Controller for the trolling motor: what to choose?


Help me choose between the Pololu SMC 18v25 and 24v23 for the trolling motor “Watersnake T18” (12 volt 15amp).
Battery lifepo4 12V45A (A123 prismatic elements).
Wire length: from the battery to the SMC = 2m, from the SMC to the motor = 0,7 m.

Please tell me:

  1. Which one SMC to choose?
  2. What are the MOSFETS are on these controllers (website information not found)? Available to download electronic circuits SMC?
  3. How to protect the controller against overloading, for example, if the motor is jammed. In this case, the battery will provide a dramatic increase in amperage.
    Enough to set the temperature threshold through usb? What is the threshold sufficient?
    It makes sense to install the 20 amp fuse?

Best regards, Alex

Hello, Alex.

  1. For your application, the limiting factor for your motor driver will probably be the current, so if you are definitely using 12V motors, the Simple Motor Controller 18v25 should work a little better than the 24v23.

  2. We do not commit to a particular MOSFET on the Simple Motor Controller, but it will be something very similar to what we use on the equivalent High-Power Motor Driver 18v25 CS. The MOSFET datasheet is on the Resources tab of that product page.

  3. I am not sure what your 15A motor current rating means, but I would not be surprised if your motor has a stall current on the order of 100A, in which case the SMC’s over-temperature feature would probably not be fast enough to protect against damage from sudden current spikes. So, using a fuse for additional protection is probably a good idea.

I am concerned about the length of your power leads. Is it possible for you to rearrange your setup so that your power leads are shorter and your motor leads are longer? If you cannot get your power supply closer to your motor controller or if your motor will be subject to abrupt speed changes, you might need to add more capacitance on the power inputs near the motor controller.

  • Grant

Sorry for the late reply.
Thank you for the necessary information and helpful tips!

I am glad that my idea is feasible.
Will put the controller into the motor head like this (photo).
Rain-protected ventilation holes, I think, will be needed.
On your advice I will try to reduce the length of the wires to 120-130 cm.
Ordered such “marine” fuse.

- Alex

Install the controller in the motor head (photo).
I know about the recommendation to increase the capacitance of the capacitor if possible. My trolling motor motor 12V15A, battery 45Ah LiFePO4. The length of the wires (12 AWG) from the battery to the controller at least 1 meter not able to do because it requires a balance of weight in the boat. Housing dimensions (photo) allow a more powerful capacitor.
What are the characteristics of capacitors are required (voltage, capacity)?
Is it possible to apply a protective lacquers, for example Can I apply lacqures on the surface of the mosfets?
Thank you.


The capacitor voltage should be at least 25V (preferably larger), and it should be at least a few thousand uF.

For the conformal coating, it might be possible, but we do not know what it will do to the thermal performance.

- Grant

Hello, Grant, thank you for the advice.
In the motor housing are placed two capacitors: 1) 4700 uF 35 volt; 2) 3300 uF 50 volts. Which is preferred?
Thank you.


If you have the space, you should use both, but if you only have space for one, then I recommend the 4700 uF capacitor.

- Grant