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Domestic alternator doing my head in.........


Bimbly1

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Don't know about grammar, but is measuring you engine speed in rmp equivalent to measuring current in amps per hour?

 

Nice One! Did you here about the man with CDO ? its like OCD but in Alphabetical Order.

 

..............Dave

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Oooer! I know I sound like a broken record but can I either have photos of the alternator or a manufacturers part number please? I want to know what sort of machine we're dealing with and what sort of regulator set up,(+ or-, battery or machine sensed etc).

I don't know about the regulator set up but I will take a couple of pics if I can't find the part no.

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If it is the same as the 110A alternator on my 2005 Barrus Shire 45 it is a Prestolite 35215315. Mine shows the same symptoms as the OP has reported.

 

This particular alternator is now obsolete and I haven't been able to identify a direct replacement.

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Pics as requested.

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If it is the same as the 110A alternator on my 2005 Barrus Shire 45 it is a Prestolite 35215315. Mine shows the same symptoms as the OP has reported.

 

This particular alternator is now obsolete and I haven't been able to identify a direct replacement.

 

I couldn't find any make/model/part no etc either on it or in the Barrus manual.

 

Meter readings as follows;

 

Alternator Battery

1300 revs 14.6volts 14.6volts

900 revs 15.0volts 15.0volts

1600 revs 14.6volts 14.6volts

 

Amps at Alternator: + cable -ve cable

1300 revs 0.62A 0.12A

900 revs 0.48A 0.26A

1600 revs 1.61A 2.42A

 

Amps at Battery

1300 revs 1.4A 0.6A

900 revs 1.2A 2.45A

1600 revs 5.8A 1.2A

 

Battery bank fully charged on landline prior to disconnecting to conduct this test.

I hope that the presentation is clear enough. I have no idea of what the figures might mean!

Bob

Edited by Bimbly1
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Well if I am reading them correctly there is something a bit odd in that irrespective of the alternator the current flowing (Amps) in the positive and negative cables should be the same. This could well be down to interference with the clamp by fields from adjacent cables or even the alternator itself. However the later would not explain the differences at the battery readings.

 

Edited to add: it might even be instructive to let the battery discharge some what and then see what happens rather that take readings when the alternator regulator may well be hunting because of fully charged batteries.

Edited by Tony Brooks
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Ampeaters used to nest and set up their ohms in the old dynamos yer know which were rented to them by the great and benevolent ''Mr Ernie Armature'' and when they were invaded by the dreaded Voltenforcer from the Central control box who tried to evict them and force the dynamo to turn like an electric motor when the cutout stayed cut in in the control box as the engine idled, the poor old Ampeaters would do great battle with them and ward them off with great venom by lashing out at em with the brushes which usually sent them arcing back. But since the demise of dynamos they had no alternative but to take up residence and make their ohms in alternators instead and to continue breeding baby Ampeaters. Hope this helps.

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Well if I am reading them correctly there is something a bit odd in that irrespective of the alternator the current flowing (Amps) in the positive and negative cables should be the same. This could well be down to interference with the clamp by fields from adjacent cables or even the alternator itself. However the later would not explain the differences at the battery readings.

 

Edited to add: it might even be instructive to let the battery discharge some what and then see what happens rather that take readings when the alternator regulator may well be hunting because of fully charged batteries.

 

Or likely the current measurement in negative lead was diluted by secondary return path via engine block, hull and hull strap back to battery negative, although that would be dependant on strap placement.

 

FWIW a recent thread on this issue confirmed courtesy of nicknorman, that battery negative strapping to hull should take the route: domestic neg - start battery neg - starter motor neg/casing (providing effective strap to engine block) - hull. That way there is no possibility of secondary path currents through hull if either the starter motor or alternator(s) don't have isolated returns.

 

TBH though, given fully charged batteries and their expected low current draw, the inaccuracies of a clamp-on meter will minimise any useful info from these readings. So yes agree that more meaningful higher readings will be gained with part discharged batteries as per your edit.

Edited by by'eck
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Edited to add: it might even be instructive to let the battery discharge some what and then see what happens rather that take readings when the alternator regulator may well be hunting because of fully charged batteries.

 

 

 

TBH though, given fully charged batteries and their expected low current draw, the inaccuracies of a clamp-on meter will minimise any useful info from these readings. So yes agree that more meaningful higher readings will be gained with part discharged batteries as per your edit.

 

Thanks for your thoughts and everyones input. I'm away for the next six weeks but will run the bank down a bit on my return and post the results again then.

Bob.

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Looks like the alts mentioned in this topic, Hitachi or some Korean make?

 

http://www.canalworld.net/forums/index.php?showtopic=69915

 

Anyway 0.5A at 15V into 4 batts doesn't sound toooo bad, but probably worth keeping an eye on.

 

cheers, Pete.

~smpt~

Thanks Pete, I'll be looking further when I return.

Bob.

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From the picture it does indeed look exactly the same as mine, which is the Prestolite 35215315. Makes sense as it sounds as though our engines are about the same age. Mine is 2005.

 

I was told that Prestolite used to get them made in South America but the factory closed down and they didn't bother to find another supplier.

 

Your voltage readings are broadly in line with mine (when the engine is warmed up) as well.

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Meter readings as follows;

 

Amps at Alternator: + cable -ve cable

1300 revs 0.62A 0.12A

900 revs 0.48A 0.26A

1600 revs 1.61A 2.42A

 

Amps at Battery

1300 revs 1.4A 0.6A

900 revs 1.2A 2.45A

1600 revs 5.8A 1.2A

 

Battery bank fully charged on landline prior to disconnecting to conduct this test.

I hope that the presentation is clear enough. I have no idea of what the figures might mean!

Bob

Looks like a hitachi. Furiously trying to visualise the inside of one of these. Will do some research as to regulation. This is a very strange "fault" and I theorised that there may be a poor connection dropping voltage in the field supply and the regulator if it senses from the same supply as is usual, would see a reduced voltage. The higher field current required at lower speeds would accentuate this volt drop and so actual output volts would rise as we have seen. However, and this is why I put "Fault" in inverted commas, there are two things which give me pause for thought. One very loud clue is that we have a chap here with the same set up reporting the same figures and I would say making comparison with a known good installation is a pretty good diagnostic tool. The other is the figures above. Where is the extra current coming from then? Now I get the impression that the OP is taking readings pretty competently so I wonder if there is a device bringing in both alternators and they are interfering with one another? Also, that is one very charged battery isn't it, the alternator is all but freewheeling.

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Looks like a hitachi. Furiously trying to visualise the inside of one of these. Will do some research as to regulation. This is a very strange "fault" and I theorised that there may be a poor connection dropping voltage in the field supply and the regulator if it senses from the same supply as is usual, would see a reduced voltage. The higher field current required at lower speeds would accentuate this volt drop and so actual output volts would rise as we have seen. However, and this is why I put "Fault" in inverted commas, there are two things which give me pause for thought. One very loud clue is that we have a chap here with the same set up reporting the same figures and I would say making comparison with a known good installation is a pretty good diagnostic tool. The other is the figures above. Where is the extra current coming from then? Now I get the impression that the OP is taking readings pretty competently so I wonder if there is a device bringing in both alternators and they are interfering with one another? Also, that is one very charged battery isn't it, the alternator is all but freewheeling.

The current figures are confusing, which is why I haven't attempted to analyse them. However I suspect I might be just down to the inherent inaccuracies of dc clamp meters. Which makes me wonder whether this whole thing is just a measurement issue caused in part by high levels of ripple at low rpm. In particular, that the voltage is higher but the current lower at idle vs 1600rpm only makes sense if it is a measurement issue.

 

Anyway, as said at those idle currents no harm is going to come to the batteries.

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The current figures are confusing, which is why I haven't attempted to analyse them. However I suspect I might be just down to the inherent inaccuracies of dc clamp meters. Which makes me wonder whether this whole thing is just a measurement issue caused in part by high levels of ripple at low rpm. In particular, that the voltage is higher but the current lower at idle vs 1600rpm only makes sense if it is a measurement issue.

 

Anyway, as said at those idle currents no harm is going to come to the batteries.

A measurement issue (interference from proximity to the alternator's magnetic influence?) or as I suggested perhaps there is another current source here and the load sharing between them is causing weird readings.
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  • 4 months later...

Well if I am reading them correctly there is something a bit odd in that irrespective of the alternator the current flowing (Amps) in the positive and negative cables should be the same. This could well be down to interference with the clamp by fields from adjacent cables or even the alternator itself. However the later would not explain the differences at the battery readings.

 

Edited to add: it might even be instructive to let the battery discharge some what and then see what happens rather that take readings when the alternator regulator may well be hunting because of fully charged batteries.

 

I have returned from an enforced absence, (not at HM pleasure, honest) and have now let the domestic bank discharge a bit.

 

Situation is as follows:

Batts left off shoreline charge for 3 days. Reading 12.9v. Discharged to 12.6v.

Engine run @ 1600rpm

Alternator readings

14.4v; 4 amp on +ve lead, 0.2 amp on -ve lead.

Bank readings

14.4v, 1.8 amp on +ve, 1.0 amp in -ve.

 

After six hours cruising:

Engine rpm 1000

Alternator readings

15.2v

0.5 amp +ve, 0.2 amp -ve

Bank readings

15.2v

0.8 amp +ve, 0.25 amp -ve.

 

I suspect that this may be a problem with something in the alternator, not picked up on the automotive bench test last October.

 

Any other thoughts please?

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Yes Pete, sealed. They have remained cool to the touch after running for 2 - 3 hours.

 

One should not allow 15V on a sealed battery, particularly some AGMs, for any length of time.

 

Experts may counter this opinion. If they do, then I will share their opinion.

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I have returned from an enforced absence, (not at HM pleasure, honest) and have now let the domestic bank discharge a bit.

 

Situation is as follows:

Batts left off shoreline charge for 3 days. Reading 12.9v. Discharged to 12.6v.

Engine run @ 1600rpm

Alternator readings

14.4v; 4 amp on +ve lead, 0.2 amp on -ve lead.

Bank readings

14.4v, 1.8 amp on +ve, 1.0 amp in -ve.

 

After six hours cruising:

Engine rpm 1000

Alternator readings

15.2v

0.5 amp +ve, 0.2 amp -ve

Bank readings

15.2v

0.8 amp +ve, 0.25 amp -ve.

 

I suspect that this may be a problem with something in the alternator, not picked up on the automotive bench test last October.

 

Any other thoughts please?

The bits in red are not possible (Kirchoff's law). Do you have more than one wire on maybe the -ve?

Sounds like it needs a reg, some component or connection devaluing with heat. Thing is I just keep coming back to the matching readings from a known good system. I would like to get a look at this purely for academic interest

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The bits in red are not possible (Kirchoff's law). Do you have more than one wire on maybe the -ve?

Sounds like it needs a reg, some component or connection devaluing with heat. Thing is I just keep coming back to the matching readings from a known good system. I would like to get a look at this purely for academic interest

Thanks for that. I agree with Loafer's comment and need to get this sorted before a battery redistributes itself around the engine 'ole.

 

I caught more than one wire in the clamp on the neg but unclamped it. Maybe I didn't reset the meter properly. I'll try again tomorrow and post the results.

 

Should the readings from positive & negative be the same, regardless of whether taken from the back of the alternator or the battery bank?

Edited by Bimbly1
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I caught more than one wire in the clamp on the neg but unclamped it.

 

I may be reading this wrong and apologise if I have done so.

 

The cable being read, by the clamp ammeter, should go through the centre of the 'ring' of the meter, not clamped in the jaws.

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I may be reading this wrong and apologise if I have done so.

 

The cable being read, by the clamp ammeter, should go through the centre of the 'ring' of the meter, not clamped in the jaws.

 

Thanks for that thought. I confirm that the cable being read is in the centre of the clamp-meter and not in the jaws. However, I had a "light-bulb" moment this morning. I balanced the bank a few years ago, so the +ve & -ve feeds are at opposite ends. I have been reading the -ve from the wrong end. Shame and embarrassment blush.png, should have checked more closely. I am a complete and utter cretinous numpty and must do better.

 

I've put the charger on to top the bank up and tomorrow I'll check the alternator output again, with the bank fully charged, the clamp meter on the right cables, (one at a time), the right way round anda post the results.

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I am a complete and utter cretinous numpty and must do better.

 

Would you like some Birch twigs. laugh.png

 

You're not the first and will not be the last do something like that.

 

???

 

No, I am not telling.biggrin.png

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