Chinese speed controllers (PWM's) - anyone try them ?

[callhow]

Has anybody tried these Chinese speed controllers for use on trolling motors ?

I'm guessing the amps are critical along with voltage (DC current - 12/24/36 volts) ?
However, I'm wondering/guessing as to what amount of amperage (resistance/load) you would
get from a prop in the water -trying to build up speed!

Any ideas-suggestions-theories ?

 

[kofkorn]

I've successfully done it on two of my TM's.



There was an earlier thread on this:
https://www.tinboats.net/forum/viewtopic.php?f=5&t=26975#p277657

The issues that I ran into were:

- Make sure that you have the polarity right EVERY TIME. The cheap Chinese controllers don't have any reverse polarity protection and it only takes a second or two to fry the controller.

- You will need to waterproof the controller yourself somehow.

The draw you will need depends on your thrust. For my 28lb thrust motor, I needed a 30A controller. You'll have to do a little research to determine the max draw for your motor. Figure at full speed, it is going to draw the full current. There isn't enough movement in your boat to allow the TM to get close to a free-spinning speed.

I loved my controllers. They were able to give me 100% control over the speed of the propeller from spinning at about 1 revolution every 5 seconds to full speed, and they were really quiet. It was perfect for creeping along the shoreline, the way I prefer fishing.

I've since gone to the Minn Kota Powerdrive with I-Pilot. I love the direction control, but I miss the fine speed adjustment at low speed that I had with the homemade controller.

Good luck!

 

[callhow]

Thanks kofkorn, For the price...they "appear" to be too good to be true. I figured the amp's drawn would
be substantial...especially if starting from a dead stop...and trying to move the weight of
boat/passengers/gear through water!

Having a flat bottom vs v-bottom helps eliminate the drag....of course steering is squirrely.
And reviewing prices the higher the amp's - the price rises quickly. By the time you find one
with30+ and reverse (ideal) you're close to U.S. priced methods.

Older TM's used "rheostats" then graduated to potentiometers (which I'm guessing) which
seem to be the generation just before the newer PWM's ? (from what I've gleaned/learned)
they have a momentary "pulse" when increasing vs the constant drawing during increase.

Again, thank you for your insight & experience. - callhow in York,PA (s. central PA)

 

[user 13737]

to figure amp draw measure the resistance of your trolling motor at the various speed settings. i = 12.4/resistance in ohms
Max turn on current will be 1.25 or 1.5 times the baseline amperage - this might help you decide on 30A or larger.

You can use the same info to calculate estimated runtime of a trolling motor compared to the battery capacity

 

[callhow]

Thanks matzilla, Do I measure the OHM's in water/water barrel or without any load ? - callhow

 

[kofkorn]

When you measure, the motor should be turned off and power disconnected, or you'll fry your meter.

Just put your motor in the maximum speed setting, and measure the resistance (Ohms) by attaching your meter to the power and ground leads, which you would normally attach to the battery.

 

[Analog Kid]

A potentiometer ( variable resistor )is all that is needed to control the speed of a dc motor. I took apart a transom mount motor guide tm and rotated it for use on my bow and there is no controller just a potentiometer

 

[kofkorn]

Hi Analog,

Just as an FYI, the potentiometer in your motor guide is only controlling a MOSFET circuit in the lower housing. So it is not doing all of the heavy lifting, only controlling a small signal voltage the same way the cheap chinese PWM potentiometer does.

Also, while it is true in theory that you can control the motor with only a potentiometer, it is probably not your best option for regulating a trolling motor.

First of all, potentiometers are as you stated, resistors. They have a wattage rating to them and exceeding that rating will cause them to fail. Now looking at a basic 12V 55lb trolling motor, at max setting you would be drawing ~50A. That gives you a power rating of 600W. I've found a couple of rheosats in the 200W range, but even those are the size of a hockey puck. You can source variable resistors at 600W and above, but they would be impossible to use in a practical sense.

Secondly, by simply using a high power rheostat to control the motor speed, you are simply dumping the extra energy into heat, which is the reason those higher power rheostats are so large. This isn't really much better than the practice of using speed coils to slow the motor down.

With the PWM controller, there is far less power loss, allowing you to conserve your battery. Also because the potentiometer in PWM controller uses hardly any power (less than 1/4 watt) you can remotely locate the potentiometer with very small wires. I attached the potentiometer in the picture above to an old mouse cord and was able to get a simple 10ft cord with a very convenient connector on it.