Post by tonyqj on Oct 27, 2016 8:49:51 GMT
Hey guys, here's something I collated a while back for a different purpose which I thought might be a useful resource here. All errors and omissions are mine so feel free to point out corrections to anything I've got wrong.
It's in two sections - general boat stuff and technical terms.
General boat terminology
Air draft
The distance between the surface of the water and the highest fixed point on the craft. It will vary depending upon the load and distribution of the load.
Anodes
More correctly known as a 'Sacrificial Anode' it is effectively a 'lump of metal' which is welded to your boat to allow it to corrode in preference to having your hull corrode. Anodes offer protection based on the Noble Series of metals. The theory is that by attaching a piece of metal to the hull that is more reactive than the hull itself then this piece of metal will corrode first. For canals the anode is generally made of magnesium. Zinc is used in seawater, and Aluminium in more brackish water.
Back Cabin
Also known as the Boatman's Cabin or just the Cabin, with 'Boatman’s Cabin' being the more modern term.
Over the generations of narrow boat use on the canals, the most efficient design for a cabin evolved and most back cabins have identical layouts, regardless of what carrying company the boat was built for or who built the boat.
On the left, just inside the door, is the cooking range; this position being chosen to keep the steerer's legs warm. In front of that is the table cupboard, with a vertical door which can double up as a table when lowered. A drawer below the table is known as the 'knife drawer' or 'crumb drawer' (due to the crumbs landing in it as the table is put away). In front of that is the 'bed ‘ole' with a cross bed that folds out across the width of the cabin. On the right side of the cabin is a simple bench for sitting on, which can also be used as a further bed, and is known simply as the 'side bed'.
Back End Beam
A large beam on the roof at the rear of the hold on a traditional boat (if it has a hold).
Base Plate
The bottom plate of a steel narrowboat. On modern boats it's usually 10mm or 12mm thick. Older boats might have 8mm or even 6mm base plates or (rarely) even thinner.
Bilge
The bottom of a boat's hull which may collect water which must be removed, usually with a pump. Narrow boats will typically be arranged such that the main cabin bilge is separate from the engine bilge, often a small compartment directly below the stern gland will also be provided.
Bow
The front end of a boat.
Bow Thruster
A small propeller, typically mounted in a tunnel or tube running through the bow. It is used to provide additional turning force when the boat is stationary or moving at slow speed.
Bulkhead
A wall within a boat, particularly a structural wall, which may also be watertight.
Chine
An angle in the hull profile. Typically canal going craft will have a single hard chine, where the sides plate and base plate meet at 90 degrees. However, boats may have a small bend in the side to prevent the base plate catching on lock walls. Wide-beam boats often have a significant double-chine, comprising two bends on the hull side before it meets the base plate.
Cratch
The area towards the front of the boat, behind the deck, typically on a modern narrowboat, a canvas covered area in front of the cabin and behind the Deck and Deck Board.
Cratch Board
Also known on traditional boats as the Deck Board, it is the name given to the vertical board at the front of the boat which protects the cratch. The shape is triangular with the top of the triangle cut off. On traditional boats it is common for the Deck Board to be highly decorated, but on modern boats is more likely to be varnished or painted a solid colour. The board is usually solid on a traditional boat but is glazed on modern boats. On a traditional boat the purpose of the Deck Board is to support the top planks and protect the cargo.
Counter
The part of the stern above the waterline that extends beyond the rear of the cabin over the swim.
Deck
The flat area at the bow of a narrowboat, in front of the Deck Beam. Often containing the Gas Locker.
Deck Beam
A large beam, traditionally made of Oak or Mahogany, at the rear of the deck and in front of the Cratch on which sits the Deck Board.
Deck Board
The 'correct' name for the Cratch Board.
Displacement
The weight of water displaced by the hull of a boat and hence equal to the total weight of the vessel.
Draft
The depth of water a boat draws, typically measured from the waterline to the lowest part under hull.
Elum
The name given to the rudder and tiller arrangement on a traditional horse-drawn boat or butty.
Foot Board
The piece of wood that makes the top step on the inside of the rear doors on a traditional boat. Another name for a Steering Step.
Gas Locker
A gas tight locker, often built into the Deck of a boat or at the stern on Semi-Trad and Cruiser-Stern boats. It contains the gas bottles. It must be gas tight to the interior of the craft and have low level vents to the outside.
Hull
The watertight part of a boat.
Narrowboat
A boat of a distinctive design, generally less than 7 feet wide, made to fit the narrow canals of the United Kingdom.
Port
The left hand side of the boat when stood on board and facing the bow.
Propeller
A type of fan that transmits power by converting rotational motion from the engine into thrust acting on the water.
Propeller Shaft
The drive shaft that passes through the Stern to supply rotational force to the propeller from the gearbox.
Rubbing strake
A strip or band fitted to the outside of the hull to provide protection when coming alongside something. Typically on a modern narrowboat these are steel and are welded to the hull.
Rudder
The plate and/or hydrofoil at the rear of the boat, which is pivoted to provide a mechanism with which to steer.
Rudder Post
The shaft which passes through the Counter and uxter of a narrowboat to which the rudder is attached.
Scantlings
A vessel's structural members. Typically on a narrowboat, steel beams welded to the baseplate to provide stiffness.
Seacock
A valve in the hull of a boat, which can be used to isolate whatever is attached to it from the water in which the boat is floating.
Skeg
The metal bar that the lower end of the rudder post is attached to which also protects the rudder from hitting obstructions. It is positioned behind the swim.
Skin tank
A steel tank, usually welded to the interior face (rarely on the exterior) of the hull, typically to provide engine cooling. It serves the same purpose as a radiator in a car. Coolant passes through the tank and is cooled by contact with the hull, or in the case of an exterior skin tank, contact with the water in which the boat is floating.
Starboard
The right hand side of a vessel when stood on board facing the bow.
Steering Step
The piece of wood that makes the top step on the inside of the rear doors on a traditional boat. Another name for a Foot Board.
Stem
The very front structural member of a boat, typically on a narrowboat a significant piece of steel plate forming the profile of the bow and connecting the two side plates together.
Stern
The rear of aft end of a boat.
Stern Gland
The stern gland is seal or gland through which the propeller shaft passes. This gland must keep water out of the boat while allowing the shaft to both exit below the waterline and turn freely.
Stop Beam
Large beam on the roof immediately in front of the engine 'ole.
Swim
The underwater section of the hull at the rear of a narrowboat where the sides come in to allow a flow of water to the propeller.
Tiller
The lever used for steering, attached to the rudder via the Rudder Post. Typically on a narrowboat the tiller or tiller bar is a brass or stainless steel tube, secured by a Tiller Pin, which can be removed when the boat is not under way.
Tiller Pin
A pin, with a shaft of approximately 1/4" diameter, which secures the tiller to the rudder post. It can have a decorative top such as a kingfisher or other moulding.
Uxter Plate
The Uxter plate, or uxter boards on a wooden boat, refer to the plate or boards which form the underside of the counter on a powered narrowboat. The plate is typically parallel to the bottom or base of the boat and joins the swim to the counter. Usually a boat is trimmed such that the uxter plate is around the same level as the Waterline.
Waterline
The line where the hull meets the water surface.
Weedhatch
A covered opening in the uxter plate of a narrowboat directly above the propeller. The cover can be removed to allow access to clear a fouled propeller while the boat is in the water.
Yoghurt Pot
A tongue-in-cheek slang description of a GRP (glass reinforced plastic) cruiser.
Technical terminology
Battery Capacity
The capacity (size, in the electrical sense) of a battery is measured in Amp-hours (Ah). A typical capacity for a single leisure battery would be 110Ah. This means that the battery could supply 5.5A for 20 hours (5.5x20=110) at which time it would be completely flat. You don't ever want to do this with a conventional lead-acid battery - it is a bad thing to completely flatten such a battery and will reduce its life dramatically. A good balance between usability and length of life for most batteries is to only ever use 50% of the battery's capacity.
There are exceptions to this 50% 'rule'.
Calorifier
A hot water tank which is usually heated by the engine, the stove, the central heating unit, an immersion heater, or any combination thereof. The calorifier is generally made of copper or stainless steel and has one or more heating coils within it, which take hot water from the heating source. It may also have an immersion heater fitted, which is powered by mains 240V.
Calorifiers can be stood vertical as you would normally find in a house, or laid horizontally. It is generally believed that the vertical position is more efficient.
The highest point of a calorifier (whether it is vertical or horizontal) will be fitted with a Pressure Release Valve (PRV) to prevent excess pressure from the hot water from splitting the tank. The PRV outlet can be piped to a skin fitting or the bilge. It is sometimes necessary to rotate the PRV by hand to clear any lime scale deposits which can cause it to leak slightly.
Charge Efficiency
More technically known as Coulombic Efficiency or Faraday Efficiency, this compares the number of Ah that have to be put into a battery under charge to the number of Ah actually available from the battery. Common figures for CE are between 70% and 95%.
As an example, if the CE for a particular battery was 80%, then to replace 100Ah would require 125Ah of charge.
Note that the Charge Efficiency of a battery is not actually a constant, it decreases as the State of Charge increases.
Depth Of Discharge
Simply, the percentage of the capacity that has been used. If we take 55Ah out of a 110Ah battery, we say it has a Depth of Discharge of 50%. If we take 11Ah out of a 110Ah battery then we'd say it has a Depth Of Discharge of 10%.
Desulphation Charge
See Equalisation Charge.
Equalisation Charge
A 12V battery is comprised of 6 supposedly identical cells. Of course, there is no such thing as truly identical, and some cells will deteriorate faster than others. This can be seen by measuring the Specific Gravity (Relative Density) of the cells. When the measurement of the cells begins to noticeably differ, it is time to perform an Equalisation Charge.
An Equalisation Charge is nothing more than a timed overcharge - charging the battery for a certain period at a higher-than-usual charging voltage. The battery manufacturer will state the equalisation voltage that should be used for your particular brand, but it is usually in the region of 15V-16V for open wet lead acid batteries. Other battery types will have different (lower) voltages, and some types (specifically Gel batteries) must never be equalised.
An Equalisation Charge can also be called a Desulphation Charge because the overcharge voltage will also help in removing sulphation from under-charged batteries, restoring some of their lost capacity.
It is important to be aware that an equalisation charge will also damage the battery somewhat, causing increased plate corrosion and shedding.
Fully Charged
This is a contentious definition as it is very difficult to define, particularly when charging from engine or generator. The State of Charge can be measured by Specific Gravity or by Charging Current and when either of these show no change over a period of 30 to 60 minutes whilst on charge it is probably safe to consider the batteries to be fully charged.
Galvanic Isolator
A device which is wired into the earth lead between the 230V shore supply socket and the consumer unit on the boat in order to prevent galvanic corrosion when a boat is moored in a marina on shore power. It has both advantages and disadvantages when compared to an Isolation Transformer.
Inverter
A device which will supply 230V AC from the battery bank. They generally come in two types - Modified Sine Wave (MSW) and Pure Sine Wave (PSW). Many items of electronics that you want to use on your boat may not operate correctly (or at all) on MSW inverters. Inverters come in a range of 'sizes' from around 200W to 3kW or larger.
Isolation Transformer
A device which is wired between the 230V shore supply socket and the consumer unit in order to prevent galvanic corrosion when a boat is moored in a marina on shore power. It has both advantages and disadvantages when compared to a Galvanic Isolator.
Ohm's Law
I = V/R
I = Current (Amps)
V = Voltage (Volts)
R = Resistance (Ohms)
Plate Corrosion
Over the period of its life, a battery's positive plates will corrode, or shed. This can be a major contributor to the end of the effective life of a battery and is a natural phenomenon that will eventually occur with all lead acid batteries if they are not first 'killed' by sulphation. It can be minimised by careful control of the charging voltage, specifically by avoiding over-charging, and also by preventing the batteries from getting too hot.
Plate Shedding
Another term for Plate Corrosion.
The Power Law
P = V*I
P = Power (Watts)
V = Voltage (Volts)
I = Current (Amps)
Variations of the power law and Ohm's law
V = P/I
I = P/V
V = I * R
R = V/I
P = V2/R
P = I2 * R
V = Square Root of P/R
I = Square Root of P/R
R = V2/P
R = P/I2
Shorted Cell
A battery will gradually shed the lead coating from its plates as it ages. This shed detritus will build up at the bottom of the battery casing and can eventually bridge two or more plates. When this happens it causes increased self-discharge and a lowered overall capacity and is sometimes referred to as a 'soft short'.
State of Charge
Simply a percentage showing how charged (full) the battery is. When fully charged we say that the SoC (Sate of Charge) is 100%. When only half charged, we say the SoC is 50%. It is the inverse of Depth of Discharge.
Sulphation
When a lead-acid battery is discharged (used) lead sulphate (or sulfate) crystals are formed on the plates. A full recharge will break down these crystals and they do no harm. However, if a battery is repeatedly not fully recharged the lead sulphate crystals can grow and harden. Because these crystals are covering part of the plates that means that those parts of the plates can no longer take part in voltage creation. The effect of this is to reduce the battery capacity. Be aware that it is perfectly possible to reduce a 110Ah battery to a 20Ah battery in a matter of weeks by repeatedly poor charging.
If sulphation is caught in the early stages it can be substantially if not completely reversed with an Equalisation (or Desulphation) charge. Once the crystals have hardened to a great degree however it appears that no amount of charging can remove them.
Voltage Drop
For our purposes in a DC circuit on a boat this can be described as the voltage that is 'lost' down a cable. The voltage is lost by heating the cable and is due to the resistance of the cable. It can be easily calculated using Ohm's law. The larger the cable cross-sectional-area the lower its resistance and the lower the voltage drop.
Work, power, energy, force
Energy - measured in Joules.
Alternate (non-standard) units are also kWh.
Energy cannot be created or destroyed (excepting nuclear), only converted from one form to another, eg electrical, potential, kinetic, chemical, heat.
"Work" is change in energy, and shares the same units.
Power is the rate of doing work, i.e. energy per unit time.
Standard units are Joules per second.
1 Joule per second = 1 Watt
Work = Force x distance
It's in two sections - general boat stuff and technical terms.
General boat terminology
Air draft
The distance between the surface of the water and the highest fixed point on the craft. It will vary depending upon the load and distribution of the load.
Anodes
More correctly known as a 'Sacrificial Anode' it is effectively a 'lump of metal' which is welded to your boat to allow it to corrode in preference to having your hull corrode. Anodes offer protection based on the Noble Series of metals. The theory is that by attaching a piece of metal to the hull that is more reactive than the hull itself then this piece of metal will corrode first. For canals the anode is generally made of magnesium. Zinc is used in seawater, and Aluminium in more brackish water.
Back Cabin
Also known as the Boatman's Cabin or just the Cabin, with 'Boatman’s Cabin' being the more modern term.
Over the generations of narrow boat use on the canals, the most efficient design for a cabin evolved and most back cabins have identical layouts, regardless of what carrying company the boat was built for or who built the boat.
On the left, just inside the door, is the cooking range; this position being chosen to keep the steerer's legs warm. In front of that is the table cupboard, with a vertical door which can double up as a table when lowered. A drawer below the table is known as the 'knife drawer' or 'crumb drawer' (due to the crumbs landing in it as the table is put away). In front of that is the 'bed ‘ole' with a cross bed that folds out across the width of the cabin. On the right side of the cabin is a simple bench for sitting on, which can also be used as a further bed, and is known simply as the 'side bed'.
Back End Beam
A large beam on the roof at the rear of the hold on a traditional boat (if it has a hold).
Base Plate
The bottom plate of a steel narrowboat. On modern boats it's usually 10mm or 12mm thick. Older boats might have 8mm or even 6mm base plates or (rarely) even thinner.
Bilge
The bottom of a boat's hull which may collect water which must be removed, usually with a pump. Narrow boats will typically be arranged such that the main cabin bilge is separate from the engine bilge, often a small compartment directly below the stern gland will also be provided.
Bow
The front end of a boat.
Bow Thruster
A small propeller, typically mounted in a tunnel or tube running through the bow. It is used to provide additional turning force when the boat is stationary or moving at slow speed.
Bulkhead
A wall within a boat, particularly a structural wall, which may also be watertight.
Chine
An angle in the hull profile. Typically canal going craft will have a single hard chine, where the sides plate and base plate meet at 90 degrees. However, boats may have a small bend in the side to prevent the base plate catching on lock walls. Wide-beam boats often have a significant double-chine, comprising two bends on the hull side before it meets the base plate.
Cratch
The area towards the front of the boat, behind the deck, typically on a modern narrowboat, a canvas covered area in front of the cabin and behind the Deck and Deck Board.
Cratch Board
Also known on traditional boats as the Deck Board, it is the name given to the vertical board at the front of the boat which protects the cratch. The shape is triangular with the top of the triangle cut off. On traditional boats it is common for the Deck Board to be highly decorated, but on modern boats is more likely to be varnished or painted a solid colour. The board is usually solid on a traditional boat but is glazed on modern boats. On a traditional boat the purpose of the Deck Board is to support the top planks and protect the cargo.
Counter
The part of the stern above the waterline that extends beyond the rear of the cabin over the swim.
Deck
The flat area at the bow of a narrowboat, in front of the Deck Beam. Often containing the Gas Locker.
Deck Beam
A large beam, traditionally made of Oak or Mahogany, at the rear of the deck and in front of the Cratch on which sits the Deck Board.
Deck Board
The 'correct' name for the Cratch Board.
Displacement
The weight of water displaced by the hull of a boat and hence equal to the total weight of the vessel.
Draft
The depth of water a boat draws, typically measured from the waterline to the lowest part under hull.
Elum
The name given to the rudder and tiller arrangement on a traditional horse-drawn boat or butty.
Foot Board
The piece of wood that makes the top step on the inside of the rear doors on a traditional boat. Another name for a Steering Step.
Gas Locker
A gas tight locker, often built into the Deck of a boat or at the stern on Semi-Trad and Cruiser-Stern boats. It contains the gas bottles. It must be gas tight to the interior of the craft and have low level vents to the outside.
Hull
The watertight part of a boat.
Narrowboat
A boat of a distinctive design, generally less than 7 feet wide, made to fit the narrow canals of the United Kingdom.
Port
The left hand side of the boat when stood on board and facing the bow.
Propeller
A type of fan that transmits power by converting rotational motion from the engine into thrust acting on the water.
Propeller Shaft
The drive shaft that passes through the Stern to supply rotational force to the propeller from the gearbox.
Rubbing strake
A strip or band fitted to the outside of the hull to provide protection when coming alongside something. Typically on a modern narrowboat these are steel and are welded to the hull.
Rudder
The plate and/or hydrofoil at the rear of the boat, which is pivoted to provide a mechanism with which to steer.
Rudder Post
The shaft which passes through the Counter and uxter of a narrowboat to which the rudder is attached.
Scantlings
A vessel's structural members. Typically on a narrowboat, steel beams welded to the baseplate to provide stiffness.
Seacock
A valve in the hull of a boat, which can be used to isolate whatever is attached to it from the water in which the boat is floating.
Skeg
The metal bar that the lower end of the rudder post is attached to which also protects the rudder from hitting obstructions. It is positioned behind the swim.
Skin tank
A steel tank, usually welded to the interior face (rarely on the exterior) of the hull, typically to provide engine cooling. It serves the same purpose as a radiator in a car. Coolant passes through the tank and is cooled by contact with the hull, or in the case of an exterior skin tank, contact with the water in which the boat is floating.
Starboard
The right hand side of a vessel when stood on board facing the bow.
Steering Step
The piece of wood that makes the top step on the inside of the rear doors on a traditional boat. Another name for a Foot Board.
Stem
The very front structural member of a boat, typically on a narrowboat a significant piece of steel plate forming the profile of the bow and connecting the two side plates together.
Stern
The rear of aft end of a boat.
Stern Gland
The stern gland is seal or gland through which the propeller shaft passes. This gland must keep water out of the boat while allowing the shaft to both exit below the waterline and turn freely.
Stop Beam
Large beam on the roof immediately in front of the engine 'ole.
Swim
The underwater section of the hull at the rear of a narrowboat where the sides come in to allow a flow of water to the propeller.
Tiller
The lever used for steering, attached to the rudder via the Rudder Post. Typically on a narrowboat the tiller or tiller bar is a brass or stainless steel tube, secured by a Tiller Pin, which can be removed when the boat is not under way.
Tiller Pin
A pin, with a shaft of approximately 1/4" diameter, which secures the tiller to the rudder post. It can have a decorative top such as a kingfisher or other moulding.
Uxter Plate
The Uxter plate, or uxter boards on a wooden boat, refer to the plate or boards which form the underside of the counter on a powered narrowboat. The plate is typically parallel to the bottom or base of the boat and joins the swim to the counter. Usually a boat is trimmed such that the uxter plate is around the same level as the Waterline.
Waterline
The line where the hull meets the water surface.
Weedhatch
A covered opening in the uxter plate of a narrowboat directly above the propeller. The cover can be removed to allow access to clear a fouled propeller while the boat is in the water.
Yoghurt Pot
A tongue-in-cheek slang description of a GRP (glass reinforced plastic) cruiser.
Technical terminology
Battery Capacity
The capacity (size, in the electrical sense) of a battery is measured in Amp-hours (Ah). A typical capacity for a single leisure battery would be 110Ah. This means that the battery could supply 5.5A for 20 hours (5.5x20=110) at which time it would be completely flat. You don't ever want to do this with a conventional lead-acid battery - it is a bad thing to completely flatten such a battery and will reduce its life dramatically. A good balance between usability and length of life for most batteries is to only ever use 50% of the battery's capacity.
There are exceptions to this 50% 'rule'.
Calorifier
A hot water tank which is usually heated by the engine, the stove, the central heating unit, an immersion heater, or any combination thereof. The calorifier is generally made of copper or stainless steel and has one or more heating coils within it, which take hot water from the heating source. It may also have an immersion heater fitted, which is powered by mains 240V.
Calorifiers can be stood vertical as you would normally find in a house, or laid horizontally. It is generally believed that the vertical position is more efficient.
The highest point of a calorifier (whether it is vertical or horizontal) will be fitted with a Pressure Release Valve (PRV) to prevent excess pressure from the hot water from splitting the tank. The PRV outlet can be piped to a skin fitting or the bilge. It is sometimes necessary to rotate the PRV by hand to clear any lime scale deposits which can cause it to leak slightly.
Charge Efficiency
More technically known as Coulombic Efficiency or Faraday Efficiency, this compares the number of Ah that have to be put into a battery under charge to the number of Ah actually available from the battery. Common figures for CE are between 70% and 95%.
As an example, if the CE for a particular battery was 80%, then to replace 100Ah would require 125Ah of charge.
Note that the Charge Efficiency of a battery is not actually a constant, it decreases as the State of Charge increases.
Depth Of Discharge
Simply, the percentage of the capacity that has been used. If we take 55Ah out of a 110Ah battery, we say it has a Depth of Discharge of 50%. If we take 11Ah out of a 110Ah battery then we'd say it has a Depth Of Discharge of 10%.
Desulphation Charge
See Equalisation Charge.
Equalisation Charge
A 12V battery is comprised of 6 supposedly identical cells. Of course, there is no such thing as truly identical, and some cells will deteriorate faster than others. This can be seen by measuring the Specific Gravity (Relative Density) of the cells. When the measurement of the cells begins to noticeably differ, it is time to perform an Equalisation Charge.
An Equalisation Charge is nothing more than a timed overcharge - charging the battery for a certain period at a higher-than-usual charging voltage. The battery manufacturer will state the equalisation voltage that should be used for your particular brand, but it is usually in the region of 15V-16V for open wet lead acid batteries. Other battery types will have different (lower) voltages, and some types (specifically Gel batteries) must never be equalised.
An Equalisation Charge can also be called a Desulphation Charge because the overcharge voltage will also help in removing sulphation from under-charged batteries, restoring some of their lost capacity.
It is important to be aware that an equalisation charge will also damage the battery somewhat, causing increased plate corrosion and shedding.
Fully Charged
This is a contentious definition as it is very difficult to define, particularly when charging from engine or generator. The State of Charge can be measured by Specific Gravity or by Charging Current and when either of these show no change over a period of 30 to 60 minutes whilst on charge it is probably safe to consider the batteries to be fully charged.
Galvanic Isolator
A device which is wired into the earth lead between the 230V shore supply socket and the consumer unit on the boat in order to prevent galvanic corrosion when a boat is moored in a marina on shore power. It has both advantages and disadvantages when compared to an Isolation Transformer.
Inverter
A device which will supply 230V AC from the battery bank. They generally come in two types - Modified Sine Wave (MSW) and Pure Sine Wave (PSW). Many items of electronics that you want to use on your boat may not operate correctly (or at all) on MSW inverters. Inverters come in a range of 'sizes' from around 200W to 3kW or larger.
Isolation Transformer
A device which is wired between the 230V shore supply socket and the consumer unit in order to prevent galvanic corrosion when a boat is moored in a marina on shore power. It has both advantages and disadvantages when compared to a Galvanic Isolator.
Ohm's Law
I = V/R
I = Current (Amps)
V = Voltage (Volts)
R = Resistance (Ohms)
Plate Corrosion
Over the period of its life, a battery's positive plates will corrode, or shed. This can be a major contributor to the end of the effective life of a battery and is a natural phenomenon that will eventually occur with all lead acid batteries if they are not first 'killed' by sulphation. It can be minimised by careful control of the charging voltage, specifically by avoiding over-charging, and also by preventing the batteries from getting too hot.
Plate Shedding
Another term for Plate Corrosion.
The Power Law
P = V*I
P = Power (Watts)
V = Voltage (Volts)
I = Current (Amps)
Variations of the power law and Ohm's law
V = P/I
I = P/V
V = I * R
R = V/I
P = V2/R
P = I2 * R
V = Square Root of P/R
I = Square Root of P/R
R = V2/P
R = P/I2
Shorted Cell
A battery will gradually shed the lead coating from its plates as it ages. This shed detritus will build up at the bottom of the battery casing and can eventually bridge two or more plates. When this happens it causes increased self-discharge and a lowered overall capacity and is sometimes referred to as a 'soft short'.
State of Charge
Simply a percentage showing how charged (full) the battery is. When fully charged we say that the SoC (Sate of Charge) is 100%. When only half charged, we say the SoC is 50%. It is the inverse of Depth of Discharge.
Sulphation
When a lead-acid battery is discharged (used) lead sulphate (or sulfate) crystals are formed on the plates. A full recharge will break down these crystals and they do no harm. However, if a battery is repeatedly not fully recharged the lead sulphate crystals can grow and harden. Because these crystals are covering part of the plates that means that those parts of the plates can no longer take part in voltage creation. The effect of this is to reduce the battery capacity. Be aware that it is perfectly possible to reduce a 110Ah battery to a 20Ah battery in a matter of weeks by repeatedly poor charging.
If sulphation is caught in the early stages it can be substantially if not completely reversed with an Equalisation (or Desulphation) charge. Once the crystals have hardened to a great degree however it appears that no amount of charging can remove them.
Voltage Drop
For our purposes in a DC circuit on a boat this can be described as the voltage that is 'lost' down a cable. The voltage is lost by heating the cable and is due to the resistance of the cable. It can be easily calculated using Ohm's law. The larger the cable cross-sectional-area the lower its resistance and the lower the voltage drop.
Work, power, energy, force
Energy - measured in Joules.
Alternate (non-standard) units are also kWh.
Energy cannot be created or destroyed (excepting nuclear), only converted from one form to another, eg electrical, potential, kinetic, chemical, heat.
"Work" is change in energy, and shares the same units.
Power is the rate of doing work, i.e. energy per unit time.
Standard units are Joules per second.
1 Joule per second = 1 Watt
Work = Force x distance