Alternator

[Voyager1]

My battery charge died, when looking over my battery wiring I found out my alternator wire going to my batteries is landed on my battery negative post. This is how it has been wired since I bought the boat two years ago. I have two battery bank, both batteries 600 CCA with battery switch 1/2/both. Only do day sailing on Lake Michigan. The previous owner never used shore power. Is this OK or should it be moved to one of the positive battery post.

 

[Voyager1]

Photo for above post, didn’t know how to update post

 

[dlochner]

My battery charge died, when looking over my battery wiring I found out my alternator wire going to my batteries is landed on my battery negative post. This is how it has been wired since I bought the boat two years ago. I have two battery bank, both batteries 600 CCA with battery switch 1/2/both. Only do day sailing on Lake Michigan. The previous owner never used shore power. Is this OK or should it be moved to one of the positive battery post.

Which wire is the wire from the alternator? The white one?

The alternator output should always go to a positive terminal. There are a number of ways to accomplish this, each have pros and cons. Some have more cons than pros.

 

[Voyager1]

In the photo there is a smaller black wire on #1 battery negative post. There is a jumper between batteries, a large wire grounded to engine and the alternator wire. The white wire is coming from battery charger.

 

[jssailem]

Voyager. The battery picture does not look right. You have large positive connections to each of the positive terminals. Only one of the two batteries is connected with a large black wire. This is wrong. The red lead to the battery in the bottom of the image looks damaged. Not good. The white wire is said to be from the dead charger.
I would not go out in that boat until a qualified marine electrician stated it is safe.

 

[DayDreamer41]

That is definitely some funky wiring there, ohm meter or test light, disconnect all wires, trace and draw a diagram of where they are going to and where they are from, something just doesn't look right there.

 

[Voyager1]

I have an old battery charger, the smaller red 2 wires come from battery charger. The white wire come from battery charger also. Large 2 red wires go to battery switch. Large black wire goes to engine block. There is a black jumper between the battery negative post. The last black wire with white tag goes to alternator. I was thinking the past owner put the alternator wire on the negative post so when the engine was running it would charge the battery regardless of the position of the battery switch. Not sure if this is safe or OK. Is there situation where you would connect the alternator to the battery negative post.

 

[DayDreamer41]

I would say unequivocally no, the alternator output should not go on the negative battery terminal, and if that is the way it was and you ran the engine, my guess is the alternator is toasted as it is a direct short circuit.

 

[Davidasailor26]

I’m with DayDreamer. If the heavy black cable goes to the engine block, and the alternator output goes to the black terminal, no good can come of that.

 

[dlochner]

Is there situation where you would connect the alternator to the battery negative post.

Not typically. Alternators need to have positive and negative connections. Some Alternators are case grounded, which means the case of the alternator is grounded to the engine block by the mounting bolts, this is an inexpensive way of grounding the alternator and completing the circuit. It is not the best way. Other installations will have a negative wire from the alternator to the grounding bolt on the engine block. This is a better method. In your case, it appears from your description that the alternator is grounded to the negative battery. I suppose this would work, however, something doesn't seem quite right about this arrangement. Some wiring issues on a boat are nuanced and this is one instance. On my boat the negative lead from the alternator goes to a ground connection on the engine block.

If that black wire is really a positive lead and that white wire from the charger is a positive lead from the charger, then I'm surprised your boat is still floating.

The big question seems to be "why did my battery charger die?" The answer is its old and died a natural death. If this is an OEM battery charger, then its death is not too soon. Older ferroresonant battery chargers are really battery assassins. You can tell if you have one by its age and weight. The ferro resonant chargers also hum when charging, modern chargers are light ~5 lbs vs ~35 lbs and quiet except for a fan. What kind of charger do you have? Send us a photo.

Also, ABYC has a standard color coding for wiring. It is really wise to try to follow the standard code. It makes tracing wires and circuits much easier. You can find a copy in Charlie Wing's Boatowners Illustrated Electrical Handbook, a book worth reading and having on your bookshelf.

 

[Voyager1]

Only photo of battery charger I have. Has three wires, two red one white, none fused. It did hum. Might need to take a closer look at the black wire from the alternator since my boat is still floating. If it is a ground, not sure how the alternator is charging the batteries.

 

[dlochner]

Only photo of battery charger I have. Has three wires, two red one white, none fused. It did hum. Might need to take a closer look at the black wire from the alternator since my boat is still floating. If it is a ground, not sure how the alternator is charging the batteries.

Time for a new battery charger. That one was good in its day, but it is now way past its expiration date. Sterling ProCharge is an excellent choice.

https://shop.marinehowto.com/products/sterling-procharge-ultra-battery-chargers

While you are looking at the charger spend some time with the articles on the MarineHowTo.com site. Well worth your time.

The current standard is to have all DC negative wires either black or yellow (try to be consistent). A white wire can be confused with an AC neutral, needless to say mixing AC and DC on the same circuit is not a good idea. The white wire is the charger DC negative and the 2 read wires are the positives to charge 2 batteries simultaneously.

Trace the small black wire back to its origin. It may indeed be an alternator ground. Or it may go somewhere else. Good to know where it goes. When you find out, label both ends.

 

[Voyager1]

If it is the ground then where would I expect to find the positive for the alternator. Would it go back the battery switch.

 

[dlochner]

The alternator positive should be red. In a boat of your vintage, it is likely to lead from the alternator to the starter lug where the power cable to the starter connects.

Yes, this doesn't seem to make much sense, but there is a logic to it. When an alternator is producing power, the output needs to go somewhere, i.e., the battery to keep it charged. If the alternator is producing electricity and the load (battery) is suddenly disconnected, the diodes in the alternator over load and get fried. The alternator is dead. Connecting the alt output to the starter virtually guarantees that the alternator will always be connected to a battery through the starter power cable. This reduces the chances of an alternator failing under warranty due to user errors and is a faster cheaper way to install the charging circuit resulting in lower production costs for the boat builder. Good for boat builders and engine manufacturers, not so good for batteries. For boat owners, the system works, just not all that well. It's getting late, so I'll save that explanation for later. Look on MaineSail's site and in his forum, I'm sure there is a discussion there about the pitfalls of the alternator to starter connection.

 

[jssailem]

I Would agree with what you said. The part that is unclear is that the battery with the White wire attached appears to be only a charged battery. Since there is not “black“ ground wire attached to the upper battery in the system How is the current circuit completed?

 

[MikeHoncho]

I Would agree with what you said. The part that is unclear is that the battery with the White wire attached appears to be only a charged battery. Since there is not “black“ ground wire attached to the upper battery in the system How is the current circuit completed?

Yea there is. Look real close. The wire with the electrical tape on the bottom battery goes under the plastic battery handle/strap and terminates on the threaded, neg stud with the white wire. You can just see the lug and more tape on it.

 

[dlochner]

One other note about the wiring, it is a little difficult to discern, however, the biggest wire goes on the bottom of the stack. On some of the lugs it appears that the big wire is on top.

 

[jssailem]

Thanks Mike some days pictures can be a bafflement.

 

[capta]

Just because a wire is red or black does not mean it is actually running positive or negative electricity. Obviously there are things we can't see if this system has been operating for two years like this. Not to say that you shouldn't do as suggested above, hire a professional to get things straightened out properly and teach you a bit at the same time.

 

[Ron20324]

Clean those lugs, man! Where is your ships devices fed the negative?