Alternator wiring question?

[BAD ORCA]

I have an1980 Universal 5432 engine with unknown stock alternator. I pulled it off yesterday to get a closer look at the back and the wiring. It has a 10Ga orange wire which i know is the power out wire and a second wire which is purple (connected to other side of black plug in pic), which according to the wire charts would be an ignition switch to coil or an instruments wire. My start panel is very badly damaged. Many of the instruments are damaged or corroded beyond recognition and the wires cut, removed or have fallen off. It looks like my instrument start panel never had a keyed ignition, just a push button to start. The purple wire has been cut or disconnected and im not sure where it originally would have gone to on the instrument panel?

Any ideas what this wires intended purpose is?

 

[Stu Jackson]

This article explains the ammeter voltmeter improvement, but I'm posting it because it has a wiring diagram with the color coding:

Engine Harness Upgrade - c34.org

c34.org

It has a 10Ga orange wire which i know is the power out wire

That orange wire is merely a jumper and connects to the starter. Many boats came OEM with one wire from the battery switch C post. That wire performed two functions, as described here:
OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

1-2-B Considerations (New 2020 - Rod finally got around to diagramming what I had done in the above link in 2009 )
1/2/BOTH Switch Considerations

 

[Stu Jackson]

And here are some diagrams I drew of my wiring, please read the text with explanations rather than copying it here:

Alternator Regulator Wiring Diagrams (all three)

Alternator Regulator Wiring Diagrams (all three)

c34.org

 

[BAD ORCA]

Thanks Stu. I will read through all of this after work and try and figure this all out, very much appreciated. Alternator/start panel wiring is still a bit of a mystery to me. I have the infamous 'ammeter and trailer plug' connectors. I want to replace the orange wire with a bit heavier gauge and connect it directly to the start bank positive busbar. While im doing this i figure i should cut out the trailer plugs. Mine is slightly melted where the orange wire comes back through the plug as a 10 gauge red wire that goes to my starter.

 

[Stu Jackson]

and connect it directly to the start bank

You're welcome.

You might want to reconsider and wire to your house bank. Here's why:

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

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.sailboatowners.com/showthread.php?t=137615

This is a newer primer for boat system wiring design with a thorough diagram: Building a Good Foundation (October 2016)
Building a DC Electrical Foundation

As far as the gummy bear trailer plugs, try this:
Critical Upgrades http://c34.org/bbs/index.php/topic,5078.0.html

 

[BAD ORCA]

You're welcome.

You might want to reconsider and wire to your house bank. Here's why:

I cant. I have a lithium house bank. Eventually when i replace my engine or alternator, i'll add an external regulator so I can send all the alternator charging to my house bank first. For now i'm stuck sending it to my lead acid start bank but i havn't read all your links yet, so im not sure if there is an easy work around.

Until then, I was considering adding a B2B charger between the house and start bank so when the engine is running, at least i can send some of the alternator output to the house bank without burning up my alternator...albeit with some voltage loss i'm guessing.

 

[Davidasailor26]

Until then, I was considering adding a B2B charger between the house and start bank so when the engine is running, at least i can send some of the alternator output to the house bank without burning up my alternator...albeit with some voltage loss i'm guessing.

A B2B is not a bad choice in that situation, though it is a compromise compared to a smart alternator and regulator. You could get a Victron Orion xs with adjustable output current and efficiency up to 98.5% if you wanted to be very efficient with it.

 

[Stu Jackson]

Understood. Have you read the Cruisers Forum Lithium threads? jedi is a trusted contributor.

Lithium Power Systems - Cruisers & Sailing Forums

Lithium Power Systems - Lithium is a great option for extended life, energy dense charging systems.

www.cruisersforum.com

I cant. I have a lithium house bank. Eventually when i replace my engine or alternator, i'll add an external regulator so I can send all the alternator charging to my house bank first. For now i'm stuck sending it to my lead acid start bank but i havn't read all your links yet, so im not sure if there is an easy work around.

Until then, I was considering adding a B2B charger between the house and start bank so when the engine is running, at least i can send some of the alternator output to the house bank without burning up my alternator...albeit with some voltage loss i'm guessing.

 

[BAD ORCA]

Understood. Have you read the Cruisers Forum Lithium threads? jedi is a trusted contributor.

Lithium Power Systems - Cruisers & Sailing Forums

Lithium Power Systems - Lithium is a great option for extended life, energy dense charging systems.

www.cruisersforum.com

I've read a lot of his stuff. Not sure about that link though. I will for sure check it out tonight.

I just finished reading through the first two links you posted above. That first one with the wiring diagrams was a godsend. The large 10Ga white wire was something i had been wondering about for a while now. I was under the cockpit poking around a bit this weekend cleaning up and cutting out orphaned wires and noticed they (large white wires) were connected to a square metal box which i thought might be a relay, but wasn't sure if it was or what it was connected to on the other end. Unfortunately I couldn't get to the back of the start panel to confirm where everything was connected. Now I know and am starting to be able to wrap my head around this project.

Eventually when i get through some more pressing projects im going to replace the start panel completely so all of this is a great help.

 

[BAD ORCA]

Im still confused about what the purple alternator excite wire does on our engines, still researching.

I will have to try and trace where it connected on my old panel. I think in very general terms i have the gist of what it does from reading some automotive articles but not sure if that applies to a small diesel engine.

Most articles describe it connected to small loads (light/s) on the instrument panel to get the alternator charging properly, but my panel has no such lights, only gauges, some push buttons and unidentified toggle switches that are corroded beyond use or recognition. There is a push/pull switch that seems to send power to the gauges though, so i wonder if its connected to this switch and if this is enough to 'excite' the alternator? The alternator does charge when the engine is running so i know it works, it just charges at very low voltage (13.5ish) but this could be due to voltage drop from long/ poor wiring circuit and those trailer park connectors.

 

[jssailem]

charges at very low voltage (13.5ish)

That is not a "Very Low Voltage". For some alternators, it’s normal to see as low as 13 volts. For some, a constant 13.6 volts is an indication of a problem. For others, it’s normal to see as high as 16 volts for long stretches. Still, it’s perfectly normal for others to see the alternator not charge at all intermittently. What are the RPM's at the time you measure a 13.5 voltage output? How many amps were being produced? Where are you measuring these readings?

You already know that the alternator will not be giving your Lithium batteries the charge voltage they want. The question is can you keep the FLD Start battery charged enough to let it charge the Lithium batteries? Or will they suck the life out of your start battery, like a vampire.

 

[BAD ORCA]

That is not a "Very Low Voltage". For some alternators, it’s normal to see as low as 13 volts. For some, a constant 13.6 volts is an indication of a problem. For others, it’s normal to see as high as 16 volts for long stretches. Still, it’s perfectly normal for others to see the alternator not charge at all intermittently. What are the RPM's at the time you measure a 13.5 voltage output? How many amps were being produced? Where are you measuring these readings?

You already know that the alternator will not be giving your Lithium batteries the charge voltage they want. The question is can you keep the FLD Start battery charged enough to let it charge the Lithium batteries? Or will they suck the life out of your start battery, like a vampire.

Good to know. Good question on the rpm's. My boat never had an rpm gauge. I will have to check again this weekend and try and do a better set of tests once i rewire the alternator output to the start bank pos. bus. At least this will eliminate the poor wiring variable.

I was getting that reading from my Balmar SG-200, but to be honest at the time was not doing any deep diagnosis. I was just trying to confirm the diodes were not blown and the alternator was at least charging.

I suppose if the start battery is near full it wont take much of a charge so i guess it would make sense to see low charging voltages. I can drain the battery a little with some house loads i suppose to get the alternator to put out a higher charge once i get organized.

I need to figure out where this exciter wire is connected on my panel. I have been researching it and it looks like i have some options on how i can connect it better either using a light, a zener diode or maybe even my oil pressure gauge.

Good question, I dont know that answer yet. I need to think that one through. I never had the ability to monitor these things before, but now at least i have shunts and an SG-200 on the battery bank and an BMV-712 on the house bank and can see whats actually happening with the alternator output.

If the alternator can output lets say 14.6 ish volts peak and the lead bank is full and not accepting a charge, if i manually switched on a B2B charger, my thinking is that i could output 13.8 volts to the lithium bank without draining the start bank. I have never actually done this before though. All the instrument and house loads would be run from the lithium house bank so there would be no additional loads on the start bank once its fully charged. As long as the engine is running and the alternator putting out power is there any reason why this would not work? Am i missing something obvious?

 

[Davidasailor26]

I suppose if the start battery is near full it wont take much of a charge so i guess it would make sense to see low charging voltages. I can drain the battery a little with some house loads i suppose to get the alternator to put out a higher charge once i get organized.

Alternators, at least ones without high end external regulators, don’t really know or care about the battery’s state of charge. They excite the field coil enough to hold their output at a steady voltage (usually in the low 14’s, but with some variation based on alternator and temperature). A battery that’s at a high SOC will not absorb much current at that voltage, and the alternator will excite itself just enough to hold the constant voltage regardless of the low output current; that’s the only “regulation” in the system based on state of charge.

 

[BAD ORCA]

Alternators, at least ones without high end external regulators, don’t really know or care about the battery’s state of charge. They excite the field coil enough to hold their output at a steady voltage (usually in the low 14’s, but with some variation based on alternator and temperature). A battery that’s at a high SOC will not absorb much current at that voltage, and the alternator will excite itself just enough to hold the constant voltage regardless of the low output current; that’s the only “regulation” in the system based on state of charge.

Ok, that makes sense. I guess It would need some sort of battery voltage sensing (the alternator) to be able to manage its output according to SOC. It sounds like thats what the high end regulators do. It sounds like a B2B charger could still be useful though because i really only need 13.8 volts going into the lithium bank.

 

[Davidasailor26]

Ok, that makes sense. I guess It would need some sort of battery voltage sensing (the alternator) to be able to manage its output according to SOC. It sounds like thats what the high end regulators do. It sounds like a B2B charger could still be useful though because i really only need 13.8 volts going into the lithium bank.

Yes, the alternator will sense its output voltage and self-excite just as much as needed to keep that voltage at the right level.

The B2B is very much a necessity for lithium without an external regulator, for three reasons - (1) as you already mentioned the B2B will give the lithium the right voltage for its charge profile; (2) It will prevent the alternator from trying to dump more current into the batteries than the alternator can put out without overheating; and (3) if the lithium BMS detects any kind of fault, like over temperature or over voltage, it will immediately stop accepting charging current. If that happens when you’re directly connected to the alternator the alternator will cause a voltage spike that could burn out its own diodes and potentially other equipment.

The question is can you keep the FLD Start battery charged enough to let it charge the Lithium batteries? Or will they suck the life out of your start battery, like a vampire.

A good DC-DC charger can be regulated to only feed the lithium as much current as the alternator can be expected to provide. They also can be configured to stop giving any charge if the source battery falls below a set voltage. So if the start battery gets depleted at all the B2B can cut out and all power can go to the start bank again.

 

[BAD ORCA]

Yes, the alternator will sense its output voltage and self-excite just as much as needed to keep that voltage at the right level.

The B2B is very much a necessity for lithium without an external regulator, for three reasons - (1) as you already mentioned the B2B will give the lithium the right voltage for its charge profile; (2) It will prevent the alternator from trying to dump more current into the batteries than the alternator can put out without overheating; and (3) if the lithium BMS detects any kind of fault, like over temperature or over voltage, it will immediately stop accepting charging current. If that happens when you’re directly connected to the alternator the alternator will cause a voltage spike that could burn out its own diodes and potentially other equipment.



A good DC-DC charger can be regulated to only feed the lithium as much current as the alternator can be expected to provide. They also can be configured to stop giving any charge if the source battery falls below a set voltage. So if the start battery gets depleted at all the B2B can cut out and all power can go to the start bank again.

I should be covered if #3 ever happens because im connecting the charge output from the alternator directly to my always on positive busbar for the start bank. It should always have a connection to the battery this way. I'll wire the B2B charger between the start bank and house busbars.

I have my eye on and will probably get the new Victron 50 amp B2B charger. Most of my other equipment is Victron already. I love the granular control you can get with their stuff. Very happy so far. The added benefit of the B2B is that the start bank has its own 60amp Sterling Pro Charge AC battery charger. When im at the dock on shore power, i could turn on the B2B charger and get an additional 50 amps of charging to the already 50 ampps i can provide to the lithium bank with its own Phoenix charger, so roughly 100ish amps total give-or-take with losses.