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Alternator

An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current. Usually the word refers to small rotating machines driven by automotive and other internal combustion engines.

Alternators are used in modern automobiles to charge the battery and to power a car’s electric system when its engine is running. Automotive alternators use a set of rectifiers (diode bridge) to convert the AC output of the alternator to the DC used in vehicle’s electrical system .

Marine alternators used in yachts are similar to automotive alternators, with appropriate adaptations to the salt-water environment. Marine alternators are designed to be explosion proof so that brush sparking will not ignite explosive gas mixtures in an engine room environment. They may be 12 or 24 volt depending on the type of system installed. Larger marine diesels may have two or more alternators to cope with the heavy electrical demand of a modern yacht. On single alternator circuits, the power is split between the engine starting battery and the domestic or house battery (or batteries) by use of a split-charge diode (battery isolator) or a mechanical switch (battery switch)

-adapted from Wikipedia

Anderson Connectors

Anderson Connectors or Anderson Plugs as they are more commonly known, are designed for connecting large cables used in high current applications.

Each plug is a mirror of the other and are simple to assemble, There is no Male & Female. One simply connects into another of the same amperage. The plugs push together to form a very solid and reliable connection.

A common application in marine would be in the wiring that distributes AC power.

From the Anderson Power Products website:

Anderson Power Products is an industry leader in the manufacture of high current, quick-disconnect power connectors and provides a variety of interconnect solutions for the material handling, telecommunications, medical, power electronics and other industries. Our connectors are available from 10 to 700 amp maximum ratings for use through 600 Volts continuous, AC or DC operation. We are well known for our ability to develop creative solutions for our customers’ power interconnect requirements. We are flexible and will make modifications to standard products or develop complete custom solutions to satisfy particular customers’ needs. APP provides a complete engineered interconnect solution for all types of power distribution needs.

Battery

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 Terminology

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

Ampere-Hour -- One ampere-hour is equal to a current of one ampere flowing for one hour. A unit-quantity of electricity used as a measure of the amount of electrical charge that may be obtained from a storage battery before it requires recharging.
Ampere-Hour Capacity -- The number of ampere-hours which can be delivered by a storage battery on a single discharge. The ampere-hour capacity of a battery on discharge is determined by a number of factors, of which the following are the most important: final limiting voltage; quantity of electrolyte; discharge rate; density of electrolyte; design of separators; temperature, age, and life history of the battery; and number, design, and dimensions of electrodes.
Anode -- In a primary or secondary cell, the metal electrode that gives up electrons to the load circuit and dissolves into the electrolyte.
Aqueous Batteries -- Batteries with water-based electrolytes.
Available Capacity -- The total battery capacity, usually expressed in ampere-hours or milliampere-hours that are available to perform work. This depends on factors such as the endpoint voltage, quantity and density of electrolyte, temperature, discharge rate, age, and the life history of the battery.
Battery -- A device that transforms chemical energy into electric energy. The term is usually applied to a group of two or more electric cells connected together electrically. In common usage, the term "battery" is also applied to a single cell, such as a household battery.
Battery Types -- There are, in general, two type of batteries: primary batteries, and secondary storage or accumulator batteries. Primary types, although sometimes consisting of the same active materials as secondary types, are constructed so that only one continuous or intermittent discharge can be obtained. Secondary types are constructed so that they may be recharged, following a partial or complete discharge, by the flow of direct current through them in a direction opposite to the current flow on discharge. By recharging after discharge, a higher state of oxidation is created at the positive plate or electrode and a lower state at the negative plate, returning the plates to approximately their original charged condition.
Battery Capacity -- The electric output of a cell or battery on a service test delivered before the cell reaches a specified final electrical condition and may be expressed in ampere-hours, watt-hours, or similar units. The capacity in watt-hours is equal to the capacity in ampere-hours multiplied by the battery voltage.
Battery Charger -- A device capable of supplying electrical energy to a battery.
Battery-Charging Rate -- The current expressed in amperes at which a storage battery is charged.
Battery Voltage, final -- The prescribed lower-limit voltage at which battery discharge is considered complete. The cutoff or final voltage is usually chosen so that the useful capacity of the battery is realized. The cutoff voltage varies with the type of battery, the rate of discharge, the temperature, and the kind of service in which the battery is used. The term "cutoff voltage" is applied more particularly to primary batteries, and "final voltage" to storage batteries. Synonym: Voltage, cutoff.
C -- The rated capacity, in ampere-hours, for a specific, constant discharge current (where i is the number of hours the cell can deliver this current). For example, the C₅ capacity is the ampere-hours that can be delivered by a cell at constant current in 5 hours. As a cell's capacity is not the same at all rates, C₅ is usually less than C₂₀ for the same cell.
Capacity -- The quantity of electricity delivered by a battery under specified conditions, usually expressed in ampere-hours.
Cathode -- In a primary or secondary cell, the electrode that, in effect, oxidizes the anode or absorbs the electrons.
Cell -- An electrochemical device, composed of positive and negative plates, separator, and electrolyte, which is capable of storing electrical energy. When encased in a container and fitted with terminals, it is the basic "building block" of a battery.
Charge -- Applied to a storage battery, the conversion of electric energy into chemical energy within the cell or battery. This restoration of the active materials is accomplished by maintaining a unidirectional current in the cell or battery in the opposite direction to that during discharge; a cell or battery which is said to be charged is understood to be fully charged.
Charge Rate -- The current applied to a secondary cell to restore its capacity. This rate is commonly expressed as a multiple of the rated capacity of the cell. For example, the C/10 charge rate of a 500 Ah cell is expressed as,
C/10 rate = 500 Ah / 10 h = 50 A.
Charge, state of -- Condition of a cell in terms of the capacity remaining in the cell.
Charging -- The process of supplying electrical energy for conversion to stored chemical energy.
Constant-Current Charge -- A charging process in which the current of a storage battery is maintained at a constant value. For some types of lead-acid batteries this may involve two rates called the starting and finishing rates.
Constant-Voltage Charge -- A charging process in which the voltage of a storage battery at the terminals of the battery is held at a constant value.
Cycle -- One sequence of charge and discharge. Deep cycling requires that all the energy to an end voltage established for each system be drained from the cell or battery on each discharge. In shallow cycling, the energy is partially drained on each discharge; i.e., the energy may be any value up to 50%.
Cycle Life -- For secondary rechargeable cells or batteries, the total number of charge/discharge cycles the cell can sustain before it becomes inoperative. In practice, end of life is usually considered to be reached when the cell or battery delivers approximately 80% of rated ampere-hour capacity.
Depth of Discharge -- The relative amount of energy withdrawn from a battery relative to how much could be withdrawn if the battery were discharged until exhausted.
Discharge -- The conversion of the chemical energy of the battery into electric energy.
Discharge, deep -- Withdrawal of all electrical energy to the end-point voltage before the cell or battery is recharged.
Discharge, high-rate -- Withdrawal of large currents for short intervals of time, usually at a rate that would completely discharge a cell or battery in less than one hour.
Discharge, low-rate -- Withdrawal of small currents for long periods of time, usually longer than one hour.
Drain -- Withdrawal of current from a cell.
Dry Cell -- A primary cell in which the electrolyte is absorbed in a porous medium, or is otherwise restrained from flowing. Common practice limits the term "dry cell" to the Leclanch" cell, which is the common commercial type.
Electrochemical Couple -- The system of active materials within a cell that provides electrical energy storage through an electrochemical reaction.
Electrode -- An electrical conductor through which an electric current enters or leaves a conducting medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum. For electrolytic solutions, many solids, and molten masses, an electrode is an electrical conductor at the surface of which a change occurs from conduction by electrons to conduction by ions. For gases and vacuum, the electrodes merely serve to conduct electricity to and from the medium.
Electrolyte -- A chemical compound which, when fused or dissolved in certain solvents, usually water, will conduct an electric current. All electrolytes in the fused state or in solution give rise to ions which conduct the electric current.
Electropositivity -- The degree to which an element in a galvanic cell will function as the positive element of the cell. An element with a large electropositivity will oxidize faster than an element with a smaller electropositivity.
End-of-Discharge Voltage -- The voltage of the battery at termination of a discharge.
Energy -- Output capability; expressed as capacity times voltage, or watt-hours.
Energy Density -- Ratio of cell energy to weight or volume (watt-hours per pound, or watt-hours per cubic inch).
Float Charging -- Method of recharging in which a secondary cell is continuously connected to a constant-voltage supply that maintains the cell in fully charged condition.
Galvanic Cell -- A combination of electrodes, separated by electrolyte, that is capable of producing electrical energy by electrochemical action.
Gassing -- The evolution of gas from one or both of the electrodes in a cell. Gassing commonly results from self-discharge or from the electrolysis of water in the electrolyte during charging.
Internal Resistance -- The resistance to the flow of an electric current within the cell or battery.
Memory Effect -- A phenomenon in which a cell, operated in successive cycles to the same, but less than full, depth of discharge, temporarily loses the remainder of its capacity at normal voltage levels (usually applies only to Ni-Cd cells).
Negative Terminal -- The terminal of a battery from which electrons flow in the external circuit when the cell discharges.
Nonaqueous Batteries -- Cells that do not contain water, such as those with molten salts or organic electrolytes.
Ohm's Law -- The formula that describes the amount of current flowing through a circuit. Voltage = Current " Resistance.
Open Circuit -- Condition of a battery which is neither on charge nor on discharge (i.e., disconnected from a circuit).
Open-Circuit Voltage -- The difference in potential between the terminals of a cell when the circuit is open (i.e., a no-load condition).
Oxidation -- A chemical reaction that results in the release of electrons by an electrode's active material.
Parallel Connection -- The arrangement of cells in a battery made by connecting all positive terminals together and all negative terminals together, the voltage of the group being only that of one cell and the current drain through the battery being divided among the several cells. See Series Connection.
Polarity -- Refers to the charges residing at the terminals of a battery.
Positive Terminal -- The terminal of a battery toward which electrons flow through the external circuit when the cell discharges.
Primary Battery -- A battery made up of primary cells. See Primary Cell.
Primary Cell -- A cell designed to produce electric current through an electrochemical reaction that is not efficiently reversible. Hence the cell, when discharged, cannot be efficiently recharged by an electric current. Note: When the available energy drops to zero, the cell is usually discarded. Primary cells may be further classified by the types of electrolyte used.
Rated Capacity -- The number of ampere-hours a cell can deliver under specific conditions (rate of discharge, end voltage, temperature); usually the manufacturer's rating.
Rechargeable -- Capable of being recharged; refers to secondary cells or batteries.
Recombination -- State in which the gasses normally formed within the battery cell during its operation, are recombined to form water.
Reduction -- A chemical process that results in the acceptance of electrons by an electrode's active material.
Seal -- The structural part of a galvanic cell that restricts the escape of solvent or electrolyte from the cell and limits the ingress of air into the cell (the air may dry out the electrolyte or interfere with the chemical reactions).
Secondary Battery -- A battery made up of secondary cells. See Storage Battery; Storage Cell.
Self Discharge -- Discharge that takes place while the battery is in an open-circuit condition.
Separator -- The permeable membrane that allows the passage of ions, but prevents electrical contact between the anode and the cathode.
Series Connection -- The arrangement of cells in a battery configured by connecting the positive terminal of each successive cell to the negative terminal of the next adjacent cell so that their voltages are cumulative. See Parallel Connection.
Shelf Life -- For a dry cell, the period of time (measured from date of manufacture), at a storage temperature of 21"C (69"F), after which the cell retains a specified percentage (usually 90%) of its original energy content.
Short-Circuit Current -- That current delivered when a cell is short-circuited (i.e., the positive and negative terminals are directly connected with a low-resistance conductor).
Starting-Lighting-Ignition (SLI) Battery -- A battery designed to start internal combustion engines and to power the electrical systems in automobiles when the engine is not running. SLI batteries can be used in emergency lighting situations.
Stationary Battery -- A secondary battery designed for use in a fixed location.
Storage Battery -- An assembly of identical cells in which the electrochemical action is reversible so that the battery may be recharged by passing a current through the cells in the opposite direction to that of discharge. While many non-storage batteries have a reversible process, only those that are economically rechargeable are classified as storage batteries. Synonym: Accumulator; Secondary Battery. See Secondary Cell.
Storage Cell -- An electrolytic cell for the generation of electric energy in which the cell after being discharged may be restored to a charged condition by an electric current flowing in a direction opposite the flow of current when the cell discharges. Synonym: Secondary Cell. See Storage Battery.
Taper Charge -- A charge regime delivering moderately high-rate charging current when the battery is at a low state of charge and tapering the current to lower rates as the battery becomes more fully charged.
Terminals -- The parts of a battery to which the external electric circuit is connected.
Thermal Runaway -- A condition whereby a cell on charge or discharge will destroy itself through internal heat generation caused by high overcharge or high rate of discharge or other abusive conditions.
Trickle Charging -- A method of recharging in which a secondary cell is either continuously or intermittently connected to a constant-current supply that maintains the cell in fully charged condition.
Vent -- A normally sealed mechanism that allows for the controlled escape of gases from within a cell.
Voltage, cutoff -- Voltage at the end of useful discharge. (See Voltage, end-point.)
Voltage, end-point -- Cell voltage below which the connected equipment will not operate or below which operation is not recommended.
Voltage, nominal -- Voltage of a fully charged cell when delivering rated current.
Wet Cell -- A cell, the electrolyte of which is in liquid form and free to flow and move.

Fratcher on Alternators

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

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.

Marine Electrical Checklist

Multimeter Safety

Using an electrical meter safely and efficiently is perhaps the most valuable skill an electronics technician can master, both for the sake of their own personal safety and for proficiency at their trade. It can be daunting at first to use a meter, knowing that you are connecting it to live circuits which may harbor life-threatening levels of voltage and current. This concern is not unfounded, and it is always best to proceed cautiously when using meters. Carelessness more than any other factor is what causes experienced technicians to have electrical accidents. Multimeter

The most common piece of electrical test equipment is a meter called the multimeter. Multimeters are so named because they have the ability to measure a multiple of variables: voltage, current, resistance, and often many others, some of which cannot be explained here due to their complexity. In the hands of a trained technician, the multimeter is both an efficient work tool and a safety device. In the hands of someone ignorant and/or careless, however, the multimeter may become a source of danger when connected to a "live" circuit.

There are many different brands of multimeters, with multiple models made by each manufacturer sporting different sets of features. The multimeter shown here in the following illustrations is a "generic" design, not specific to any manufacturer, but general enough to teach the basic principles of use:

You will notice that the display of this meter is of the "digital" type: showing numerical values using four digits in a manner similar to a digital clock. The rotary selector switch (now set in the Off position) has five different measurement positions it can be set in: two "V" settings, two "A" settings, and one setting in the middle with a funny-looking "horseshoe" symbol on it representing "resistance." The "horseshoe" symbol is the Greek letter "Omega" (Ω), which is the common symbol for the electrical unit of ohms.

Of the two "V" settings and two "A" settings, you will notice that each pair is divided into unique markers with either a pair of horizontal lines (one solid, one dashed), or a dashed line with a squiggly curve over it. The parallel lines represent "DC" while the squiggly curve represents "AC." The "V" of course stands for "voltage" while the "A" stands for "amperage" (current). The meter uses different techniques, internally, to measure DC than it uses to measure AC, and so it requires the user to select which type of voltage (V) or current (A) is to be measured. Although we haven't discussed alternating current (AC) in any technical detail, this distinction in meter settings is an important one to bear in mind.

There are three different sockets on the multimeter face into which we can plug our test leads. Test leads are nothing more than specially-prepared wires used to connect the meter to the circuit under test. The wires are coated in a color-coded (either black or red) flexible insulation to prevent the user's hands from contacting the bare conductors, and the tips of the probes are sharp, stiff pieces of wire:

boat wiring image

The black test lead always plugs into the black socket on the multimeter: the one marked "COM" for "common." The red test lead plugs into either the red socket marked for voltage and resistance, or the red socket marked for current, depending on which quantity you intend to measure with the multimeter.

To see how this works, let's look at a couple of examples showing the meter in use. First, we'll set up the meter to measure DC voltage from a battery:

boat wiring image

Note that the two test leads are plugged into the appropriate sockets on the meter for voltage, and the selector switch has been set for DC "V". Now, we'll take a look at an example of using the multimeter to measure AC voltage from a household electrical power receptacle (wall socket):

boat wiring image

The only difference in the setup of the meter is the placement of the selector switch: it is now turned to AC "V". Since we're still measuring voltage, the test leads will remain plugged in the same sockets. In both of these examples, it is imperative that you not let the probe tips come in contact with one another while they are both in contact with their respective points on the circuit. If this happens, a short-circuit will be formed, creating a spark and perhaps even a ball of flame if the voltage source is capable of supplying enough current! The following image illustrates the potential for hazard:

boat wiring image

This is just one of the ways that a meter can become a source of hazard if used improperly.

Voltage measurement is perhaps the most common function a multimeter is used for. It is certainly the primary measurement taken for safety purposes (part of the lock-out/tag-out procedure), and it should be well understood by the operator of the meter. Being that voltage is always relative between two points, the meter must be firmly connected to two points in a circuit before it will provide a reliable measurement. That usually means both probes must be grasped by the user's hands and held against the proper contact points of a voltage source or circuit while measuring.

Because a hand-to-hand shock current path is the most dangerous, holding the meter probes on two points in a high-voltage circuit in this manner is always a potential hazard. If the protective insulation on the probes is worn or cracked, it is possible for the user's fingers to come into contact with the probe conductors during the time of test, causing a bad shock to occur. If it is possible to use only one hand to grasp the probes, that is a safer option. Sometimes it is possible to "latch" one probe tip onto the circuit test point so that it can be let go of and the other probe set in place, using only one hand. Special probe tip accessories such as spring clips can be attached to help facilitate this.

Remember that meter test leads are part of the whole equipment package, and that they should be treated with the same care and respect that the meter itself is. If you need a special accessory for your test leads, such as a spring clip or other special probe tip, consult the product catalog of the meter manufacturer or other test equipment manufacturer. Do not try to be creative and make your own test probes, as you may end up placing yourself in danger the next time you use them on a live circuit.

Also, it must be remembered that digital multimeters usually do a good job of discriminating between AC and DC measurements, as they are set for one or the other when checking for voltage or current. As we have seen earlier, both AC and DC voltages and currents can be deadly, so when using a multimeter as a safety check device you should always check for the presence of both AC and DC, even if you're not expecting to find both! Also, when checking for the presence of hazardous voltage, you should be sure to check all pairs of points in question.

For example, suppose that you opened up an electrical wiring cabinet to find three large conductors supplying AC power to a load. The circuit breaker feeding these wires (supposedly) has been shut off, locked, and tagged. You double-checked the absence of power by pressing the Start button for the load. Nothing happened, so now you move on to the third phase of your safety check: the meter test for voltage.

First, you check your meter on a known source of voltage to see that it's working properly. Any nearby power receptacle should provide a convenient source of AC voltage for a test. You do so and find that the meter indicates as it should. Next, you need to check for voltage among these three wires in the cabinet. But voltage is measured between two points, so where do you check?

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The answer is to check between all combinations of those three points. As you can see, the points are labeled "A", "B", and "C" in the illustration, so you would need to take your multimeter (set in the voltmeter mode) and check between points A & B, B & C, and A & C. If you find voltage between any of those pairs, the circuit is not in a Zero Energy State. But wait! Remember that a multimeter will not register DC voltage when it's in the AC voltage mode and vice versa, so you need to check those three pairs of points in each mode for a total of six voltage checks in order to be complete!

However, even with all that checking, we still haven't covered all possibilities yet. Remember that hazardous voltage can appear between a single wire and ground (in this case, the metal frame of the cabinet would be a good ground reference point) in a power system. So, to be perfectly safe, we not only have to check between A & B, B & C, and A & C (in both AC and DC modes), but we also have to check between A & ground, B & ground, and C & ground (in both AC and DC modes)! This makes for a grand total of twelve voltage checks for this seemingly simple scenario of only three wires. Then, of course, after we've completed all these checks, we need to take our multimeter and re-test it against a known source of voltage such as a power receptacle to ensure that it's still in good working order.

Using a multimeter to check for resistance is a much simpler task. The test leads will be kept plugged in the same sockets as for the voltage checks, but the selector switch will need to be turned until it points to the "horseshoe" resistance symbol. Touching the probes across the device whose resistance is to be measured, the meter should properly display the resistance in ohms:

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One very important thing to remember about measuring resistance is that it must only be done on de-energized components! When the meter is in "resistance" mode, it uses a small internal battery to generate a tiny current through the component to be measured. By sensing how difficult it is to move this current through the component, the resistance of that component can be determined and displayed. If there is any additional source of voltage in the meter-lead-component-lead-meter loop to either aid or oppose the resistance-measuring current produced by the meter, faulty readings will result. In a worse-case situation, the meter may even be damaged by the external voltage.

The "resistance" mode of a multimeter is very useful in determining wire continuity as well as making precise measurements of resistance. When there is a good, solid connection between the probe tips (simulated by touching them together), the meter shows almost zero Ω. If the test leads had no resistance in them, it would read exactly zero:

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If the leads are not in contact with each other, or touching opposite ends of a broken wire, the meter will indicate infinite resistance (usually by displaying dashed lines or the abbreviation "O.L." which stands for "open loop"):

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By far the most hazardous and complex application of the multimeter is in the measurement of current. The reason for this is quite simple: in order for the meter to measure current, the current to be measured must be forced to go through the meter. This means that the meter must be made part of the current path of the circuit rather than just be connected off to the side somewhere as is the case when measuring voltage. In order to make the meter part of the current path of the circuit, the original circuit must be "broken" and the meter connected across the two points of the open break. To set the meter up for this, the selector switch must point to either AC or DC "A" and the red test lead must be plugged in the red socket marked "A". The following illustration shows a meter all ready to measure current and a circuit to be tested:

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Now, the circuit is broken in preparation for the meter to be connected:

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The next step is to insert the meter in-line with the circuit by connecting the two probe tips to the broken ends of the circuit, the black probe to the negative (-) terminal of the 9-volt battery and the red probe to the loose wire end leading to the lamp:

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This example shows a very safe circuit to work with. 9 volts hardly constitutes a shock hazard, and so there is little to fear in breaking this circuit open (bare handed, no less!) and connecting the meter in-line with the flow of electrons. However, with higher power circuits, this could be a hazardous endeavor indeed. Even if the circuit voltage was low, the normal current could be high enough that an injurious spark would result the moment the last meter probe connection was established.

Another potential hazard of using a multimeter in its current-measuring ("ammeter") mode is failure to properly put it back into a voltage-measuring configuration before measuring voltage with it. The reasons for this are specific to ammeter design and operation. When measuring circuit current by placing the meter directly in the path of current, it is best to have the meter offer little or no resistance against the flow of electrons. Otherwise, any additional resistance offered by the meter would impede the electron flow and alter the circuit's operation. Thus, the multimeter is designed to have practically zero ohms of resistance between the test probe tips when the red probe has been plugged into the red "A" (current-measuring) socket. In the voltage-measuring mode (red lead plugged into the red "V" socket), there are many mega-ohms of resistance between the test probe tips, because voltmeters are designed to have close to infinite resistance (so that they don't draw any appreciable current from the circuit under test).

When switching a multimeter from current- to voltage-measuring mode, it's easy to spin the selector switch from the "A" to the "V" position and forget to correspondingly switch the position of the red test lead plug from "A" to "V". The result -- if the meter is then connected across a source of substantial voltage -- will be a short-circuit through the meter!

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To help prevent this, most multimeters have a warning feature by which they beep if ever there's a lead plugged in the "A" socket and the selector switch is set to "V". As convenient as features like these are, though, they are still no substitute for clear thinking and caution when using a multimeter.

All good-quality multimeters contain fuses inside that are engineered to "blow" in the event of excessive current through them, such as in the case illustrated in the last image. Like all overcurrent protection devices, these fuses are primarily designed to protect the equipment (in this case, the meter itself) from excessive damage, and only secondarily to protect the user from harm. A multimeter can be used to check its own current fuse by setting the selector switch to the resistance position and creating a connection between the two red sockets like this:

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A good fuse will indicate very little resistance while a blown fuse will always show "O.L." (or whatever indication that model of multimeter uses to indicate no continuity). The actual number of ohms displayed for a good fuse is of little consequence, so long as it's an arbitrarily low figure.

So now that we've seen how to use a multimeter to measure voltage, resistance, and current, what more is there to know? Plenty! The value and capabilities of this versatile test instrument will become more evident as you gain skill and familiarity using it. There is no substitute for regular practice with complex instruments such as these, so feel free to experiment on safe, battery-powered circuits.

REVIEW:

A meter capable of checking for voltage, current, and resistance is called a multimeter,
As voltage is always relative between two points, a voltage-measuring meter ("voltmeter") must be connected to two points in a circuit in order to obtain a good reading. Be careful not to touch the bare probe tips together while measuring voltage, as this will create a short-circuit!
Remember to always check for both AC and DC voltage when using a multimeter to check for the presence of hazardous voltage on a circuit. Make sure you check for voltage between all pair-combinations of conductors, including between the individual conductors and ground!
When in the voltage-measuring ("voltmeter") mode, multimeters have very high resistance between their leads.
Never try to read resistance or continuity with a multimeter on a circuit that is energized. At best, the resistance readings you obtain from the meter will be inaccurate, and at worst the meter may be damaged and you may be injured.
Current measuring meters ("ammeters") are always connected in a circuit so the electrons have to flow through the meter.
When in the current-measuring ("ammeter") mode, multimeters have practically no resistance between their leads. This is intended to allow electrons to flow through the meter with the least possible difficulty. If this were not the case, the meter would add extra resistance in the circuit, thereby affecting the current.

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

Nanobots

Nanobots are full-time employees of Ancor Wire who move copper to those areas of a boat’s marine electrical system that most require it.

Employed in a process called Nanotechnological Overload Sensing Heat Induced Tranference, the nanobots work to allow a boat wiring harness to move copper according to the power demands of attached accessories. This feature is currently found exclusively in Nanotech Brand Wire.

Because of limited production, this clever boat wiring product is only available one day each year.

VSR – Smart Battery Switch

The VSR, or Voltage Sensitive Relay, is a very handy little box that solves a load of traditional charging problems on marine electrical systems. It essentially serves as a smart battery switch deciding automatically when either one or two batteries are charged – or discharged. It works great on almost any boat with multiple batteries – and eliminates all of the guesswork that used to come with manual battery switches.

What a VSR does

The VSR is installed between two batteries. Many people are surprised to learn that it is NOT connected to either the alternator or charger output wires! Its setup is much more clever.

If either battery goes above 13.7 volts (due to either alternator or charger output), the VSR connects both batteries together. Both batteries are now charging – without the boater ever having to throw a switch.

Alternately, when the system voltage drops back below 12.6 volts, i.e., no more charging, the relay opens and the batteries are separate. This means that both batteries now discharge independently.

How a VSR changes real world boating

Let’s say that a fishing boat has a two battery setup. As is often the case, one of the batteries is dedicated to an important job – starting the engine. The other battery is used for other operations, including trolling.

As the fisherman runs the boat from hole to hole, the engine alternator elevates the voltage to the cranking battery above 13.7 volts. This triggers the VSR to automatically connect the starting battery and trolling battery together. Both are now charging.
Upon reaching his destination, the boater kills the engine – and, the alternator output – and begins trolling. Because of the lowered voltage, the VSR now disconnects the batteries. Because he is now discharging only one battery, our fisherman is going to have starting power when he needs it later – no matter how long he uses the trolling motor and depletes that trolling battery.
Once underway again, the alternator power causes the VSR to reconnect the batteries and begins replenishing the trolling battery.
Back home, the fisherman powers up his onboard battery charger. This increased voltage causes the VSR to once again link the batteries. This means that even a single output battery charger would now be charging both batteries!
Our fisherman has had a great day on the lake, getting to and from his fishing hole, trolled for hours without killing a battery and never once had to worry about the settings on a manual battery switch.