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. JosephT
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    JosephT Senior Member

  2. BertKu
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    BertKu Senior Member

    Hi JosephT, I like the high bridgedeck, refer the cursing Malasia in 2 threads back, when he had to overcome 1,5 meter waves. Bert
     
  3. JosephT
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    JosephT Senior Member

    Agreed. That high bridge is good for bad weather. That vessel, in my opinion, could be retrofitted or scaled up for a fishing vessel. Toss out the human tourists and stuff in the fish containers! :p Catamarans have potential for more space on deck and good stability. I have a friend who was a US Coast Guard pilot up in Kodiak, Alaska. He rescued a lot of fishermen swept overboard. Very dangerous job!

    A catamaran fishing vessel would be restricted in heavy seas though (over 6ft in this design study). If used wisely though (good weather planning), I can this concept reducing costs on diesel fuel.

    Someone else mentioned the earlier days of fishing vessels powered by sail. This is definitely an option too, but less efficient with time (slower) and staff (more crew required to man the sails). One has to do whatever is needed though to harvest fish and feed the population!
     
  4. Rumars
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    Rumars Senior Member

    If I understood the requirements corectly this will not be a deep sea fishing vessel, or a high volume one. The OP mentioned beeing able to reach most fishing grounds by kayak and being prevented to reach more interesting spots by a fast running tide. He also said that a tour around the island would be around 18km (10 nautical miles) and that he would like to take 2-4 paying customers. Based on this I would expect a tipical day to be a short run to a fishing spot somewhere around and near the island, fishing for an hour or so by fishing rod or handline while drifting or at anchor, move to the next spot, repeat a few times, make a run home. The worst conditions I would expect are wind against the tide. With good weather predictions like one expects in a first world country like Japan and normal common sense he should be ok. Basicly he wants what in the US would be a typical sportsfisherman.
    This usage pattern can be sustained with electric propulsion, but I agree that a generator is cheap insurance. If I got the pattern wrong then all bets are of and it can not be done by electric propulsion alone.

    The economic sense of all this is a different thing and I can not begin to asses if it makes sense or not. 40 000USD buys a lot of fuel, even in Japan and even on a tiny island where fuel must be carried by drum. On the other hand if he has a steady supply of eco-friendly or novelty hungry customers and if you add the local subsidizing maybe he can make a net profit and live of it.

    I see a 9-10m catmaran with a small cuddy housing the electronics, a toilet and offering some wind protection, a bimini for sunny days, and icebox fishholds in the hulls. Maybe a separate icebox for the clients food/drinks, a grill outside and a meth stove in the galley if he wants to be fancy.
    For emergency backup a 15hp 2stroke outboard and two canisters of fuel stored in a locker should always bring him home.

    Would I be in his place I would contact Mr. Woods about his Jazz 30 design, buy two Nissan Leaf battery packs from wrecked cars, put an electric motor of the required power on a outboard leg, aquire the needed control and instrumentation from established EV sources and find an electrical engineer to wire the whole mess togheter. Put the big electric outboard on one hull, a gas outboard of similar power and a 2hp electric (either a conversion or something like a Torqueedo) on the other and go fishing. This setup is redundant and allows everything, high speed using either electric or fossil fuel, slow speed under optimized small electric motor, two engined manoevers and double the needed power for dire situations. The only concern would be the weight of the batteries, but with careful calculations of predictable usage, some speed shaving and maybe some solar on the bimni I bet I could cut the pack to one 24kW Leaf pack.
     
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  5. BertKu
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    BertKu Senior Member

    I agree, that maybe the best concept. Special to have some lightweight flexible solar panels from Switzerland on the Bimini. in average he should be able to do 120 watt per square meter and that would top his battery with 6 m2 Bimini and 5 hours of fishing, some 3 .6 Kw in his battery, not to exclude that additional travelling and have the battery kept being charged. However one never knows what could go wrong and the wind picks up. To have a higher bridge is still something to consider, also with some solar on top. Bert
     
  6. Rumars
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    Rumars Senior Member

    I agree on the high bridgedeck. The solar panels I see as a mixed bag. You are of course right that a solar bimini is a usefull addition. But this being a fishing vessel for rod fishing, a big bimini is mostly in the way. I would expect even a small one to be folded down rather often. Good quality semi-flexible or flexible panels are expensive. For a " daily return to base" vessel I would rather put that money in the batteries. Would it have been a cruiser I would have said make any compromise and have the biggest solar array you can fit and pay for. But in this case I think I would not bother. Just one or two panels on the cabin top to keep the 12V auxiliarry battery charged for house loads and starting the gas outboard. Anyway a solar bimini is easy to add at a later stage if it is deemed useful. For the initial fitout I think battery capacity to be the priority.
     
  7. xellz
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    xellz Senior Member

    Yes, everything is right. For my use and location electric might be just about right. One factor i didn't mention too, it doesn't really get cold here, even in winter rarely drops below 10C. Price for similar size used fishing vessel with inboard diesel 30-80hp in more or less decent condition is around 50.000USD and it's far from new, i.e. some repair work bound to happen sooner than latter. So regarding price, electric won't be much more expensive that common fishing boat and lower running costs should more or less counter higher price. Usual bottom shape V, maybe it's superior to catamaran in rough sea, but at rest it sways really strongly even in small waves. And almost all fishing will be done when boat is drifting, if i can't stop the boat and fish securely there is no point going out to sea anyway.

    Solar panels, i might add few latter if i can, but cost vs actual benefit is not that good.

    Weight capacity is not really an issue, as long as it can safely carry 5ppl it's more than enough for my purpose. Although live bait tank is necessary, but doubt it will posses any problems. Since it's rather far and inconvenient place for commercial fishing, focus is on large and expensive species that are abundant here. I.e. quality over quantity. Local fisherman association also releases 2000 baby fishes every year for most sought after target species. I believe it was some kind of large grouper, common size 5-10kg, time to time up to 20kg. Just an example on rather common fish, japanese greater amberjack if catched by nets sold at about 4-5usd per kg because fish is rarely alive by the time it got on boat or simply in bad shape, if fished on a single line (lure or live bait) and properly killed, blood removed sale price jumps to ~13-16usd/kg.

    I was born and grown up with no sea or ocean nearby, at most small rivers. Since i moved to island only 2 years passed, but already i can't imagine my life without ocean :) It's not exactly easy sure, mostly because it's difficult to find decent work over here, but for us it's worth it. If anyone interested what island i'm talking about, google "Mishima Iojima" or 30°47'18.13" N 130°17'14.36" E
     
  8. Rumars
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    Rumars Senior Member

    Contact Mr. Woods. The Jazz 30 open deck sounds perfect for you. It also has live bait wells.

    If you have a rough ideea for how long you need to motor at certain speeds the necessary battery capacity can be calculated based on the power needs of the hull. For example if you need 10 knots for 1 hour and it takes 11kW (15hp) to do it, then you will need approx. 20kW of battery (80% DOD + controller eficiency + motor eficiency + transmission).

    I would certainly use a catamaran even if staying with gas outboards. It is simply a more efficient platform overall for the intended use. I would build the cat, put on second hand conventional outboards and determine the actual power needed with them. Then sell one outboard, keep the other for reserve and convert to electric. Might be easyer to get subsidizing if you have the actual vessel operating, money givers like to see hard facts.
     
  9. BertKu
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    BertKu Senior Member

    Hi xellz, Maybe you should have a look at EEMB, they make professional power systems for the telecommunication industry. beautiful LifePo4 3,2 Volt 100A batteries and packs for 50 KWh www.eemb.com click on rechargeable batteries and click on LiFePo4 batteries. Maybe you would be able to get for 50 Kwh a quote from them. Lipo Battery, Li-ion Battery, LiFePO4 Battery, Nimh Battery, Portable Solar Power -EEMB http://www.eemb.com/battery/rechargeable-battery.html
    Pity that wind probably is not blowing hard, when you go out for fishing, otherwise a a few 1 Kw wind generators would do well on your project.

    Rumars, you are right. I am not a fisherman and thus a Bimini is not a good idea, when you hook your fishhook all the time on the Bimini and that thing is in the way.

    Bert.
     
  10. fredrosse
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    fredrosse USACE Steam

    For the fully electric boat, your criteria will be very expensive, however a reasonable compromise can produce a reasonable boat. A displacement hull, turning a relatively large and efficient propeller can get by with a little more than about one horsepower per ton of displacement. With this arrangement, a good displacement hull (say 25 feet long x 6 feet beam, 1 ton displacement) would be able to cruise at 5 knots. Ten group 27 lead acid batteries will give the 5 to 6 hour endurance at that speed. For safety and security, a 5 to 10 horsepower high thrust outboard motor will allow plenty of extra power for wind and waves, and be able to give 6-7 knots speed, and almost unlimited endurance compared to a pure electric arrangement.

    My small electric boat, based on an O'Day Javelin sailboat hull, 14 feet, with 14 inch three blade propeller at 400 RPM could run at about 4 MPH for about four hours. It had two group 27 marine 12 volt batteries, with a simple switching scheme that would put the two batteries in series for high speed, or in parallel for low speed. At low speed the boat runs at half speed, and had an endurance of about 20 hours. I found that having these two speeds, both forward and reverse, was adequate for my use, and only requires two DPDT switches. The details are on the Yahoo electric boat forum.
     
  11. xellz
    Joined: Jul 2017
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    xellz Senior Member

    I'm currently negotiating about financial support for charger station and boat assembly. Even for old fashioned japanese people, who rarely try something new when old way works. Idea wasn't refused straight away, so good chance on success :) Also searching for local hull building companies and old cats. There is abundance of old really cheap mono hulls (almost everything is fiberglass), but catamarans are rather rare. If nothing reasonable available, most likely will try to build one of cats from Woods designs as recommend here. Even if in the end will have to abandon full electric, i still want a catamaran. But first need to find one for trial run in open seas, which might be a problem.

    Sadly, lead acid batteries won't be anywhere enough for my purpose, it's either lithium batteries or diesel/petrol. And outboards most likely is also a bad idea.

    I still have quite a bit of time until i will need my own boat, so will think carefully over various solutions. Since i'm planning to use this boat for work and pleasure, might as well invest little bit extra for comfort and fun.
     
  12. xellz
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    xellz Senior Member

    Just found a video on lightweight 27' catamaran with 9.6hp outboard engine, 4ppl on board achieving 13knots. This was a nice example of catamaran efficiency.
     
  13. BertKu
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    BertKu Senior Member

    Xellz, that is the way to go. OK the water is flat and the 7 KW engine would give you with 50 KWh battery 7 hours gliding over the water. (Bear in mind that LiFePo4 can give the power to nearly the last breath of 2 Volt per cell) With waves it will be less, but nevertheless very impressive. Silly question. If you made the pontoons wider apart, and utilise some space for sole solar panels, you could extend the 7 hours to 9 or 10 hours. But the concept becomes more and more a reality. I would split the 50 Kwh in 3 banks. One for reserve,one for going to the farthest point on your island and 1 for returning base. I would not make a massive 50 Kwh single bank. Bu that is my personal opinion. Bert
     
  14. Rumars
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    Rumars Senior Member

    It is a nice video, but you will not achieve that. Depending on specific lithium chemistry and packaging your battery will weigh between 400 and 800kg. That is the equivalent of 5-10 standard people. To this you add another 400kg of the actual people on board with their equipment, food and drink, and then hopefully the cached fish.

    In your boat search you need to keep that in mind, the boat must be able to carry the weight. Look also at sailing catamarans, they are also suitable. Not the small beach cats, but bigger cruising ones.
     

  15. BertKu
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    BertKu Senior Member

    OOhps, that indeed is the hard facts. Lithium is 125 wh per 1kg and then we indeed have to add some "packaging" weight to it. Yes that was a bloop from me. Bert
     
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