Kayak brushless motor + ESC

Discussion in 'Electric Propulsion' started by Ozne, Jan 16, 2019.

  1. Ozne
    Joined: Jan 2019
    Posts: 1
    Likes: 0, Points: 1
    Location: Australia

    Ozne New Member

    Hi,
    I'm adding a trolling motor to my sit on top kayak.I have decided to go with Li-ion and I have ordered and received most of the parts.
    For the kayak a 30-40 lb thrust should be enough but unfortunately I can't find any low thrust trolling motors that are not 12 v. This means higher currents than I'd like (bigger cables, harder to solder, more expensive etc.) and, also, harder to use solar in the future (with outriggers or in a catamaran configuration with two kayaks). Solar charge controllers are rated by amps and 24 v makes everything cheaper, smaller and possibly cooler.
    Anyway, for 24v I found this 90 lb brushless trolling motor. It is probably an overkill and ~3 kg heavier than a 40 lb ones, but maybe not for a possible upgrade to a catamaran configuration.
    I would also like to use an ESC (Electronic Speed Controller) and a CPU like Arduino.
    Has anyone used one of the existing ESCs like this one for controlling brushless trolling motors ?
    They are designed for a completely different purpose but both voltage and amp look ok. Please let me know.
    Some functions that can be relatively easily implemented with Arduino :

    Circuit breaker : Arduino can measure the current and shut down the motor if it crosses a dangerous threshold. And shutting down by throttling down to zero, not by interrupting tens of amps abruptly that can cause dangerous voltage spikes. I probably would still have an analog circuit breaker for extra safety but have Arduino on a lower threshold : after clearing the weed or line that got the motor suck, turning the knob again has got to be a lot easier than to re-arm the circuit break on a small boat.

    Kill switch : again, voltage spike asides, I don't think that the inexpensive kill switches for outboard motors are designed to have tens of amps through them but it can be connected to one of the Arduino I/O pins. If detached, Arduino can simply throttle down to zero and avoid complications like this one.

    Smooth throttle with a potentiometer. This is easy and obvious.

    Voltage monitoring and shut down to protect the battery from undercharge. State of charge report.

    Measuring temperature in the battery and elsewhere for problems. Thermistors are very inexpensive and Arduino has multiple analog inputs.

    Voltage and amperage together can be used to calculate the power used.

    Measuring atmospheric pressure to monitor incoming bad weather. Many years ago I had a Casio watch that did that and I clearly remember showing rapidly dropping pressure as a storm was approaching.

    A GPS module is cheap and it can estimate speed and/or range with a given the charge status.

    If I get around to do this, I'll post everything, including circuits and source code.

    Any comments/suggestions, especially regarding the ESC question, welcome. Thank you.
     
  2. JamesG123
    Joined: Mar 2015
    Posts: 655
    Likes: 74, Points: 28, Legacy Rep: 10
    Location: Columbus, GA

    JamesG123 Senior Member

    Most motor controllers have circuit protection and charge controllers maintain the status/protect the battery, built in. No need for a separate computer doing all sorts of data collection and control. You can do all that if you want to as an exercise in electronics, but its not necessary if your goal is to just get electric propulsion on your kayak.
     
  3. Will Fraser
    Joined: Feb 2014
    Posts: 157
    Likes: 13, Points: 18, Legacy Rep: 11
    Location: South Africa

    Will Fraser Senior Member

    Something to consider with regards to voltage: an ESC employs pwm at partial throttle to reduce the voltage to the motor. This high frequency switching is superimposed on the low frequency 3-phase ac signal. All this switching (6 MOSFETS) means more efficiency losses in the ESC than at full throttle. A brushless trolling motor will have a fully functional ESC already integrated in its circuitry.
    I have yet to test and confirm this, but it might be more efficient to use a buck-converter to first step down the voltage into the ESC. The ESC can be left at full throttle and the power controlled directly using the buck. A buck still employs pwm but uses only two MOSFETS.
     
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