Hitachi (Yanmar) alternator - machine sensed, or battery sensed?

[Jetx]

Hi All. I'm planning to install a dedicated start battery. Following advice of Maine Sail and others on this forum, I plan to move alternator and shore charger connections to the house bank, and use an Echo Charger to charge the start battery.

My question concerns moving the alternator output to the house bank (want to make sure I don't inadvertently screw something up!). Engine is a Yanmar 3JH4E, with Hitachi LR180-03C alternator. Does anyone know if this alternator is "machine sensed" vs "battery sensed". Alternator wiring diagram and Engine wiring diagram from the Yanmar service manual are attached below.

If it's machine sensed, then I simply need to connect the output (B+) to my house bank. But if battery sensed, then I gather things might be a little more complicated.

I've found conflicting answers online. This post indicates it's machine sensed (and this "feels" right to me, though I don't have an electrical background). But this thread indicates that the R terminal on this alternator is a battery sense terminal, and that it can't simply be connected to the house bank, since doing so would connect the house and start batts even when the engine is off. Does anybody know which is correct?

Much thanks in advance!

Jeff

[exMaggieDrum]

I don't recall ever seeing the term "machine sensed" related to alternators. The alternator output should be connected to the battery bank you need to charge. You should fuse this wire although lots of people don't (and definitely should). I think you are trying to overthink this. I am not sure actually what issue the post you linked to was trying to solve but the inner workings of alternators is probably a bit too much info for you right now. The Hitachi drawing is showing the windings inside the alternator and you will never need to know that in a normal life of cruising. There are tests that can be done by a competent technician for an inop alternator but you are not at that point here.

One thing that the drawing shows is the battery switch between the battery and the start circuit. You should never/ever completely turn off the battery before you turn off the alternator. Some battery switches do that for you (field disconnect before off). If the switch does not have that feature, or it is not wired for it, turning off the battery will fry your alternator diodes in a flash and you will need to repair or replace the alternator.

So - wire the alternator to the batteries via a wire direct to the batteries or to some connection to the batteries (battery switch e.g.). Best of all is to get an external regulator to take better care of your batteries but the alternator output will still be wired the same. The "sensing" will be done by the regulator and not by the alternator itself (internally). When it does that internally it senses the battery voltage at the output wire, which should be the same voltage as at the batteries if the wire is big enough. (the voltage will be different when the alternator is putting out big amps but for this don't worry about that)

Good luck. You might want to get an electrically savvy buddy to help you with this.

BTW - the way you intend to charge the start battery with an Echo Charger is a good idea so you got good advice there.

[Jetx]

Thanks exMaggieDrum, and of course you're right, I could use a more electrically savvy buddy. I do understand a bit of DC electrical circuits.. but not extending to the internal working of alternators, obviously!

I see now that the threads I read/referenced (found by googling for info on my alternator) were UK based, so I suppose that's where the "machine sensed" terminology comes from. This is what I get for trying to use alternator-jargon... I got alien jargon instead .

To try and ask the question sans-jargon then, how can I find out if...

1. The alternator's internal regulator senses and regulates voltage internally... sensing and regulating based on the B+ voltage, or
   
   
2. If it senses and regulates based on an external/battery voltage (the R terminal voltage)?

If it's #1, then all I have to do is connect B+ to the house battery and I'm done.

But if it's #2, then I may also need to connect the R terminal to house, so the regulator can sense the same battery that it's charging (not sure about this, but it's not relevant if the answer is #1... so that's what I'm hoping for of course!).

Thanks again!

[Stu Jackson]

Maine Sail has posted this many times, so i just copied it for reposting:

Hitachi/Yanmar Alternators:

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 absorbtion 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:

Musings Regarding External Regulation - SailboatOwners.com

and this, too:

http://www.cruisersforum.com/forums/...on-125843.html

[Jetx]

Originally Posted by Stu Jackson

Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop.

Thanks for the chuckle, Stu! I had read a couple of Maine Sail's posts regarding the crummy Hitachi (temp compensated) alternators, just not this particular one. Unfortunately, the Hitachi poop is what's on my engine, and it's the poop I have to work with right now. External regulation, and maybe a better alternator, might be in the cards down the road, but not now. Today, I'm just trying to confirm whether hooking my existing poopy alternator to the house batteries is drop-dead simple, or a tad more complicated.

To do that, I just need to understand what controls the poop excreted by the beetle. Does the beetle sense B+ and modulate his poop based on that?

Or does the amplitude of the beetle's poop vary based on a tingly sensation that he gets from R?

Any Hitachi beetle gurus out there??

[exMaggieDrum]

I am going to eat my own poop here. I think I am out-gunned and out-classed by Maine Sail and the other worthies on this thread and others. Alternators are indeed a strange breed with humongous variety. I should have remembered all the trouble I had 10 years ago when I was actually working full time and not just on my own boat now. My expertise, if any, is more on the externally regulated side of the world, and I don't have any experience with Hitachis in any case. I am learning some new stuff following the previous threads.

I remain much humbled and will be more of a student......

Thanks for all the good posts and info from the others

I think I got what is probably a good answer in the other posts but there isn't any value in me trying to rephrase it.

[delmarrey]

Hi JE,
The alt wire (stock) is attached to the battery terminal of the starter. So it goes to which ever battery your selector switch is on, if you have one. And it's not wise to change the selector switch with the motor running unless you have the special sensed switch. That's if you system is set up that way.

In my case I added a combiner and ran the alt wire directly to the start batteries and use the combiner to go to the house batteries and another combiner to the windlass battery.

And I don't recommended fusing the alt wire. If the fuse fails or a connection comes loose the alternator fries.

One more reason for wiring this way is I can turn off my selector switch, in case of fire, without frying my alt and can keep the motor running if I have to w/o the batteries. But if the alt wire gets grounded the alt is toast. So I carry a spare alt & belt.

[Ex-Calif]

Not a Hitachi guy but according the 12.1.1 wiring diagram - your second picture

10AWG Red wire form terminal "B" on the alternator to Starter Post B
10AWG Black wire from terminal E on the alternator to an engine bolt (engine grounded to battery)
Yellow wire from Alternator "R"(?) post to tachometer.
"L" post not used.

In this case the regulator sense must be from the B terminal.

In your case I would wire the B cable (Red 10 AWG) to the house battery positive upstream of 3-way switch.

I would wire the E cable (Black 10AWG) to the DC negative bus or battery negative post. It will work as is but I prefer a dedicated ground run to the negative bus (preferably) or batteries for charging sources. One doesn't want a dirty or loose engine ground messing up the charge regime.

The alternator will always be on and connected to the house battery. I would fuse the B cable at the battery end. And Del is right if this fuse breaks while engine running the alternator might fry. If the wire chafes the boat might catch fire. Choose your poison...

[Jetx]

Thank you Ex-Calif. Very much appreciate the advice!

Jeff

[hellosailor]

JE-
In my limited experience I've never heard "machine sensed" either. That sounds like a translation from Spanish into English. In the US we generally refer to "one wire" versus "three wire" systems. A three-wire system uses a dedicated voltage sense line to the battery (usually) while a one-wire system has the voltage sense lead tied back to the alternator output. It is dumb as a rock, it never actually senses battery voltage.

The advantage is that there's no sense lead to switch when you switch battery banks, and it saves a buck or three on the wiring harness.

From the schematic you post, I don't see any battery sense lead going to the battery, just the primary charge output. Which would make it a dumb 1-wire system. Not good for battery longevity and a good reason to switch to a better system, but not needing anything switched when you change batteries either.

[d4raffy]

Interested in the conclusion of this thread - please let us know . .

From my research - I have 4JH4 factory Hitachi 80 amp Alt
R = alternator excite - I don't believe it uses this for voltage sensing
L = control panel warning light - goes out when Alt generating
P = ac phase for tachometer
B = + volts out
E = ground

I also concluded that the Yanmar schematic is wrong, somebody pasted a correction - see my earlier thread on Hitachi Prestolite swap out. (Couple of pages down, Not sure how to link to thread on my ipad)

So I am hoping the answer to your question is option 1
So all you need to do is swap B to the house bank (assuming you have common ground)

Happy to be shot down .. As I am yet to do my swap over.


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