Trolling motor expertise

[Fish'n John]

Originally Posted by Mee-n-Mac

In any case we're just a little bit away from knowing what to do with the charger and now I want to understand what happened when you disconnected the charger and wired up the TM to the batts for 24V operation. That looks to have be correctly done. The TM worked (and I assume well) until the plug melted. So that seems like a bad plug or very lossy connections at the plug. Plugs have current ratings, do you know what this one was rated for ? In any case it's time for a new plug and socket. Get ones rated for the proper current (60A) and when the charger issues are settled, I think you'll be good to go.

Yes, The trolling motor ran well when I direct wired it at 24V. When the plug melted, I got nervous and backed off. I fixed the plug with spares I had from the original installation but I rewired everything through the charger and yelled for help. Now I see that the charger is a problem.

Just this morning I was looking through my West Marine catalog and I noticed that these connectors have ratings of 12v or 24v and designated wire sizes of #8 or #10. At this point I have to assume that I had 12v connectors and #10 wire size. Connections may also have been a little dirty. I just ordered two new TM connectors from West Marine at 24v and #8wire. Anyway, I will switch out these connectors when they arrive and I think I should be good to go. I should be able to wire the TM direct with the existing #8 wires and 60A fuses. I will also pull the battery charger and have a look inside and see if it is salvageable. If not, I should be able to replace it with a new and more conventional unit.

I really appreciate your help in all this. I'll let you know how I make out.

[Fish'n John]

Here are a few more pages of the manuals just for grins.

You asked about the indicator lights. That is shown on (7). The charger actually sequences the charging of the batteries so that the main is recharged first, then the auxillaries. The sequence is shown in the light patterns. I don't know what the sense wire is for...

[Fish'n John]

I have removed and inspected the battery charger. There are no internal fuses that I recognize and no places where the original wiring seems to have been altered. The only abnormality that I notice is some apparent heat damage to the wire that leads in from Aux battery #2. The black negative wire appears to have been overheated at the spot where it is connected to a one of three 1" x 1" x 1" components. They are black with a white top with a number (951221B) inscribed on the side. There is a second heavy black wire leading from this component to a black device that also appears to be heat damaged. This device has an enscription "Short Stop", and below that "12v A46 4OR". None of this means anything to me, and since the company is out of business, I assume I need a new charger.

I have rewired the batteries direct to the trolling motor using #8 wire and 60a fuses as much as I can. I am waiting for the 24v #8 connector for the TM before I can try this system out with direct wiring...

[Mee-n-Mac]

Originally Posted by Fish'n John

I have removed and inspected the battery charger. There are no internal fuses that I recognize and no places where the original wiring seems to have been altered. The only abnormality that I notice is some apparent heat damage to the wire that leads in from Aux battery #2. The black negative wire appears to have been overheated at the spot where it is connected to a one of three 1" x 1" x 1" components. They are black with a white top with a number (951221B) inscribed on the side. There is a second heavy black wire leading from this component to a black device that also appears to be heat damaged. This device has an enscription "Short Stop", and below that "12v A46 4OR". None of this means anything to me, and since the company is out of business, I assume I need a new charger.

I have rewired the batteries direct to the trolling motor using #8 wire and 60a fuses as much as I can. I am waiting for the 24v #8 connector for the TM before I can try this system out with direct wiring...

Hmmm, I'll offer up this sage guess ... it's dead.


It might be repairable but w/o any schematics or even a parts list that'll probably cost more than a newer, betterer charger. I might hazard a SWAG that the "short stop" device is some sort of fuse or circuit breaker made for 12v and 46A. Or perhaps it's the switch to go from 12V to 24V configuration ? In any case the negative lead for the Aux2 battery would carry the full current when in 24V mode which, according to your TM manual, might be as much as 48A (0.75A/lb x 64 lbs). Maybe the "new" TM was more than the "old" charger could handle ? If you care to post a pic of the charred devices I'll have a look but I'll guess parts are now obsolete.

As for your 24V connector ... I looked briefly at the connectors/plugs in the WM catalog. I couldn't imagine why there would be 12V and 24V connectors, there's just not enough difference in voltage to make a difference in design. What I did see were 2 wires (+ and -) for the 12V sets and 3 wires (+24V, +12V and -) for the 24V ones. If you got one of these you'll end up using only 2 of the wires/contacts. If at all possible I would recommend getting a plug/socket set with 4 contacts (I didn't see one but I didn't look all that hard) and using 2 of the contacts (in parallel) for the +24V and the other 2 (in parallel) for the -. Indeed if you wanted to double up the AWG8 wires (for the longest run) that would be prefered as well. Somewhere I read than ideally the voltage drop in the wiring and connectors from the batts to the TM head should be <1v. I think the online calculator I previously listed estimates you'll have something more (1.3v) for a single AWG8 to and from batts carrying 50A and at what I guessed to be 20 away (40' round trip). I didn't see any current ratings on any of the plugs/sockets, which surprised me a bit.

[NoBozo]

Originally Posted by Mee-n-Mac

I couldn't imagine why there would be 12V and 24V connectors, there's just not enough difference in voltage to make a difference in design. current ratings on any of the plugs/sockets, which surprised me a bit.

I seem to remember a simple electrical principle from my studies some 40 years ago. This principle still works today as far as I know. If you raise the voltage in a supply line (Picture the overhead lines you see supplying power to the GRID).....you can REDUCE the amperage....which allows you to REDUCE the WIRE SIZE..therefore lighter weight...and still have the same power at the end of the line. Correct me if I'm wrong.......

This seems to me to be the case with this Trolling Motor. Having lighter wire seems to be a good thing...NO..?? NB

[Mee-n-Mac]

Originally Posted by NoBozo

I seem to remember a simple electrical principle from my studies some 40 years ago. This principle still works today as far as I know. If you raise the voltage in a supply line (Picture the overhead lines you see supplying power to the GRID).....you can REDUCE the amperage....which allows you to REDUCE the WIRE SIZE..therefore lighter weight...and still have the same power at the end of the line. Correct me if I'm wrong.......

This seems to me to be the case with this Trolling Motor. Having lighter wire seems to be a good thing...NO..?? NB

You are correct vis-a-vis supplying power like over the electric grid. IF the power is constant, a higher voltage reduces the current supplied. Of course there's some limits on how high the voltage can go ... but you remember correctly. In the case of trolling motors what's happened is that over time more powerful motors were wanted (boats got bigger and heavier I guess). This lead to very high currents and large wires at the old 12V standard. At some point they couldn't make a more powerful 12V motor and so 24V and 36V systems were designed.

In this case the TM manual says to expect a current = to 0.75 times the thrust. At 64 lbs this gets the OP about 48A current draw. With the wires he has this should be safe but he'll "lose" something like 1.3+ V in the wiring so IF he had exactly 24V at the battery terminals, he'd have 22.7V at the TM itself. I think the manual wanted the voltage loss to be 1V or less. The way to do this is with thicker (AWG) wires or more wires (of the same size). Doubling up on his AWG8 wiring would give the equivalent of using AWG5 wiring. That's a bit better then the AWG6 recommended at the fishing sites I looked at. It's more $$ but you get slightly better motor performance and more reliability. Then again how often will F'n'J be running his TM at full power ?

[Lakepilot]

The current only goes down if the load is a constant power. The national grid delivers a fixed number of watts, so if they use higher voltages in the transmission lines the current goes down. But most loads consumers are familiar with are not constant power. With a resistive load as you increase the voltage the current goes up. Switching power supply loads (like in a computer) are more or less constant power so if you increase the voltage the input current goes dow.

[SIKSUKR]

In the case of AC,20 amps @ 120 volts equals 10 amps @ 240 volts.

[Fish'n John]

Last night I completed the wiring of the trolling motor direct from the batteries using the new 24v #8 connector in the bow panel. Rain kept me from trying it last night, but I was out early this morning and the Trolling motor is performing beautifully with no evidence of overheating in any wires or connectors. Even the Minn Kota on-board battery charge indicator and the Auto-pilot performed flawlessly. I have plenty of power to spare for even windy days. I am deliriously happy!

I will search for a more conventional on-board battery charger at my leisure, having relegated the failed Dual Phase II to the junk heap. Unanswered is how Expo North could have wired the unit as it was for 24v operation and how it could have worked at any level for as long as it did.

I am very grateful for the suggestions I received from all on The Forum, but especially to Mee-N-Mac for his hard work, inciteful analysis and probing questions. I could not have fixed the problem without your help.