Critique my wiring diagram?

[Gene Neill]

This is a simplified version of a diagram I "borrowed" from Maine Sail's fabulous marinehowto.com site. I stripped away all the things I didn't need, leaving nothing but the most basic foundation that would serve my immediate needs.


Would any of you wise old salts be kind enough to proofread my work?? I'm in the process of building a battery box as well as a new breaker panel box (the old one was in the companionway, the new one is going somewhere drier and more protected). But I want to make certain I have this diagram right before proceeding. Something tells me I might be at least be missing a fuse or two, or perhaps overlooked a better way to do things.


Many thanks!!

[DanaTucker]

Your diagram looks pretty tight. I went through this about two years ago. I have two house batteries that each have their own main cutoff switch as well as the starting battery. My + and - strips where increased to 12 & 24 lugs to accommodate future tie ins like USB chargers, radios etc. I will post some pics when I figure out how.

[billknny]

I don’t understand the reason for a switch on the alternator line. If it is turned off when the engine is running, the diodes are toast. If you want to disconnect the power for service, just pull the fuse. Save money and complexity.

[s/v Jedi]

The only problem I see is the starter motor circuit. Big problem. You eliminated the starter battery and wired a circuit to the main breaker panel and an emergency switch to the same battery. That whole part is wrong.

To fix it, simple delete the starter circuit to the main breaker panel. From the fusion the battery, to the on/off switch, to the starter motor.

That said, I highly recommend you use a starter battery, setup like in Rod’s diagram. Make a wise choice for that battery, so it can be a backup to the house bank if that fails. I always recommend an Odyssey 2150 battery as starting battery and a Firefly or Lifeline for house battery. They are perfect for their jobs while they are able to take over the other battery’s job in case that fails

[s/v Jedi]

Originally Posted by billknny

I don’t understand the reason for a switch on the alternator line. If it is turned off when the engine is running, the diodes are toast. If you want to disconnect the power for service, just pull the fuse. Save money and complexity.

Oh I missed that.. Yes, eliminate that switch

[Red Sky]

I don’t get the on/off switch before the starter, it’s not the starter switch??? Wouldn’t there be a fuse and on/off switch from the house bank, after the bilge pump connection but before the + strip?

[DanaTucker]

Originally Posted by billknny

I don’t understand the reason for a switch on the alternator line. If it is turned off when the engine is running, the diodes are toast. If you want to disconnect the power for service, just pull the fuse. Save money and complexity.

The purpose for the service switch in most cases, is so you can simply turn off the circuit to work on or replace the component, in this case the alternator, without having to go to back to the battery and disconnecting it from that point. My motor/house batteries are a pain to get to.

[DanaTucker]

Power lugs upgraded. This panel supports both the shore power, on the left and the 12 volt system on the right.

[Gene Neill]

Just for fun, this is the diagram I borrowed from Maine Sail:

[DanaTucker]

Originally Posted by Gene Neill

Just for fun, this is the diagram I borrowed from Maine Sail:

There ya go. I noticed the other main switches as well as the AC trickle charger. I am a big fan of being able to turn off main circuits using one switch. If I am sailing, the starter and shore power circuits are always switched off.


When I am at the dock and off the boat, I turn three switches and nothing leaves the batteries except for the bilge pump circuits and they have float switches. If I am anchored or mooring, then I only switch on one of the two house batteries. Everyone has their own way of doing things, this just works for me.

[smac999]

why do you only have one battery bank? I would never have a boat with one battery. and that includes a ~10' tender.

if you do go with one bank. you should have a seperate swtich for the engine starter and house panel. 99% of the time the engine switch can be off, but the house switch can still be on. you want to be able to power one and not the other.

since you only have one battery bank, and the alt is only 75 amp. just wire alt to starter post as per factory. no fuse or switch needed. no need to complicate on a simple system. it will lose power to work on the engine, when the engine switch is off. since it's not fed from a seperate house bank.

the fuse for the DC panel should be at the output of switch. not closer to panel. if the switch is beside panel and the panel has a main breaker I wouldn't bother with the fuse.

if the alt is 75a. the alt fuse should be ~100a. not 225a

[Stu Jackson]

Originally Posted by Gene Neill

>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>


. But I want to make certain I have this diagram right before proceeding. Something tells me I might be at least be missing a fuse or two, or perhaps overlooked a better way to do things.
>>>>>>>>>>>>>>
>>>>>>>>>...........

These links have all of Maine Sail's diagrams.


You seem to be confusing things from a simple one bank situation.


OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4....html#msg30101

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowner...d.php?t=137615

This is a newer primer for boat system wiring design with a thorough digram: Building a Good Foundation (October 2016)
http://forums.sailboatowners.com/ind.../#post-1332240

[s/v Jedi]

Originally Posted by Gene Neill

Just for fun, this is the diagram I borrowed from Maine Sail:

Yes now it makes sense. The breaker panel gets it’s feed from the house bank, the starter from the start battery and then there’s the emergency switch.
Voltage sensing relay is called the Blue Sea Systems ACR in real life. It combines the batteries when a charge voltage is detected.

There’s the service switch on the alternator which I suspect Rod has a use for that I don’t have.

[Gene Neill]

Originally Posted by Red Sky

I don’t get the on/off switch before the starter, it’s not the starter switch??? Wouldn’t there be a fuse and on/off switch from the house bank, after the bilge pump connection but before the + strip?

The diagram is not 100% complete in that regard. The hot line does not go directly to the starter itself, it goes to the engine control panel and through the ignition switch. Sorry, I should have mentioned that.


Perhaps I should change out the image of the starter for this one:

[Gene Neill]

Originally Posted by s/v Jedi

There’s the service switch on the alternator which I suspect Rod has a use for that I don’t have.

I'm paraphrasing here, but RC says he likes to be able to isolate the alternator so it can be worked on without any power going to it. My boat had a switch like this on it from the factory, so I assumed it was common. The switch is located inside the engine compartment so it's unlikely to be used accidentally while the engine is running.


The engine (which is my first diesel ever) is a brand new Beta 14. I installed it last year to replace the old Volvo MD7a.