18V25 Voltage control with PWM and MAx current

We are looking to use the 18V25 in a project trial and later in production quantities.
Two questions

  1. Can the unit, when using Voltage Control 0-5V, accept a PWM input (Approx 8 kHz)
  2. All of the literature states that is can do up to 25A with no heat sink. What is possible with a heat sink ? We MAY need up to 40A …is this possible. I assume that we connect to the FET’s on the rear of the PCB?

Hi John,

Most of my projects are related to propulsion systems for fishing kayaks.

About a year ago I did some heatsink testing with the 18v25.
I was using an off the shelf 30-pound thrust trolling motor. Brushed motor.

I discovered that getting even close to the 25A max rating was not realistic without a heatsink.
I tested out some heatsink ideas and they worked very well, allowing me to operated to the 25 amp rated max.

Attached are some links to a couple of YouTube videos I made related to this topic as well as a couple of files related to my results and 18v25 setup. The videos are nothing special. I made them for a buddy of mine that was going to make me some heatsinks on his CNC setup.

I used MX-4 Thermal Compound on the heatsink. It has a Thermal Conductivity = 8.5 W/(mK)

My whole fishing kayak propulsion project changed when I moved from a brushed motor setup to a brushless motor (thruster) setup.

In my opinion, the 18v25 board is not the easiest thing to mount to a heatsink. :wink:

Also, I am not sure your 40 amp goal is realistic. One might be able to remove the heat for the FETs but I am not sure the connections and other associated high current components can tolerate sure high currents. You might get away with 40 amps for a very short period of time, maybe measured in seconds. Best I can remember there is no max current setting but you can set the max temp limit, via the Simple Motor Control Center.
Pololu will know the answer to this question.

As you probably know, Pololu sells a range of brushed motor controllers,
maybe some of these can have their outputs connected in parallel.
A quick check of these controllers did not indicate if they could but Pololu will know.


Pololu Simple High-Power Motor Controller 18v25 - Temp Test

Brushed DC Motor Speed Controller Heatsink


smc_settings.txt (3.0 KB)

Hello, John.

We have four different boards (with different features) with 18v25 in their product name. Could you provide a product number or a link to the specific board you are interested in?

Do you have a datasheet for your motor and have you characterized its current consumption in the mechanical application for which you want to use it?

In general, the amount of additional current capacity adding a heatsink or fan will provide depends on the application and we do not have any specific advice for doing so. The results Phil posted here for the Simple Motor Controller boards seem to have a lot of useful information you might be able to apply to your application, but a different board will likely have different results and we recommend performing your own testing.

By the way, to address some things Phil mentioned, on the Simple Motor Controller board we do not have current limiting, but we do have options to monitor temperature and respond to over-temperature conditions. Also, we do not recommend connecting multiple motor controllers or drivers parallel except in some very specific circumstances, and we generally specify in a product’s documentation if it is recommended.