----- Original Message -----From: cpatourauxSent: Friday, April 23, 2010 12:07 AMSubject: Re: [Electric Boats] Conversion of Traditional Thai fishing boat to ElectricHi Denny,
Thank you for that. I will check the MARS motor. It is Brush Type, so does it need a lot of brush attention? Is is straightforward to maintain? The selector is indeed a good idea. I did not think about that.
Your suggestion to use them straight into the longtail is indeed an excellent one. This would reduce the cost and also allow an easier adoption from the fishermen because that is the system they know how to handle...
The boats are usually used for coastal fishing, withing 3 to 4 miles from the coast, typically to visit crab cage sites or bottom nets sites.
The fisherman would use his engine / motor for about 2 to 3 hours per day at medium speed I would say. The trips usually take place during the night.
They tend to be quite safe and do not go out at sea during the monsoon or during large swell, so that the motor typically would not have to cope with very rough conditions, but rather a steady run with intermittent stops at the sites.
When back on shore, the boats are usually either moored in tidal protected coves with some pontoons or actually most of the time in mangroves next to their houses. So drawing an electric cable is indeed feasible.
The LFP is indeed a 3.2V cell.
I have done some research about LFP versus Lead Acid and I may be wrong, but from what I gathered, the lead acids cannot be discharged as deeply as the LFPs without substantially reducing their lifetime. Apparently LFPs can be discharged to less than 10% whereas it is not recommended to drive lead acids lower than 50% discharge. In addition, the LFP have an easy 3000 cycles and actually 5 to 6000 cycles if not pushed to hard. Lead acid have only less than 1000 cycles from what I gather.
So my rational was that although the LFP is 3 times more expensive per nameplate V-AH, because it can use this power fully by doing almost twice as deep discharges without damage and it has at least 3 times more cycles in a lifetime, I thought that LFP are actually less expensive than lead acid per equivalent V-AH. But again, this is all from various articles I read and I have not had personal experience with them. Any other perspective would be welcome.
My idea was to mount about 5kWH of batteries giving 1 hour at full speed , i.e. 5kW.
The weight is indeed not a big deal. 5kWh of LFP would give me about 120lb, not too sure about the lead acid though. I believe it would be twice as much, but still acceptable I guess.
Now the next question would be the protection of the motor and of the batteries. Any suggestion?
Thank you..
Christian
--- In electricboats@yahoogroups. , "dennis wolfe" <dwolfe@...> wrote:com
>
> Christian,
>
> You might try a MARS brush-type motor http://www.marselectricllc.com/ and run it on 12v, 24v, or 36v with a switching system to select the voltage - that would eliminate a controller and throttle reducing cost and complexity. You would get about 5kw at 36v but not very long battery life.
>
> Is your $1.50 / ah figure for one 3 volt LFP cell? If so that works out to be $6 for a 12v equivalent ah. Quality lead acid batteries are about $2/ 12v ah. The extra weight probably would not matter with a 30' boat going 3 or 4 mph.
>
> Can the fishermen recharge the batteries from mains power on shore? The answer needs to be "yes" for your idea to be less expensive than buying diesel fuel. Are the fishing trips short (10 - 20 miles, maybe a little more) and not generally into a strong headwind or foul current. That answer also needs to be "yes" to have the modest power and range of an electric system work out.
>
> A simple downwind sail could help range a good bit and little cost or need for sailing skill.
>
> It would be easy to mount an electric motor in place of the diesel on the long-tail assembly. The MARS motors are not much bigger than the alternator on your diesel.
>
> If you could provide more detail about the boat's "mission" we could be more specific about the electric system needed.
>
> Denny Wolfe
> www.wolfEboats.com
>
>
>
> ----- Original Message -----
> From: cpatouraux
> To: electricboats@yahoogroups. com
> Sent: Thursday, April 22, 2010 7:35 PM
> Subject: [Electric Boats] Conversion of Traditional Thai fishing boat to Electric
>
>
>
> Hello,
>
> I have a small charity shipyard in Thailand where we build boats for fishermen.
> I have been doing this since the tsunami which I lived through in 2004 and so far we have already built 88 of those boats.
>
> Those boats are usually called "long tail" boats because they use engine mounted on a swivel on the aft deck and a long shaft driven straight into the water from the deck. I will try to post a few pictures.
> Now most of those coastal fishermen are no longer using the boats because the fuel price has become too high to pay with the sales of their catch.
> We successfully converted one of those boats to a sailboat last August, but the issue is that most fishermen are.. well.. fishermen and not sailors.
> So now I am considering the electric option and any help, guidance and advice would be very welcome.
> The boats are somewhere between 30 and 40 feet and the engines that we have been using were 11HP Yanmar, so I think I could replace those with a 5kW with similar max RPMs as the Yanmar and use the same propellers. My idea would be to build an inboard motor and drive the shaft straight through the stern and use a rudder. The power would come from LFP batteries.
> Those boats cannot have a propeller shaft or a drive protruding under the hull because they rest on the sand at low tide.
> My main concern with all this is what parts to use and especially how to protect them from seawater.
> I have tried procuring a 5kW BLDC motor from China through the sites Alibaba and Globalsources for the last 2 months but they are unable to demonstrate their quality, give me efficiency curves, etc... so now I have turned to US products and started the search a few days ago. But I am quite concerned as to how how protect the assembly from seawater.
> I managed to secure good LFP batteries at $1.5 per AH so at least that s good.
> So once again, any suggestions and recommendation on what parts to use, would be most welcome. Oh and yes, it is a charity, so my budget is limited for this prototype. Probably less than 3 thousand US without the batteries.
>
> Thank you..
> Christian
>
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