Pulse Width Modulation (PWM) motor controller issues

I hooked one of these to a new Newport Vessels trolling motor, 48 amp max draw, protected by a 50 amp breaker. The PWM quit working and started smoking. It also took out the battery meter on the trolling motor, but otherwise the trolling motor still works and still gets power through the devise, but the variable speed PWM does not work.

The description of the PWM is DC10-55V 12V 24V 36V 60A Reversible PWM Motor Speed Controller Switch, it looks identical to most of those that are for sale. In fact I bought two from different sources and they are the same, with the same description.

What went wrong?

I am not familiar with those trolling motors at all, I am guessin but did you disable the speed switch on the trolling motor and hook directly to the motor leads? As it seems they only have one switch as it is not a true variable speed trolling motor. Just takin a wild stab.

I did not disconnect the factory switch in the top of the trolling motor. Is that necessary? I would rather use the factory on/off, forward/reverse switch, than the switch that came with the PWM.

When I used one a long time ago, I just placed the trolling motor control in high (this should be straight through with no resistance added), and used the PWM to adjust motor speed. You shouldn't have to remove the factory switch, unless it is already a digital motor, it should just be a variable resistor, with highest speed being no resistance, just on/off. It will work fine in the lower speeds as well, but the double speed reduction is redundant.

You may have had the leads reversed, that would be a dead short across the PWM controller.

I double checked the connection, they had the connection listed on the back of the circuit board. Also I ended up with two identical PWMs to compare. I had it wired correctly and it worked for a while. I don't want to hook up the other one until I have it figured out.

I've been using a similar PWM with a Newport 12V 45 lb TM for about 2 years now, with no issues. I put it in a small WP box from Walmart. I omitted the display, but used the switch and control pot. I did bypass the controls in the TM and wired directly to the motor leads.

If you smoked the PWM, you had to have something miswired; likely the input power, because the PWM would work fine with reversed motor leads, just in reversed direction. The input power from the battery cannot be reversed, or connected to the output terminals, without something bad happening (smoke).

A couple folks copied my implementation and theirs also works fine. I built one for a friend and his is still working fine. There is a thread on the GON.com forum search for "speed control".

The module I used looks just like this one. Robot Check I threw out the display and the metal shield. The switch is crappy and has been replaced a few times - it isn't waterproof I guess.

That "Robot Check" one is the same as the two I have. It worked for a while then it fried the battery meter on the trolling motor, blew a capacitor. then the motor still worked through the PWM but there was no variable speed on the PWM. I had it wired correctly. Could it be too much amps? These PWMs say 60amp max, but some say 40amp and my 86lb thrust motor is 48amp......

Hard to say without a crystal ball (I do have a magic 8-ball), but your motor is much bigger than mine, also you didn't bypass the controls and meter, like I did. Without knowing the exact circuit design of the module, it is just a guess, but the small heat sinks and size of the semiconductor device used suggests to me it can't handle that much current. Also because it worked for a little while and then smoked jives with this theory.

PS: The "Robot check" is something the site does to links, not my text or link.

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Originally Posted by bkvanbek

That "Robot Check" one is the same as the two I have. It worked for a while then it fried the battery meter on the trolling motor, blew a capacitor. then the motor still worked through the PWM but there was no variable speed on the PWM. I had it wired correctly. Could it be too much amps? These PWMs say 60amp max, but some say 40amp and my 86lb thrust motor is 48amp......

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It is rated for 60 amps maximum, but only 40 amps continuous. If you run the motor at high speed for any length of time, 48 amps will eventually let the smoke out of the PWM

I found this one with a higher amp rating, they are hard to find. 10-50V 100A 5000W Reversible DC Motor Speed Controller PWM Control Soft Start 761710976961 | eBay

What do you think? Will this work? Can I use the switch on my motor? Why did the meter on the motor blow?

I don't know why the meter blew on your motor. This PWM should be fine, the description rates it at 60 amps continuous and your motor is only 48 amps maximum. The 100 amp maximum draw on this PWM is only for a very short period of time, not 100 amps of continuous use.

There is no way to know why the "meter" stopped working without troubleshooting it, but I think I know why. SWAG: The PWM cannot increase voltage, but it can reverse it. The meter, which is cheap junk and probably not polarity-protected, is normally connected to the battery input leads before they go thru the wafer switch, so it may not (probably won't) handle reversing the input power polarity externally with the PWM. Not sure what you did with the switch; I'm guessing it was either set (or defaults with no switch) to reverse, and the reversed DC input killed it.

This is why I disconnected the meter on mine, along with all the control/speed coil wires, and wired directly to the main wires going down directly to the motor. Not sure why you don't do this if you are going to use a PWM.

Meter got spicked