Charging with the Alt.

Ok my brain is not working today. Came down to troubleshoot the alternator.

The alt puts out 13.9v at the positive orange wire and the amp and volt gauges all show an increase but the start and house batteries are not getting charged by the alt with the engine or engines running.

Each alt has one orange wire going into the wire harness then forward to the helm panel but have been unable to locate the end point so far.

I know its simple but what am i overlooking today?

How do you know they aren't getting charged? did you take a voltage across them with the engine running?

is the disconnect on? Ground connected?

Assuming your's are internal regulated alternators, the Ammeter (s) on your dash and flybridge are most likely wired in series. This is a simple diagram which is typical of factory installations.

Check the main DC feed area of your CB panel and see if there are any orange wires going into you battery switch....or like mine was...they went to the main buss bar area and were jumpered into the hot ignition wire...lot's of possibilities though.

A couple of quick basic checks.
When you have 13.9 at the alt. do you have 13.9 at the battery? If you do, all may be well w/ the wiring & maybe you have a charge acceptance problem. If you have 12.5 or so on a rested battery (no use or charge for 24 hrs) then it is charged. If a charged bat and drops below 10.5 while cranking the engine, it lacks capacity and the same test at the starter should be within 1/2v of the voltage at the battery. If lower it is a cable, ground problem.

Thank you. To answer some questions above.

Have checked voltage at house and start batts with no increase in voltage.

The selector switch is on but no increase of voltage when the alt kick in.

Have not found the orange wire going to the batt switch. But see that it runs up behind the dash and i assume to the amp gauge since it shows a charge when the alt kicks in.

Crap Did not think to check if the main buss bar hard an increase in voltage. Will check that out.

That's a little strange because if the ammeter moves then current is flowing and it must be going somewhere. If the charge wire were broken or disconnected, the ammeter would not move AND your alt would be damaged.
13.9v IS charging so if you have 13.9 at the battery it is charging. Maybe not as you would like it but charging nontheless.

One other thing that can cause reduced voltage at the battery is a diode charge splitter they usually eat up .5-.6v. Enough to always undercharge your batteries. The wire that leaves you ammeter would go to the charge splitter. Look for this.

We have 13.9 from alt POS.
Batt show 12.6 prior to start then stays at 12.3 after start. When Alt kicks in the voltage at both banks stays at 12.3 and goes down with more DC load applied. It does not come back up.
When RPM gets to 1200 the Alt output goes from ~12.2 to 13.8-13.9 amp gauge shows a positive charge. But the batt stays at 12.2 to 12.3. Even after several minutes.
All readings are using 2 DVM not the helm gauges.
Still cant figure where the power is going and why the helm gauges show that something is working but not getting back to either of the batteries banks.
One bank is start and this bank starts both engines.
The other is the house bank. Either can be used to start or as a house or combined depending on the selection of the battery switch

Looks like time time to pull the helm panel. Could there be a blown fuse behind it not allowing a charge?

I think you might be misreading something. There shouldn't be any fusing between the alternator on a single engine and the battery positive terminal on the start battery. If there is and some people place on high amp fuse in line, if the engine starts then the fuse is good. There should be nothing that would cause a different voltage reading. The orange wire you are referring to is not in the charging circuit to the battery. You need to make the measurement on the 2/0 or 4/0 wire from the alternator running to the starter and then to the start battery. If you don't see the voltage there, then I would suspect a problem in the voltage regulator. On my boat, my instrument gauge looks at voltage not amperage. I watch that after start to determine if I am charging ~13.6 VDC and then watch for the ACR to kick in and send charge to the house bank which is reflected in a voltage drop at the helm. Once the ACR kicks in I look at the battery monitor to see how much amperage is being thrown at the house battery bank.

Tom

Alot depends on how your system is wired. On the previous boat the alternator outputs were wired seperate of the starters. So I had a 2/0 going from the alternator to the battery. When I sold the boat the surveyor required a fuse be put in this line. He was satisfied with a 150 amp fuse that attached to the battery. If you have this kind of a setup then the fuse could be the problem.... More convetional setup is to have the alternator output connected to the starter lead. As mentioned above with this wiring if the engine starts you should have the alternator out connected to the battery.

If you have checked all of the obvious stuff, then its time to make a long negative test lead and start taking voltage readings from the running alt at 13.9 volts and work your way through each connection all the way back to the battery. Somewhere, the voltage will drop to 12.3 and that will id the culprit. Look for bad crimps, loose nuts, SS lockwashers, green balls of used-to-be copper wire, hidden splices under electric tape, secret fuses, etc. The possibilities are endless! The digital voltmeter will find it. Let us know what you find.
Since you have ammeters, I'm going to take a S.W.A.G and say bad (high resistance) engine harness orange wire plug/socket connection under the dash.

Not sure why some think there must be...but many boats (my last 2) do NOT have a wire going from the alternator to a battery....even via the starter terminal (I think it is done by many but usually not the factory in my experience). 2/0 is huge to connect to the back of an alternator.... I have never have seen anything that big directly on the back of an alternator on smaller boats....maybe 2 ga or 4 ga (especially if the run is just alt to starter or a short run to a batt).

Mine (and most I see) have had a rather small (10-12ga....probably due to less than 100 amp stock alt)) wire running in the engine wiring harness back to the start panel or at least to the set of terminal busses and from there its jumpered over to the start/run hot or main DC buss which provides the link back for charging. Of course with todays electrical demands and house banks...10-12 ga wiring is way inadequate and the root of many boat's electrical problems. Very prevalent in pre-90's boats , especially those without "house banks" and just start batteries where one side is the house bank.

Without tracing the wire...you can be stabbing in the dark as I have seen that "orange" wire spiced into all diiferent color wires.

Fault with battery selector switch or (more likely) regulator. Is your reg internal or external?

Here is an example of what to look for. Notice under the fan belt pulley, the black cable has some electric tape then comes out red! Underneath was the ends of stranded battery cable seperated slightly, jammed together, then tightly taped. Not even solder and it still worked somewhat!!!

Ok I have looked again. I have only 1 Orange wire on the Alt it looks to be 12gauge.
The only wires on the starter are for the starter solenoid wire colors are red and yellow/red and of yes the black for ground.

Like PSNEELD and Highwire have said it seems to agree with what i am seeing is the Orange wire goes towards the dash thru the eng wire harness. Have not yet found the end point or a splice in yet.

However yesterday just prior to leaving i found a what appears to be a fuse that is between the helm and the battery selector switch. Will go look at it today as well as pull the helm panel.

Harbor Nights said:

Ok I have looked again. I have only 1 Orange wire on the Alt it looks to be 12gauge.
The only wires on the starter are for the starter solenoid wire colors are red and yellow/red and of yes the black for ground.

Like PSNEELD and Highwire have said it seems to agree with what i am seeing is the Orange wire goes towards the dash thru the eng wire harness. Have not yet found the end point or a splice in yet.

However yesterday just prior to leaving i found a what appears to be a fuse that is between the helm and the battery selector switch. Will go look at it today as well as pull the helm panel.

Click to expand...

This might be of some help. It is from the USCG Boatbuilder's Handbook. Note the orange alternator charging wire is now required to be 8AWG. It terminates at the ammeter. This follows what PSNEELD said about it often being undersized on older vessels.



Good luck,

Larry
M/V Boomarang

Just to prove things out, you might consider paralleling (w/ a jumper) the orange wire that goes from the alt to the ammeter and see if things change. Then do from the ammeter to the battery/starter wherever the return orange goes now, & finally from the alt directly to the battery; each time checking bat voltage. By that process you could find the offending wire if there is one.
You could also do the same thing with your volt meter and get a voltage drop under load from each wire.

Did you ever discover a diode charge splitter? That could explain some of the problem.

Harbor Nights said:

Ok I have looked again. I have only 1 Orange wire on the Alt it looks to be 12gauge.
The only wires on the starter are for the starter solenoid wire colors are red and yellow/red and of yes the black for ground.

Like PSNEELD and Highwire have said it seems to agree with what i am seeing is the Orange wire goes towards the dash thru the eng wire harness. Have not yet found the end point or a splice in yet.

However yesterday just prior to leaving i found a what appears to be a fuse that is between the helm and the battery selector switch. Will go look at it today as well as pull the helm panel.

Click to expand...

If it's not exactly a fuse, but more like a slug, it is probably a fusible link. I have seen them used in some installations.

You mentioned you have Ammeter(s). Since they measure the flow of current (amps), to work properly they are installed in series between the alternator and the battery. The red wire from the Alternator most likely leads to the dash board and terminates on one lug of the Ammeter. I would expect the wire to be a lot heavier than 12ga though, more likely at least 8ga. If you have an ammeter on the flybridge dash, that meter is also in series with the lower ammeter. Clean all the connections and terminals on that circuit and don't forget the battery switch.

You can also take the Alternator to an auto parts store and have them test it under load. It takes just a few minutes and they usually don't charge for that service.

Running these things down can be a nightmare. When you find it, you'll wonder why you didn't look there in the first place.

My Ocean 40 was originally wired with 3 sq. mm wire from the alternators, as identified in the wiring diagrams and confirmed by what's still in the bundles. The original alternators were Prestolites rated at 42 amps, internally regulated.

The alternator output wire ran from the alternator up to an ammeter at the lower helm station and back to the starter lug, a common set-up for that age boat. That makes the wire distance from the alternator to the starter connection around 20 feet.

3 sq. mm is equivalent to 12-gage wire,which is completely inadequate for that load. Looking at GenuineDealz' voltage drop calculator, if the alternator puts out 42 amps at 13.9 v, 20 ft. of wire will drop 2.6 v, giving a voltage at the starter lug of 11.3 v, which won't charge batteries.

It's not actually that straight-forward, since the small wire size will make the internal regulator think the battery is charged -- the charge current will drop off, so the voltage drop will be reduced, so voltage at the starter terminal will increase some. Over a long run the battery may be brought back to a full charge.

The only correction for this is to install a wire big enough to handle the load. I'd certainly recommend spending time in Calder's book for his views on how to set up an electrical system.

A quick test is to run #4 or #6 cables from the alternator output to the starter lug or battery buss connections. Prudence would dictate protecting the wire with a fuse at the battery or starter lug connection.

It is possible that your fuse/slug is a shunt which would have 2 light gauge wires going to the ammeter and 2 heavy wires (on the same terminals) going from alternator to battery (by battery I mean bat, starter, bat switch, bus bar or whatever depending on how it was wired)

This would explain why the wire to your ammeter isn't larger, it doesn't need to be because it is only measuring milvolts which the ammeter (really a voltmeter) interprets as amps. Look up shunt online images and see if you see yours and how it works.

HarborNights

Did you get to the bottom of your problem. So many times we all engage with our opinions to help with a problem; then never get the benifit of knowing the outcome...

Got back to boat today and did find a few answers.
My start bank is 2 8d wired together for a 12 volt starter. This double bank starts both engines and both Alts go to the start bank. Then to the battery switches then to the house bank.

I was measuring with the DVM from the forward battery. When i moved the DVM to the aft battery it would show a charge when the alt kicked which is the same time the amp gauge shows a charge. And the fwd battery would charge at a lower rate.

Well the alt is putting out, not as high as one would like but it is working. So it looks like the voltage drop from the alt to the battery will mean more battery cable replacement. The suspect cable between the start batteries will be investigated later this week. The suspect is the welding wire. The entire boat was wired this way but its getting better. Just rewired the house bank side last month. Battery cable is getting pricy these days....

The joy of boats continues.

Thank you all for your help