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Go Back   SailNet Community > On Board > Gear & Maintenance
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Old 04-25-2011
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Obvious electric boat idea

I've been following the electric propulsion of boats for some time now. The problem is of couse the energy density of the batteries. Fuel is 100 or more times more dense.
You need a lot of batteries to equal just a couple gallons of gas.
For the right boat used the right way with dockside electric to charge the batteries and acceptance of very, very limited run-time between charges on the order of a few hours at best some folks have successfully implimented electric propulsion.
The problem is where to put the extra batteries so they don't change the characteristics of the boat.

So on to my question. Several popular boat designs have integrated keels, that is keels that are not bolted on but are part of the mold.
These keels are usually filled with heavy stuff, lead, iron, steel often just random sized pieces with some kind of filler like concrete.

Would it be possible to dig out the mess and make a compartment to hold batteries. The AGM batteries are sealed and need no maintanence.

I'm thinking of a good quality battery with a emergency vent connected via a hose and the terminals waterproofed. Anyone seen this done already?
Waterproofing would be tricky but possible yes?
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Old 04-25-2011
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Quote:
Originally Posted by davidpm View Post
I've been following the electric propulsion of boats for some time now. The problem is of couse the energy density of the batteries. Fuel is 100 or more times more dense.
You need a lot of batteries to equal just a couple gallons of gas.
For the right boat used the right way with dockside electric to charge the batteries and acceptance of very, very limited run-time between charges on the order of a few hours at best some folks have successfully implimented electric propulsion.
The problem is where to put the extra batteries so they don't change the characteristics of the boat.

So on to my question. Several popular boat designs have integrated keels, that is keels that are not bolted on but are part of the mold.
These keels are usually filled with heavy stuff, lead, iron, steel often just random sized pieces with some kind of filler like concrete.

Would it be possible to dig out the mess and make a compartment to hold batteries. The AGM batteries are sealed and need no maintanence.

I'm thinking of a good quality battery with a emergency vent connected via a hose and the terminals waterproofed. Anyone seen this done already?
Waterproofing would be tricky but possible yes?
I once saw a boat with a keel full of batteries at Svendsen's Boat Works, in Alameda. It was a kinda funny-looking boat, with a disproportionately thick and long keel to accommodate all the batteries. This was at least 15 years ago, before AGMs were nearly as common as they are today. So, I suppose the batteries were deep-cycle flooded units. Remember, as heavy as batteries are, they are not nearly as dense as solid lead, or even iron. A Trojan T105 weighs about 62 pounds, but the same volume of solid lead would weigh about 440 pounds, and solid iron would tip the scales at about 305 pounds. So, yeah it can be done, it has been done, but at the cost of having a less than ideal keel size and shape and a lot more surface area and projected frontal area (both of which add to drag).
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Old 04-25-2011
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One would have to consider the propensity for bilge water to want to travel to the lowest spot. You would have to seal the battery storage area in the keel, while still allow access for maintenance. This could probably be done, but you would still require a way to evacuate water if it were somehow flooded anyway and that method wouldn't be able to rely on power from those batts to do it.
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Old 04-25-2011
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I really hope this technology advances quickly. My 35 year old Atomic 4 is a ticking time bomb... er, I mean it would be nice to repower with electric.
Not sure what a normal bilge size is, but my 27' boat holds 20 gallons and the water level is still about 5" from the floor boards. Plus, assuming an electric motor is much more compact than gas or diesel, there would be a lot of space in the engine room for batteries.
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Old 04-25-2011
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Davidpm,
You know this, just remember that nothing needs no maintenance.
John
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Old 04-25-2011
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until you go lipo or other high tech battery, it is not really feasible, even then its going to be limited range.

if i ever build a cat, its going to have a 15 to 20 k diesel genny with 2 electric motors. that way i can save space with the smaller motors but have AC when on anchor.
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Old 04-25-2011
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Hunter did a nice job on the 27e and i would like to see how they have done out in the wild

Alerion did a state of the art install on a 33e and it would also be nice to see how it has worked out
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Old 05-01-2011
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Quote:
Originally Posted by SlowButSteady View Post
I once saw a boat with a keel full of batteries at Svendsen's Boat Works, in Alameda. It was a kinda funny-looking boat, with a disproportionately thick and long keel to accommodate all the batteries. This was at least 15 years ago, before AGMs were nearly as common as they are today.
I knew someone must have done it. It seems pretty obvious.
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Old 05-01-2011
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Mars metals says a square foot of 1" lead is 60 lbs so a cubic foot would be 720 lbs and cubic inch .4167 lbs. A T105 is about 10.3 x 7 x 11 or 793 cubic inches or about 330 lbs if it was solid lead.
Thanks for the wake-up call. Batteries seem so heavy I would never have guessed that they are so light compared to solid lead.
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Old 05-01-2011
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Electric propulsion

Check out Electric Yacht - Electric sailboat propulsion systems that are cost-effective, yet CLEAN, GREEN and QUIET!

I've looked at several options for a future replacement with electric when my (currently good running) atomic 4 bites the dust. These guys seem to have come up with a truly commercially viable system and now are introducing a hybrid to add on to an existing diesel (or atomic 4 gas engine).
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