Alternator - questions

[Sir Nibble]

I'm not going to go down the "I know more about alternators than you do" route. I'm sure that you are very knowledgeable.

 

You asked me for a reference, and I gave you one. "He's wrong." is not a reasoned argument.

 

It doesn't matter how many alternators Nick Billingham has repaired, serviced, or otherwise fiddled with, it has nothing at all to do with whether he is right or wrong. [Caveat: it may not have been Nick Billingham - only my recollection]. I'm sure he's aware that marine units are essentially the same as automotive ones. Actually, that's the whole point. They were designed for automotive use, not marine. So, derate the unit for marine use - or, in other words, overspecify it.

 

Narrowboat engines are usually tucked away in a badly-ventilated box in the bottom of a slow-moving steel container. Automotive alternators, however, are usually contained in a box which is pretty much open at the bottom and front, and whizzes though the air at an average speed of 30 mph (according to the computer in my car). I recognise that this is a generalisation and that there will be badly designed vehicle installations, too.

 

Taking your power consumption example and transferring it into a marine situation, I would not recommend a 50A alternator to do the job. I'd suggest a 75A unit would be more reliable.

I'm not going to go down the "I know more about alternators than you do" route.

Nor am I, but....

But, with all due respect, how many books on boat maintenance have you had published?

comes close.

 

It doesn't matter how many alternators Nick Billingham has repaired, serviced, or otherwise fiddled with, it has nothing at all to do with whether he is right or wrong.

I agree, same applies to....

But, with all due respect, how many books on boat maintenance have you had published

Automotive alternators, however, are usually contained in a box which is pretty much open at the bottom and front,

Not so, most if not all cars these days have "get-in-the-way-plates" enclosing the bottom of the engine compartment and modern buses and coaches are even more restrictive, air usually gets in through the radiator!

The point is, I have huge catalogues of components in front of me, I spend my life specifying, supplying and repairing alternators for both road and marine use, and marine alternators are not de-rated from their road going equivalents. There is anyway no way of de rating an alternator without using special lower output windings and they are not available, a 70A lucas marine stator is not a tuned down 90A road stator, it's the same part number!

[PaulG]

The point is, I have huge catalogues of components in front of me, I spend my life specifying, supplying and repairing alternators for both road and marine use, and marine alternators are not de-rated from their road going equivalents. There is anyway no way of de rating an alternator without using special lower output windings and they are not available, a 70A lucas marine stator is not a tuned down 90A road stator, it's the same part number!

 

I think that we are slightly at cross-purposes here. When I said "de-rated", I did not mean that they were modified in any physical sense to supply less current. They are not.

 

From Wikipedia:"Derating is the technique employed in power electrical and electronic devices wherein the devices are operated at less than their rated maximum power dissipation taking into consideration the case/body temperature, ambient temperature and the type of cooling mechanism used."

 

So what I meant was that they are derated from a specification point of view. i.e. If you have a 75 amp alternator, then assume that you can only safely draw 50A from it continuously.

 

Looking at it from the alternative point of view, if you need a 50A supply, then specify a 75A alternator.

Edited April 15, 2008 by PaulG

[Keeping Up]

Looking at it from the alternative point of view, if you need a 50A supply, then specify a 75A alternator.

I have a 70 Amp alternator. If I am cruising at a moderate speed when the batteries are low in the mornings, for up to an hour it supplies approx 55 Amps into them even if I disconnect the alternator controller (and it puts a little over 60 Amps into them if I leave it connected, which of course is what I do). It doesn't matter if I ask it nicely or shout at it to take it easy, it simply insists on doing the same thing; the only way I could draw a lower current from it would be to cruise everywhere at tickover speed.

[chris w]

I know that my ageing Lucas 45A jobbie gets very hot if run at anything near full output for any length of time. I've adjusted my alternator controller to allow about 25A max, and it's fine now.

 

That's interesting......................... how did you do that? The only way of doing it would be to run, say, wet cell batteries at the gel setting (14.4v) instead of 14.8v. If you are going to do that though, you might as well remove the alternator controller because it will be doing nothing.

 

An alternator controller is essentially a very simnple device - a voltage source in parallel with the alternator's own regulator. There is no way to turn down the current.

 

Chris

[Sir Nibble]

There is no way to turn down the current.

 

Chris

Quite, an alternator has a maximum output dictated by it's winding specification which is fixed. I am perfectly willing to believe that outputs are over specified, but in many cases marine engines will be supplied with a single 45-55A alternator and the supplier has no idea what sort of boat the engine is going into nor the conditions under which it will work, then the boatbuilder slaps a 120A second unit on! Narrowboat alternators tend to be the one with the biggest number on the label that the owner can find or afford, the output is if anything limited by our low canal speeds and that presents a cooling issue of its own.

[PaulG]

An alternator controller is essentially a very simnple device - a voltage source in parallel with the alternator's own regulator. There is no way to turn down the current.

 

Chris

 

Chris - I agree, my alternator controller is a relatively simple, unsophisticated device. But it does have a charge current limiting pot. When you turn it, it does what it says on the tin. The max. charge voltage is set by a seperate pot.

[MoominPapa]

Chris - I agree, my alternator controller is a relatively simple, unsophisticated device. But it does have a charge current limiting pot. When you turn it, it does what it says on the tin. The max. charge voltage is set by a seperate pot.

What sort is it? Are they still available?

 

MP.

[Sir Nibble]

By the way Paul, I note that you have only recently joined and I have been on (ahem) "sabbatical" so this is really our first meeting and re reading this I fear we may have got off on the wrong foot. I regret this very much.

I am as guilty as anyone of spouting recieved wisdom on subjects I know a bit about, and like most people I perhaps leap too readily to correct misapprehensions on things I know a LOT about. My quarrel really is with the author of your book, and who can blame you for believing him?

At the end of the day, this is my work, the "official" boats in Portsmouth harbour (Pilot, QHM etc) charge their batteries with my handiwork as do half the boats on the solent, and I assure you that there is no attempt whatever in unit selection or voltage setting to de rate marine units. On the contrary, they get well and truly thrashed!

[dave_2A_]

Off topic - but as you knowledgeable chaps are discussing (arguing about?) alternators.....

 

The one fitted to my Vetus engine is probably wrong/different as it doesn't have a connection for the rev counter in the instrument panel. No - I don't NEED the rev counter, but like things that are there to work. I seem to think that I should be able to take a feed for this from somewhere, but I can't remember where. Anyone point me in the right direction?

[Sir Nibble]

Off topic - but as you knowledgeable chaps are discussing (arguing about?) alternators.....

 

The one fitted to my Vetus engine is probably wrong/different as it doesn't have a connection for the rev counter in the instrument panel. No - I don't NEED the rev counter, but like things that are there to work. I seem to think that I should be able to take a feed for this from somewhere, but I can't remember where. Anyone point me in the right direction?

You are looking for an AC output. Without knowing the make and model of alternator it's difficult to be precise but you are looking for a terminal marked W, P, or N. If non exists, then you will have to open the machine up and solder a wire to one of the stator winding output leads. If this is the case, then if you can post the part number of the alternator or a pic I am sure I can help with a little guidance.

[PaulG]

What sort is it? Are they still available?

 

MP.

 

It's a Kestrel K90 made by Acorn Engineering. I'm not sure if they still make them. I wouldn't recommend one to you, as, IMHO, the're not very good!

[dave_2A_]

You are looking for an AC output. Without knowing the make and model of alternator it's difficult to be precise but you are looking for a terminal marked W, P, or N. If non exists, then you will have to open the machine up and solder a wire to one of the stator winding output leads. If this is the case, then if you can post the part number of the alternator or a pic I am sure I can help with a little guidance.

 

Thanks. Will be having a look tomorrow. Been more concerned with getting her home up to now.

[PaulG]

By the way Paul, I note that you have only recently joined and I have been on (ahem) "sabbatical" so this is really our first meeting and re reading this I fear we may have got off on the wrong foot. I regret this very much.

 

Hi Snibble. Don't worry - my wife says that I'm extremely thick skinned (or was it just thick?). I may have succumbed to the temptation of winding you up a bit, too, for which I apologise. I'm lighting the pipe of peace as we speak...

 

I am as guilty as anyone of spouting recieved wisdom on subjects I know a bit about, and like most people I perhaps leap too readily to correct misapprehensions on things I know a LOT about. My quarrel really is with the author of your book, and who can blame you for believing him?

At the end of the day, this is my work, the "official" boats in Portsmouth harbour (Pilot, QHM etc) charge their batteries with my handiwork as do half the boats on the solent, and I assure you that there is no attempt whatever in unit selection or voltage setting to de rate marine units. On the contrary, they get well and truly thrashed!

 

In that case we have a lot in common. I've been shouted at by the QHM in Portsmouth!

[MoominPapa]

It's a Kestrel K90 made by Acorn Engineering. I'm not sure if they still make them. I wouldn't recommend one to you, as, IMHO, the're not very good!

Ah, OK. Does anybody know if it's possible to do the same thing on an Adverc? The 70A Lucas alternator fitted to the FR2 is driven by a belt which wraps around the flywheel, so the pulley ratio is very high - I'd guess 8:1 or 9:1 from memory and without measuring it. That means that the Adverc can wind the alternator up almost to maximum output even when the engine is at idle. This is good for charging, but I think it may be overloading the engine. The governor opens the fuel-racks quite wide and the exhaust tends to smoke. If I could find a way of limiting the current that the adverc demands, that may be more healthy for the engine.

[Sir Nibble]

Ah, OK. Does anybody know if it's possible to do the same thing on an Adverc? The 70A Lucas alternator fitted to the FR2 is driven by a belt which wraps around the flywheel, so the pulley ratio is very high - I'd guess 8:1 or 9:1 from memory and without measuring it. That means that the Adverc can wind the alternator up almost to maximum output even when the engine is at idle. This is good for charging, but I think it may be overloading the engine. The governor opens the fuel-racks quite wide and the exhaust tends to smoke. If I could find a way of limiting the current that the adverc demands, that may be more healthy for the engine.

It's power mate, 'sgotta come from somewhere! Try a micro switch on the throttle linkage to shut off the adverc and revert to the standard reg when idling.

[PaulG]

Ah, OK. Does anybody know if it's possible to do the same thing on an Adverc? The 70A Lucas alternator fitted to the FR2 is driven by a belt which wraps around the flywheel, so the pulley ratio is very high - I'd guess 8:1 or 9:1 from memory and without measuring it. That means that the Adverc can wind the alternator up almost to maximum output even when the engine is at idle. This is good for charging, but I think it may be overloading the engine. The governor opens the fuel-racks quite wide and the exhaust tends to smoke. If I could find a way of limiting the current that the adverc demands, that may be more healthy for the engine.

 

Hi. I found the website for the Kestrel.

 

http://www.acornengineer.com/kestrel_alt_controller.php

 

As you can see, it's not a very sophisticated unit, but it does allow you to adjust the max charge voltage (and I certainly WOULD change this from the factory-set 15.5V) and the max charge current. I suspect that your current Adverc unit is better.

[Sir Nibble]

I am quite interested in the idea of adding current regulation, both how, and more importantly why? I have encountered one CAV system with a fully enclosed alternator which incorporates current regulation. It does of course require a shunt in the charge cable and I presume Paul's regulator does connect to a shunt.

 

Edited to say:

I have just looked at the kestrel on Paul's link, a batteries best friend? at 15.5V? I note also that the device switches off when bulk charge is complete. I prefer my £20 adjustable reg. On the subject of which, Diesel Duck's charging system which I started by modifying for slow speed has had one of these added and adjusted to a steady 14.8V and he now declares that charging is no longer an issue for him. Which isn't bad considering we started with batteries permanently discharged even after a days cruising.

Edited April 16, 2008 by snibble

[PaulG]

I am quite interested in the idea of adding current regulation, both how, and more importantly why?

 

Hi Snibble. At the risk of reopening old wounds, the K90 installation instructions say "We advise you to never set a charging rate which is more than about 2/3 of the alternator capacity. ie if you have a 55amp alternator, do not set the charging rate higher than approx 30amps. This is to compensate for the fact that Boat Engine alternators are usually very poorly cooled."

 

Don't shoot the messenger! That's just what it says!

[RobinJ]

Hi Snibble. At the risk of reopening old wounds, the K90 installation instructions say "We advise you to never set a charging rate which is more than about 2/3 of the alternator capacity. ie if you have a 55amp alternator, do not set the charging rate higher than approx 30amps. This is to compensate for the fact that Boat Engine alternators are usually very poorly cooled."

It also says that charge rate should be set to 10% of battery capacity, the two may not be equatable with a small alternator!

Another reason is that it operates in parallel with the internal controller, so initially at any rate it could be operating all full capability and getting quite hot!

The reason why 15.5V sounds quite high, is because at C/10 the 100% charge voltage of a normal wet lead acid is 15.5V, but it is adjustable to individual requirements, as is the charge rate.

Although performing a relatively simple function i.e. delivering a single bulk charge to obtain maximum charging cabability from a simple alternator system at startup, it does need some complicated electronics to accomplish it.

If you want more than this you pay for it.

[Sir Nibble]

Hi Snibble. At the risk of reopening old wounds, the K90 installation instructions say "We advise you to never set a charging rate which is more than about 2/3 of the alternator capacity. ie if you have a 55amp alternator, do not set the charging rate higher than approx 30amps. This is to compensate for the fact that Boat Engine alternators are usually very poorly cooled."

 

Don't shoot the messenger! That's just what it says!

I wouldn't trust the technical expertise of anyone who thinks it reasonable to charge batteries at 15.5V! But what interests me is

We advise you to never set a charging rate which is more than about 2/3 of the alternator capacity

How does the controller know what current is flowing? There is I presume a shunt?

[MoominPapa]

Hi Snibble. At the risk of reopening old wounds, the K90 installation instructions say "We advise you to never set a charging rate which is more than about 2/3 of the alternator capacity. ie if you have a 55amp alternator, do not set the charging rate higher than approx 30amps. This is to compensate for the fact that Boat Engine alternators are usually very poorly cooled."

 

Don't shoot the messenger! That's just what it says!

I've had problems with "that toasty alternator smell" from my A127 when it's working hard. It's in an engine room and therefore should be well cooled, but on dismantling it, I found large amounts of fluff and crud blocking the airways. Hopefully with that cleared it will cool OK. Hobson's choice: cook the alternator in an engine compartment and keep it in an engineroom and have it collect hair, fluff and dust from the domestic activites aboard.

 

 

MP.

[RobinJ]

But what interests me is How does the controller know what current is flowing? There is I presume a shunt?

It doesn't (as its not intelligent), it is set to match the alternator it is supplied for, or adjusted during installation, so for a 40A alternator the field current will be set to deliver about 25A. To overcome any conflict with the internal controller delivering full capacity at initial startup there is a delay built in.

[PaulG]

The reason why 15.5V sounds quite high, is because at C/10 the 100% charge voltage of a normal wet lead acid is 15.5V, but it is adjustable to individual requirements, as is the charge rate.

 

Hi Robin

 

Conventional wisdom seems to suggest 14.8V as typical for a wet lead/acid battery. Can you explain this a bit more?

 

Thanks

[Keeping Up]

I too had a K90 once upon a time, and even fitted them to several people's boats. At that time it was the best thing around. but 1990 is a long way behind us.

 

While I had it fitted to our boat it burned out numerous light bulbs, destroyed countless fluorescent light tubes, and set fire to a relay, because of the high (15.5) charging voltage. It was stubbornly unreliable, being constantly tripped out by the spikes that were generated whenever any appliance was switched on or off (the water pump was the worst culprit) so that the only way to charge the batteries properly, was to keep resetting the blasted thing (and as it was inside a cupboard that I couldn't reach without leaving the tiller, that was a right pain in the ar$e too).

 

Thankfully the Adverc controller came along soon afterwards, at which pont the K90 becasme obsolete. If I had one now, it would be heading for the rubbish bin as fast as I could throw it.

[PaulG]

If I had one now, it would be heading for the rubbish bin as fast as I could throw it.

 

Sadly, I've got other calls on my boating cash at the moment. But the K90 is gradually working its way up the list of replacement kit.