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Category Archives: Basic Marine Electrical

Aerator Pump

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

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

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

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

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

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

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.

Basic AC Theory

Most students of electricity begin their study with what is known as direct current (DC), which is electricity flowing in a constant direction, and/or possessing a voltage with constant polarity. DC is the kind of electricity made by a battery (with definite positive and negative terminals), or the kind of charge generated by rubbing certain types of materials against each other.

As useful and as easy to understand as DC is, it is not the only "kind" of electricity in use. Certain sources of electricity (most notably, rotary electro-mechanical generators) naturally produce voltages alternating in polarity, reversing positive and negative over time. Either as a voltage switching polarity or as a current switching direction back and forth, this "kind" of electricity is known as Alternating Current (AC): Figure below

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Direct vs alternating current

Whereas the familiar battery symbol is used as a generic symbol for any DC voltage source, the circle with the wavy line inside is the generic symbol for any AC voltage source.

One might wonder why anyone would bother with such a thing as AC. It is true that in some cases AC holds no practical advantage over DC. In applications where electricity is used to dissipate energy in the form of heat, the polarity or direction of current is irrelevant, so long as there is enough voltage and current to the load to produce the desired heat (power dissipation). However, with AC it is possible to build electric generators, motors and power distribution systems that are far more efficient than DC, and so we find AC used predominately across the world in high power applications. To explain the details of why this is so, a bit of background knowledge about AC is necessary.

If a machine is constructed to rotate a magnetic field around a set of stationary wire coils with the turning of a shaft, AC voltage will be produced across the wire coils as that shaft is rotated, in accordance with Faraday's Law of electromagnetic induction. This is the basic operating principle of an AC generator, also known as an alternator: Figure below

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Alternator operation

Notice how the polarity of the voltage across the wire coils reverses as the opposite poles of the rotating magnet pass by. Connected to a load, this reversing voltage polarity will create a reversing current direction in the circuit. The faster the alternator's shaft is turned, the faster the magnet will spin, resulting in an alternating voltage and current that switches directions more often in a given amount of time.

While DC generators work on the same general principle of electromagnetic induction, their construction is not as simple as their AC counterparts. With a DC generator, the coil of wire is mounted in the shaft where the magnet is on the AC alternator, and electrical connections are made to this spinning coil via stationary carbon "brushes" contacting copper strips on the rotating shaft. All this is necessary to switch the coil's changing output polarity to the external circuit so the external circuit sees a constant polarity: Figure below

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DC generator operation

The generator shown above will produce two pulses of voltage per revolution of the shaft, both pulses in the same direction (polarity). In order for a DC generator to produce constant voltage, rather than brief pulses of voltage once every 1/2 revolution, there are multiple sets of coils making intermittent contact with the brushes. The diagram shown above is a bit more simplified than what you would see in real life.

The problems involved with making and breaking electrical contact with a moving coil should be obvious (sparking and heat), especially if the shaft of the generator is revolving at high speed. If the atmosphere surrounding the machine contains flammable or explosive vapors, the practical problems of spark-producing brush contacts are even greater. An AC generator (alternator) does not require brushes and commutators to work, and so is immune to these problems experienced by DC generators.

The benefits of AC over DC with regard to generator design is also reflected in electric motors. While DC motors require the use of brushes to make electrical contact with moving coils of wire, AC motors do not. In fact, AC and DC motor designs are very similar to their generator counterparts (identical for the sake of this tutorial), the AC motor being dependent upon the reversing magnetic field produced by alternating current through its stationary coils of wire to rotate the rotating magnet around on its shaft, and the DC motor being dependent on the brush contacts making and breaking connections to reverse current through the rotating coil every 1/2 rotation (180 degrees).

So we know that AC generators and AC motors tend to be simpler than DC generators and DC motors. This relative simplicity translates into greater reliability and lower cost of manufacture. But what else is AC good for? Surely there must be more to it than design details of generators and motors! Indeed there is. There is an effect of electromagnetism known as mutual induction, whereby two or more coils of wire placed so that the changing magnetic field created by one induces a voltage in the other. If we have two mutually inductive coils and we energize one coil with AC, we will create an AC voltage in the other coil. When used as such, this device is known as a transformer: Figure below

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Transformer "transforms" AC voltage and current.

The fundamental significance of a transformer is its ability to step voltage up or down from the powered coil to the unpowered coil. The AC voltage induced in the unpowered ("secondary") coil is equal to the AC voltage across the powered ("primary") coil multiplied by the ratio of secondary coil turns to primary coil turns. If the secondary coil is powering a load, the current through the secondary coil is just the opposite: primary coil current multiplied by the ratio of primary to secondary turns. This relationship has a very close mechanical analogy, using torque and speed to represent voltage and current, respectively: Figure below

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Speed multiplication gear train steps torque down and speed up. Step-down transformer steps voltage down and current up.

If the winding ratio is reversed so that the primary coil has less turns than the secondary coil, the transformer "steps up" the voltage from the source level to a higher level at the load: Figure below

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Speed reduction gear train steps torque up and speed down. Step-up transformer steps voltage up and current down.

The transformer's ability to step AC voltage up or down with ease gives AC an advantage unmatched by DC in the realm of power distribution in figure below. When transmitting electrical power over long distances, it is far more efficient to do so with stepped-up voltages and stepped-down currents (smaller-diameter wire with less resistive power losses), then step the voltage back down and the current back up for industry, business, or consumer use use.

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Transformers enable efficient long distance high voltage transmission of electric energy.

Transformer technology has made long-range electric power distribution practical. Without the ability to efficiently step voltage up and down, it would be cost-prohibitive to construct power systems for anything but close-range (within a few miles at most) use.

As useful as transformers are, they only work with AC, not DC. Because the phenomenon of mutual inductance relies on changing magnetic fields, and direct current (DC) can only produce steady magnetic fields, transformers simply will not work with direct current. Of course, direct current may be interrupted (pulsed) through the primary winding of a transformer to create a changing magnetic field (as is done in automotive ignition systems to produce high-voltage spark plug power from a low-voltage DC battery), but pulsed DC is not that different from AC. Perhaps more than any other reason, this is why AC finds such widespread application in power systems.

REVIEW:

DC stands for "Direct Current," meaning voltage or current that maintains constant polarity or direction, respectively, over time.
AC stands for "Alternating Current," meaning voltage or current that changes polarity or direction, respectively, over time.
AC electromechanical generators, known as alternators, are of simpler construction than DC electromechanical generators.
AC and DC motor design follows respective generator design principles very closely.
A transformer is a pair of mutually-inductive coils used to convey AC power from one coil to the other. Often, the number of turns in each coil is set to create a voltage increase or decrease from the powered (primary) coil to the unpowered (secondary) coil.
Secondary voltage = Primary voltage (secondary turns / primary turns)
Secondary current = Primary current (primary turns / secondary turns)

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

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 Boxes

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

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

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

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

Battery Cables

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

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

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

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

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

Battery Management

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

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

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

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

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.

Bilge Pumps

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.