Pulse Width Modulated trolling motor controller hack

[DanielG]

When I pull the boat out of the water in about a week from now I'm going to winterize it and make a few repairs/alterations. One thing I'm doing is substituting the standard Minn Kota 5 speed switch with a variable speed controller. I've already ordered the electronics and watched all the youtube vids on it. It's a 60 amp unit, the motor pulls under 40 amps. Anyone retrofitted one of these before? I've included a picture but there are many others that may look different.

 

BTW: My boat is a homemade fishing platform made out of a sailing catamaran with two trolling motors for propulsion. So, I'm not taking apart and modifying  a bow mounted unit like many have. The whole thing is a type of Jules Verne retrofitted personal hack. I'm modifying it all the time. It's a labor of love always in progress.

[schplurg]

This is the type that you simply connect between the motor and the battery and it "just works" I believe.

 

Stick it in a waterproof project box maybe. Perhaps replace the knob and switches, maybe not. Lots of ways to mount it. These are less than $20 on Amazon. I'd do it too in a heartbeat. Was gonna use one on my kayak but I'm selling the yak now. May use it on a new boat though

[DanielG]

On 9/16/2019 at 11:38 PM, schplurg said:

This is the type that you simply connect between the motor and the battery and it "just works" I believe.

 

Stick it in a waterproof project box maybe. Perhaps replace the knob and switches, maybe not. Lots of ways to mount it. These are less than $20 on Amazon. I'd do it too in a heartbeat. Was gonna use one on my kayak but I'm selling the yak now. May use it on a new boat though

Yes, that describes it exactly. This unit handles 60 amps and my motor draws max about 40. I have a second motor that I use only on full so it's a battery switch that turns it on. Yes, two electric motors gets me around the lake. 

 

I'm putting a dpdt switch in the mix to add reverse. You can get these units with a reverse switch built in but I couldn't find one that had as good ratings as this one.

I'm going to place it in a lexan box with a small dc computer fan to keep it cool and mount it inside the console with just the control knob showing.

Right now I've got a remote console mounted 5 speed switch like the ones you find in the handle. But it's been acting up lately after a few years. So, instead of changing it out I'll give this a try for a change. Fingers crossed.

[Way2slow]

It's a beefed up version of the old Maximizer you could buy before the PWM motors became popular, it's just they are only rated for about 30 amps, so motor sizes out grew them and Minn kota never made a larger one.

As for being worth it, if you can keep it dry and from getting short out, should work great.  When just easing around with the TM they can quadruple run time on a TM, but the higher you go, the less effective they are.  At max thrust, they make no difference in run time.  https://www.ebay.com/p/Minn-Kota-Maximizer-Electronic-Power-Control/1224647897?iid=113799998987&chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=113799998987&targetid=541453988052&device=c&mktype=pla&googleloc=9011203&poi=&campaignid=6470549460&mkgroupid=81274343007&rlsatarget=pla-541453988052&abcId=1139336&merchantid=113780940&gclid=EAIaIQobChMIxuq4xtTa5AIVEdbACh13ugBLEAQYASABEgJjAfD_BwE

There is a potential problem I see with the one shown.  They are using individual heat sinks on the FETs so inclosing it to make it water proof will most likely make it overheat.  If the FETs were on a solid heatsink, it could be enclosed into a small package.

Have you looked at this one.  https://www.ebay.com/itm/10-55V-60A-5000W-Reversible-DC-Motor-Speed-Controller-PWM-Control-Soft-Start-US/202576542955?hash=item2f2a80bceb:g:HrkAAOSwydZcTBLF

[schplurg]

@Waytooslow

 

That looks good. Saves the trouble of making a box. If mounted properly and tucked away it probably doesn't need to be waterproof.

[DanielG]

On 9/18/2019 at 11:08 AM, Way2slow said:

There is a potential problem I see with the one shown.  They are using individual heat sinks on the FETs so inclosing it to make it water proof will most likely make it overheat.  If the FETs were on a solid heatsink, it could be enclosed into a small package.

Have you looked at this one.  https://www.ebay.com/itm/10-55V-60A-5000W-Reversible-DC-Motor-Speed-Controller-PWM-Control-Soft-Start-US/202576542955?hash=item2f2a80bceb:g:HrkAAOSwydZcTBLF

I agree. I've ordered a 12 volt computer cooling fan that I'm going to wire in parallel with the rheostat. I'm mounting it in a plastic electrical box and the air from fan will run from one side of the box to a vent out the other side over the circuit board.

 

I see multiple types that are of the ebay one in your link on Amazon. I chose this one because of the more favorable reviews of it compared to the type of the one in the link you sent. It may mean nothing but we'll see. I would have put a fan on any unit I chose.

 

I did get the unit the other day and hooked it up with a battery charger in the shop. The thing works so I guess it's a go to put on when I take the boat out of the water this weekend. We'll see. Thanks for the reply.

[bkvanbek]

I hooked one of these to a new Newport Vessels trolling motor, 48 amp max draw, protected by a 50 amp breaker. It 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 does not work.

 

The description of the PWM is DC10-55V 12V 24V 36V 60A Reversible PWM Motor Speed Controller Switch

 

What went wrong?

[Jimbojackson]

Anyone reccomend a hack to build var.speed for trolling motor?

[DanielG]

I used the one I originally posted (I'm the OP here) for the season last summer. It worked really good. I have two motors and one is connected directly. The only thing I notice is that with the controller I lose about 10% of the speed but it doesn't drain the battery faster. In fact it seems to me that the battery lasts longer with the controller. It's mounted under a console with a shield over the top of it. But it is protected from water so it hasn't been an issue at all.

 

I have found out one thing. This unit is a PWM (Pulse width modulator) There are some sold as DC controllers but the are resistance based and heat up. This one doesn't get that hot. The resistance ones use up some battery too. The resistance units usually are the ones that look like the're in the silver metal cases with all the air holes punched into them.

[BKeith]

At slower speeds, the battery should last a lot longer with the PWM.

Someone mentioned using a rheostat.  That does nothing to increase run time, it will actually reduce run time.  A rheostat is nothing but a variable resistor and they work by restricting the current and that restricted current is dissipated in heat, and heat is wasted energy. 

 

 

[DanielG]

Ah.. another thing I've noticed  using this unit is that it interferes, static, with my garmin unit. And it's not because I've got it connected to the same battery as the motor. sometimes I turn off the unit and run my other motor with the same battery, which is connected directly, no interference. If I put tin foil around the PWM the interference disappears. The interference appears a regular spikes from the bottom up on the screen. Looks like weeds but with regularity. The fish also seem to disappear from the screen a lot too.

 

Another note is that this unit doesn't heat up much, so the comment I made very early on about possibly using a small computer fan over it wasn't necessary. I check it sometimes after it's run wide open and can put my hand directly on the heat sinks and feel them just warm. Nothing more. I guess it's because it's not a resistance unit???

[wasabi_VA]

Got a link to the one you bought?

 

I have a foot controlled 5-speed motorguide. Would I hook this one up between the factory switch and the trolling motor, and leave the factory switch set to high? This way the PWM only sends whatever current I set it to? I might try this as on my small boat my setting 1 can sometimes be too slow but setting 2 just too much.

[BKeith]

That has always been an issue with TMs, especially with PWM ones.  That's why you should never connect the sonar/depth finder to the TM battery.  There are tons of tricks out there to help reduce/prevent it.  One of the easiest is to just get you a small 12v battery to run the sonar.  Back when there were Radio Shacks, you could go in there and get a suppressor made to keep alternator noise  out of your car radio.  Some of the car stereo places might sell those.  It's nothing but a small coil/transformer of a specific value and sometimes a capacitor across them.   Another is to use a toroidal ferrite core and make several wraps of the sonars power cable through it, but that's kind of hit and miss because it should be of a specific value.  You will see a lot of electronic devices that use that method.  That big knot you see on the end of some USB cable and small power cables, that's all it is. 

Also, if it's not shielded they can radiate an EMF that cause the problem.  That can also be picked up by the power cables, they work like an antenna.  Using a braided shielded can help

[Bankc]

1 hour ago, wasabi_VA said:

Got a link to the one you bought?

 

I have a foot controlled 5-speed motorguide. Would I hook this one up between the factory switch and the trolling motor, and leave the factory switch set to high? This way the PWM only sends whatever current I set it to? I might try this as on my small boat my setting 1 can sometimes be too slow but setting 2 just too much.

It would probably be best to remove the factory switch all together.  If you accidently knock it down, it could starve the unit and cause issues.  

 

4 hours ago, DanielG said:

Ah.. another thing I've noticed  using this unit is that it interferes, static, with my garmin unit. And it's not because I've got it connected to the same battery as the motor. sometimes I turn off the unit and run my other motor with the same battery, which is connected directly, no interference. If I put tin foil around the PWM the interference disappears. The interference appears a regular spikes from the bottom up on the screen. Looks like weeds but with regularity. The fish also seem to disappear from the screen a lot too.

 

Another note is that this unit doesn't heat up much, so the comment I made very early on about possibly using a small computer fan over it wasn't necessary. I check it sometimes after it's run wide open and can put my hand directly on the heat sinks and feel them just warm. Nothing more. I guess it's because it's not a resistance unit???

The tin foil was a good move.  If you can ground it, it'll work even better, acting as a faraday cage.  Or move it into a metal housing and ground the housing.  

 

Basically the PWM is generating a rapid pulse of electricity to control the motor.  That is generating magnetic waves, which are exerting an influence on your transducer, which also runs on electromagnetic waves.  So it's kind of like having a loud stereo on in the room while you're trying to talk to someone on the telephone.  A bit a bleed over is gonna occur, unless you can isolate it.

 

PWM units can still generate a lot of heat, and they tend to be much more sensitive to overheating than resistive units.  That's a large reason why they're more prone to failures.  Yours is probably not getting too hot because it's only running at 40 amps, and the unit was designed for 60.  So that too was probably a good move.  

 

The reason why you loose some top end speed is because at full power, you're wasting some electricity on the PWM controller, even though you don't need it.  You could install a bypass switch to go around it when you want to hit top speed, but if it's not bothering you, then I wouldn't mess with it.  

[DanielG]

1 hour ago, Bankc said:

It would probably be best to remove the factory switch all together.  If you accidently knock it down, it could starve the unit and cause issues.  

 

The tin foil was a good move.  If you can ground it, it'll work even better, acting as a faraday cage.  Or move it into a metal housing and ground the housing.  

 

Basically the PWM is generating a rapid pulse of electricity to control the motor.  That is generating magnetic waves, which are exerting an influence on your transducer, which also runs on electromagnetic waves.  So it's kind of like having a loud stereo on in the room while you're trying to talk to someone on the telephone.  A bit a bleed over is gonna occur, unless you can isolate it.

 

PWM units can still generate a lot of heat, and they tend to be much more sensitive to overheating than resistive units.  That's a large reason why they're more prone to failures.  Yours is probably not getting too hot because it's only running at 40 amps, and the unit was designed for 60.  So that too was probably a good move.  

 

The reason why you loose some top end speed is because at full power, you're wasting some electricity on the PWM controller, even though you don't need it.  You could install a bypass switch to go around it when you want to hit top speed, but if it's not bothering you, then I wouldn't mess with it.  

Hey, great info. Yes. Two batteries, two motors. I can be three miles away and I can be sure of at least one battery and one motor working right? I actually have a converted sailboat catamaran that I fish with with a deck and bimini top. i live on a lake so it's docked all summer and I take off trolling. The full power thing doesn't really matter as one motor is for trucking faster and the PWM is to get trolling speed, moving around while stationary, and reverse. With trolling motors if you run two of them full speed you really don't gain that much as their designed for a certain top speed.. Not really meant as a get from here to there type of motor.

[Jimbojackson]

Still looking for link to purchase.

[DanielG]

10 hours ago, Jimbojackson said:

Still looking for link to purchase.

https://www.amazon.com/gp/product/B07B4B2X35/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1