Full size electric boat controller questions

[lincpimp]

Ok, so I picked up a boat!!! It is one of those small, plastic, 2 person pedal boats, but it does have a trolling style motor on it.

Only issue was the motor was shot, water got in and rusted the internals. Luckily I had a freind with a damaged bass boat trolling motor and he gave it to me. Between the two motors I got a working example.

Problem is the new franken-motor is more powerful than the original and the internal wiring in the boat is not really good enough to run it.

What I am looking for is an alternative.

Dc motor, runs on 12v. I use a car battery. The motor has a large resistor mounted in the nose cone that coupled with the existing rotary switch gives 5 forward and 3 reverse speeds. I do not really care about the variable speed, as it cannot be very effecient (think old tamiya mech speed control).

I would like to have forward and reverse.

I am guessing max amp draw will be around 50amps. Might be more, but I did some research on trolling motors and that seemed to be the norm for a trolling motor on a bigger bass boat, and my pedal boat is ALOT lighter, so less load.

I think a simple switch would be the easiest, but I do not know the terminology (sp?) to describe it.

Basically the switch needs to take a pos and neg feed, be able to switch polarity on the output wires, in order to run this brushed dc motor in both directions. This switch would need to handle 10gauge wire, and not melt under a 50amp load.

What do you call a switch that can do this? It would be nice if the switch had a centered position that would not pass any current, thus acting as OFF.

I know I can use a pair of 5 pin relays and a 3 pos toggle switch to do the same thing, but I figured you electric geniuses could point me in a simpler direction.

[lincpimp]

Alright, looks like I need a DPDT switch, and cross wire the outpus to handle just 2 wires. Seems simple enough, now to find a switch rated to handle big amps...

Any other suggestions will be greatly appreciated, I am still on the conceptual stage here.

[lincpimp]

Ok, canned the switch idea as dpdt 50 amps switches are rarer than rocking horse poo.

So how about this: http://www.texasindustrialelectric.com/relays_24452.asp

Sure it is 60 bucks but it looks like it can handle the load.

[PBO]

I'm looking at an electric boat also...a retired electrical engineer near me is selling up & has a custom aluminium (tinnie) dory shaped version on a trailer. Just need the hardware & some batts

To be honest I hadn't thought further than buying everything from Golden Motor & adapting it to work...well making a cooling jacket for the motor that is

[hemiblas]

What about one of those automotive relays? They are pretty cheap and you can get them in 60A or 80A versions?

[What's_nitro?]

That module should work fine. It looks like two 50A SPDT auto relays potted in epoxy. You could do it cheaper if you wanted to build it yourself.

I am curious; why no variable speed?

[lincpimp]

Originally Posted by hemiblas

What about one of those automotive relays? They are pretty cheap and you can get them in 60A or 80A versions?

Not sure how to wire them, but I have an idea.

Originally Posted by What's_nitro?

That module should work fine. It looks like two 50A SPDT auto relays potted in epoxy. You could do it cheaper if you wanted to build it yourself.

I am curious; why no variable speed?

I have been using it with the variable speeds and it does not really do anything for me. It is pretty slow on max speed, any slower and I may as well just swim!!!

Plus due to the rudder loaction the boat does not handle well at slow speeds with the motor powering it. It will turn very tight with the pedal powered prop, so that is how I get it up to my dock.

I do have all of the electronics that came with the broken trolling setup, which includes a variable speed setup and on/off switch. I may just take that apart and adapt it. Not sure how easy that will be...

I guess I can look into a pair of stdp relays, I liked the potted sealed one I linked to, and found it for about 50 bucks shipped.

[sikeston34m]

How about a Castle MMM ESC and a servo tester pot?

Reversible variable speed plus a neutral position.

Just be sure to put it in brushed mode.

btw.........my 55 pound thrust trolling motor in my 18 foot deep V boat pulls 50 amps at full speed.

[lincpimp]

Originally Posted by sikeston34m

How about a Castle MMM ESC and a servo tester pot?

Reversible variable speed plus a neutral position.

Just be sure to put it in brushed mode.

btw.........my 55 pound thrust trolling motor in my 18 foot deep V boat pulls 50 amps at full speed.

Interesting idea Sike.

Any chance for a link to a servo tester, I vaguely remember seeing one of those a while back.

[_paralyzed_]

servo tester: http://www.hobbyking.com/hobbyking/s...idProduct=8296

[sikeston34m]

Originally Posted by lincpimp

Interesting idea Sike.

Any chance for a link to a servo tester, I vaguely remember seeing one of those a while back.

Yes, what he said on the link, Linc. LOL

I kinda like the idea because you have the built in LVC if you want to get interesting and use some of those Lipo Packs you have laying around.

A trolling motor cools itself pretty well. I wonder if you could bump it up to 4S voltage and travel faster than you can swim?

How many pound thrust motor are you working with?

One thing about trolling motors, much is lost in the crappy factory wiring. The more voltage drop you have, the less total watts of power the motor puts out.

Think overkill. Even 10ga. silicone wire gets warm after 10 or 15 minutes at 50 amps. Maybe rewire everything with 8Ga.?

My 55lb thrust motor is putting out about 650 watts now.

PS.....have you seen my trolling motor thread lately?

http://www.rc-monster.com/forum/show...187#post406187

[bruce750i]

Maybe a contractor for a Atv winch and the handle bar rocker control switch?

[lincpimp]

Not sur eif that contacotr will run continous.

Looking at costs, I will try to break down the original trolling motor controller and see if I can remake it in a useable form for this box.

I gave the boat a try again, and it did well. Top speed is pretty good, but I only got a few mins before it started to overheat. I plan to step up the wire sizes all the way to the motor, and try to keep everything as short as possible. Will likely go to 2 batterys, in parallel to help keep the voltage drop to a min.

[BrianG]

An ESC in brushed mode using a servo tester would be the easiest and give you variable speed.

But, if you want to use common automotive relays:



Some notes:

- Make sure the relays can handle the current you are running.

- The SPST switches are low current (less than 1A) so pretty much anything will work

- The reversed diode is meant to shunt the inductive kickback from the coils to prevent damage to the power source. But if it's a battery, it's not needed. If you do use it, any 1A+ diode with a PIV of 50v or more will work.

- The thicker lines are the high current paths. The thin lines are the low current paths and will be passing less than 1A.

- The green and blue wires don't have to be those colors. They are colored different just to show that they are different wires and do not connect together.

The top relay is your system on/off relay. This could be replaced with a SPST switch capable of whatever current you are running, but switches that large tend to be expensive and/or not meant for continuous duty.

The other two are the reversing relays. I set up the wiring so that when the reversing relays are not powered, the motor runs forward. I figure you'll be running forward 99% of the time, so no need for the coils to suck power (albeit really little) for nothing.

I suggest getting the matching sockets for the relays. That way, if a relay blows, simply plug another in and you don't have to re-do the wiring. You just have to find a socket that is rated for the current levels you'll be running; if you can't, you'll just have to wire up replacements manually.

EDIT: Oh, and if are sharp enough to notice that the coil terminals (#85 and #86) have the polarity switched around on the reversing relays: that's not a problem. The coils in these relays are not polarized so you can hook + and - to whichever terminals you want and it will work fine. Doing it this way in the diagram simply made for a cleaner looking schematic...

[lincpimp]

Thanks Brian, that was basically what I was thinking to do with the relays.

Looking at 50amp cont duty relays seems like this bosch would be the best bet:

http://www.texasindustrialelectric.c...0332209138.asp

Any other relay suggestions? I have all of the wire needed to do this,and would probably direct solder the main wires as I have never had much luck with crimp connectors handling any sort of load. I guess I could solder some good bullets to the relay!!!