Will a trolling motor generate electricity and charge a battery if it is pulled thru the water?

Specific application I'm looking at is using a high thrust trolling motor on a small sailboat for the auxiliary propulsion. Research indicates this will work great. However, the various sites advise using solar/wind/ or shore power for recharging.

Suppose the motor was left down, we raised the sail, and the prop began to freewheel. Seeing as how this is a DC motor, wouldn't it start generating electricity? Has anyone tried this? What type of controlling circuitry would be needed if any to charge the house batteries?

7 Answers

  • 1 decade ago
    Favorite Answer

    Here is the Biggest problem with the trolling motor generator...Its not with the motor but with the capture area of the prop...Lets do the math here real quick ...I promise not to take to long...If your trolling motor uses 10 amps at 12 volts thats about 120watts ...756watts is about one horsepower,....... to get enough drag surface on the prop you need about 60 sq inches....120/756=.16hp or 480 sq inches per hp....more or less..so thats a pretty good size prop lets say 5" x 12" now to get it to spin you need a very easy rotating motor/gen set if its a permanent magnet type you have a problem getting it past the first pole is pretty hard...now lets look at rpm for a moment normally your motor cranks out that 120 watts at say 500-600 rpm to get a sail surface relationship and pitch to get your 12 vdc back... your gonna need to have one heck of a pitch or loose your voltage for lack of rpm.. So I would say this ...your idea of using the regenerative power of a dc motor to make a little wattage is quite sound ..However using a trolling motor made to puLL your boat might not be as efficient as some other means...Keep working on the idea though try using a right angle gearbox being driven by a floating paddle wheel ..or perhaps a flexible driveshaft underneath the boat with a helix coil driving an inboard alternator. Regulation for all the voltage is as easy as pie... a couple of big caps and one transistor and 30 minutes and you can build a regulator for nearly any thing up to 200watts...Ever hear of the 12v Light bulb from the old days being used as a regulator? See didnt even need a cap for that one....Anyhow have a good day from the E...

  • 1 decade ago

    No...apart from the electrical issues,

    there are also mechanical issues

    that would need to change for this to work.

    The velocity of water that is created in the

    motoring direction is much faster than the

    speed of the boat. In the regenerative

    direction you couldn't get that kind of speed.

    You would need a much bigger prop

    to operate at the speed of the boat and then

    convert that back into speed at the motor

    by providing a gear ratio that increases the

    speed at the motor. Motors like speed, not power.

    If I were to try this, I'd use a paddle wheel.

    then the motoring and regen speeds would be similar.

  • 6 years ago

    Im looking into trolling motors as I have personally used a 12v scooter motor to produce curent, have to block the flow with diodes so your not running it.

    the problem I ran into was the speed required to produce enough voltage to keep a battery topped up.

    I then found a Nordic trac treadmill. That dc perment mag motor makes 12 volts by spinning by hand.

    so the folks out there who have these advanced degrees in trolling ,may make them expert's on topics including trolling in their title.

    they certainly have no idea as they have never connected a dc motor to a meter or bulb and gave it a spin.

    years ago I installed a hayden 12 inch 12 volt cooling fan on a weekend cruising car.

    it was low amperage so it was powered when the igition was on grounding a temp switch for when aditional cooling was needed.

    if I pulled in some where while the fan was spinning and killed the ignition power the small block chevy hei dist kept receiving power from that fan alowing the engine to continue to run.

  • ?
    Lv 6
    1 decade ago

    It can, depending on the motor's circuit. If it has a permanent magnet field, then no problem. A motor is nothing more than a generator operating in reverse.

    Large power companies have been using this for years - pumped storage plants.... During the day, water coming from above drives the water turbines and generators to produce electricity. At night, they're connected as a motor and brought up to synchronous speed, paralleled, then water is introduced at the tailrace, and it begins pumping back uphill.

    Not a problem.

    Fred P.

    Source(s): Electrical engineer (power) in California since 1976.
  • How do you think about the answers? You can sign in to vote the answer.
  • 1 decade ago

    I would say no. There would have to be some serious circuitry changes to the trolling motor to change it to a dc generator. Specifically, you would have to have a dc field applied to the commutator while pulling the motor to cause the voltage to be generated. The motor is set up to rotate when you have dc applied to it so there would have to be some serious modifications. The best bet might be to follow the advice and use solar/wind turbines.

  • Anonymous
    5 years ago

    For the best answers, search on this site https://shorturl.im/ayj3K

    Certainly a microphone converts sound energy to electricity. But sound contains a very feeble amount of energy. THis would certainly not be a practical means of generating useful quanities of energy. Sound simply doesn't have enough energy to be a viable economic source..

  • Anonymous
    1 decade ago

    No. A propulsion motor is not an alternator and it won't generate electricity by running 'backwards'.

Still have questions? Get your answers by asking now.