtwork.com
Mr. Fratcher’s highly regarded books include
- How to Make Money with Boats
- Metal Boat Repair and Maintenance
- How to Buy Your Cruising Boat Now
- Earthrace – First Time Around
Mr. Fratcher also has an excellent website that is highly recommended to all easyacdc.com readers. Please be sure to visit Team Yachtwork and thank him for his thoughtful generosity.
A GFCI, or ground fault circuit interrupter, is an inexpensive (~$20 each), switch-like device that continuously monitors current in the hot and neutral conductors. When the GFCI detects an imbalance between the two, as would occur if there were a short to ground, it instantly trips the circuit.
A single GFCI can protect persons throughout the boat if it is located on the main AC feed, but because boats usually have various small current leaks, the unit may trip frequently with no indication of the source of the fault. It may be more practical to install one GFCI on each of the circuits to wet locations, such as head, galley, engine room, and weather deck.
GFCIs are extremely sensitive and can be tripped by “steam” or dense moisture in the air such as from cooking or showering, so they should be mounted in dry locations. On gas-powered boats, GFCIs must be ignition protected, or located in areas where fumes cannot collect. GFCIs should be checked at least monthly.
