New project w/ wiring questions

[Team Liquid]

I've read several electrical posts but still confused. I have no wiring experience so please be patient with my very basic understanding.

I purchased a 2004 Weldcraft 1548 which I am building out. The outboard is a 2004 Nissan 18hp pull start and does not have charging capabilities. (as far as I know).

I am setting it up with 2 batteries in the bow for the primary trolling motor and FF and a third battery in the stern for a second TM and fuse box with aux connections. My electrical questions are as follows:

I purchased a 3 position battery switch and circuit breaker for the forward two batteries. I understand how the battery switch is wired with the POS wires but I am confused as to wear the ground NEG wires from each battery route and/or terminate.
Where do I connect the circuit breaker?
Also, after the POS wire leaves the battery switch to the trolling motor plug forward, where does the ground wire from the trolling motor plug connect?

Any other input for my wiring?
Thanks in advance for the help.

 

[Sawdust Farmer]

12V or 24V trolling motor up front? -It makes a big difference in the proper answer.

sf

 

[Team Liquid]

The trolling motor up front is 12V and each battery will be used independently @ 12V each.

 

[RivRunR]

Before we can really answer, we'd need to know what you're trying to accomplish by having the 2 batteries up front on a switch, but I'm going to guess that you want to be able to switch batteries on your TM if one runs down.

If that's the case (and because I've never wired up a battery switch )....for the bow I'd eliminate the switch from the equation and just run the batteries in parallel (+ to + / - to -), assuming that they are of the same size and age.

This will give you the same time on the water without the extra switch, wiring, etc. The downside will be that your FF will be on the same battery as your TM which may cause noise when it's running. And this set-up makes if difficult if you have to remove the batteries for charging - if you can get a 2-bank on-board charger you won't regret it.

So, for the bow TM your setup would be battery->breaker->TM. Circuit breaker within 7 inches of your battery. Wire gauge and breaker size are dependent on the length of run and amp-draw of your TM, but typically a 50A breaker with a minimum of 8AWG (6AWG is better) is installed. Ground for the TM should be the same gauge AWG as the positive, and can connect either directly to the battery with a ring terminal, or to a negative buss bar which is in turn is connected to the battery. If the only other connection up front is the FF, I'd run that on an in-line fuse directly to the battery.

The stern TM should be set up exactly like the bow, and on a separate circuit from your fused accessories, so again that would be battery->breaker->TM.

Your other circuit in back would be set up as battery->breaker->fuse panel->switch->accessory(lights, bilge, etc). I'd use 6 or 8 AWG between the battery and the breaker, and breaker size should be based on the total amp draw running thru the fuse panel (usually 20A or 30A). Wire size is typically 14 or 16 AWG for the runs to the accessories, but (again) those are dependent on amp draw and total length of run (in both directions). There's charts all over the place for figuring out AWG sizes. I highly recommend using marine-grade tinned AWG wire.

Hope this helps!
RR

 

[Bob Landry]

I agree with RivRunR. There is no advantage to using a switch to connect the forward batteries. If one should fail, it's easy enough to disconnect one of them. Wire them in parallel and use the hot from one battery and the ground from the other to equalize current flow through the batteries. The grounds from all three batteries and also anything that is connected should be run to a common ground buss. If you want a two output, onboard charger, that will handle both battery banks
As far as cable size, the installation doc for my MotorGuide TM specifies that any wire used other than the wire provided with the TM should be 6ga. They make this statement without reference to the length of the run. This is a good wiring practice as all TMs are going to be high current users and no one ever created a problem by using wire that was to big. This would also be good advice for wiring MinnKota motors. Use 6ga wire to connect the batteries as this wire will also have to handle the current load for the TMs. I always recommend marine wire as it is pre-tinned. You probably are not going to solder, but the marine wire resists corrosion and will pay for itself in time not having to be spent tracking down and fixing bad connections over time. Aleo, use AWG wire, not SAE, as AWG is larger and will handle more current with less voltage drop