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Wywern 02-07-2008 04:22 PM

Motor, battery and solar panels for a boat
Hello. I'm new to this forum and it looks like you know a lot about modding cars. Same princibles can be applied on water. Atleast the motors and batteries. I'm trying to find info about what kind of motor (power) I can supply with solar power on a sunny day. That all depends largely on the solar panels used. What kind of solar panels are out there and for what price? Is it still better to go with sails than with solar power? I'm not thinking of high speeds or a big boat, but speed is surely helpful in some cases.

Requirements for the boat: able to carry 4-6 people and sleep in it, cook food and move about even if the sun doesnot shine all day.
So I'll need lots of batteries to store the energy when I can get it. What is the best (cheapest/lightest)?

I read that you salvage big dc motors from forklifts. I think those would be very good for a boat also. Is there some other machinery which has salvage potential?

Ryland 02-07-2008 04:44 PM

there are a number of reasons that boats have sails, cloth is cheap and light is a big one, the other is that water has very little resistance for the wind, altho it's also reflective, it is pretty well agreed on that if you are near water wind power is the way to go, if you want something a big weird, go for kite power.
solar on a boat is best for powering things like lights, and the radio.
price for solar, just for the panals tend to be $4-5 per watt of output, and you might get 5 hours of sun per day if you are on the water, so at best you would get one watt per dollar per day... not bad, add the cost of a battery bank to that and you have enough to power some lights, add a 5,000 watt motor (like is on a forklift) and sudenly your house is morgaged.

MetroMPG 02-07-2008 04:51 PM

Hi Wyern,

You can probably find some of the information about solar & battery requirements at links like this:

The owner of this company is a member of one of the local electric vehicle lists I'm on. (He also just placed his order for an Aptera EV.)

This one crossed the Atlantic last year on solar power.

You may not be going for that scale, but there's information on both sites that will help you figure out what size motor, battery bank & solar array you may want.

I don't have a lot of experience with electric boats. Here's mine:
(details about my e-boat)

Doesn't sleep 4-6 people though :)

EDIT: this summer I made a solar powered boat:


AndrewJ 02-07-2008 07:36 PM

yur pic broke Darin!

WaxyChicken 02-07-2008 07:49 PM

One thing that can help you down the road when you are modding your boat is the use of hydrofoils. The most resistance to movement that a boat gets is due to the amount of water that it has to push out of the way. By lifting your boat off the water, or simply having less boat in the water, you will improve your MPG or batt efficiency. Most hydrofoils act as a wing and, as you move forward, LIFT up your boat. There is also the pontoon approach which also can reduce water resistance.


You are asking what equipment other than forklifts have good motor salvage chances. Are you looking for speed or power? (eg: light and fast, or heavy)

MetroMPG 02-07-2008 08:02 PM


Originally Posted by AndrewJ (Post 8752)
yur pic broke Darin!

You can't see my electric boat?

EDIT: pic fixed.

Waxy: true about higher efficiency on foils. The big challenge is having a good enough POWER to weight ratio to get a displacement hull out of the water and up onto the foils.

Ryland 02-08-2008 03:06 PM

If you do put solar on a boat, POINT THEM AT THE SUN, panals that lay flat are getting a fraction of the sun they would if they were st up at an angle, and if you are relying on them for powering your boat it becomes a poor use of the panals.

MetroMPG 02-08-2008 03:37 PM

True enough. It's kind of like putting up a sail, and then not trimming it for the wind!

basjoos 02-08-2008 10:34 PM

If you angle the solar panels at the sun while there is a stout wind blowing, the panel might start acting as an imprompto sail with unintended consequences. Also if the boat is bobbing around in heavy seas, if might be difficult to keep the panels pointed at the sun.

bennelson 02-09-2008 12:18 AM

Last summer, I was zipping around on my electric motorcycle. Stopped to talk to a guy with a golf cart. He mentioned that he had seen a guy on the lake with an electric boat.

I tracked down the boat owner and spoke with him.
He has a Duffy Electric Boat

The boat uses 12 Trojan 125s (6V each) in two parrallel 36V legs. The on-board charger is 15 amp 120V. Zips around the lake all day. Goes around 10 mph.

This boat uses a GE golf cart motor.

This boat has a roof shade, so solar panels could be installed on top, but why bother if you can just charge up at the dock?

Otherwise, if you are more into sailing, get an ok sized sail boat, set it up with an electric motor and batteries, use that to get in and out of port, and use the sails while out in the open.

Sailboats sometimes also use wind turbines. They are cheaper for the power output, but solar is so slick because of its quiet simplicity.

The photo at the top uses the same motor I have in my motorcycle. Here is an interesting little web page about an electric boat conversion

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