Eric,
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
Martin
To: electricboats@yahoogroups.com
From: ewdysar@yahoo.com
Date: Tue, 7 Feb 2012 19:24:36 +0000
Subject: Re: [Electric Boats] Looking at the options
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
Martin
To: electricboats@yahoogroups.com
From: ewdysar@yahoo.com
Date: Tue, 7 Feb 2012 19:24:36 +0000
Subject: Re: [Electric Boats] Looking at the options
Hi Michael,
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.
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).
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.
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.
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.
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.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "Michael" <barrowbyuk@...> wrote:
>
> 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.
>
> Doesn't really sound like I am ready to go electric does it?!
>
> ...having spent time in Tiberon and Sausalito I've seen your water behave...
>
> Thanks for the thoughts, I will ponder some more.
>
> Michael
>
>
> --- In electricboats@yahoogroups.com, "aweekdaysailor" <aweekdaysailor@> wrote:
> >
> > Even with an ICE you're only going to do 1 or 2 knots against that current. So when would it be worth it?
> >
> > 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).
> >
> > 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.
> >
> > 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.
> >
> > 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.
> >
> > HTH,
> >
> > -Keith
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.
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).
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.
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.
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.
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.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "Michael" <barrowbyuk@...> wrote:
>
> 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.
>
> Doesn't really sound like I am ready to go electric does it?!
>
> ...having spent time in Tiberon and Sausalito I've seen your water behave...
>
> Thanks for the thoughts, I will ponder some more.
>
> Michael
>
>
> --- In electricboats@yahoogroups.com, "aweekdaysailor" <aweekdaysailor@> wrote:
> >
> > Even with an ICE you're only going to do 1 or 2 knots against that current. So when would it be worth it?
> >
> > 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).
> >
> > 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.
> >
> > 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.
> >
> > 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.
> >
> > HTH,
> >
> > -Keith
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