Drive electric trolling motor to generate power

[Billgas]

I have a variable speed trolling motor, it's controller, and a battery. These are mounted on a boat that is docked in a river. The prop turns pretty fast in the current.

Can the motor/controller (generator/controller) recharge the battery?

Can the motor (generator) be used to power an electrical load, say security lighting?

 

[waross]

Theoretically yes. In the real world, probably not. The mechanical efficiency may be so low as to make the project futile.
If this is a permanent magnet motor, measure the voltage comming back on the motor leads when the river current is turning the motor. If it is more than the battery voltage you may be able to charge. Try some lightbulbs across the motor leads and measure the voltage and the current.
yours

 

[aolalde]

In theory you can. The mechanical power taken by the propeler is converted to electric power.
Your problem is how to controll that power to get adecuate voltage that will charge your batteries.
At least you need acces to control the field intensity. If your field is constant, the voltage will change as the generator speed changes. The power you can get will be proportional to the speed and torque that the propeller provides.

 

[jraef]

There are stream generators that look a lot like trolling motors, here's one.

http://www.ampair.com/ampair/waterpower.asp

They only put out about 100W (8A at 12VDC), hardly enough for a security light but if you can run all day and store in a battery, you may have something usefull. You also need a method of preventing overs=charging of your battery, somethiong your trolling motor will not be likely to have.

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> faq731-376

 

[itsmoked]

Should work fine as long as you control the charging.

http://www.fieldlines.com/story/2005/6/27/41048/5123

Also trolling generators are used regularly in sailing. They look like a trolling motor being dragged by the power cord. They generally become a problem above seven knots which means a river current would probably be perfect.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

For an installation this small, a large zener diode will serve as a regulator. At one time this was a common regulation scheme for small motorcycle charging alternators.
respectfully

 

[OperaHouse]

Seems there is nothing new under the sun. I'm an antique boat fanatic and a few years ago I saw an electric boat from the 1920's that was designed to do this. They even had the factory literature.

Since the prop will turn at a slower speed than it is designed to run at, a boost inverter will be necessary to charge the battery. A simple TL494 regulator driving a fet and inductor can easily double the voltage. By monitoring the input voltage instead of the output, the prop can free wheel until the desired start voltage is reached.