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

    OK that is indeed a problem. In that case XELLZ has to make the boat and pontoons longer to enable to carry 400 kg' . It is only 0.2 cubic meters of space on each pontoon. Bert
     
  2. xellz
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    xellz Senior Member

    Yes, sure it won't go that fast. I will be going for larger catamaran anyway. But still was surprised at speed with that little power. Especially from what i know, rated output is usually higher than it actually is in outboards. One of options is to go with newer chemistry with higher energy density and less cycles, 1000-2000 full cycles is still plenty, but allows for lower price and lower weight than LiFePo4. I just thought i might shoot myself in the leg with LiFePo4, heavy and expensive, sure can be used for many many years and safe, but in last 6-7 years battery price dropped significantly and capacity also had noticeable increase. So might as well plan for 7-10 years of use and replace with whatever will be available at that time.

    For example slightly used Tesla 5.3kW packs go for 1.400usd and weight 25kg. That's an option too. Even if add 10kW extra to balance out faster battery capacity loss than LiFePo4, still decent option.
     
    Last edited: Jul 9, 2017
  3. Rumars
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    Rumars Senior Member

    If you can get Tesla packs sure, go for it. I suggested the Leaf modules based on availability in Japan, the Leaf sold a lot so there must be batterys available. S-h electric car batteries are the best option you have, they are cheaper and higher quality then big chinese cells.
     
  4. BertKu
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    BertKu Senior Member

    Is that maybe the proof that brushless motors can be compared with substantial more powerful diesel and petrol/gas engines?
    A company like Ocean Volt made a public statement on their website and I heard it from other sources also. Would they risk of misleading the potential customers and risk potential court cases?

    Yes indeed LiFePo4 is expensive and good, if you think that the previous used Tesla modules are worth every penny, go for them. At least you should be able to get a decent charger on the market for them at Tesla or their dealers. What voltage have those Tesla units as an output? 300 Volt ? 400 Volt? Be careful if you are messing around with high voltage on a boat. You cannot have solar panels then on your boat also, except for charging some small battery. Bert
     
  5. gonzo
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    gonzo Senior Member

    Tesla nominal voltage is 375V, but fully charged around 400V. That is a problem in that it can't be wired like a low voltage circuit that is usually on a boat. Those potentials are deadly.
     
  6. Rumars
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    Rumars Senior Member

    A Tesla module is 444 Panasonic 18650 3400mA cells arraged in a 6s74p arhitecture inside a box also containing watercooling and a BMS. One module weighs 25kg. The complete battery consists of 16 of this modules in series inside another waterproof aluminium box with dividing walls, fireproofing and gas vents. The chemistry is Nickel Cobalt Aluminium Oxide (NCA) and each module has 24V, 240Ah for a total of 5,3kWh. This individual modules can be combined to whatever voltage you like in 24V steps. Paralelling them is possible but more difficult from a BMS standpoint. The BMS inside them has been hacked, but it is a dumb BMS, only monitoring, higher functions are elsewhere in the onboard computer, so people use a separate BMS for them. Right now this modules have the highest energy density in the EV market.

    The leaf modules are different, they consist of a sealed aluminium box (sardine can) containing 4 pouch cells in a 2s2p configuration. Since the cells have a Mangan chemistry they are 7,6V, 60Ah and weigh 3,8kg. They do not have any BMS or cooling. They reside in a waterproof steel box also containing the BMS. The factory BMS is in the process of being hacked. The cells are made by NEC as far as I know.

    Buying a battery from a wrecked EV is at the moment the most cost effective way to get high quality batteries at low cost. What might be available depends on the local market. In the USA Tesla, Leaf and Chevy Volt batteries are ready available because of the big market. In the EU on many markets there is a battery lease system, and the market for used batteries available to private customers is much smaller. I don't know about Japan but te Leaf sold well there and if no leasing system was employed then there should be a market.

    Motors from this cars are also available but they are to powerful for this application.
     
  7. BertKu
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    BertKu Senior Member

    Thank you Rumars, very interesting information. Bert
     
  8. BertKu
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    BertKu Senior Member

    Here is the official statement from Ocean Volt. Your concept has a good chance of succeeding. You may need substantial less usage of your 50 - 60 Kwh batteries and have then plenty spare capacity. Here is official website declaration from Ocean Volt.
    >>>
    Q:
    WHY IS THE 15KW OCEANVOLT MOTOR EQUIVALENT TO A 45HP DIESEL ENGINE?
    A:
    The torque of Oceanvolt electric motors is significantly higher than that of a diesel engine - and they both have the same propeller.
    <<<<<
    Bert
     
  9. gonzo
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    gonzo Senior Member

    Torque alone is meaningless. Power is what needs to be calculated, which is a function of torque and angular velocity. If they both have the same propeller, someone did the wrong calculations. Propellers are calculated for several parameters. Blade area is directly proportional to power. If they installed a propeller with the same area for an engine with less power, it is inefficient.
     
  10. kerosene
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    kerosene Senior Member

    Here we go again... this has been addressed several times. Hp is hp regardless whether it's an old man twisting a crank, e-motor, or a diesel
     
  11. Rumars
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    Rumars Senior Member

    Bert Oceanvolt is plain wrong. Gonzo explained why. Don't you find it interresting that no serious electric vehicle manufacturer in the world makes such bogus claims? I am talking here about companies with sales volume, the people who actually develop and manufacture. Nissan, Renault, Tesla, Mercedes, GM, BMW, etc. not one of them tries to sell you a car with a 15kW motor and claim it is equivalent to a 45hp diesel. Why do you think that they all migrated to electricaly comutated 3 phase motors (with or without permanent magnets) when the simple DC motor has so much torque and the electronics are simpler (read cheaper)? Even forklifts and golfcarts move to AC.
     
  12. xellz
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    xellz Senior Member

    I'm assuming that 0.77kW is 1hp right now, from information that i could find on hull speed calcuclation. 2x6kw engines should be able to push Jazz 30 up to 10knots. I.e. with twin 8-10kw engines should be enough power for emergency. This speed won't used for long periods, mostly slow maneuvering on fishing grounds, drifting or trolling. I've sent email recently to Woods Design to confirm my guessing.

    There is another matter that bothers me now. Inboard vs outboard. Outboards are simple to install and overall cheaper solution. Possible to use petrol engines and shift to electric latter. Jazz 30 fishing catamaran also designed for outboards. I've talked with local fishermen association and they think outboards are not safe here due to sometimes rough seas, especially with following seas. Engines might get damaged by water, can loose control easily due catamaran shallow draft and outboard engines. Outboards on catamaran might get in the way of trolling. However they have zero experience with catamarans and are rather strongly prejudiced for anything uncommon.

    I would add my own concern regarding outboards, even electric outboards are fairly noisy, inboard could reduce noise quite a bit. Acid rain, there is active volcano on island (level 0, but constantly degassing), most things rust a lot faster than they normally would. Inboard solution could add decent protection from acid rain and volcanic gasses.
     
  13. gonzo
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    gonzo Senior Member

  14. xellz
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    xellz Senior Member


  15. gonzo
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    gonzo Senior Member

    Have you looked at the specifications? They are rated up to 100HP, that is about 75kW. You are using only 6kW.
     
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