Turbines and electrical propulsion for a schooner

Discussion in 'OnBoard Electronics & Controls' started by james.smith, Mar 19, 2016.

  1. BertKu
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    BertKu Senior Member

    Lithium batteries for the Tres Hombres

    I was last week in Ireland and we were discussing Lithium batteries. It was an interesting discussion and it was also felt, that there are safe lithium batteries and possible tricky li batteries. In the 40 batteries I am using I can hammer a nail in the battery and nothing will happen. While in other compositions, there is a risk. The only risk I see, is a short circuit or if somebody is so stupid to drop a spanner on the battery connections and create havoc. But I can also use a match too light at my petrol (gas)engine and my car will go up in flames. Does that mean we should not drive petrol motorcars anymore?.

    Unfortunately one cannot put lots of small fuses between each parallel/serial connected batteries, the reason is they will pop like a domino effect when the electric motor starts, as a fraction of a second the one will be overloaded. Thus we need good fuse management. i.e. the maximum current needed for the motor should be a indication on how to protect a large battery bank of serial and parallel connected batteries. I have a LED with a resistor is serial over the fuse. Should the fuse pop, I can immediately see whether the fuse is gone. (in serial placed batteries) Because Lithium can handle high currents, the protection of a large current fuse versus maximum current a battery could supply, has to be taken into consideration. i.e. a 16 Amphour in serial placed battery, 20C maximum discharge current, the fuse should be not more than 320 Ampere. Such a 22.8 Volt battery bank x 2 would be able to give you 20 Horsepower for 3 minutes. 200 batteries parallel/serial would give you 3 hours. 200 batteries would cost you only 20.000 to 25.000 Euro's .

    But Zinc- Manganese would be the solution for Lithium fire risk ( if the wrong batteries are selected), but not for safe Lithium batteries. This does not changes the short circuit and fuse management system of a large battery bank. They will have to be correct in both type of batteries or any type of batteries.

    Moral of the story James, go for electrics but talk to a lot of good engineers who can help you in battery management systems. Bert
     
    Last edited: May 11, 2016
  2. BertKu
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    BertKu Senior Member

    Hi James, that brings us to a different topic. Charging of a large battery bank.
    You are not able in most of the harbours, to get more than 15 Ampere on 230 Volt AC and 25 Ampere at 380 Volt AC outlet. This makes it much more difficult to charge your batteries in a short time. This is the real problem I see for large electric systems in boats. O.K. you could say, we use a diesel generator to charge the batteries, but then you may as well use a diesel to power your boat.
    I see the solution, to use multiple chargers, charging each bank in an acceptable time. Each charger charging its own battery bank, which bank is then disconnected from the other banks while charging. Bert
     
  3. Barry
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    Barry Senior Member

    Are there not solutions to the high current start issues with motors etc. Zener diodes, capacitor start motors, or an electronically controlled bypass circuit or slow burn fuses??
     
  4. BertKu
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    BertKu Senior Member

    Yes Barry, one could come up with some solutions, which has to be tested first. I have 30 Ampere slow fuses, but because my experience has been that, although I may draw sometimes 80 Ampere, none of the 30 Ampere fuses will blow. However when I had first 15 Ampere fast fuses between 2 in serial placed batteries, they occasionally blew. Most likely because of the one, a fraction of a second (how much? I don't know, did not have the equipment to test it out) the one fuse will be loaded more than the other, and than you have the domino effect. My advice to James would be to go maybe for 72 Volt, with 4 motors in his boat, should it be possible with 4 motors driving the single propeller. Have 4 separate battery banks with synchronised controllers. I am not at home. I could otherwise download pictures of speedboats which has 3 or more motors driving the single propeller.

    One must understand the need for fuses. One need to ensure that no fire could be started with such a high power capacity in a boat. The batteries itself are not the problem. (provided you select the right kind of lithium battery). At home I have names of telecommunications 48 Volt battery manufacturers , very high power, which are used by many telecommunications organizations.

    In case of a fire on board?, you need to have the correct fire extinguisher close to the batteries. Not that it will that easy happen, but to satisfy the safety standards.

    If I was James? I would trust the Germans and go for a small 30 Hp engine. However, not 1 massive electric motor but I would go for multiple motors driven propeller, with multiple battery banks. Also multiple chargers to make life easier in a harbour. Each motor should be able to be disconnected to the shaft in case of a system failure.

    Also with a number of small 800 watt wind generators to top up the batteries during sailing. Solar is not really suitable in my view on such a sailing boat, but if there is wind, why not charging the batteries with wind?. The electric motor is only used in harbours, and maybe once in a while when there is no wind and the crew is in the hurry to get to land. With wind it can be charged as soon the wind comes op. If they really come across a very bad situation, the crew has to start rowing.

    Also If I was James, I would first go with a number of smaller Lithium battery banks and then when the Zinc-Manganese batteries are matured to go over to those larger battery banks. By that time the Lithium batteries would have given enough pleasure . Bert
     
  5. serow
    Joined: Mar 2016
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    serow Junior Member

    Just a thought.

    The problem is that harbours cannot easy provide you with a max. 25 Ampere outlet and at maybe 380 V AC, Thus you need multiple sockets to spread over the harbour outlets.

    What could possibly go wrong.:)
     
  6. BertKu
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    BertKu Senior Member

    Nothing, they just have to stay a little longer in the harbour and get a portable charging unit hired. Or wait until the wind has charged the batteries a little from the 4 wind generators.
    Bert
     
  7. BertKu
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    Location: South Africa Little Brak River

    BertKu Senior Member



    The only issue I see what could go wrong, is when the boat takes a lot of sea water on and the batteries get flooded. A solution would be, to have the batteries in 4 (or whatever quantity banks) water tight compartments. Sea water is a nice conducting path and could be an issue for short circuiting. The fuses will no longer help as the sea water will create short circuits from the battery leads. Bert
     
  8. BertKu
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    BertKu Senior Member

    Hi James,
    Somebody (Oleboynow ) placed a thread and you could use this possible on your project. Instead of expensive wind chargers, something more costs saving.

    Thread :
    Thinking about this
    Can also be water driven, there are youtube vids
    https://youtu.be/0ieFZI4-6K8

    Attached Files
    File Type: pdf FPall.pdf (1.12 MB, 963 views)

    I truly hope you dropped the idea to place a 400 HP smelly engine in your beautiful boat.

    Bert
     
  9. BertKu
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Hi James,
    I have some bad news. I wanted to order more 16Amph 22.8 Volt Lithium batteries and I see they have increased the price since January/February 2016 by 2,4 times. A battery bank of 200 lithium batteries of 20 - 25.000 Euro is now 48.000 to 60.000 Euro per bank.
    I for myself, will be shopping for an alternative.

    In 2 weeks I am at home and can then let you have the manufacturer for 48 Volt telecom Li batteries. Hope they are more cost effective.

    The system I see for your beautiful boat is:

    4 x 72 Volt brushless motors with sensored positioning. Each 7,5 Kw drawing +/- 100 Ampere at full load and speed. Water cooled.
    4 x chargers 230/115 Volt 50/60Hz 15 Ampere /25Ampere 3 phase .
    4 x 800 watt wind chargers or 800 watt sea water chargers with lots of wind and speed, the drag should not be a problem for your bait with dull sails.
    4 x controllers with synchronization.
    4 x lithium battery banks with proper fuse management system. In waterproof compartments
    4 x clutch systems for disconnecting a motor in the event of a problem with a motor system/controller
    1 x Central dashboard with full control.

    James you have to understand the difference between a brushless motor and a diesel engine. The diesel engine provide you with full torque at +/- 1600 - 1800 revs per minute. The brushless sensored motor has the full torque at the first rev per minute. In other words, you can at very low energy enter a harbour without using much energy, while the diesel is goggling up nearly the same amount of diesel as at full speed.
    Thus you really don't need 400hp to enter a harbour.
    Bert
     
    Last edited: May 14, 2016
  10. powerabout
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    powerabout Senior Member

    would that electric set up ever pay for itself or would the guy driving the diesel boat still have enough money left over to drink champagne every day fo rthe life of the boat and or himself?
     
  11. Barry
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    Barry Senior Member

    Bert, just because you have a diesel rated to 400 hp say at 2000 rpm, it does not mean that the engine is producing 400 hp at any time the engine tach is reading 2000 rpm

    The rating of an engine is the maximum that it can produce for a given rpm under FULLY LOADED conditions.

    So your comment that the diesel is gobbling up nearly the same amount of diesel as at full speed is incorrect.

    The amount of energy that the boat requires to move into a harbor for a specific speed will be the same amount of energy, if you ignore losses from the efficiencies of the propulsion unit.
     
  12. BertKu
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    BertKu Senior Member

    O.K, O.K, Barry, I just exaggerate, because I don't like smelly engines on a boat. My car is a 2.8 Colt diesel and it always smells in the garage when starting the car. I love electrics, it is the future for many applications in my view. Sorry for misleading the readers.
    How do you see this lovely project progressing? If James put all the masts and sails back, why an oversized diesel engine? 4 x 7,5 Kw electric motors with 105 - 110 Ampere each at 72 Volt is manageable. Also, if there is wind, you have 4 x 800 watt = 3.2 Kw x 10 hours of wind gives you 32 Kwh, good enough to re-charge a battery bank when flat. Thus over a period of sailing , all 4 battery banks are fully re-charged. James should try to get captains to tell more about their experience with a sailboat in storms, whether they really use their engines, or like my friend does when delivering yachts, he just let the storm run out of steam. I don't know, I don't have the experience in sailing over large distances in storms. When I was young, just in heavy sea I used the jib rolled half out. Somebody told me that in flat water, you need only 1 hp per ton weight. I estimate that James ship is 40 - 50 ton, included cargo, thus 30 Kw will get him going for some time. Bert
     
  13. BertKu
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    BertKu Senior Member

    The cost for the proposal to make the ship electric is in my view approximately the same as a large diesel engine + fuel. As soon the fuel is used up, he can start drinking champagne!!. Look readers, I think it is a proposition. Not a 400 Hp electric system, but a moderate 30 KW engine should do fine. Lets not forget that this ship was sailing without an engine at all. Bert
     
  14. SamSam
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    SamSam Senior Member

    When it is all said and done, it will be a project with a large amount of money invested in it.

    In making a long passage, perhaps something breaks so sails can't be used or everybody gets too sick to deploy them.

    It's a large gamble to install a backup power system that is pretty much untried, expensive, without any proven reliability, and has only a few hours running time if working correctly. The main reason I see for it here is that diesels are messy and smelly.

    It's not a requirement that engines are messy and smelly, they aren't naturally that way, but that's how they can get when you don't take care of them.
     

  15. gonzo
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    gonzo Senior Member

    Then he needs to find better crew if they can't use sails.
     
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