Wednesday, February 2, 2011

[Electric Boats] Need help on deciding on a system configuration

 

Hi, I've been lurking here for quite some time now and this is the year I'm going electric (well at least I'm 99% sure I will).

I have checked all options I know of, e-mailed and talked to many vendors and also looked up the possibility to build my own system.

At this moment, I *think* I will go with an electric yacht system and I'm trying to figure out if I need the 4.8kw engine or 8.6kw one. If money wasn't an object I would go with the larger one but.. since I will be unemployed later this year I could use all the money I can spare. However, I don't want to buy an undersized engine and regret it later.

My boat is a 30 feet (25 feet in the water line) sailboat 7500lbs from the late 50's. I'm currently doing a lot of work with it and I'm planning to get it in the water by May/June with an electric engine.

The waters I sail in could have strong currents, normal is 0.5-2 knots in either direction but sometimes it builds up to 3 or even 4 knots, but that is rare.
Now this hasn't really been an issue before since I have been sailing with an old outboard engine which only gave me 3 knots - together with sails up I have still managed to get back to the marina, but it has been frustrating sometimes almost standing still while trying to enter the marina while facing the wind head on. Also we have a lot of large ships passing thru here so "power when needed" is one of the things that makes me go electric.

Will the 4.8kw engine make me reach hull speed if needed or should I go for the larger one? Electric yacht says I can go either way but the stronger one would be better.

The other thing I can't decide on is the power bank. Lifepo4's or AGM batteries. I don't have a lot of space for large AGM batteries and the space I do have will have to be rebuilt for holding those heavy things (4 * 150-200A).
Been mailing a lot of lifepo4-suppliers for prices and they seem a bit more expensive, but a charger + bms is cheaper then chargers for the AGM system (at least the ones I've been looking at) but I have some concerns about managing them correctly since I'm not an electrician and I don't think I can't afford the luxury ones with built in management.

If going with AGM's, I'm thinking of going with 4 c-tek M300 chargers (25A 12v each) for being able to run a genset and charging while running the motor at a decent speed, but they are kind of expensive and if lifepo4 prices drops even more in a couple of years and I buy a lifepo4 power bank - I would be sitting there with useless expensive chargers.

I will also be buying a genset for being able to charge the batteries at sea.

I live in Sweden and when buying/shipping things from the US we have to add 25% tax and 2-10% customs, even on the shipping fee, so a 4000 dollars system in the US will be more like 6000 dollars for me when including the shipping.

If I lived in the US, I would not hesitate to buy the larger electric yacht system with one of their lifepo4 packs, but with shipping, tax and customs - that combo just gets too expensive for me.

I would love some input on the size of the engine and suggestions on different systems/parts then I have been listing here.

Thanks,
JH - who is dreaming of a trouble free electric sailing season

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