Alternator voltage - regulator?

[Tom Richmond]

Hi there,

 

My alternator (Lucas 50/70 amp, not sure, running from Lister SW2 charging 3x100AH leisure and 1x75AH starter via relay) outputs a max voltage of 14.2v, on a good day with some revs, after a couple of hours of absorption. Most of the time it will not get above 14.1v.

 

I have recently installed a new shore power charger and spent time on shore power for the first time. Noticed the voltage going up to 14.6 or 14.8, and I am wondering if my alternator is doing what it should do?

 

Generally when charging I need to rev the engine up a bit over tick over to get the volts up. At start tick over will output 13.3v, but higher revs = 13.8v, then after a few hours tick over will give me 13.6v but higher revs will have reached 14.1v/14.2v). This is not so bad as increasing the revs a bit tends to induce less vibration throughout the boat.

 

Is there anything I can do to adjust it? Alter the regulator? And if so, how do I do this?

 

Is my tick over revs set right? Might I need to adjust throttle control to tick over a few rpm faster, or would this just cause unnecessarily high fuel consumption? My guess is that tick over should be as slow as engine can handle without stalling, but I am brainstorming here...

I CC for most of the year, and do have a genny which can/will be used to charge batts through the 240v charger. Is it enough to just top them up with a blast of this every week or two? I do also have 330W of solar, so certainly in summer only use engine to pump batteries full - which engine is doing badly! Often find that running the engine will only get bank up to voltage that solar was providing already (often 14v) but feel that it would appreciate more!

 

Thanks!

[blackrose]

14.2v max does seem a bit low (assuming you have open lead-acid batteries). 14.8v from your charger is right for open lead-acid batteries, but possibly too high for sealed batteries (other opinions are available).

 

My Lucas alternators put out 14.4v with their internal regulators but I have external Sterling alternator regulators which puts the voltage up to 14.8v.

 

If you don't want to install an external regulator you could try changing the alternator's internal regulator for a new one - easily obtained from ebay for a few quid and not that difficult to fit. You've just got to be quite gentle as you put them in as the brushes can snap very easily.

 

Check which regulator you need. This is the A127: http://www.ebay.co.uk/itm/LUCAS-A127-TYPE-ALTERNATOR-12V-REGULATOR-HD-FORD-MASSEY-PERKINS-CASE-131277-/180942047140?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2a20fc87a4

 

Edit: The other thing worth checking first is the belt tension. If it's slipping that could be the cause.

Edited December 28, 2014 by blackrose

[Tom Richmond]

Cheers BR,

 

Belt tension is good, and yes they are regular flooded batts.

 

What is involved in installing external regulators?

[blackrose]

Cheers BR,

 

Belt tension is good, and yes they are regular flooded batts.

 

What is involved in installing external regulators?

 

You're basically bypassing the internal regulator. It's not that difficult. There's lots of opinion on this forum (including Gibbo) that says they're unnecessary if your alternator already achieves 14.4v. However, many users (including myself) claim good results.

 

Personally I'd buy a couple of spare internal regulators first and see if they give you better results. The regulator fits in at an angle before laying square against the alternator and that's where the brushes are prone to snap as they are brittle and don't like any bending tension. Once you get the regulator square the brushes can be pushed in on their springs without a problem and the regulator can be screwed into position.

[Tom Richmond]

Great.

 

So, to confirm, I should be looking at 14.4v out of my alt (after a bit of time I assume?)

 

Any thoughts on tick over speed vs higher revs? Or do you think that I may achieve this voltage at tick over?

 

Looking forwards to trying to get alt off of front of engine to access regulator! Will have to run engine a bit first to warm it up down there...

[blackrose]

I just found this:

 

http://www.waterexplorer.co.uk/hosted/detailed-guide-to-installing-sterling-advanced-regulator-pdar.pdf

Great.

 

So, to confirm, I should be looking at 14.4v out of my alt (after a bit of time I assume?)

 

Any thoughts on tick over speed vs higher revs? Or do you think that I may achieve this voltage at tick over?

 

Looking forwards to trying to get alt off of front of engine to access regulator! Will have to run engine a bit first to warm it up down there...

 

14.4v or 14.5v will be the maximum from an internal regulator.

 

I would say your engine tickover speed should be determined by boat speed in gear and ease of handling, not battery charging. That is a secondary requirement.

Edited December 28, 2014 by blackrose

[MtB]

Great.

 

So, to confirm, I should be looking at 14.4v out of my alt (after a bit of time I assume?)

Yes, although battery charging is never simple. Your alternator may not be able to raise the voltage to 14.4 if the charging current is high, at the start of charging. In addition when I has similar probs on REGINALD, the alternator was chucking out 14.4v (IIRC) but the voltage at the battery terminals was about a volt lower due to a series of slight resistances in all the intervening electrical connections.

 

 

 

Any thoughts on tick over speed vs higher revs? Or do you think that I may achieve this voltage at tick over?

This is dependent on the ratio of your alternator pulley size to thew crankshaft pulley size. Once the alt is spinning fast enough to bung out 14.4v on its output terminals (about 2000rpm typically IIRC), running it faster will not increase voltage or output current. This is a feature of alternators, they can give full output as a small fraction of their max speed.

 

MtB

[nicknorman]

Regarding the tickover, this really should be set according to the engine manufacturer's recommendation. Whether or not the alternator charges at idle is not the primary consideration - after all, you can easily use the throttle lever to increase the revs above tickover for charging if necessary.

 

The minimum idle speed is not necessarily that which just prevents stalling. There are other considerations for the engine running below its design idle speed such as low oil pressure and possible torsional / resonance issues with the crankshaft, increased load on the conrod/bearings due to the fixed advance of the injectors, and probably a lot of other stuff.

[Tom Richmond]

OK,

 

So engine tick over all seems fine (taking charging out of the mix). I shall discard that series of thoughts, and focus on alternator output... Which leads me to think:

 

If, after replacing regulator, I am able to achieve 14.4v only by raising revs, should I then be looking at a different pulley ratio?

 

I understand that 14.4v will not be achieved immediately, and that there may be a drop in the system (though I have done work to eliminate this drop, which I hope to prove successful).

 

Cheers for your thoughts!

[nicknorman]

The revs needed depend on circumstances.

 

To initially get the alternator to charge at all, you need to increase the revs momentarily so that the alternator starts to produce its own excitation current. Typically you could then put the revs back to idle and the alternator would continue charging, but maybe only a bit.

 

So with the alternator charging, the revs needed depends on the load - ie how much current the alternator is required to produce. When you first start the engine in the morning, the batteries are low and can take the maximum current that the alternator can throw at them. You therefore ideally need to increase the revs until the current from the alternator reaches its maximum - more revs after that won't achieve anything except wasted fuel. However as the batteries become charged, they will accept less and less current and so the revs can be gradually reduced whilst still maintaining as much (reducing) current as the batteries will take. It might therefore be that at the end of the charging process, when the batteries are only taking a few amps, that the alternator will produce its 14.4v or whatever, at tickover.

 

This is why it is a good idea to have adequate monitoring equipment, ideally an ammeter but at least a voltmeter that can be read accurately to 0.1v or so. You can then see the optimum revs for the particular state of charge of the battery to minimise charging time whilst not wasting fuel.

 

If you find that you have to rev the engine quite high to get max output then yes, there may be scope to look at the pulley ratios. Trouble is, whilst the easiest thing to do is to make the alternator pulley smaller, you then increase the belt "pull" required whilst reducing the ability of the belt to transfer the "pull" to the alternator, and belt slip becomes a problem. So ideally increase the size of the crankshaft pulley, but that is sometimes easier said than done, as well as reducing the size of the alternator pulley.

[Tom Richmond]

Thanks Nick.

 

That all makes sense with what I already know (but fills in some gaps!)

 

I will fit new regulator, and then do a little research. And may look at getting an ammeter (at the moment I have voltmeter (to nearest 0.1v) installed in distribution panel). I have always had to increase revs to get max voltage out of alternator, at any and all SoC, but maybe this will change with better regulator.

 

Must be said the increase is minimal...

[by'eck]

The existing alternators voltage regulation can be increased cheaply using diodes if you feel confident in accessing connections to it. The whole issue is described in detail here

 

The advantage of using an external alternator regulator such as offered by Sterling or Adverc is that they can be programmed for varying battery types and offer a float mode when charging is complete, to avoid gassing etc.

[MtB]

May I hijack your thread? Any answers I get you'll probably find relevant or informative.

 

I also have a charging problem on ALDEBARAN which was disguised during the summer months by the solar panels.

 

My domestic batteries go flat remarkably quickly. I have two 100ah cheapy open cell batteries (purchased new about a year ago) in series. Yes, a 24v domestic battery bank but all the voltages from alternators etc are simply doubled. Yesterday morning for example they were down to 22.9v, 11.45v each battery. The morning before that they were at 20.4v having drained them completely the previous evening. 10.2v each battery.

 

This morning I started the engine and the charge voltage was only 26.2v. 13.1v per battery in series. No detectable cable losses or loose fan belt, the alternator is genuinely bunging out 26.2v. It was charging the domestics at only 9 Amps initially, falling after three hours to just 2.5 Amps. I think this suggests my 24v alternator is not working properly,

 

After charging the batteries for just three hours at 9 amps falling to 2.5 amps, I rested them for nine hours and their voltage was 24.6v, exactly 12.3v each. I think this charging behaviour indicates the batteries are also knackered. What does the team think?

 

Thanks,

MtB

 

 

(Edit to clarify/add some missing detail.)

Edited December 28, 2014 by Mike the Boilerman

[nicknorman]

May I hijack your thread? Any answers I get you'll probably find relevant or informative.

 

I also have a charging problem on ALDEBARAN which was disguised during the summer months by the solar panels.

 

My domestic batteries go flat remarkably quickly. I have two 100ah cheapy open cell batteries (purchased new about a year ago) in series. Yes, a 24v domestic battery bank but all the voltages from alternators etc are simply doubled. Yesterday morning for example they were down to 22.9v, 11.45v each battery. The morning before that they were at 20.4v having drained them completely the previous evening. 10.2v each battery.

 

This morning I started the engine and the charge voltage was only 26.2v. 13.1v per battery in series. No detectable cable losses or loose fan belt, the alternator is genuinely bunging out 26.2v. It was charging the domestics at only 9 Amps initially, falling after three hours to just 2.5 Amps. I think this suggests my 24v alternator is not working properly,

 

After charging the batteries for just three hours at 9 amps falling to 2.5 amps, I rested them for nine hours and their voltage was 24.6v, exactly 12.3v each. I think this charging behaviour indicates the batteries are also knackered. What does the team think?

 

Thanks,

MtB

Probably a diode or two gone in the alternator. Do you have a 'scope? If so the uneven waveform will be obvious. Yes it does seem as though the battery voltage is coming up fairly quickly considering the low current, but I would be inclined to fix one thing at a time. Fix the alternator, and then see how the batteries behave.

[MtB]

Probably a diode or two gone in the alternator. Do you have a 'scope? If so the uneven waveform will be obvious. Yes it does seem as though the battery voltage is coming up fairly quickly considering the low current, but I would be inclined to fix one thing at a time. Fix the alternator, and then see how the batteries behave.

 

 

Thanks Nick.

 

Yes I have a telescope thanks, where do I look?

 

 

MtB

[nicknorman]

Yes I have a telescope thanks, where do I look?

 

Try Uranus for a start (if you are a contortionist!).

[ditchcrawler]

OK,

 

So engine tick over all seems fine (taking charging out of the mix). I shall discard that series of thoughts, and focus on alternator output... Which leads me to think:

 

If, after replacing regulator, I am able to achieve 14.4v only by raising revs, should I then be looking at a different pulley ratio?

 

I understand that 14.4v will not be achieved immediately, and that there may be a drop in the system (though I have done work to eliminate this drop, which I hope to prove successful).

 

Cheers for your thoughts!

Fit some new pulley

[Tom Richmond]

The existing alternators voltage regulation can be increased cheaply using diodes if you feel confident in accessing connections to it. The whole issue is described in detail here

 

The advantage of using an external alternator regulator such as offered by Sterling or Adverc is that they can be programmed for varying battery types and offer a float mode when charging is complete, to avoid gassing etc.

That doc implies that some older alternators were only designed to output a low voltage (it says 13.8 I think). Might my alt be like that? If so maybe regulator is fine and it needs diodes? Or I should replace completely?

[MtB]

That doc implies that some older alternators were only designed to output a low voltage (it says 13.8 I think). Might my alt be like that? If so maybe regulator is fine and it needs diodes? Or I should replace completely?

 

Do you have a telescope?

 

 

MtB

[MtB]

But being serious, Nick asking if I have a 'scope prompts me to get one. It's of the few test instruments I have never owned or played with so I'm inclined to buy one regardless.

 

A brief poke about on ebay reveals these, which look completely brilliant compared to the briefcase sized devices we had at college:

http://www.ebay.co.uk/itm/Handheld-ARM-DSO201-PRO-Mini-Portable-Pocket-Size-Digital-Storage-Oscilloscope/200988737886?_trksid=p2047675.c100010.m2109&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D1%26asc%3D20140221143405%26meid%3D64e91ca782854d2c84402af1f7475a81%26pid%3D100010%26prg%3D20140221143405%26rk%3D3%26rkt%3D24%26sd%3D360559023322

 

What does the team (by which I mean Nick) think? Just the job for diagnosing a busted rectification diode, yes?!

 

 

 

MtB

P.S. Tom, if I buy it then we can use it to test your alternator rectification diodes too (different from the diodes Chris Gibson is suggesting for stepping up the regulator/charge voltage on the smartgauge website) should we ever get together to complete the geetar deal struck so long ago! Unless you have flogged them to someone nearer by now

[nicknorman]

But being serious, Nick asking if I have a 'scope prompts me to get one. It's of the few test instruments I have never owned or played with so I'm inclined to buy one regardless.

 

A brief poke about on ebay reveals these, which look completely brilliant compared to the briefcase sized devices we had at college:

http://www.ebay.co.uk/itm/Handheld-ARM-DSO201-PRO-Mini-Portable-Pocket-Size-Digital-Storage-Oscilloscope/200988737886?_trksid=p2047675.c100010.m2109&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D1%26asc%3D20140221143405%26meid%3D64e91ca782854d2c84402af1f7475a81%26pid%3D100010%26prg%3D20140221143405%26rk%3D3%26rkt%3D24%26sd%3D360559023322

 

What does the team (by which I mean Nick) think? Just the job for diagnosing a busted rectification diode, yes?!

 

MtB

My scope has one of those archaic things called a cathode ray tube, so I don't have any experience of these new fangled things that probably don't even have any valves in them!

 

Anyway, it looks quite good for the size and money. Limitations I note are: DC coupled only, and max input voltage is 80v pk to pk. If those limitations are OK then go for it but if you want to use it to look at mains voltage waveforms for instance, it can't do that directly.

Edited December 28, 2014 by nicknorman

[by'eck]

That doc implies that some older alternators were only designed to output a low voltage (it says 13.8 I think). Might my alt be like that? If so maybe regulator is fine and it needs diodes? Or I should replace completely?

Your OP suggested that the alternator may be regulating at 14.2 volts which is a tad low as suggested. However the mod may be beneficial as it will fool the alternator into regulating at something closer to 14.8 volts. This will allow useful charge current to be maintained longer, providing its run with enough engine revs to reach the higher voltage.

[MtB]

Ah yes, thermionic valves. My 1960s hifi amp has them. Lovely!!!!

 

Good point about the 240v applications, Mebbe I'll get a suitcase one after all. I like the way they glow out of the air vents in the dark...

[Arthur Brown]

OP

If your alternator has multi stage charge profile then it should get to 14.4 or so then drop back to a float voltage around 13.5v. Holding a battery at 14.4 or more kills it by gassing off the water (unless of course you top up the levels weekly).

If the alternator charges to constant voltage 13.8 isn't a bad voltage, it's more suited to someone genuinely CCing and doing 5+ hours a day and always keeping the battery full.

 

This is the difference between cyclic charging, and float charging.

 

MTB

it does seem as if your batteries now have about 30AH capacity which may mean end of life.

[Sir Nibble]

The existing alternators voltage regulation can be increased cheaply using diodes if you feel confident in accessing connections to it. The whole issue is described in detail here

This is what I would go for in this case if it is an A127 alternator. I have seen lots of listers still struggling on with ACRs and they do seem to be a bit borderline in terms of pulley ratio. I think to be properly helpful we need to sort out the actual machine type for sure?

 

Probably a diode or two gone in the alternator. Do you have a 'scope? If so the uneven waveform will be obvious. Yes it does seem as though the battery voltage is coming up fairly quickly considering the low current, but I would be inclined to fix one thing at a time. Fix the alternator, and then see how the batteries behave.

Certainly agree it sounds like a diode gone but I can usually diagnose that by watching the warning light! I've not put a scope on an alternator since I was an apprentice. What kind of machine is this Mike? Might be a good idea to remove the output lead and shove an ammeter in to see if the alternator is drawing current when stationary, often a failed diode will allow the battery to drain through the field.