24 volt -- wiring question

[CaptainMusky]

So, my boat came wired to allow for a 24 volt trolling motor front and rear. How it is implemented may be a bit different than some and I was curious if I may run into issues down the line with the current configuration.

Basically I run 2 12 volt batteries, but each has its own positive and negative that go to the power recepticals. The Marinco (brand name) plug then takes the two together to provide the 24 volts for the trolling motor. The plug could be used for either 12 or 24 volts you just attach the wires differently inside.

Not seeing other boat's wiring configuration, I have a feeling this may be different than others where they are actually sending 24 volts through one set of positive and negative wires to a receptical.

If I check voltage in my receptical I get two sets of 12.5 volts.

I am wondering if the better idea would be to have the two connected together to act as one 24 volt and sent that power to the receptical.

Ideas? What issues, if any could I have with my current situation?

I was told that since the two are separate if I had a weak battery that the "strong" one could play games with the other one. I dont see how that could happen since they are not at all connected to each other.

Thoughts?

[timjones]

My Alumacraft Tournament Pro is wired that way. When the Minn-Kota trolling motor is plugged into the receptacle the wiring in the plug makes the series connections to supply 24 volts to the trolling motor. Been that way for 10 years now and have never had any sort of problem. I think it was done that way so you can use either a 12v or 24v trolling motor without having to change any wiring in the boat. The only real difference between this way and just running the two wires is that in the two wire system the + from one battery is connected to the - of the second battery with a short piece of wire instead of running the + from the one battery and the - from the other battery all the way to the receptacle. This may result in some minor line lose but not enough to worry about.

[B-man715]

My Warrior uses the same system. Leave it the way it is. Right now you have 4 heavy wires bringing all that juice up to the plug. If you switch it to a two wire system, you are essentially cutting your wire

gauge in half, which will lead to more resistance and heat.

My boat also has a dual plug in the back so I can jump my trolling motor batteries to my starting battery. It has one big downside. If you have the same setup, make sure to unplug the front trolling motor (if 24v) before jumping. If you don't you will short out the whole system....

[CAMAN]

You're running a very common system in new boats. Leave it the way it is, it works great and is no different than running a jumper to the batteries with two wires.

[CaptainMusky]

Thanks guys! I thought it was fine the way it was, but admittedly I know little about DC systems and the guys with me last week on our Canada fishing trip had some comments that made me question the way it was setup.

The only issue I have ever had was when I first got the boat, I didnt tighten down firmly the one set of screws inside that plug and it shorted out. Thankfully only the plug was destroyed.

I will leave it as it is because admittedly it has been working fine.

[Savage Brewer]

So for my information, do the plugs have 4 pins or connectors?

and in a 24V environment the plug has one of the + bridged to the - of the other battery to achieve 24Vdc differential?

That is interesting, I have only dealt with older boats where I had to run all the wiring myself.

[CaptainMusky]

Yes, there is a bridge inside the plug that combines the voltage together. They are a 4 prong plug. If you search Marinco 12-24 volt plug you can see what they look like.

My previous boat from 1995 even had this along with my new one. So its been around a while.

[WalleyeWarrior]

I currently have my two batteries set up with the jumper. Should I leave it as is or would there be a benefit to going with this plug and system?

[delcecchi]

The jumper setup saves some voltage drop in the path, but if the wire is the proper size in the plug setup it shouldn't matter.

[Whoaru99]

As delcecchi eludes to with the information about increased voltage drop, the detail is the 12/24 system uses essentially twice as much wire as a straight 24V system (assuming the batteries are located similarly).

With a straight 24V system (assuming your batteries are next to each other) there is roughly a 1ft jumper between the two batteries then the two lengths of wire to the trolling motor receptacle.

With the 12/24V system there are four lengths of wire from the batteries to the trolling motor receptacle. However, instead of the short jumper directly between the two batteries, the jumper is now the added lengths of two of those wires because they're joined at the receptacle in the 24V configuration.

So, with the 12/24V setup, you go from roughly a 1-ft jumper to a jumper that is roughly 2 times the length from the batteries to the trolling motor receptacle. This is where the increased voltage drop comes from.

[Savage Brewer]

I would say if you are like me and have your 24v system already wired up, there is no reason to go change it just because...

Heck, I actually like the short jumper setup better myself, but thats me.

Use it as it is and use the money to buy more beer.

[B-man715]

I rescind my above statement about resistance and heat Whoaru99 is dead on, not sure what I was thinking when I wrote that