Alternator wiring question

[Scott T-Bird]

I am finally pulling all of my electrical improvements together. One thing left undone was modifying the negative cable from the alternator. I have an Hitachi 80A alternator that was factory installed with my new 2YM15 (Yanmar) engine. Original install included a red 10 awg pos lead to the starter + post and a black 10 awg neg lead to (presumably) engine grounding.
Last year, I disconnected the + lead and routed a new 4 awg cable to a POS buss bar near the battery terminals. Luckily, the POS lead was readily accessible. I'm using a Blue Seas ACR with DCP switch. The ACR is wired with 6 awg cables as shown in MS's wiring diagram for DCP with 2 emergency isolation switches. I have the cable from the alternator fused at the buss bar. The cable is 10' long to snake around the engine and back to the batteries. (I didn't need 10' and could shorten it to 7').
My question is about the NEG lead from the alternator. I simply can't get to it, probably unless I take the alternator off for access. So I've left it alone, thinking it alright. I know that wiring diagrams show the alternator lead routed to a NEG buss bar, which is then grounded to the engine and I want to make this system ABYC compliant. Should it be necessary to run a 4 awg cable to the NEG buss? What are the consequences for leaving the original 10 awg lead in place instead? I understand the size is based on the round trip circuit, but does this apply to the alternator? Basically, I'm concerned about that small diameter grounding wire and will replace if necessary, but how do I get to it? It is tight against the engine and even if I could see the connection well, I doubt I could get my fingers in there. Does this mean removing the alternator? Thanks for any and all replies!

 

[Mark Maulden]

Some more info is needed. But assuming the alt is internally grounded and the engine has a decent size wire between it and the neg bus, you're ok, technically, for awhile. I say that because most of the alt return current will come through the alt mounts. In time, that would probly change because things get dirty causing resistance and things loosen up..You don't say how long the neg wire is. I don't have a wire chart handy, but assuming assumptions are good, this isn't something that needs immediate attention "technically"... It's not the best design but it should be changed at some point in time. I do not know what ABYC says here...If you have to remove the alt then that's the way it goes. hey! Its's a boat! When you decide to change it, make sure that the "big" wire doesn't flop around breaking the stud on the alt as it looks like everything would have to go together at the same time...Answering your question of if it matters if its an alt or not, it doesn't..amps is amps whether from an alt or battery...

 

[Mark Maulden]

Further thought, would the alt have to be removed? Can you pull the adjustment bolt and swing it out on the lower mount?

 

[Scott T-Bird]

Thanks Mark, if I understand your answer correctly, you seem to be saying that if the return cable from neg buss to engine ground is sized correctly then it should be ok at least temporarily (practically speaking). I would assume that the alternator would be internally grounded. Wouldn't that be typical for an Hitachi alternator factory installed on a new Yanmar engine? I have a 2/0 battery cable, 4' long, connecting neg buss to engine ground. I have all loads, including start batt, connecting neg buss to load side shunt for LinkPro monitor as well. House bank neg is connected to Batt side of shunt. So the ground to engine should be fine.
The black wire on neg post of the alternator is 10 awg and it disappears into a bundle that seems impossible to trace without pulling everything apart. There is no telling how long it is or where the other end is attached. The wiring diagram from Yanmar installation manual simply shows it connected to ground. If the alternator is internally grounded via attachment to engine block, why does that wire exist? Could it be a ground wire for something else connected via that wiring harness? Perhaps I shouldn't disconnect it when I complete installation with a properly sized cable to neg buss.

 

[Scott T-Bird]

Mark, the factory installation of the alternator to the engine block has a 10 awg + lead to post on starter and 10 awg - lead to who knows where (presumably engine ground). This for an 80 amp alternator. I assume this is adequate only for a very short run. I had a 10' cable made for + lead to house batt (via pos buss). I made it with 4 awg based on Blue Seas chart at 80 amps. I don't think I've ever seen more than 14 amps on the batt monitor when alternator is charging. Perhaps the cable is overkill?

 

[Maine Sail]

The Hitachi LR180-03 80A is an isolated ground alternator not case ground.. Best to bump that wire up and then run the jumper over to your main engine negative lug, clean it and physically stack it directly on top of it. Do not pass your alternator current through the block. Ideally the B+ and B- from the alt would be the same size. You'll still get pretty poor charging from that alternator, but better than you were...

 

[Stu Jackson]

Scott, don't know if you've seen this by Maine Sail, it's been posted many times:


Hitachi/Yanmar Alternators: (by Maine Sail)


Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?

Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorption voltage, then we also reduce the current the alternator is supplying.. The battery simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?

The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....

If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.

If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.


This is from:


http://forums.sbo.sailboatowners.com/showthread.php?t=125392


and this, too:


https://marinehowto.com/automotive-alternators-vs-deep-cycle-batteries/

 

[Scott T-Bird]

Now I remember reading about this! Thanks for pointing me to it. Unfortunately, much of it passes over my head, but I think that the fact that I am slowly killing my batteries is sinking in with my Hitachi alternator. Mine is indeed the LR180-03B. I couldn't seem to find specifications or a manual for it with a quick google search, so I gave up. I will change the negative cable, but it doesn't look like an easy job.
So if the alternator is undercharging the batteries, is it important to improve the alternator if I rely primarily on an AC charger? My next step is to finally get the Sterling 30A charger on line. My inclination is to put the alternator out of my mind once the neg lead is changed out.

 

[Stu Jackson]

Scott, this is simply a management issue for how you plan to charge your batteries. If you plug in after your sails and do not rely on your alternator to do much for charging your house bank, then that's just fine. If, however, your were a cruiser who didn't plug in very often, or at all, it would be a serious issue.

Don't think it's above your head. You're a smart guy. You married Sue!

Read the material a few more times, get a boating electrical book like Charlie Wing's, and spend a few nights studying it. None of us was born an electrician. We learned, so can you.

I couldn't seem to find specifications or a manual for it with a quick google search, so I gave up.

What more do you need to know than what Maine Sail wrote? 99% of all alternators do NOT have "manuals." No wonder you couldn't find one.

 

[Ward H]

Scott, let me know if you need a third hand. Schedule is open.

 

[Scott T-Bird]

You're a smart guy. You married Sue!

What more do you need to know than what Maine Sail wrote? 99% of all alternators do NOT have "manuals." No wonder you couldn't find one.

Ha! You got that right. But you might question her sanity for marrying me!
Well, I am just a little embarrassed by the fact that I can't tell the difference between an isolated ground alternator vs. a case grounded alternator (and what is "internal grounding"?? - the same as case grounding??). I'm not intuitive about these terms at all. I suppose the hint is that there is a separate post and wire for the neg return vs the lack of a neg post for grounding and bolted connection to the engine serves as the ground. I thought, possibly, that the neg post is simply for redundancy, but I suppose that doesn't make sense either. So change the 10 awg wire to a 4 awg cable , I will.
Ward, if you want to help with this, I'm all for it! I'll try to get away one of these weekdays and I'll call you ahead of time. I told Richie that he knocked my masthead transducer kittywhompus when he raised the mast, so he said he would use the lift to go up if I come down on a weekday.