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calon

Alternator ( am I expecting to much)

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Hi, 

 Our new boat has a dm2 with a niehoff a1 104 80amp alternator, now I know it's got it's work cut out with 5 110 leisures and 2 bow thrusters 1 starter , but I've not been seeing the charging I was expecting with low battery's this morning it doesn't kick in at tick over and at cruising only seems to put out 20ish amps despite whining quite loudly about it , the belts a thick ribed job round the flywheel so the ratios big and the belts tight so I assumed I would see nearer the full 80a output breifly at start up with the engine at cruising speed reducing as the battery's charge but I'm not I think the most I've seen is 30amps as measured by the mastervolt panel but if I put the Genny on and the charger that does put in 100amps to start so I am taking that as the panels accurate .

I've previously had modern engines with twin alternators so the trad engine and split charge systems new to me am just expecting to much and need to accept that even when cruising I need to use the genny/charger or do you think there is a problem with the alternator/regulator .

Thanks Sam 

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Hi, thanks for the reply.

I went through looking at connections found one loose nut on an isolator tightened that yesterday no change today . Alternator has a  niehoff a2 102 regulator on it .

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3 minutes ago, calon said:

Hi, thanks for the reply.

I went through looking at connections found one loose nut on an isolator tightened that yesterday no change today . Alternator has a  niehoff a2 102 regulator on it .

Time for the experts---

The link I gave you above has one or two hints that might help (as in re- energising the field coil)

In passing an 80 amp alternator seems a bit small for your large battery bank to me? The experts may advise... 

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Thanks for the link that's handy I see from the table the voltage shouldn't be below 13.8 that was definitely only 12. Something I can't remember exactly sorry to start with today raising to 13. Something later in the day I'l have a better look at voltages tomorrow as well . I see it gives instructions on the link to reestablish the magnetic field perhaps that's worth a try as well

Thanks for the help

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I have a DM2 with Neihoff alternator driven from flywheel too. Mine does very little at idle, but happily puts out 50amps into batteries first thing in the morning at say 400rpm upwards. Voltage at that stage is 13 point something. After a 3-4 hours voltage is up to 14.1 and say 8 amps. I’m not sure which model Neihoff it is, but I have in my head it is rated at 60amp. Battery bank is 675ah. A second alternator does the engine battery. Oh and it whines like a teenager.

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A thought, is the mastervolt panel, getting a reading that is only coresponding to part of the output of the alternator? Not sure how it is all wired up, but could some of the amps be bypassing the shunt (assuming that is how the Mastervolt works) to go to say bowthruster batteries?

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thanks it does sound like there's a problem with mine then I will try the reestablishing the magnetic field as per old goats link tomorrow then ( ived had the genny/ charger going for a bit now so  the battery's will be fairly charged and at a high voltage anyway now) and hope for the best.

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I had a big Leece-Neville 24v unit that needed energising - even with a tiny current (that's usually supplied via an indicator lamp). Without the connection, I got some charge, but norra-lot. As soon as I replaced the generator lamp (in the panel) with a larger bulb everything worked fine. There was usually enough residual magnetism in the alternator to self energise, but if I left the boat for several weeks that disappeared  and it wouldn't charge. Took me a while to realise...

(My boat is 24V but the control panel runs at 12V - so I'd lazily left the lamp connection off.) 

 

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OK I tried re-energizeing the magnetic field but that's not fixed it unfortunately this morning with the engine in neutral at cruising speed the meter climbed to 12.9v and 22amps I assume from what I've read I should be seeing the regulators lower voltage of 13.8v and a higher ampage to start ?

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An alternator has 3 static windings inside and uses 6 diodes to turn the AC into DC. If some of the diodes have burnt out you will get lower output. The only way to test this is to open up the alternator.

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80 amp is also working very hard. We have only  2 leisure and one start battery and a 70 amp alternator, and we see 40 amps once the engine revs are high enough to trigger the alternator. We have an advec fitted and this causes the alternator to get very warm, if we throw in big loads early in the recharging process. This has in the past caused diode failure due to heat.

given your massive batt pack  and low voltage under charge suggest you may have already had this.

 

our last ‘living boat’ had 6 batts plus start. When we got it it had a 45 amp alternator and was hopeless. ( we discovered the owner only used it for one day trips and had a shoreline. We put on a 140 amp alternator big pulley and advec. A weeks sitting and then starting up would put so much load on the engine we used to wait at least 20 minutes before going into gear or raising the revs too much because of the howling from the alternator belt. Both boats have lister hbs in. However in 5 years we never blew another alternator in spite of the advec hitting 14.4 volts by the third cycle.

 

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1 hour ago, rogeriko said:

An alternator has 3 static windings inside and uses 6 diodes to turn the AC into DC. If some of the diodes have burnt out you will get lower output. The only way to test this is to open up the alternator.

Correct plus three more small diodes to provide the rotor current once it has started charging but alternators (and most other charging devices) will lower the charging voltage as the charging current rises so before stripping the alternator we really need to know both the charging voltage and the charging current.

 

A further complication is this dual output regulator. I would expect the lower voltage to be a float voltage that will only come into play once the charging voltage has fallen to a suitable level but the document linked to is silent (as far as I can see) on this topic so I don't know when to expect 13.8 and when to expect 14.5. It si even possible the 13.8 to 14.5 MIGHT refer to the range within in which the regulator will be set to.

 

However from the figures quoted I also suspect a diode problem but the  OP needs to check both the positive and negative charging paths for voltdrop at highish engine revs first thing in the morning. Voltmeter battery post lead to alternator B+ and then battery neg to alternator B- or case. If both are below 0.5V (0.3 V is better) then its definitely worth having the alternator looked at.

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Thanks for the help guys,  I'll check the charging paths as Tony suggests in the morning if I do need to get the alternator repaired can anyone recommend anyone that could do it I'm at shebdon embankment heading towards norbury junction at the moment then planning on going down the staffs and worcester

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Have a chat with David Ray in the office/shop at Norbury Junction.  He is usually helpful  and will know someone.

 

N

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Hi folks sorry I've not updated this for a while something came up. 

Anyway the saga continues sorry it's a bit epic but here goes having exhausted my testing knowledge I've given in and got a local yard to help here's what we've found , there's two completely knackered battery's and the other three arnt great the reason I had been misled about battery levels by the mastervolt micc panel the starter battery reads volts accurately but domestics reads half a volt high if any one has any idea how that can happen I'm all ears!  Without the knackered battery's in the alternator puts out 13.6v and up to 35a so better but still not what I would have expected from a 80a unit remembering the flywheel is 24inch the pullys 3inch .

The splitcharge diode looses 0.8v so that won't help at all if this alternator only outputing 13.6v the battery's are only seeing 12.8v it's not got alot to hammer those amps home.

Its looking like I've no real option but to splash out on new battery's and probably makes sense to change the splitcharge diodes for a sterling 0volt splitter at least the alternator stands a chance of charging a bit then but is there any way an alternatorcan have these symptoms basically working but at about half power? Dodgey regulator maybe?  There apears to be one dealer for nichoff in the UK so we will ring them Mon see if they have any ideas. 

Edited by calon

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I’m suspicious about the diagnosis. The symptoms you originally described, including that the charger would happily put 100A into the batteries, whilst the alternator can’t, aren’t explained by bad batteries. Exactly how did they determine that some batteries were knackered? How can removing knackered batteries increase the charge current? Does not compute.

 

You need to have an alternator that puts out an adequate voltage, 14.4 minimum after allowing for split charge diodes etc. Best to get rid of diodes, connect alternator to domestics direct and to engine battery via a split charge relay. Don’t buy new batteries until the charging is properly sorted, otherwise you will just kill the new batteries.

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Yes I know what you mean about the charging I do have a Genny to use if I need in the short term to look after them but I do agree the alternator needs sorting problem is these alternators seem to be a bit unusual the only place that deals with them is closed till Monday the battery's were all tested individualy , with hydrometer and a loadtester (I think that's the name the tool that goes across pos and neg ) the knackered ones dropped like a stone to 3 /4 v and to be fair just looking in the cell on one it's all cloudy if that's any indication .

 

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Perhaps another option is buying a new cheaper alternator now then I could look at getting this one sorted when I'm home in Sept and have a spare,  but Is there a reasonably priced straight replacement for these ones does anyone know? 

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55 minutes ago, calon said:

Its looking like I've no real option but to splash out on new battery's and probably makes sense to change the splitcharge diodes for a sterling 0volt splitter at least the alternator stands a chance of charging a bit then but is there any way an alternatorcan have these symptoms basically working but at about half power? Dodgey regulator maybe?  There apears to be one dealer for nichoff in the UK so we will ring them Mon see if they have any ideas. 

 

Do you have solar? If so the best way to go (and I would say this even without solar) is not to spend £s on branded Sterling electronic gizmos but to fit a Voltage Sensitive Relay wired as (I think) Nick said. They are totally automatic and will allow solar to charge both banks. The one I fitted to my boat last winter is branded Cargo and cost £40 ish. Probably can be had cheaper. Easy to test to see if its faulty, unlike some electronic stuff (although they do contain electronics). Keep things simple I say.

 

With batteries like that the alternator voltage is low probably because its delivering a massive output - as to be expected.

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The engineer measured the output of the alternator with a clamp meter on the output it read 36 amps  at it's highest and I then charged the battery's with Genny and charger and retested voltage the Max was 13.6 at the alternator .

No solar on this boat I could use a relay but it's split three ways (start, bowthruster and domestic so I thought a straight swap for the sterling unit would be easyier, I'l have a look at the relay option as well. 

Tried remagnetising no diffence unsure how to bypass the regulator it only has pod and neg lead to alternator and four wires from within alternator case to the plug on the regulator is it just as simple as unplugging the regulator and seeing what happens then?  

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