Tracing wiring from alternator to battery

[spemmons]

I recently purchased hull #0063 (2003) and have discovered that the engine is not charging the batteries.

I've tested the alternator and it is putting out 13+ volts but when testing the voltage at the batteries, it is clear they are they are not charging.

I'm having trouble tracing the the path of the wires from the alternator.

They disappear into the space between the deck and the interior paneling just above the engine and I can't think of any way to figure out where they go from there.

I suspect a loose wire or something, but not sure where to look.

Any suggestions?

[russp]

Just a thought, although I am sure others will have smarter ideas. Yes the heavy battery/alternator cables run under the flooring up then up to the battery switches under the electrical panel and then into battery compartment, the size of these should allow you to trace them and I wouldn't expect they are broken, they are very heavy gauge.

An added precaution, these carry big currents and are a potential fire hazard if you do have loose or broken connections somewhere, if you can't clearly find both ends, do a continuity check and be sure no break or resistance, then stay close to the panel when you are running the alternator. Maybe if you aren't sure you should get an eleco to check them out.

[Olivia Mae]

Red wire should go from engine to the common terminal to the battery switch. From there it would go to the battery bank chosen by the switch.. The ground goes directly to the batteries.

This would have been the original setup and should be shown on a wiring diagram in the manual. Could have been modified but a previous owner, though.

[knitchie]

On my 2007, the wire runs from the forward port side on the engine bay, under the cabin sole to the port side of the battery box. It’s a tight run, but if you unscrew and lift the teak holly ply on the sole, there is an access the wires half way through.
Fair winds,
Ken
Reverie, #447

[scott.monroe]

Good morning Ken,

I am of the school, "simple things first". Before going too far, are you really reading 13+ volts at the batteries when the engine is running (and no other charging source connected, solar, shore power etc)? A charging source is "working" when it is generating 0.5 v above resting voltage of the batteries. Fact you read 13+ volts is suspicious.

Double check your readings. Let your batteries "settle", i.e. all charging sources off for a short time (15 min or so) and surface charge has dissipated. Measure the voltage, should be no more than ~12.6V (fully charged). Start your engine and rev to momentarily get rpms up, measure the voltage at battery again. If you see an increase of at least .5 V, alternator is outputting (e.g. 13.1V) and connected. Another test you can do is check for AC ripple. Switch your meter over to AC voltage and re-read your batteries. Alternators actually generate AC voltage which is then converted to DC by diodes in the alternator, when they go you will see AC ripple, if above .4 volts the diodes have failed, alternator is on the way out.

But if you did see an increase of .5 Vs in your charging source, and your batteries are not getting charged then you may have a problem with your batteries accepting/keeping a charge. They may get up to 12.6V but they die off quickly, is a good indication that they have reached the end of their service life. If your yard has a conductance tester that will tell you for certain.

Take care,
Scott

[spemmons]

Sorry, I might not have been clear. The 13+ volt reading is at the alternator terminals. Testing voltage at the batteries before and after turning on the engine showed now change, just under 12v after running some stuff for a while -- expected a bump up.

That said, I have a ProTech4 battery charger that is mounted at an odd angle under the chart table -- I'm suspecting this was added some time later. Large heavy-gauge wires come from that unit to the house and engine switches then to the batteries (I have 2 house batteries and 1 engine battery). This charger works.

I read the several responses here after leaving the boat yesterday, so there is something I need to check again (boat is 1 hour away ).

The red wires I found coming from the alternator are not heavy gauge. I now know they run up into the small cavity where (I believe) the fuel line w/ cutoff makes a loop. They are un-terminated which I find alarming.

I do not think any heavy gauge wires run from the alternator anywhere, but I will check again -- and now I'm thinking maybe they do run to the engine batter (under port settee), and I've only been looking at the house batteries (under chart seat) -- doh!

[wolfe10]

Clearly with the previous owner's change in battery technology (I assume it was a previous owner), all bets are OFF as far as wiring.

What wire (color and gauge) do you have from the alternator's B+ terminal???

Alternators without smart regulators are NOT designed to charge LI batteries. Indeed, it may not be connected. This was NOT how the boat was wired from the factory (nor did they fit LI batteries).

[Olivia Mae]

Concerning the smaller charge wire from the alternator, it would go to the starter solenoid. Heavy red cable goes back from there. This article may help you. The graphic doesn't blow up well but you may get enough out of it to help. Your boat owners manual should have the wiring diagrams in the 3 ring binder. Sounds like yours has some modifications, so may not have the original configuration.

https://catalina350.com/technical/artic ... 0Nov05.pdf

[Olivia Mae]

Come to think of it...didn't you say that the wire from the alternator was just left loose and not connected to anything? Maybe someone replaced the starter or did some work on it and just never hooked it back up properly.

[man4sail]

How Are you measuring the output at the alternator? 13 volt output sounds low. As was mentioned, the stock alternator is a 10 not sure. Does the starter turn over ok? If so you have a good connection from the starter to the battery bank. I would then check continuity from the alternator output to the starter terminal. If that checks out, it’s not a wiring issue. I'm assuming you’re using a stock 55 amp alternator with an internal regulator. Did you ever shut off the key or the battery switch with the engine running? That would fry the alternator and the 13 volts would just be the battery voltage.

Let me know

[man4sail]

How Are you measuring the output at the alternator? 13 volt output sounds low. As was mentioned, the stock alternator is a 55 amp Mando or Prestolite and uses a AWG 10 wire from the alternator to the starter. The wire from the starter to the battery bank is a 1/0 or 2/0...not sure. Does the starter turn over ok? If so you have a good connection from the starter to the battery bank. I would then check continuity from the alternator output to the starter terminal. If that checks out, it’s not a wiring issue. I'm assuming you’re using a stock 55 amp alternator with an internal regulator. Did you ever shut off the key or the battery switch with the engine running? That would fry the alternator and the 13 volts would just be the battery voltage.

Let me know

[tmh]

Don't forget to check the external regulator too.
I am very much of a novice on all of this and maybe your issue is different, but I was having battery charging issues on the hook.
Very slow charging and low amperage
I replaced the 2 4-D batteries (not cheap), removed the alternator and had it bench tested (it was good), and checked all the connections (they were good)
Turns out it was the external regulator. Replaced it ($350-400)
All is fine now.

Mike
Irish Ayes

[spemmons]

I have some updates.

In answer to how the voltage was measured on the alternator -- I had a rigger helping me and he measured it on the 2 posts of the alternator with his multimeter I believe.

I've now figured out some things:

As I understand it, originally the boat had 2 house batteries which also served the engine and would have been connected to the alternator to charge them when the engine is running.

Someone in the past (I think I am owner #4) added a ProTech4 battery charger, 2 AGM house batteries, AND a separate engine battery. All of these are charged by the ProTech4 but I've learned that this charging unit will stop charging when ONE of the batteries is fully charged, potentially leaving the other batteries low -- not sure what to do about that...

The boat has an inverter that is disconnected -- not sure why, but I have a guess.

At this point I'm certain that the alternator does NOT have heavy gauge wires coming from it, BUT but the ProTech4 charger has VERY HEAVY gauge wires coming from it to the 3 batteries (in series, I believe).

I suspect that when the charger was added, and given that the boat has been primarily a day cruiser, whoever at the time made the change felt that the charger was sufficient and didn't bother to reconnect the alternator to any of the batteries -- I also suspect that this was when the inverter was disconnected because it makes no sense to use an inverter when the charger has AC power and it also makes no sense to use an inverter if you have batteries that cannot be kept charged by the engine.

I'm hauling the boat out before Thanksgiving for a new bottom job and to replace the cutlass bearing which the surveyor said has some "slop" -- I will take that opportunity to get a professional electrician to help review/revise the charging situation.

Any recommendations on how to configure this setup would be welcome. Thanks!

[wolfe10]

First, if the alternator B+ is not connected to a/any battery, the internal diodes will be blown. Said another way, the alternator will not function. It would be the same as turning off the battery switch with the engine running-- death to the alternator. But, even a relatively small wire to a battery or starter lug which is connected to the battery through the battery switch will keep it happy.

Any reasonable tech familiar with 12 VDC systems can wire your alternator/batteries/inverter to perform how you want them to (yes, assuming the components all function).

This is NOT rocket science. As you have already discovered, there is no "here is how they all should be wired". Much of the answer for you (just like previous owners) depends on how you intend to use the boat as well as the thickness of your wallet.

Let us know that and we can help. Example: if you will be doing a lot of motoring/long distance travel with some anchoring out, a smart regulator makes an excellent addition to a high output alternator. That combination will charge quickly (bulk rate) if at anchor and also will reduce charge voltage once battery charged on those long motoring days so you don't overcharge/boil the batteries. For occasional use, that set up would be significant over-kill.