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SAIL LAGOON 420 - Electric Motors as Standard Equipment
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Brief description >>
Advantages >>
Interactive tutorial >>
Basic principles >>
How it works >>
The 5 operating modes >>
Battery autonomy and vessel range >>
Perfomance >>
Frequently asked questions >>

A brief description of the principle involved

  • Complete installation is composed of two electircal motors connected to propellers by straight shaft transmissions, one generator and two set of 6 batteries.
  • When batteries are 100% charged, the boat will be able to function with both motors for approximately two hours (depending on speed).
    When batteries are 80% charged, the generator will automatically start and charge the batteries and provide electricity for the motors.
  • When sailing, propellers will turn freely and charge batteries.

Advantages
  • A modern, forward-looking solution;
  • A clean and ecological system: low fuel consumption, little carbon dioxyde emission;
  • Runs in silence;
  • Only one fuel engine to maintain;
  • Electric motors are maintenance free;
  • Energy savings: the generator provides electricity for the motors, the batteries and the daily boat needs (air conditioning, power sockets, washing machine, etc.).


Basic Principles

  • Generator 220V: 11 KW 50Hz or 11 0V 133 KW 6OHz
  • Charger I inverter 220V - 72V 120A
  • Energy stored in one battery bank dedicated entirely to the electric engines, actually 2 (X 6) individual and separable battery banks port and starboard (safety measure: in case a battery dies one bank can still operate one or two engines)
  • Propulsion comes from 2 X 8 KW each 72V electric engines

HOW IT WORKS
    • Boat at the dock, batteries fully charged or in charge.
    • Generator battery switches are located at the front of the AFT STD cabin bed (next to the house battery switches).
    • Engines themselves are switched on by two switches located at the front of the AFT PORT cabin bed.
    • The ignition keys on the electrical panel (STBD salon) turn on the electric engine system. The engine batteries can then power the electric engines. The operating mode is selected at the electrical panel (5 modes available) with a selector switch (refer to chapter: "The 5 operating modes"). Only operating modes 4 and 5 are propulsion modes.
    • At the steering station the control panel needs to be switched to "on" : engine throttle controls are then operational and the boat can motor. The power delivered is at the highest level available from the battery bank. Switching the control panel "off" is an additional safety measure allowing you to deactivate the propeller rotation. For even more security the ignition key on the electric panel should be removed, for example to allow swimmers to approach the stern of the boat without the propellers accidentally turning.
    • As soon as the battery bank capacity drops to 80% of the maximum charge level, the generator automatically starts ; the electric engines receive proportionate power related to output from the generator, since the generator also recharges the propulsion batteries and the house batteries.
    • In 220V power available from the standard generator is around 11 KW in operating mode 4 and changes tot 13.5KW in operating mode 5.
    • If the generator has been upgraded to 17,5 kW (optional) then the power available is always greater than the power required by the engines, the "governing" effect is non-existent.

    Note : the generator starts automatically as soon as the engine battery level is below 80% of maximum charge and will stop automatically every hour to test the battery bank. It will restart again if the batteries are still below 80% of their maximum charge or will stay off if the charge is adequate, unless there other demands for 220V or 11 0V on board.


5 OPERATING MODES


There are 5 different operating modes selected by a 5-position selector switch at the electric panel.

  • Mode 1: Vessel connected to dockside AC power source. Onboard electric appliances run off of dockside power. Power for domestic appliances is supplied with no output for propulsion. Power is also diverted to charge the battery banks. The engine controls are rendered inoperable.
  • Mode 2: No source of AC power available: when sailing, the propellers turn freely.
  • Mode 3: Generator supplies 50Hz 220V AC power (or 60Hz for 110V AC). Power for domestic appliances is supplied with no output for propulsion.  Onboard 220V AC electrical appliances run off of the generator. Power is also diverted to charge the battery banks. The engine controls are rendered inoperable.
  • Mode 4: Generator supplies 230V 50Hz (or 1 10V 60Hz) power for propulsion and power for domestic appliance needs: 60% of the power of the generator is dedicated to the domestic appliances, 40% dedicated to propulsion and/or engine battery charging.
  • Mode 5: Propulsion only, no power available for domestic needs. Vessel at sea. When sailing: regeneration is automatically activated. 

    When motoring, power is supplied by the batteries. When 
    batteries are low, generator starts automatically.

OPERATING MODE 4 & 5: REGENERATION

  • In order not to slow the boat down while sailing under light conditions, the controller is calibrated for propeller rotation speed equal to 4.5 kts (approx 150 rpm). 
    Below this speed, no regeneration, the propeller turns freely, rpm determined by the boat's speed.
  • Sailing above speeds of 5 kts, the controller "brakes" the shaft and uses the energy created by the drag to regenerate power to charge the engine batteries. At 5 kts, instead of a turning freely at 230 rpm, the drag created by a rotation of150 rpm produces approximately 3 amps.
  • Up until the regeneration reaches its o timum charge value (measured by the controller), the prop is "bridled" at 150 RPM. Once optimal charge is obtainez the controller allows the shaft and prop to accelerate gradually (the controller releases the brake on the shaft). The optimum value is set at 18 amps per motor, the consequent drag for example would reduce sailing speed of 9.5 knots by I knot.
  • At very high sailing speed, (around 18kts), regeneration is deactivated in order to avoid overcharging.
  • Engine batteries charge the service batteries via the 7211 2V 50A charger/inverter. This way, the service batteries are always kept charged and under sail they are also recharged by regeneration. When at anchor or during heavy house energy consumption, when the engine batteries are down to 80% the generator automatically starts. Both house and engine battery banks are protected from overdischarge.
  • It is still possible to bypass the regeneration mode by switching the engine panel off or by turning the selector at the electric panel ( to operating mode 1,2,3) in order to no longer create drag on the shaft.
  • When the batteries are fully charged, the propeller shafts are released and the system will test itself to calculate when to regenerate according to the battery charge level.
  • The regenerating system is fully automatic (just like a standard battery charger).
  • Regeneration never reduces the boat's speed by more than one knot.

BATTERY AUTONOMY and VESSEL RANGE
  • Battery autonomy when operating under battery power only is based on an average speed of 5 kts with less than 5 kts of wind (after all, it is a sailing catamaran).
    • Estimated 2.5 hours from 100% to 80% of maximum battery capacity.
    • If the generator is purposely turned off in its attempt to recharge at the 80% level,
      • There remains an estimated 1.5 hours from 80% of battery capacity down to 60%
  • This means a total of 4 hours range at 5 knots on battery power only, knowing that battery damage may occur after only 2.5 hours.
  • At the 60% capacity level the generator again starts automatically again to protect the batteries from over discharge. If it is purposely turned off again, it will restart again, until the batteries are full charged. The only way to turn it off definitively is to cut the generator battery switch in the AFT STBD cabin.

THEREFORE

  • To maintain optimal battery capacity, it is advisable not to navigate under battery power only for a distance of more than 12.5 miles, which leaves more than enough margin to get to a harbour and perform docking maneuvers.
  • Should you motor more than 20 miles under battery power only, you run the risk of irreversibly damaging your battery bank.

 

PERFORMANCE

  • Maintainable cruising speed under power with a 11 KW generator running: approximately 7 kts.
  • Max speed with batteries at 100% charge or 17,5 KW generator: approx 8 kts.

 

FAQ

Q: When running on the batteries only, how long and how fast can you motor? 
READ MORE >>
Q: At what speeds is it dangerous to recharge with the propellers?
READ MORE >>
Q: What are the various power outputs that can supply the engines and how do they work?
READ MORE >>
Q: You say that max RPM was 660. During sea trials you measured a speed of 7.5 kts at 626 rpm and 9kts of wind from astern. How can you go over 8kts with only 30 additional RPM?
READ MORE >>
Q: Is it expensive to change the engine bearings at 20,000 hours? Who can do it?
READ MORE >>
Q: Recharge of the engine battery banks by the generator. How many Amps? If the larger Generator is selected, is the charger different in order to be adapted to the power output of the large generator?
READ MORE >>
Q: Is the engine battery charger that runs off the shore power the same as the engine battery charger that runs off the generator?
READ MORE >>
Q: Can we fit folding props? If so, which brand? Will this have an impact on the engine's performance?
READ MORE >>
Q: How sensitive are the engine controls: setting speeds from 1 rpm to 100%?
READ MORE >>
Q: How can we tell that the boat is <<in gear>>, even at 1 RPM?
READ MORE >>
Q: Is the regeneration noisy?
READ MORE >>
Q: How hot do the electric engines get?
READ MORE >>
Q: Do Gel batteries provide a benefit in terms of life span and performance?
READ MORE >>
Q: What is the generator diesel (11 KVA and 17.5KVA) fuel consumption at full throttle?
READ MORE >>
Q: During a long ocean crossing, how can you use the energy regenerated by the props for the household appliances?
READ MORE >>
Q: Why use 72V motors and not more?
READ MORE >>
Q: 2 x 8kw available power seems to be weak for a catamaran of this size and windage, especially since it isn't always possible to have calm seas for anchoring or for leaving/entering harbours. Plus, taking into account the variables in electric power, it is conceivable that only half of the power is actually available from the theoretical amount.
READ MORE >>
Q: The battery banks and overall capacity seem very undersized. The surface area of the roof and the bimini would allow a generous solar panel installation, but what for, with such a ridiculously small battery park. The batteries would be quickly charged (overcharged!) and then quickly discharged, and you would still need to use your genset all of the time. That's really too bad! Where are the battery banks? Is it possible to increase the capacity with other small batteries, or even better, with golf cart batteries or with 6V lithium L16 batteries (dimension problems notwithstanding)?
READ MORE >>
Q: The choice of 72V is surprising and seems to be unique, since all electric motors of this type used for intensive industrial use are 120, 250, or 500V depending on the power source
READ MORE >>
Q: You probably wanted to play up to the uninformed the safety issue by talking about 80v being dangerous to humans, but really, as far as electrical safety is concerned, it's the intensity and not the voltage that is most dangerous. So won't this commercial explanation be counterproductive?
READ MORE >>

Q: When running on the batteries only, how long and how fast can you motor?
A.: Our calculations: Batteries in full charge (60% margin) - 205 * 0.6 = 123 Ah.
Available Power = 123 Ah * 72V = 8856 Wh ---> Resulting in total of 8856 Wh available per motor, and a top speed of approximately 6.5 kts. So, as far as the range is concerned, it all depends on the average speed but at full speed
(8kW per engine) you can motor for 1 hour.

Q: At what speeds is it dangerous to recharge with the propellers?
A.: The controller knows when and if it has to start or stop regeneration.

Q: What are the various power outputs that can supply the engines and how do they work?
A.: The generator alone delivers 9.6 kW (through the charger; the generator sends 11 KW to the charger, the charger then delivers 9.6 KW) of direct power to the engines.
1. In continuous mode 24h/7d, the generator sends power directly to the engines (without using the battery banks) 9.6 KW which is the equivalent of 4.8 KW per engine giving a speed of 7 kts. It is possible to manually disconnect the battery bank with the 72V DC circuit breakers when motoring.
2. At the maximum engine output (8 KW) the batteries provide 3.2 kW to each engine. Therefore at max throttle with the generator running and batteries providing power as well, the range is 2.75 hours.
3. Theoretically, after 2.75 hours at full speed, the battery power is reduced and the boat speed will gradually slow down until it reaches the speed explained in point 1.

Q: You say that max RPM was 660. During sea trials you measured a speed of 7.5 kts at 626 rpm and 9kts of wind from astern. How can you go over 8kts with only 30 additional RPM?
A.: Theoretically, the question is valid. However, the important data is the power output at that speed and the torque available.
For example: 7.5 kts - 626 RPM - Torque 78 Nm - Motor Power output 51 13.27 W. Bearing in mind that the max torque is 11 5 Nm and the max power output is 8000 W, we still have 36% more power in reserve! But one must not focus on the relevance of RPM, it is not a diesel engine.

Q: Is it expensive to change the engine bearings at 20,000 hours? Who can do it?
A.: The bearings are common parts and we are working to ensure that their replacement can easily be carried out by a worldwide Leroy Somer service network.

Q: Recharge of the engine battery banks by the generator. How many Amps? If the larger Generator is selected, is the charger different in order to be adapted to the power output of the large generator?
A.: 120A with operating mode 5. With the 17.5 kW genset, we install two chargers, in order to be able to deliver 19.2KW to the engines without having to take from the batteries.

Q: Is the engine battery charger that runs off the shore power the same as the engine battery charger that runs off the generator?
A.: Yes, it is the same regardless of AC power source (dockside or generator).

Q: Can we fit folding props? If so, which brand? Will this have an impact on the engine's performance?
A,: With folding props, you will no longer regenerate, unless you are using manual pitch control propellers. We will be testing the Autoprop brand.

Q:
How sensitive are the engine controls: setting speeds from 1 rpm to 100%?
A.: They work similarly to electronic diesel engine controls.

Q: How can we tell that the boat is <<in gear>>, even at 1 RPM?
A.: The amp meter tells you that the engines are consuming power.

Q: Is the regeneration noisy?
A.: Propeller shaft rotation can be heard but the sound is below 46db.

Q: How hot do the electric engines get?
A.: Between 40 et 65°c (104°F and 150° F).

Q: Do Gel batteries provide a benefit in terms of life span and performance?
A.: Gel batteries require no maintenance and no ventilation. Otherwise, they have the same characteristics as the standard acid batteries.

Q: What is the generator diesel (11 KVA and 17.5KVA) fuel consumption at full throttle?
A.: Generator diesel fuel consumption at 100% power: 11 KW: approx 3.4 I/h (0.9 Gal/hour) 13.5 KW: approx 4.5 I/h
(1.2 Gal/hour) 17.5 KW: approx 6.1 I/h (1.6 Gal/hour) 21.5 KW: approx 7.2 I/h (1.9 Gal/hour). These are high estimations since generator does not always deliver at full power.

Q: During a long ocean crossing, how can you use the energy regenerated by the props for the household appliances?
A: Electricity is available right away since the service batteries are charged by the engine batteries which are charged by regeneration or the generator.

Q: Why use 72V motors and not more?
A.: The danger limit for human beings has been determined to be 80V. We wanted to stay 10% below this maximum, and 72 V is plenty in this application.

Q: 2 x 8kw available power seems to be weak for a catamaran of this size and windage, especially since it isn't always possible to have calm seas for anchoring or for leaving/entering harbours. Plus, taking into account the variables in electric power, it is conceivable that only half of the power is actually available from the theoretical amount.
A,: Based on measure taken from the Lagoon 440 : 5 knots speed under power in 25-30 knots of wind in moderate seas. (Consistent readings with the 17.5kw genset). There is a lot of power loss in diesel engine configurations (propeller with imperfect pitch or diameter, vibrations, transmission loss, etc.); and when one looks at the hull drag curves, on can see that as a matter of fact the theoretical kilowatts needed to attain target speeds are very similar to the values of electrical propulsion. In addition, we purposely limit the target speed, because the power needed to pass the 8 knot level is exponential: you need twice as much power to go from 8 to 9 knots!

Q: The battery banks and overall capacity seem very undersized. The surface area of the roof and the bimini would allow a generous solar panel installation, but what for, with such a ridiculously small battery park. The batteries would be quickly charged (overcharged!) and then quickly discharged, and you would still need to use your genset all of the time. That's really too bad! Where are the battery banks? Is it possible to increase the capacity with other small batteries, or even better, with golf cart batteries or with 6V lithium L16 batteries (dimension problems notwithstanding)?
A.: The engine battery bank is calculated to have a range of 20 miles (4 hours at 5 knots).  It is made up of 2 x 6 12V batteries, or 210A/h and weights approximately 840 kg. Our premise is that you will use your engine batteries for entering and leaving harbours and in case of emergencies (when the genset is inoperable).  The engine batteries are located in the stern compartments.
There are lots of types of batteries that could work in this configuration. We chose these types of batteries because they represent the best value for cost/quality/power/size and worldwide market availability.
Battery regeneration is assured once the vessel reaches 5 knots of speed under sail. You will easily have 1500 W/h charging the batteries.
Finally, solar panels would only allow you to draw a maximum of 120 watts/hour per m2 under best conditions (clear exposure under bright sunlight)

Q: The choice of 72V is surprising and seems to be unique, since all electric motors of this type used for intensive industrial use are 120, 250, or 500V depending on the power source
A. It really isn't that surprising or unique. For instance, it is the voltage used by the French national railway company, and most common traction-type machinery (forklifts, pallet stackers, etc.)

Q: You probably wanted to play up to the uninformed the safety issue by talking about 80v being dangerous to humans, but really, as far as electrical safety is concerned, it's the intensity and not the voltage that is most dangerous. So won't this commercial explanation be counterproductive?
A.: When talking about protecting people, it's best to work with low voltage levels.
We cannot disassociate the risks involving voltage and intensity since the 2 variables are proportionately related.
Max voltage tolerance for the human body: 50v AC
Max intensity tolerance for the human body: 30 mA
Human resistance: R = U/I = 5010.03 =I667 Ohms
Here, we are working with 72v DC: I = UIR = 7211667 = 43 mA
But, with direct current, the maximum intensity tolerance for the human body is 130 mA. (according to the manufacturer)
So, the choice of voltage is relative, and judicious.
If we were working with 220v: I = 131 mA, and that's dangerous!

In conclusion, voltage REALLY counts since that is what intensity is "based" on.