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Old 01-01-2021, 03:00 AM   #1
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How crucial is an alternator?

Noticed several weeks back when doing night passages we weren't getting charge into our house bank, so figured the VSR had died, but there was no evidence of smoke escaping.

Did some rudimentary tests, (check start batt voltage prior to start and after) and it seemed the alt was OK as volts were slowly climbing so got onto Victron, made a warranty claim and had a new one sent out , fitted it and......still no joy.

Realised after the fact that I have trickle charge wire off of the inverter/charger to start giving the impression of alt charge. (Old VSR back on, new one ready to send back after all sorted)

Have now disconnected and taken off alt altogether in anticipation of getting somewhere to get it tested when businesses open again but now about 6 weeks in and , even though I will get it sorted, just how crucial is that alternator?

Seems ours is a single wire unit so never actually fired up until at a certain RPM, so never helped with anchor retrieval either, yet 4+ years on of daily use and it seems to be working.
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Old 01-01-2021, 05:39 AM   #2
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My engines suck a fair bit of juice as the injectors have their own ECU's as well as the master engine ECU. Your engine I think has mechanical injection so will need a lot less, but may still need some to run? If you can get sufficient current into the engine (start) battery to meet running needs, either via genny or solar, then an alternator is not really needed although I would think of that as a short term solution.

But I would regard it as an opportunity: now is the time put in a large frame engine alternator with an external programmable regulator. Set it to charge house bank first then an ACR to the start battery. I have 2 x 200A alts, and ditched the gennies! With up to 400A available a short run in the morning to a new anchorage plus some solar later puts the house bank into float even if it was fairly deeply discharged.
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Old 01-01-2021, 07:18 AM   #3
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On most engines the alt is belted from the water pump. It needs to spin if it helps anything else to function.

"Seems ours is a single wire unit so never actually fired up until at a certain RPM, so never helped with anchor retrieval either, yet 4+ years on of daily use and it seems to be working."

The single wire unit should be replaced with one with a remote field voltage regulator ,

IF you desire to shorten the time to recharge the batts.


A large frame 130A-150A should run under $150 at a truck parts store , extra will be the V regulator , the pulley to match your V belts and perhaps a directional fan blade.
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Old 01-01-2021, 07:46 AM   #4
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My engines suck a fair bit of juice as the injectors have their own ECU's as well as the master engine ECU. Your engine I think has mechanical injection so will need a lot less, but may still need some to run? If you can get sufficient current into the engine (start) battery to meet running needs, either via genny or solar, then an alternator is not really needed although I would think of that as a short term solution.

But I would regard it as an opportunity: now is the time put in a large frame engine alternator with an external programmable regulator. Set it to charge house bank first then an ACR to the start battery. I have 2 x 200A alts, and ditched the gennies! With up to 400A available a short run in the morning to a new anchorage plus some solar later puts the house bank into float even if it was fairly deeply discharged.
Question for you. Putting such a charge into your batteries, won't that shorten there life. Granted, the bigger the bank the less this would be a problem.
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Old 01-01-2021, 08:24 AM   #5
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some alternators have magnets in the fields that require a brief higher than idle speed to get them started. run up to 900 RPM or so and see if it kicks in.
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Old 01-01-2021, 08:40 AM   #6
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Have now disconnected and taken off alt altogether in anticipation of getting somewhere to get it tested when businesses open again but now about 6 weeks in and , even though I will get it sorted, just how crucial is that alternator?
If you're living on the hook, and have enough solar, it may not be critical, but options are always good, especially when they already exist. If something renders your solar inoperable, having more than one alternative is definitely a good thing. I second the large frame alternator and external regulator. When cruising every other day, my batteries are maintained solely by that system.

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Old 01-01-2021, 08:47 AM   #7
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If you have a non electric assisted diesel and some solar, you don't need the alternator to run. However, your gauges may not work.

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Old 01-01-2021, 08:59 AM   #8
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If you have a non electric assisted diesel and some solar, you don't need the alternator to run. However, your gauges may not work.

pete
Pretty sure the gauges will work as he will need to recharge the starter battery, probably from the solar panels. No reason the gauges won't work from the same power source.

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Old 01-01-2021, 11:17 AM   #9
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Pretty sure the gauges will work as he will need to recharge the starter battery, probably from the solar panels. No reason the gauges won't work from the same power source.

Ted
Maybe what Pete meant is the tach might not work since so many older diesels use the alternator to provide the tach pulses?

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Old 01-01-2021, 12:26 PM   #10
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I have a large house bank. If my alternator were to die I would probably not know for years. I don’t have a solar option so it would take one of those multi day round the clock coastal transits before I noticed my batteries were low. Then I would fire up the generator for a 4 hour recharge and all would be fine again. So, on my boat an alternator is completely unnecessary but I think I’ll keep them anyway.
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Old 01-01-2021, 12:29 PM   #11
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The alternator is just a source of charge. If you have a genset running all the time, it can supply that charge. If you have solar and it's daytime and sunny, it can supply that charge. Many older diesels can run without an electrical system at all, once started (and starting takes minuscule energy). Since you've gone 6 weeks and haven't missed it, your boat is probably one that can live without it, but that is pretty unusual for modern boats.

My sailboat is a bit similar: it is a mechanical diesel with a 12V system, the rest of the boat is 24V. The alternators on the engine charge the house bank, not connected to the engine electrical. The engine is run from a small DC-DC down converter, just keeps the instruments alive and the fuel shutoff solenoid open. Been that way since we built it.
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Old 01-01-2021, 01:34 PM   #12
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As long as we're talking about alternators, I haven't been able to find an answer to this question if somebody has a minute. Our twins (Marine Power/GM 454, EFI) both have the original 55 amp alternators. The port side isn't putting out like it should (12.5v) according to the volt meter. I did swap the voltmeters at the upper helm to make sure it wasn't a bad or sticky gauge and still got 14v for starboard, 12.5v for port (at 1200 rpm, our fuel consumption sweet spot and the speed we run most comfortably; I know that's a low cruising rpm according to some advice). Anyway the boat's a '96 so I figure 25 years is a good run for alternators so I'm thinking of replacing at least the weak one. Even if I'm wrong and the port alternator isn't failing, 55 amp is pretty wimpy. I've been thinking of Ballmar but boy they're expensive. So here's the question: does it make any difference or hurt anything if I replace just the weak one, or should I replace them both? I just don't have a natural talent for electrical systems and I know some of you are experts. Thanks.
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Old 01-01-2021, 01:45 PM   #13
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Do both alternators change the same batteries?

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Old 01-01-2021, 01:54 PM   #14
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My old mechanical engine doesn't have an altenator.

My 12v house is totally separate to this engine and the 24v start batteries are topped up by my larger genset's altenator when ever it is started. I've also got house to AC to battery charger as a fall back option. My guages work fine and my coolant water pump is belt driven, though the belts are much shorter than normal.

I'm actively looking at options to simplify my 415, 240, 24 and 12v electrical system. This will likely include the removal of the 24v/415v noise generator and have any remaining 24v house loads supplied by dcdc converter and the start battery predominately topped up by solar with the existing AC charger as a back up. Any extended cloudy days or zombie apocalypse will be catered for by my large house bank or small portable genset.

I'll then have no main engine/start bank altenator and dont see any reason to buy and retrofit one.
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Old 01-01-2021, 02:04 PM   #15
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Originally Posted by Insequent View Post
But I would regard it as an opportunity: now is the time put in a large frame engine alternator with an external programmable regulator. Set it to charge house bank first then an ACR to the start battery. I have 2 x 200A alts, and ditched the gennies! With up to 400A available a short run in the morning to a new anchorage plus some solar later puts the house bank into float even if it was fairly deeply discharged.
Pretty sure it is a large frame alt there now, but also pretty sure it was only 45amp same shape as below
No labels, no markings, the one sticker painted over at factory



I can get a new Delco 100amp replacement for around $400, but may have better luck getting a 150amp when everyone is back at work

While looking came across this 150 amp model for $3500
Must have golden innards
https://www.keoghsmarine.com.au/mast...g-sur-48524150
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Old 01-01-2021, 02:08 PM   #16
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Originally Posted by Pete Meisinger View Post
If you have a non electric assisted diesel and some solar, you don't need the alternator to run. However, your gauges may not work.

pete
All gauges work inc tach.

Like I said, it was several weeks of use before I even noticed

Big solar array and inverter/charger has a trickle charge start battery wire
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Old 01-01-2021, 02:15 PM   #17
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I am just going to add that alternators sometimes are a critical piece of equipment as F.F. printed out.

Some engines, as Simi found out don't need it, for the actual operation of the engine. Although Simi, depending upon your injection system, it may require voltage to hold the fuel valve open for running. As long as the rest of the system looks after that function you should be OK. Cummins 855 uses the PT system which often/usually had an electrical fuel control valve which needs DC voltage to hold it open. THere is an over ride as long as you know about it.

But depending upon the engine it may be much more critical. Alternators also have bearings which can fail.

Many engines incorporate the alternator drive AND the coolant water pump drive on the same belt[s]. Removal of the alternator is not possible unless you have had the foresight to purchase different length belts to allow for no alternator but still run the coolant pump. That may still not cut the mustard as usually the alternator is ALSO the belt tension adjustment point. Without the alternator or a suitable work around you still can't run the engine without overheating it.

Which means there are two failure possibilities depending upon the engine.
Failure of the electrical power production but also the bearings.

That is why I carry my old but still viable alternator as a spare as I have one of the engines that NEED the alternator bearings.

Have a look at your engine to see what that alternator is also hooked up to and is driving. That alternator may be more important than many of us realize. Especially if you wander into remote areas..

Now not to start a panic these things are usually quite long lived, 10+ yrs. of regular and reasonable use.

Of course the need now for high outputs can change that unless the alternator is one that was built for that use.

A hot rodded stock alternator may not last as long from too much heat.

But just be aware that the alter. should be serviced also, brushes, new bearings, check for winding overheating. If you are handy new bearings are not hard but will require a few tools depending upon the alternator mfgr.

Just my thoughts
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Old 01-01-2021, 02:15 PM   #18
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Quote:
Originally Posted by FF View Post
"

The single wire unit should be replaced with one with a remote field voltage regulator ,

IF you desire to shorten the time to recharge the batts.
Is this going single wire to 3 wire?
I did find a brand new Delco 100amp 3 wire I can get here from the US for about 50% of the cost of same here
But getting the 3 wire system to work is beyond my pay grade
And paying someone to get it to work negates any saving.


Quote:
A large frame 130A-150A should run under $150 at a truck parts store , extra will be the V regulator , the pulley to match your V belts and perhaps a directional fan blade.
It should, but its Australia
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Old 01-01-2021, 02:16 PM   #19
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Depends on how the boat is wired and what equipment.

I do diesel engine surveys and it is very often that I find alternators not working. This flabbergasts the owners as they say they never have a problem with low batts. Well that is because they run the gennie all the time and the AC charger takes care of the batts.

Nothing wrong with that, batts stay up just fine. Until the gennie or charger takes a poop. Now you have a problem if alt is out.

It's nice to have multiple ways of providing DC power. Nice to occasional check batt volts with engine running and charger off.

Some boats have had multiple owners add multiple DC systems, no wiring diagrams, cables running all over, some batts charged by something, more batts added and I do my simple test (engine on, charger off) and some batts are showing charge volts, some not. Buyer asks how does this system work? I respond I have no clue without tracing each cable and drawing a schematic. Big friggin' headache. Worst offenders are gadget crazy electrical engineers (just kidding, sort of...).
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Old 01-01-2021, 02:44 PM   #20
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I am just going to add that alternators sometimes are a critical piece of equipment as F.F. printed out.

Some engines, as Simi found out don't need it, for the actual operation of the engine. Although Simi, depending upon your injection system, it may require voltage to hold the fuel valve open for running. As long as the rest of the system looks after that function you should be OK.
As mentioned, its been running fine for weeks so obviously the 2 big truck start batteries with 24v trickle charge are coping


Quote:
Cummins 855 uses the PT system which often/usually had an electrical fuel control valve which needs DC voltage to hold it open. THere is an over ride as long as you know about it.
I know it is there, have read about it but was filed in the not important section of my brain - manual is onboard if I need it

Quote:
But depending upon the engine it may be much more critical. Alternators also have bearings which can fail
.
Funnily enough I did notice unusual noises coming from the alt a month or 3 back but was not in a position to do anything about it.
Now the alt is off it spins freely so I suspect it wasn't bearings
Will find out when we get it tested.

Quote:
Many engines incorporate the alternator drive AND the coolant water pump drive on the same belt[s]. Removal of the alternator is not possible unless you have had the foresight to purchase different length belts to allow for no alternator but still run the coolant pump. That may still not cut the mustard as usually the alternator is ALSO the belt tension adjustment point. Without the alternator or a suitable work around you still can't run the engine without overheating it.
With ours there is a big pulley driving 3 belts.
1 serpentine belt with its own adjustment point and also 2 v pulleys to the alt which is their adjustment point, so all good.
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