Hybrid speedboat

[qbee42]

Originally Posted by hampdenwireless

Hybrid makes far more sense for sailboats. They can make power while under sail and have it for cruising in and out of port. The weight of the batteries can be put in low and not effect the boat badly.

In a hybrid sailboat you entirely replace the diesel with electric. The boat is powered by wind and electricity exclusively.

What we need is a battery shaped like our keel, then we could have a 5,000 lb battery. With my luck, the battery company would upgrade to Li-ion and our boat would float upside down.

It would be great to get rid of the diesel. We have a fabulous diesel engine, but it's still big, smelly, and noisy, plus it requires a big tank of fuel.

Tom

[daniel]

Originally Posted by qbee42

What we need is a battery shaped like our keel, then we could have a 5,000 lb battery.

The battery pack for the Tesla Roadster is an extremely irregular shape, specifically designed to fit into the shape of the space available for it. Since it's constructed of small laptop batteries, it's a fairly simple matter to build it in whatever shape is wanted.

So, for your keel boat, it would be easy to build a Li-Ion battery pack shaped to fit in the keel. Since you probably have ballast in there now, there would be no weight penalty. The Tesla requires liquid cooling because those laptop Li-Ion batteries (unlike the LiFePO4 pack in my Xebra) are subject to thermal runaway and must be cooled. But in your sailboat, cooling would be easy as the keel is surrounded by sea water, and if conduction through the hull is inadequate, a small pump could deliver cool sea water to a circulating cooling system without the need for a refrigeration unit like the Tesla requires.

Of course, when you are becalmed you have no way to charge the batteries. You'd want to design your BMS to conserve some charge for emergency use during calms. Or maybe a small propane-powered Stirling cycle engine (clean and quiet) as an emergency generator.

[qbee42]

I like the idea. I have kicked around thoughts like that for a lot of years. I may build another boat along these lines sometime in the future, when I feel like having another big project. Often times a small genset is used for auxiliary power. They are small, self-contained, and reasonably efficient. It doesn't take much power to move a sailboat.

As for a weight penalty, as you point out, we have a lot of ballast. Our boat carries 5,000 lbs of lead. Li-Ion batteries are not as dense as lead, so you would need a lot of them, or perhaps a combination of ballast and batteries, but it is certainly possible.

There is a power boat on the market that uses this sort of system for propulsion. It has a large coach roof covered with PV panels, which are alleged to provide enough power to move the boat at cruising speed with only the sun. For night, or higher speed, you kick in the genset. It's too new to know how well it works, but the idea is attractive.

Tom

[daniel]

I would anticipate that lithium batteries would not entirely replace your lead ballast. My point was merely that since you already have so much ballast, unlike an electric car, which pays a weight penalty for the batteries, your sailboat would not.

I am extremely skeptical of the solar boat. I believe it takes far less energy to move a car on level ground at moderate speeds, than a boat, considering the enormous drag of the water. And we know that a conventional car has not nearly enough surface area for solar panels to provide more than 1 or 2 percent of the energy it needs. But there are plenty of grandiose claims in the EV world, ranging from dreams to scams.