Hi Eric,
Many thanks for your comments, they have helped me to clarify the whole thing in my mind and for now at least, I will stay with diesel. If my habits change, ie the way I use the boat, I will certainly re-consider.
Best
Michael
--- In electricboats@yahoogroups.com, martin demers <mdemers2005@...> wrote:
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> Eric,
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> I think your post could clarify the situation or interrogation someone might have about switching to electric
> In my case I will stick to diesel for long distance blue water cruising
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> Martin
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> To: electricboats@yahoogroups.com
> From: ewdysar@...
> Date: Tue, 7 Feb 2012 19:24:36 +0000
> Subject: Re: [Electric Boats] Looking at the options
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> Hi Michael,
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> These are serious considerations. By pure math, assuming a 3 to 1 increase in efficiency from deisel to electric, one gallon of diesel (38kWh) can be replaced by 12.5kWh (265Ah @ 48V) of battery storage. But the conversion isn't really that simple. Factoring in usable capacity means that the battery bank should be bigger, I use 80% Depth of Discharge (DoD) for my Lithium batteries, many AGM owners use 70% DoD, and flooded battery (FLA) owners use 50-60% DoD.
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> But that math still doesn't tell the real story. Using my 30' ketch as an example, my 8kWh (160Ah @ 50V, 90kg, $3500USD) Lithium battery pack will drive my boat almost 7nm at 6kts, my old 12hp diesel would burn just under a gallon to do the same work. Slowing down to 4kts, my pack has a usable range of more than 20nm, the diesel would have burned more than 2 gallons to travel the same distance at the same speed. So let's say that my battery pack is about the same as a 1.5-2 gallon fuel tank for my typical usage. Unfortunatly, under normal shore power (15A @ 120VAC), it takes almost 5 hours to "fill the tank" from empty (80% DoD).
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> If you are in an area where you might have to fight strong currents, you can empty an electric "fuel tank" pretty quickly. I know that we would all prefer to plan our outings to avoid adverse currents or even put the current to our advantage, but sometimes we don't get to choose.
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> One type of backup is a portable generator, I have a 50 lb Yamaha EF2000iS that can drive my boat through the battery charger at 4.3kts without draining the batteries for as long as the gasoline lasts, though it is a fairly noisy configuration. As soon as one considers a permanent marine generator below decks, in my opinion, a regular diesel drive without electric would be cheaper, simpler, lighter, and have more power on tap to deal with scary situations for boats my size.
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> But if you're already using your boat, you can easily get an idea of whether you can live with electric by checking your actual fuel usage over time. When I realized that in 10 years, I had only used more than 1 gallon in a single outing a couple of times, it became obvious that electric alone would be sufficient for more than 95% of my voyages. With quiet, clean, and more reliable power compared to my diesel, my boat is vastly improved - FOR THE WAY THAT I USE IT. For another owner of an identical boat, electric may be an expensive disappointment.
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> Electric drive is not "one size fits all", however, it is a very good alternative to IC engines for some people. You have to decide for yourself if it would work out for how you actually use your boat.
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> Fair winds,
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> Eric
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> Marina del Rey, CA
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> --- In electricboats@yahoogroups.com, "Michael" <barrowbyuk@> wrote:
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> > Maybe I am not in the right mindset but the sound of a thrashing diesel is awfully re-assuring when one is fighting against a tide...and the thought of the batteries quietly discharging wouldn't give me the confidence I'd get from a few spare cans of fuel.
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> > Doesn't really sound like I am ready to go electric does it?!
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> > ...having spent time in Tiberon and Sausalito I've seen your water behave...
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> > Thanks for the thoughts, I will ponder some more.
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> > Michael
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> > --- In electricboats@yahoogroups.com, "aweekdaysailor" <aweekdaysailor@> wrote:
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> > > Even with an ICE you're only going to do 1 or 2 knots against that current. So when would it be worth it?
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> > > We have similar tides here in San Francisco - 4-6kts depending on where you are. You just learn to never (ever!) fight the tide, since you will lose (at least with battery-only such as mine).
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> > > Minor changes to your boating habits can accommodate electric, and if you have deck-space for a generator, there's really no difference to an ICE if you have enough charging capacity.
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> > > The peaceful nature of an electric drive - even if you can't always use it exclusively - is really a game-changer. Suddenly music, conversation, the sounds of nature - are all accessible.
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> > > You will have a challenge carrying enough battery unless you go to lithium or carry a generator - 6 hours is going to consume a rough guess of 6KWh (assuming 50% duty cycle of 40amp draw) - so that's about 24 12v conventional deep cycle (115AH 12v) - maybe 700kilos in lead-acid but only about 300 in lithium (but that's ~$3000US...). If you carry a generator this is a non-issue and you can get by with 1/2 (or less) that.
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> > > HTH,
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> > > -Keith
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