Boat SRM
Content
ABSTRACT A lot of interest has been stirred up with powering a boat with an electric motor in the last couple of years. Why would a boat owner choose to have an electric boat? It has a lot of advantages of electric boat such as cheaper than gasoline fueled boat, environmental friendly and etc. The consolidation of propulsion power on electric boats results in lower fuel consumption, less maintenance, and overall a more pleasant experience for the boat owner. In our design, we choose to design a boat for touring. Therefore, the specifications of our boat must be suitable for smooth wave condition. The number of passenger available for this boat is 14 people. Here, we use 2 brushless DC motor, with output power of 4 hp each, 48 Volt and with speed of 10-12 km/h. For the source of the motor, we decided to use 10 pieces of Deep Cycle AGM Battery 220AH 6V DC and Xantrex Truecharge2 Battery Chargers as its charger. Also, the controller for the boat is the 4-Channel Interleaved DC-DC Buck Converter.
INTRODUCTION While most boats on the water today are powered by diesel engines, and sail power and gasoline engines, it is perfectly feasible to power boats by electricity too. Electric boats were very popular from the 1880s until the 1920s, when the internal combustion engine took dominance. Since the energy crises of the 1970s, interest in this quiet and potentially renewable marine energy source has been increasing steadily again, for the first time making possible motorboats with an infinite range like sailboats. The main components of the drive system of any electrically powered boat are similar in all cases, and similar to the options available for any electric vehicle; y Electric motor o A wide variety of electric motor technologies are in use. Today many boats use lightweight permanent magnet DC motors. Some boats use AC motors or permanent magnet brushless motors. The advantages of these are the lack of commutators which can wear out or fail and the often lower currents allowing thinner cables. y Speed controller o To make the boat usable and maneuverable, a simple-to-operate forward or stop or backwards speed controller is needed. This must be efficient; it must not get hot and waste energy at any speed and it must be able to stand the full current that could conceivably flow under any full-load condition. y Battery o There have been significant technical advances in battery technology in recent years, and more are to be expected in the future. The one that designed in our assignment was Valve-regulated lead-acid (VRLA) batteries, usually known as sealed lead-acid, gel, or AGM batteries, minimize the risk of spillage, and gases are only vented when the batteries are overcharged. These batteries require minimal maintenance, as they cannot and usually do not need to be refilled with water.
y
Charger o Electric energy has to be obtained for the battery bank from some source. Why buy an electric boat? Electric boat actually has a lot of advantages. One of them is
because of the low maintenance. The electric drive system itself is very low maintenance, especially when compared to a gasoline fueled boat. The electric motor s bearings and brushes should be replaced on average once every four to five years, the same for the underwater shaft bearing. These are very simple tasks for any marine mechanic. As far as the woodwork, the real concern here is keeping the boat clean and out of direct sunlight as much as possible. Another advantage is it has higher durability. The varnish used on electric boats has better durability than conventional varnish. Still, any clear finish won t last as long as a painted finish when left exposed to the sun for prolonged periods. On average one should expect to recoat the varnish work every four to six years. Other advantages are they are environmentally friendly because this technology can decrease pollution. Exhaust fumes, the smell of fuel, noise and vibration pollution are all decreased or eliminated. It is also extremely economical to operate since we do not need to use fuel. Ideal for no wake or limited speed controlled zones; they are well suited for both fresh water lakes and saltwater harbors. Therefore, for this subject, we were asked by the lecturer to design an electric boat, with capacity of 14 passengers, using permanent magnet drives and control system. Further information about the boat is written throughout this report.
SPECIFICATION OF THE ELECTRIC MOTOR AND THE BOAT Specification LOA Width Depth Full Load draft Passenger Capasity Tare Weight Power Voltage Speed Cruise duration per charge Navigation Area Electric Motor Controller 7.70 m 2.20 m 1.10 m 0.65 m 14 Passengers 1 Crew 1000 kg 8 HP(2 x 4 HP) 48 V 10-12 km/h 10 hours Lakes, Parks, Reservoir 6 kW 4-Channel Interleaved DC-DC Buck Converter Apparatus Chairs Fire Extingguisher Life Vest Life Buoy Stainless steel shaft Battery(Maintenance free) 15 seats 1 15 1 Stainless steel rudder 10 Pcs 6V 220AH
PLAN VIEW OF THE BOAT
ELECTRIC MOTOR In our design, we use a permanent magnet brushless DC motor. This motor have pulsed DC fed to the stator field windings to create a rotating magnetic field and a permanent magnet rotor. It depends on electronic drive systems which produce rotating magnetic fields to pull the rotors around.
Figure 1 : Brushless DC Motor
No current is supplied to, nor induced, in the rotors which are constructed from permanent magnets and which are dragged around by the rotating field. With no currents in the rotors these machines have no rotor I2R losses. Without the mechanical commutator and rotor windings, permanent magnet brushless DC motor have low rotor inertia allowing much higher speeds to be achieved and with the elimination of this high current mechanical switch, the source of sparking and RFI is also eliminated. Since all the heat generating circuits are in the stator, heat dissipation is easier to control and higher currents and motor powers can also be achieved. Permanent magnet brushless DC motor has large starting torque because it is designed with NdFeB magnet. NdFeB is considered one of the best PM materials presently since it offers much higher residual flux density and coercive force. It develop maximum torque when stationary and have linearly decreasing torque with increasing speed as shown in Figure 2.
Figure 2 : Torque vs speed characteristic This motor has high efficiency and more efficient at converting electricity into mechanical power than brushed DC motors. This is due to the absence of electrical and friction losses due to brushes. This motor are microprocessor-controlled to keep the stator current in phase with the permanent magnets of the rotor, requiring less current for the same effect and therefore resulting in greater efficiency.
Besides of the good efficiency this motor provide longer lifetime (no brush and commutator erosion), reliability, reduced noise, and overall reduction of electromagnetic interference (EMI).With no windings on the rotor, they are not subjected to centrifugal forces, and because the windings are supported by the housing, they can be cooled by conduction, requiring no airflow inside the motor for cooling. This in turn means that the motor's internals can be entirely enclosed and protected from dirt or other foreign matter. The power factor of this motor close to 1 and the reactive power loss is low. This motor is small in size, light in weight and particularly suitable for electric vehicles to reduce weight and save battery power.
CONTROLLER For controller design, we decided to use an interleaved 4-channel DC-DC converter. It was designed and constructed which has the ability to control high currents. The efficiency of the interleaved converter of the application is about 95 %, so it is a good solution for driving low voltage and high current dc motors. This types of electric motors are used in electric transportation applications such as electrical motorboat. A basic structure of the converter which is constituted by 4 parallel channels shown in Figure 3.
Figure 3 : The basic structure of the four channel interleaved buck DC-DC converter
The disadvantage of the typical buck converter is its discontinuous pulsating input current waveform. This pulsating input current of the converter is harmful for the batteries. Therefore, to obtain a continuous input current a LC filter in the input of the converter is necessary. In the output there is a capacitor which filters the AC component of the output current. In the application, on account of practical and safety reasons we were led to the choice of a low voltage permanent magnet DC brushless motor. This is resulting to a high value of current to get the nominal power of 1.5 kW. The converter has been designed and constructed for 2 kW (Vout=25 V, Iout=80 A), it is 0.5 kW more than the nominal power of the propulsion motor.
Each channel consists of one IGBT, one freewheeling power diode and one inductor. The 4 parallel channels have a number of important properties. The total current is shared in each of the four channels. Due to this sharing the total conduction losses (I2*RON) of the semiconductor devices decrease depending on the number of the channels. Equation 1 shows the relationship for the conduction losses between the number of channel interleaved and the 1-channel typical step-down converter (buck). In this application by using four channels we have four times less conduction losses comparing to the typical 1-channel buck converter.
Equations 1: y y y y PCOND.LOSS.BUCK = I2TOTALRON ................................................................... PCOND.LOSS.INTER. = N(I2CHANNELRON) = N(ITOTAL/N)2RON ............................. PCOND.LOSS.INTER. = I2TOTALRON/N = PCOND.LOSS.BUCK/N ................................ PLOSS.IGBT = PCOND.LOSS. + PSW.LOSS. = 26W + 2W = 28W .......................... (1) (2) (3) (4)
Where : RON : power semiconductor ON resistance PCOND.LOSS.BUCK : the conduction losses in the typical buck converter PCOND.LOSS.INTER : the conduction losses in the N - channel interleaved converter PLOSS.IGBT : the total losses for an IGBT
PCOND.LOSS : the conduction losses for an IGBT PSW.LOSS : the switching losses for an IGBT N : number of channels
The main drawback of adding more channels is that the switching losses would be increase, depending again on the number of the channels. In our application, taking account the chosen IGBTs, the switching frequency has been chosen at 20 kHz, a value that leads to switching losses essential lower in comparison to the conduction losses. Equation 1(4) shows the bigger possible IGBT losses in each of the four channels. The phase angle between the channels is given by 3600 divided by the number of the channels. In this case we use four channel, therefore the phase angle is 900. The total current ripple is therefore reduced in comparison to the current of each single channel. It is obvious that parallel channels can manage high currents.
The 4 channels are developed in two levels, with 2 channels in each level. This type of development enables the ability to test the right operation of each channel. Also a very important advantage of this converter, except its regular operation with 4 channels, is its ability to work with 1, 2 or 3 channels in case of a problem. In case of a problem occur, there should be a way to drive the boat back to the port using a part of its nominal power.
The 4-channel interleaved buck DC-DC converter and the propulsion motor have been placed in the boat, both in waterproof boxes for their safety. The captain of the boat regulates the armature voltage (output voltage of the interleaved converter), by adjusting the duty cycle of the converter, to control the rpm of the DC propulsion motor.
The topology and the operation of the high efficient power converter result to a simple, reliable and efficient electric drive system for the electric boat. The converter can be applicable to bigger vessels applications as well, with the same topology for the electric drive system and the propulsion system. The converter meets well the requirements of the low voltage current applications. high
BATTERY A battery is an electrical storage device. Batteries do not make electricity, they store it. As chemicals in the battery change, electrical energy is stored or released. In rechargeable batteries this process can be repeated many times. Batteries are not 100% efficient-some energy is lost as heat and chemical reactions when charging and discharging. If you use 1000 watts from a battery, it might take 1200 Watts or more to fully recharge it. Slower charging and discharging rates are more efficient. A battery rated at 180 amp-hours over 6 hours might be rated at 220 AH at the 20-hour rate and 260 AH at the 48-hour rate. Typical efficiency in a leadacid battery is 85-95%, in alkaline and NiCad battery it is about 65%. Batteries are divided in two ways, by application on what they are used for and construction on how they are built. The major applications are automotive, marine, and deepcycle. The major construction types are flooded (wet), gelled, and AGM (Absorbed Glass Mat). AGM batteries are also sometimes called starved electrolyte or dry because the fiberglass material is only 95% saturated with sulphuric acid and there is no excess liquid. Nearly all AGM batteries are sealed valve regulated. Sealed batteries are known as maintenance free batteries. Most valves regulated are under some pressure - 1 to 4 psi at sea level.
Figure 4: Deep Cycle AGM Battery 220AH 6V DC Absorbed Glass Mat Batteries do not leak, freeze and do not require any maintenance. An AGM Battery can be stored for a long period of time without charging. To fully recharge 6V battery, maximum voltage 7.8 Volts (regulated) is needed and also no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 A. With a full charge, the boat will operate for more than 10 hours at 5 MPH or a 50 miles range. Therefore 10pcs of AGM batteries are used in the design of a 14 sitter electrical motor boat. This newer type of sealed non-spillable maintenance free valve regulated battery is used. The advantages of AGM batteries are no maintenance, sealed against fumes, hydrogen, leakage, or non-spilling even if they are broken, and can survive most freezes. AGM batteries are recombinant which means the oxygen and hydrogen recombine inside the battery. These
gas use phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99% efficient, so almost no water is lost. Charging voltages for most AGM batteries are the same as for a standard type battery so there is no need for special charging adjustments or problems with incompatible chargers or charge controls. Since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. AGM batteries have a very low selfdischarge rate (from 1% to 3% per month). So they can sit in storage for much longer periods
without charging. The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery. Due to their sealed design, AGM batteries eliminate water loss due to heat and evaporation. Most people don't check their conventional battery's water level on a regular basis, and as the electrolyte level in the battery goes down, sulphating begins, which will dramatically shorten a conventional battery's life. Also the AGM battery's tight pack lead calcium construction provides better resistance to vibration, thereby increasing its service life. Most AGM motorcycle and power sport batteries can use the same low amp battery chargers that conventional motorcycle batteries use. Furthermore AGM batteries are safer the conventional wet or flooded motorcycle batteries. The AGM design incorporates special safety valves in the battery case, which are designed to prevent pressure build up inside the battery during periods of excess over charging.
CHARGER The main charger needs to be carefully sized in relation to the battery bank and the time that is allowed to charge the batteries from depleted to full. All good chargers are '3 stage', meaning that as your battery fills up, the charging rate is adjusted to the optimum, finally going in to top-up mode. Chargers, particularly the smaller and lighter HF chargers, are normally carried on-board, but if the boat always returns to the same base when charging - or one have more than one boat that needs charging, then the charger might be better based shore-side. Mains charger allows the boat to be charged from shore-side power when available. Shore-based power stations are subject to much stricter environmental controls than the average marine diesel or outboard motor. Both types will require an umbilical to the boat, and some clever systems stop the boat from running its motor whilst it is still attached to the shore.
In any cases, a charge regulator is needed. This ensures that the batteries are charged at the maximum rate that they safely can stand when the power is available. It also ensures that they are not overcharged when nearing full charge and not overheated when a large charge current becomes available. Charging time will depend on the batteries used and the charger. The suggested charger size is a minimum of 10-20% of the battery capacity. If 100 Ah batteries are used, the charger needs to be 10-20 A. The time needed to charge the battery pack will be 5-10 hours. A larger ampere charger will be able to charge the batteries more quickly. Offering a revolutionary technology and power to weight ratio, Xantrex technology is said to be the benchmark for premium integrated power systems. DC Battery Chargers providing longer battery life. Xantrex is technologically superior 3-stage charging for longer battery life. In addition to meeting global safety and regulatory standards, Xantrex Truecharge2 Battery Chargers feature low electrical interference and efficient, power factor corrected multistage charging. Truecharge2 Battery Chargers can be mounted virtually anywhere, given their unique drip-proof design. Trouble-free installation is ensured with easyto-access AC and DC wiring compartments and reverse-polarity battery protection. This charger is available in three 12-Volt models. They are versatile enough to be used in a wide variety of conditions and locations. Auto-ranging AC input voltage capability (90 265 Volts AC) makes traveling abroad and handling poor-quality power a breeze. The easy-toread display can be augmented with an optional remote panel. Other than that, it is also set for two and 3-stage charging. This charger is settings for flooded, gel, AGM or lead-calcium batteries. Its features including auto-ranging universal input voltage (90-265 Vac, 47-63 Hz) is also compatible with a generator or other lowquality power sources. It also has power factor corrected for efficient charging.
For protection, this charger is equipped with reverse battery polarity protection, drip-proof design, ignition protection, battery overcharging protection, DC over-voltage protection and also over and under-temperature protection.
LIMITATION Some limitation also can be obtained from electric boat. One of them is that the weight of the boat really influences the specification of the electric motor. For example, if we have to add more batteries, the speed of the boat will decrease and therefore slower the boat.
INTRODUCTION While most boats on the water today are powered by diesel engines, and sail power and gasoline engines, it is perfectly feasible to power boats by electricity too. Electric boats were very popular from the 1880s until the 1920s, when the internal combustion engine took dominance. Since the energy crises of the 1970s, interest in this quiet and potentially renewable marine energy source has been increasing steadily again, for the first time making possible motorboats with an infinite range like sailboats. The main components of the drive system of any electrically powered boat are similar in all cases, and similar to the options available for any electric vehicle; y Electric motor o A wide variety of electric motor technologies are in use. Today many boats use lightweight permanent magnet DC motors. Some boats use AC motors or permanent magnet brushless motors. The advantages of these are the lack of commutators which can wear out or fail and the often lower currents allowing thinner cables. y Speed controller o To make the boat usable and maneuverable, a simple-to-operate forward or stop or backwards speed controller is needed. This must be efficient; it must not get hot and waste energy at any speed and it must be able to stand the full current that could conceivably flow under any full-load condition. y Battery o There have been significant technical advances in battery technology in recent years, and more are to be expected in the future. The one that designed in our assignment was Valve-regulated lead-acid (VRLA) batteries, usually known as sealed lead-acid, gel, or AGM batteries, minimize the risk of spillage, and gases are only vented when the batteries are overcharged. These batteries require minimal maintenance, as they cannot and usually do not need to be refilled with water.
y
Charger o Electric energy has to be obtained for the battery bank from some source. Why buy an electric boat? Electric boat actually has a lot of advantages. One of them is
because of the low maintenance. The electric drive system itself is very low maintenance, especially when compared to a gasoline fueled boat. The electric motor s bearings and brushes should be replaced on average once every four to five years, the same for the underwater shaft bearing. These are very simple tasks for any marine mechanic. As far as the woodwork, the real concern here is keeping the boat clean and out of direct sunlight as much as possible. Another advantage is it has higher durability. The varnish used on electric boats has better durability than conventional varnish. Still, any clear finish won t last as long as a painted finish when left exposed to the sun for prolonged periods. On average one should expect to recoat the varnish work every four to six years. Other advantages are they are environmentally friendly because this technology can decrease pollution. Exhaust fumes, the smell of fuel, noise and vibration pollution are all decreased or eliminated. It is also extremely economical to operate since we do not need to use fuel. Ideal for no wake or limited speed controlled zones; they are well suited for both fresh water lakes and saltwater harbors. Therefore, for this subject, we were asked by the lecturer to design an electric boat, with capacity of 14 passengers, using permanent magnet drives and control system. Further information about the boat is written throughout this report.
SPECIFICATION OF THE ELECTRIC MOTOR AND THE BOAT Specification LOA Width Depth Full Load draft Passenger Capasity Tare Weight Power Voltage Speed Cruise duration per charge Navigation Area Electric Motor Controller 7.70 m 2.20 m 1.10 m 0.65 m 14 Passengers 1 Crew 1000 kg 8 HP(2 x 4 HP) 48 V 10-12 km/h 10 hours Lakes, Parks, Reservoir 6 kW 4-Channel Interleaved DC-DC Buck Converter Apparatus Chairs Fire Extingguisher Life Vest Life Buoy Stainless steel shaft Battery(Maintenance free) 15 seats 1 15 1 Stainless steel rudder 10 Pcs 6V 220AH
PLAN VIEW OF THE BOAT
ELECTRIC MOTOR In our design, we use a permanent magnet brushless DC motor. This motor have pulsed DC fed to the stator field windings to create a rotating magnetic field and a permanent magnet rotor. It depends on electronic drive systems which produce rotating magnetic fields to pull the rotors around.
Figure 1 : Brushless DC Motor
No current is supplied to, nor induced, in the rotors which are constructed from permanent magnets and which are dragged around by the rotating field. With no currents in the rotors these machines have no rotor I2R losses. Without the mechanical commutator and rotor windings, permanent magnet brushless DC motor have low rotor inertia allowing much higher speeds to be achieved and with the elimination of this high current mechanical switch, the source of sparking and RFI is also eliminated. Since all the heat generating circuits are in the stator, heat dissipation is easier to control and higher currents and motor powers can also be achieved. Permanent magnet brushless DC motor has large starting torque because it is designed with NdFeB magnet. NdFeB is considered one of the best PM materials presently since it offers much higher residual flux density and coercive force. It develop maximum torque when stationary and have linearly decreasing torque with increasing speed as shown in Figure 2.
Figure 2 : Torque vs speed characteristic This motor has high efficiency and more efficient at converting electricity into mechanical power than brushed DC motors. This is due to the absence of electrical and friction losses due to brushes. This motor are microprocessor-controlled to keep the stator current in phase with the permanent magnets of the rotor, requiring less current for the same effect and therefore resulting in greater efficiency.
Besides of the good efficiency this motor provide longer lifetime (no brush and commutator erosion), reliability, reduced noise, and overall reduction of electromagnetic interference (EMI).With no windings on the rotor, they are not subjected to centrifugal forces, and because the windings are supported by the housing, they can be cooled by conduction, requiring no airflow inside the motor for cooling. This in turn means that the motor's internals can be entirely enclosed and protected from dirt or other foreign matter. The power factor of this motor close to 1 and the reactive power loss is low. This motor is small in size, light in weight and particularly suitable for electric vehicles to reduce weight and save battery power.
CONTROLLER For controller design, we decided to use an interleaved 4-channel DC-DC converter. It was designed and constructed which has the ability to control high currents. The efficiency of the interleaved converter of the application is about 95 %, so it is a good solution for driving low voltage and high current dc motors. This types of electric motors are used in electric transportation applications such as electrical motorboat. A basic structure of the converter which is constituted by 4 parallel channels shown in Figure 3.
Figure 3 : The basic structure of the four channel interleaved buck DC-DC converter
The disadvantage of the typical buck converter is its discontinuous pulsating input current waveform. This pulsating input current of the converter is harmful for the batteries. Therefore, to obtain a continuous input current a LC filter in the input of the converter is necessary. In the output there is a capacitor which filters the AC component of the output current. In the application, on account of practical and safety reasons we were led to the choice of a low voltage permanent magnet DC brushless motor. This is resulting to a high value of current to get the nominal power of 1.5 kW. The converter has been designed and constructed for 2 kW (Vout=25 V, Iout=80 A), it is 0.5 kW more than the nominal power of the propulsion motor.
Each channel consists of one IGBT, one freewheeling power diode and one inductor. The 4 parallel channels have a number of important properties. The total current is shared in each of the four channels. Due to this sharing the total conduction losses (I2*RON) of the semiconductor devices decrease depending on the number of the channels. Equation 1 shows the relationship for the conduction losses between the number of channel interleaved and the 1-channel typical step-down converter (buck). In this application by using four channels we have four times less conduction losses comparing to the typical 1-channel buck converter.
Equations 1: y y y y PCOND.LOSS.BUCK = I2TOTALRON ................................................................... PCOND.LOSS.INTER. = N(I2CHANNELRON) = N(ITOTAL/N)2RON ............................. PCOND.LOSS.INTER. = I2TOTALRON/N = PCOND.LOSS.BUCK/N ................................ PLOSS.IGBT = PCOND.LOSS. + PSW.LOSS. = 26W + 2W = 28W .......................... (1) (2) (3) (4)
Where : RON : power semiconductor ON resistance PCOND.LOSS.BUCK : the conduction losses in the typical buck converter PCOND.LOSS.INTER : the conduction losses in the N - channel interleaved converter PLOSS.IGBT : the total losses for an IGBT
PCOND.LOSS : the conduction losses for an IGBT PSW.LOSS : the switching losses for an IGBT N : number of channels
The main drawback of adding more channels is that the switching losses would be increase, depending again on the number of the channels. In our application, taking account the chosen IGBTs, the switching frequency has been chosen at 20 kHz, a value that leads to switching losses essential lower in comparison to the conduction losses. Equation 1(4) shows the bigger possible IGBT losses in each of the four channels. The phase angle between the channels is given by 3600 divided by the number of the channels. In this case we use four channel, therefore the phase angle is 900. The total current ripple is therefore reduced in comparison to the current of each single channel. It is obvious that parallel channels can manage high currents.
The 4 channels are developed in two levels, with 2 channels in each level. This type of development enables the ability to test the right operation of each channel. Also a very important advantage of this converter, except its regular operation with 4 channels, is its ability to work with 1, 2 or 3 channels in case of a problem. In case of a problem occur, there should be a way to drive the boat back to the port using a part of its nominal power.
The 4-channel interleaved buck DC-DC converter and the propulsion motor have been placed in the boat, both in waterproof boxes for their safety. The captain of the boat regulates the armature voltage (output voltage of the interleaved converter), by adjusting the duty cycle of the converter, to control the rpm of the DC propulsion motor.
The topology and the operation of the high efficient power converter result to a simple, reliable and efficient electric drive system for the electric boat. The converter can be applicable to bigger vessels applications as well, with the same topology for the electric drive system and the propulsion system. The converter meets well the requirements of the low voltage current applications. high
BATTERY A battery is an electrical storage device. Batteries do not make electricity, they store it. As chemicals in the battery change, electrical energy is stored or released. In rechargeable batteries this process can be repeated many times. Batteries are not 100% efficient-some energy is lost as heat and chemical reactions when charging and discharging. If you use 1000 watts from a battery, it might take 1200 Watts or more to fully recharge it. Slower charging and discharging rates are more efficient. A battery rated at 180 amp-hours over 6 hours might be rated at 220 AH at the 20-hour rate and 260 AH at the 48-hour rate. Typical efficiency in a leadacid battery is 85-95%, in alkaline and NiCad battery it is about 65%. Batteries are divided in two ways, by application on what they are used for and construction on how they are built. The major applications are automotive, marine, and deepcycle. The major construction types are flooded (wet), gelled, and AGM (Absorbed Glass Mat). AGM batteries are also sometimes called starved electrolyte or dry because the fiberglass material is only 95% saturated with sulphuric acid and there is no excess liquid. Nearly all AGM batteries are sealed valve regulated. Sealed batteries are known as maintenance free batteries. Most valves regulated are under some pressure - 1 to 4 psi at sea level.
Figure 4: Deep Cycle AGM Battery 220AH 6V DC Absorbed Glass Mat Batteries do not leak, freeze and do not require any maintenance. An AGM Battery can be stored for a long period of time without charging. To fully recharge 6V battery, maximum voltage 7.8 Volts (regulated) is needed and also no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 A. With a full charge, the boat will operate for more than 10 hours at 5 MPH or a 50 miles range. Therefore 10pcs of AGM batteries are used in the design of a 14 sitter electrical motor boat. This newer type of sealed non-spillable maintenance free valve regulated battery is used. The advantages of AGM batteries are no maintenance, sealed against fumes, hydrogen, leakage, or non-spilling even if they are broken, and can survive most freezes. AGM batteries are recombinant which means the oxygen and hydrogen recombine inside the battery. These
gas use phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99% efficient, so almost no water is lost. Charging voltages for most AGM batteries are the same as for a standard type battery so there is no need for special charging adjustments or problems with incompatible chargers or charge controls. Since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. AGM batteries have a very low selfdischarge rate (from 1% to 3% per month). So they can sit in storage for much longer periods
without charging. The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery. Due to their sealed design, AGM batteries eliminate water loss due to heat and evaporation. Most people don't check their conventional battery's water level on a regular basis, and as the electrolyte level in the battery goes down, sulphating begins, which will dramatically shorten a conventional battery's life. Also the AGM battery's tight pack lead calcium construction provides better resistance to vibration, thereby increasing its service life. Most AGM motorcycle and power sport batteries can use the same low amp battery chargers that conventional motorcycle batteries use. Furthermore AGM batteries are safer the conventional wet or flooded motorcycle batteries. The AGM design incorporates special safety valves in the battery case, which are designed to prevent pressure build up inside the battery during periods of excess over charging.
CHARGER The main charger needs to be carefully sized in relation to the battery bank and the time that is allowed to charge the batteries from depleted to full. All good chargers are '3 stage', meaning that as your battery fills up, the charging rate is adjusted to the optimum, finally going in to top-up mode. Chargers, particularly the smaller and lighter HF chargers, are normally carried on-board, but if the boat always returns to the same base when charging - or one have more than one boat that needs charging, then the charger might be better based shore-side. Mains charger allows the boat to be charged from shore-side power when available. Shore-based power stations are subject to much stricter environmental controls than the average marine diesel or outboard motor. Both types will require an umbilical to the boat, and some clever systems stop the boat from running its motor whilst it is still attached to the shore.
In any cases, a charge regulator is needed. This ensures that the batteries are charged at the maximum rate that they safely can stand when the power is available. It also ensures that they are not overcharged when nearing full charge and not overheated when a large charge current becomes available. Charging time will depend on the batteries used and the charger. The suggested charger size is a minimum of 10-20% of the battery capacity. If 100 Ah batteries are used, the charger needs to be 10-20 A. The time needed to charge the battery pack will be 5-10 hours. A larger ampere charger will be able to charge the batteries more quickly. Offering a revolutionary technology and power to weight ratio, Xantrex technology is said to be the benchmark for premium integrated power systems. DC Battery Chargers providing longer battery life. Xantrex is technologically superior 3-stage charging for longer battery life. In addition to meeting global safety and regulatory standards, Xantrex Truecharge2 Battery Chargers feature low electrical interference and efficient, power factor corrected multistage charging. Truecharge2 Battery Chargers can be mounted virtually anywhere, given their unique drip-proof design. Trouble-free installation is ensured with easyto-access AC and DC wiring compartments and reverse-polarity battery protection. This charger is available in three 12-Volt models. They are versatile enough to be used in a wide variety of conditions and locations. Auto-ranging AC input voltage capability (90 265 Volts AC) makes traveling abroad and handling poor-quality power a breeze. The easy-toread display can be augmented with an optional remote panel. Other than that, it is also set for two and 3-stage charging. This charger is settings for flooded, gel, AGM or lead-calcium batteries. Its features including auto-ranging universal input voltage (90-265 Vac, 47-63 Hz) is also compatible with a generator or other lowquality power sources. It also has power factor corrected for efficient charging.
For protection, this charger is equipped with reverse battery polarity protection, drip-proof design, ignition protection, battery overcharging protection, DC over-voltage protection and also over and under-temperature protection.
LIMITATION Some limitation also can be obtained from electric boat. One of them is that the weight of the boat really influences the specification of the electric motor. For example, if we have to add more batteries, the speed of the boat will decrease and therefore slower the boat.
