Need help with electric boat modification planning, rough estimation on engine and battery capacity

Discussion in 'Boat Design' started by xellz, Jul 2, 2017.

  1. BertKu
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    BertKu Senior Member

    Xellz, you quoted in your first thread " I won't be assembling or repairing it myself, helping or which is most likely, stay away and don't get in the way of more skilled people :)"
    I strongly would suggest you stay away from difficult electronics. If you are willing to learn basic principles of electronics and electrics then, there will be no problem and have backup of some critical items and understand Lithium batteries, I charge my 40 lithium LiFePo4 batteries with a normal modified charger for 7 years, but I don't dare not to keep an eye on certain issues, LIKE PER CELL not to fall below 2 Volt and ensure to watch that NONE of the parallel placed batteries are deviating from the other parallel placed batteries too much. I don't agree with some people that hobby batteries are bad. Lithium is lithium, but all what differs is that some are packed in some cartons and others in a hard pack of plastic. You have in that case to create a metal water proof container and ensure that all batteries are properly fused. You don't want an problem at sea that your solar panels are overcharging your lithium batteries. Yes if you fast charge Lithium batteries you need a proper Lithium battery charger, but if you charge at way below 20 % of the "5 C" = 1 C , in the case of thread dated 2/7/2017 , *( 6 x 20 Ampere batteries parallel = 120 Ampere x 5 C = 600 Ampere maximum thus maximum with not more than 120 Ampere, but preferable at not more than 60 Ampere (0,5 C) ) you do not heat the batteries up. So, if you use lots of flexible solar panels and only have a 2,or 3 or 4 or 5 KWh hobby batteries, switched parallel and in series , and use 2 Mars motors from China as per attached photo, you don't need complex electronics, just some method to switch the motors from 12 Volt to 24 Volt to 36 Volt to 48 Volt your motors from your solar cells and battery, you will have a simple system on the sea and if you understand very basics electricity, you can handle all kind of situations.
    1) Why? you must stay below the 50 Volt DC, which is regarded as dangerous at sea, because when you touch it without gloves, there is a good chance your hand cramps and you hang onto the bare connection point and die at sea.
    2) Flexible solar panels does not create a stability problem, while with normal solar panels it will be quite heavy and not stable when going over a wave.
    3) Have a few LCD battery voltage meters, which verifies continuous all your critical parameters, like not below 2 Volt per cell etc.
     

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  2. kerosene
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    kerosene Senior Member

    Yeah e-motor can do that. Too bad it is not a crucial need for any boat.
     
  3. xellz
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    xellz Senior Member

    I certainly will learn some parts so i won't kill myself by accident or injure anyone else. Currently i can't even select proper cable. I won't risk doing everything by myself. Cell balancing and monitoring was a part of decent controller and where i don't want to save money. Either everything is build well and safe or skip this idea completely. From recent posts here it looks like ~50kw battery bank should be enough to achieve my goal, not so sure on hull type and motor yet. 2x6kw units? 50kw LiFePo4 is still more or less within budget, need more research. From what i know, LiFePo4 is rather safe and should not posses much danger, as long as i keep watching state of each battery pack.

    p.s.
    I'm kind of electric propulsion fan, so even if it's inconvenient for some parts or initial price is higher i would still choose electric.
     
  4. Rumars
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    Rumars Senior Member

    Sorry I missed the "I will not do it myself thing". In this case your only option may be flooded lead acid technology. I am not aware of anybody that will do and support a 50kW lithium bank for 30-40000USD. It is possible to buy all the battery system components for the money but paying for labor and knowledge is another thing. Turnkey systems come at a price, and the batteries are the cheap part.
    Even with 50kW of lithium batteries (around 400-500kg installed) you still need a low power hull, so start searching for older displacement trawlers or catamarans or a sailboat.

    BertKu I am sorry but kerosene is right. A propulsion system is planned from the stern, meaning you begin with the prop the boat can swing and the target speed. No small boat can use 10rpm as cruising rpm, maybe something the size of a container ship. And solar panels are of no use either, on a 8-10m monohull with a 50kW battery they are decoration or shade spenders.
    The boat will need a robust charging station at the dock capable of pushing 40kW in 10h into the batteries, wich in Japan probably means a 50kW charger fed by a three phase 200V line.
     
  5. xellz
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    xellz Senior Member

    For this project i will be buying parts only. If i can show that it can be done and possible benefits, work and charger station can be subsidized. I probably would not even try to pull this off without possibility of financial support.
     
  6. Rumars
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    Rumars Senior Member

    Ok, then you must look for following things:
    1. Suitable boat. Something designed for low power, sea capable in the desired area, capable to take the battery weight and in budget. First option for paying customers applications a catamaran, lots of space for guests to fish, no heeling to make them sea sick, reasonable speed with low power motors, two motors for easy harbour manoevering. Option two older trawler. No planing boats.
    2. A naval arhitect to determine needed power, propeller and rpm range, and instalation details for the selected hull. First you need to have the boat, he can not work with nothing. You may find suitable hulls and present them to the naval arhitect to select the best one for you.
    3. A company specialized in electric car conversions or electric forklifts and floor sweeping machines or golf carts that also works with lithium. They are to design the electrical system, choose the charger, BMS, motor controller and motor, etc. according to the directions given by the naval arhitect. They will determine system voltage and motor type. You cannot arive to them with a load of parts and say make it functional since even if everything works togheter they will not do it. A company needs to offer warranty so they will select what they know and are confortable with, put the system togheter and sell it to you. They will probably also sell you the batteries to go with this. If the system then is a 400V battery with an AC motor or a 48V DC motor installation it makes no difference to you.
    3.1. Convince one of the above firms to design a system based on generic available components, then buy the components yourself and have a third party (specialized firm) install them. You will get no warranty and it might be difficult to find someone to do it. The drivetrain is no problem, any forklift or golf cart place can sell you and electrically install the needed components. Any boatyard will handle the mechanical instalation.
    The battery is another thing since the company doing it must be familliar with the batteries, the BMS and it's capabilities. It is a difference if the BMS is a standalone unit or integrated with the motor controller and charger or if it is split between charger and controller. Flooded lead acid instalations are easy in this regard because there is a lot of knowledge and no BMS. A good charger and you are set. But the boat must be able to handle the weight and space of the batteries.
    4. A place to buy the batteries if you succeed with option 3.1. Chineese prismatics (Winston, Calb, etc.) either directly from China (ad transport and taxes) or from a local supplyer. Other batteries usually only from their distributors. You usually have to ask directly "how much for a 50kW pack?" because they won't have a price on the website. Integrated battery packs including BMS and charger are available but at a premium price.
     
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  7. BertKu
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    BertKu Senior Member

    Hi Xellz, In that case go for AC motors. Yes, LiFePo4 are very reliable and one can hit a nail into the battery and nothing will happen, no explosion. I can post you the specs and tests done of my LiFePo4. I am not too sure whether I can do that with the 20Ah battery, 3.7 Volt from the hobby people. But there are hundred thousand hobby people who have purchased them. Ask them what they think and experienced. But you are crazy to ignore flexible solar panels, not only cost those LiFePo4 an arm and a leg, for what reason.? With solar you always get some energy into your batteries, (excluded during the nights) , provided you haven't forgotten to have a MPPT regulator or MPPT charger. Just because sometimes there is a fire on a yacht who was using petrol, does not mean people don't buy petrol engines anymore. Here the same, you can use LiFePo4 batteries and does something stupid with the fuse and I can guarantee you that you will have a fire on board.

    Hi Kerosine, maybe not essential and certainly not meant for cruising (refer Rumars) , but is sometimes very handy to have a very low speed and that is my experience.

    Xellz, you will make it and at the end does the correct thing . I enjoy my solarboat, but am in the process to add a small sail to it, just in case.
    Bert
     
  8. messabout
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    messabout Senior Member

    Here are some basic numbers that you can contemplate . One electrical horsepower is equivalent to 746 watts. You need to figure a bit more juice because of normal losses from friction and several other energy robbers. For now lets just use the standard equivalent, 746. Let us imagine that you need 10 horsepower to drive the boat at some speed. Then you will need an input of 7,460 watts and a little bit more.

    A watt is calculated as voltage times amperage. Usually written as P = I * E. where P represents watts, I is amperage, and E is voltage...... OK lets make that easier to remember with Watts = Amps times Volts. you can rearrange the equation such that W/V = A or W/A =V You can see that if you have a 7,460 watt demand and a voltage of perhaps 36, then 7460/36 = 207 amps. That is a fearsome lot of amps that will require some very large supply wire and some switches that are capable of dealing with that amperage. Simplistically, if you had batteries capable of delivering 1000 amps you would have a theoretical 5 hour running time until the batteries gave up. That is a much too elementary explanation but it will give you some information that will be useful for back of the envelope calculations.

    I am all in favor of electric power for playing around in my local lake but not for industrial use. For your application a nice little Yanmar or similar diesel is the most practical deal in terms of operating cost, reliability, and initial cost. Consider that a marina that you might visit will almost surely have a diesel mechanic either on site or on call. Few of those marinas will have an electric boat technician.
     
  9. BertKu
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    BertKu Senior Member

    Xellz, Did you had a look at ww.Oceanvolt.com or Electric powered outboards for boats - Torqeedo http://www.torqeedo.com and see what you could use from them.

    Just something about charging. Because I placed 10 lithium batteries of 3.35 Volt parallel and 4 x in serial the total voltage is 4 x 3.35 = 13.4 Volt and the maximum Voltage allowed on LiFePo4 is 3.6 Volt per battery i.e. 4 x 3.6 = 14.4 Volt. The charger I have is a lead acid battery, but it limits the current to way within the amperage allowed for charging the batteries i.e. at 1C till the voltage reaches to 13.8 Volt, thereafter it does constant voltage to 14.4 Volt. I have done this for 7 years and the logic is that the parallel connected batteries are keeping each other balanced, while I only have to keep an eye on the 4 voltages on each group. Only when one discharge extreme high currents, will most likely the batteries go out of balance. Up to now, my Li batteries are in good condition.

    By the way, I saw that Ocean Volt copied me most likely, in placing the motors in liquid substance for cooling by the seawater. I think they also use transformer oil, but it sound better and is much more marketing oriented to state "liquid substance approved by ". You could also consider that if you use separate purchased motors.

    Ever considered an DC motor on your battery bank, which powers a generator, which powers AC motors? You can keep the very heavy thick copper cables very short between batteries and DC motor and then with 220 V ac motors driving your propellers. Simple, you stay within the 48 Volt and can easy control with AC speed control your AC motors.
    Bert
     
  10. xellz
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    xellz Senior Member

    Thanks, this helps to finish up my paper work for initial review. If it's approved can move to talking with boat design company for most fitting hull, size and type.

    Displacement monohull seems little bit limiting on top speed. 7 knots and from what i understand, if go really close or over hull speed energy necessary will be a lot higher. Catamaran might be good for extra speed and stability when not moving. But i can't really find speed limitations for displacement catamarans, if it's possible to go for short time near 9-10knots then it's the only option left. Will talk soon with people, who can advice if particular hull could be safely used in waters around here.
     
  11. Rumars
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    Rumars Senior Member

    Yes the catamaran is the only option if you want speed. For displacement catamarans, the speed limitations have to do with hull spacing and motor power, but normal displacement limitations do not apply for hulls over 8:1 L/B ratio.

    You might like Woods Jazz 30, a catamaran specially designed for fishing. Sailing Catamarans - First Choose a Design http://www.sailingcatamarans.com/index.php/designs-2/6-powercats
    The designer indicates 2x40hp for 21kn speed for the Jazz and his Skoota 28 design makes 16kn with 2x20hp. If you only want 10kn 2x10-15hp will probably be ok, but you would have to ask the designer (he is a member here) so please contact him about that.
    The only problem is of course that you would have to build the boat, but that is not that complicated, because you only need a simple interior.

    Even if you have bigger motors the battery size does not need to change. Top speed would probably be needed only for a short time, most of the time the boat will move slowley under one motor alone.
    Bigger motors need higher voltages or more amps. There are controllers on the market that can deliver 2000A and high voltge instalations are not that dangerous as many believe.

    Here a link to a company that can deliver a robust battery system. They have different waterproof and shockproof units that can be wired in paralell or series and includ the BMS. Also DNV-GL certified if that helps in some way. The price was high a few years ago, you would have to ask about current pricing. Clean, compact, safe & reliable energy - EST-Floattech http://www.est-floattech.com/
    For a plug and play system you need something similar to this.
     
  12. BertKu
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    BertKu Senior Member

    Hi Xellz, Malasai had an electric catamaran build in Australia and is since 3 or 4 years cruising around Australia, He was last on this forum site in January 2015, His experience could be very useful to you. Why don't you give him a private message.
    Bert
     
  13. BertKu
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    BertKu Senior Member

    An example of Malasia experience >>>>
    Speed is a major consideration.

    Also, the times that I cursed the most the designer of my old 42' sailing cat with 600mm bridgedeck was when motoring through steep 1 to 1.5m waves.
    Once I had a 5h demolition ride at no more than 4kn into a 25kn wind, any faster and I would have had structural damage.

    If you look again at my drawing of the Mantacat at speed, the design of the 'double arch' relies on the speed to create turbulence/ foam on which the powercat rides. If you slow down, then you start pounding, till you really slow to a few knots and start climbing the waves rather than cutting through.
    Never been on a sailing cat with 'double arch', but my guess is that it would not work the same. Other benefits might apply: extra stiffness, some pounding reduction etc.

    IMO for a sailing cat you must make it long, light and with high bridgedeck, this way you climb over big waves and slide through little ones without bashing.
    Anything diverging from that will be a compromise.

    Not a bad idea to contact him Bert
     
  14. gonzo
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    gonzo Senior Member

    42HP=31kW. That is the value that should be used to calculate the batteries.
     

  15. JosephT
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    JosephT Senior Member

    Rumar's list of requirements is good. Despite this, an all electric fishing boat seems a bit risky to me unless you strictly operate it within its power consumption range. I would suggest tacking on teh requirement for an auxiliary generator. Be it diesel, hydro or wind generator at least you've got a way to re-charge. For fishing, I would suggest a diesel generator because the re-charge rate will be better.

    Here is a reference to a catamaran tour vessel project. Less drag than your typical fishing boat. You'll have to factor in maximum loading & operating limitations. Catamarans are not as good in heavy storms so factor that in.

    Tongass Rain | Water powered boats? http://tongassrain.com/

    [​IMG]
     
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