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#376339 - 05/30/11 7:15 pm Alternator wiring  
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plonkerboy Offline
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Firstly, thanks to all who replied to my 'battery charging' query - I've opted for a Boyer Bransden powerbox.
I suspect that my 1965 A65 Lightning has had a new 12v alternator fitted as the 3 wires from it aren't colour coded. I think that I've managed to work out which is which by putting a multimeter across the wires and measuring the resistances viz:- 1.8, 1.2 and 0.6 ohms so it seems easy now to identify the black, yellow and white cables.
Is this the normal way to do it or is my thinking all wrong? I'd hate to buy a powerbox and ruin it!!

Last edited by plonkerboy; 05/30/11 7:19 pm.
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#376383 - 05/31/11 12:40 am Re: Alternator wiring [Re: plonkerboy]  
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Stuart Online content
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Hi,

Originally Posted By: plonkerboy
new 12v alternator fitted as the 3 wires from it aren't colour coded.
black, yellow and white cables.

confused How do you work out they "aren't colour coded"? They might not be the same colours as the original Lucas stator but that they are different colours means ime you need to proceed very carefully before connecting anything else to it. Imho, your next steps should be to try and identify the stator maker, contact them and identify exactly what you do have.

Alternatively, you might have a Lucas stator but, at some point in its life, a p.o. has replaced the original Green/Yellow, Green/Black and White/Green wires with the three you have. Imho, you need to identify with absolute certainty which current colour corresponds to which original before proceeding further.

Finally here, there's another way of telling at least between single- and 3-phase stators - single-phase have six coils and 3-phase have nine; if the coils themselves aren't visible because of encapsulating material, their ends are visible as slightly raised areas in the inside diameter of the stator, where the rotor fits in use.

Originally Posted By: 1968BSA
there are 3 alternator types, 6v

Nope. The Voltage of a vehicle electrical system is down to the regulation, nothing to do with the alternator.

Aiui, a '65 A65 would've originally been fitted with a Lucas RM19 (or very rarely a RM20). This one does have three wires from the stator; internally, one of the Green/xxx (insulation mainly Green but with thin Yellow or Black tracers) wires is connected to two stator coils, the other Green/xxx wire is connected to four stator coils. So it's single-phase.

Connected to the rotary switch, which simply connected in more stator coils as the demand was increased (lights, etc.) by the rider, the RM19/RM20 output was crudely 'regulated' (in the widest sense of the term) by the 6V battery. Which is why a boiled battery was a familiar situation to riders of the era.

The same RM19 or RM20 alternator can supply 12V when both Green/xxx wires (i.e. all six stator coils) are connected to one side of a rectifier (the White/Green being connected to the other side) with a Zener diode in parallel regulating the Volts to a nominal 12 (there weren't 6V Zeners).

In the late 1960's, the RM19 and RM20 (the latter simply being a more powerful - in terms of Amps generated - version) were developed into the two-wire RM21 and RM23, which supply 12V single-phase because all six stator coils are connected within the stator, and because they're connected to a rectifier with one or two nominally-12V Zener diode(s) in parallel for regulation.

Finally, in 1978, Lucas launched low- and high-power versions of the 3-phase RM24. Unfortunately, some nitwit decided to use exactly the same wire colours as the old RM19 and RM20, even though the internal stator coil connections are entirely different, and don't need different colours! crazy

Afaik, any pattern alternators - Sparx, Wassell, etc., which could be a reason for the different wire colours - are copies of either RM21, RM23 or high-power RM24; I don't know of any pattern RM19 or RM20 stators. Hence my suggestion that 'plonkerboy' looks very closely for evidence that a p.o. has changed his alternator wires, and my advice that he proceeds with caution 'til he's established exactly what he's got.

Hth.

Regards,

#376394 - 05/31/11 1:43 am Re: Alternator wiring [Re: plonkerboy]  
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BONZO R.I.P. Offline
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Stuart , I am very confused about your comment about system voltage having nothing to do with the alternator???All regulation? The way I understand it , and I am certainly no genius , if you dont have voltage/current being generated within set parameters all the regulation you wanna apply isn't gonna get the job done .I guees you could talk current amplifiers or voltage doublers , HF switching circuits or whatnot but at the end of the day if you dont have power in you dont have power out.Is this wrong?
Personally I would suspect the lead wires may have been replaced , the original stuff gets brittle and the insulation cracks but this could easily be an aftermarket unit .I dont know how this bike is gonna be used but if it were mine and I were looking at this I would simply get a fresh high output single phase alternator and call it a day .simple and done , but not cheap. An alternative might be a good used two wire unit ,not expensive and generally OK.I have the BB powerboxes on several bikes because I like their simple and effective approach to their ignition and I bought a bunch of them at once . I've had a couple of them fail,the company is good about replacing them but I wouldn't do it again.I have podtronics on a couple things and never seen one fail.I like things simple and reliable and I have found an A-65 to be a fine example of both with a handful of little mods like this .

FWIW-BONZO

#376408 - 05/31/11 3:22 am Re: Alternator wiring [Re: plonkerboy]  
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I understand Stuart's comment somewhat, e.g., the 12V alternator on my bike will generate around 20 volts (revved) without the zener diode in the circuit. I don't have any experience with 6V systems, so I don't know if the alternators are actually different, but even if they are, it's conceivable that they might generate in excess of 12 volts, yes?

I don't understand, though, the comment: "...the RM19/RM20 output was crudely 'regulated' (in the widest sense of the term) by the 6V battery." Or perhaps this is a question, Stuart, do you mean to say that there was no regulator, i.e., no zener diode on these models?


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
#376429 - 05/31/11 8:42 am Re: Alternator wiring [Re: plonkerboy]  
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All Lucas alrernators can run in 12V systems, in 12V systems they are voltage regulated by a Zener diode or the modern equivalent.

When the same alternators run in a 6V system they are regulated partially (read badly) by the battery and a crude (read badly again) coil switching where the coils are switched in and out by the lighting switch in some sort of approximation of the load (in the emergency postion all coils are switched on but only the ignition and battery are in circuit). Result is undercharged or boiled batteries.

#376433 - 05/31/11 9:36 am Re: Alternator wiring [Re: plonkerboy]  
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Join the two wires that show 1.8 ohms between them.Its a single phase stator.

#376449 - 05/31/11 12:11 pm Re: Alternator wiring [Re: ]  
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Hi,

Originally Posted By: BONZO
if you dont have voltage/current being generated within set parameters all the regulation you wanna apply isn't gonna get the job done .

This is true, but if you have an alternator that can't generate 6V or 12V unregulated, it's a pretty crap alternator?

What I've described is fairly easy to see for yourself. Connect a meter with a big scale - 50V? - across the battery, disconnect the Zener and rev. the engine; you'll see the Volts fly up with engine revs. For obvious reasons, don't do this with an electronic ignition, lights connected, etc. whistle

Originally Posted By: Mark Z
"...the RM19/RM20 output was crudely 'regulated' (in the widest sense of the term) by the 6V battery."
there was no regulator, i.e., no zener diode on these models?

Correct.

Originally Posted By: 1968BSA
I think that the way alternators are wired into systems on a 6v are done as so,

a) you can have an emergency starting

Or emergency starting was required, as 'kommando' points out, to allow for starting despite an undercharged battery?

It's notable that 'emergency starting' disappeared at the same time as the move to 12V and better voltage regulation?

Originally Posted By: 1968BSA
b) the wattage is trimmed by its wiring route as to cut down over charging.

Mmmm ... Watts don't really come into it - a Watts figure is simply a product of multiplying Amps and Volts, hence it's so useful to the likes of Sparx for bamboozling alternator-buying Joe Public, but that's another story ...

As 'kommando' corrected me, the 6V systems we know and love were 'regulated' to that voltage by the battery and that only enough stator coils were connected to roughly balance the load imposed by the rider operating the rotary switch.

Hth.

Regards,

#376458 - 05/31/11 1:09 pm Re: Alternator wiring [Re: Stuart]  
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plonkerboy Offline
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Sorry Stuart for confusing you, it's my fault. The 3 alternator wires are all black and I was referring them to the wiring diagram (Fig G20 in the workshop manual). They are the 3 wires labelled GB GY & WG. The green/yellow and white/green go to the rectifier and the green/black goes to the ignition switch. If I can identify which is which, it is a simple matter to connect together gb and gy and put them to one of the yellow wires from the control box, the wg going to the other yellow one.

#376546 - 05/31/11 11:09 pm Re: Alternator wiring [Re: plonkerboy]  
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Stuart,I'm struggling to figure this out , I like to have things make sense in my skull before I accept it as correct.

Your point about the alternator being irrelevent and the regulation is everything just blew my mind Until I read your followup stating that an alternator that doesnt put out6 or 12 V is crap. This leads me to believe that you are referring to any alternator designed for this bike will do the job,if that's where you are at it would make more sense to me as any alternator designed for that application is engineered within prescribed parameters ,in turn making the alternator/regulation sorta ying and yang .If you attempt to install an alternator designed for a Kenworth and try to regulate it with a zener diode from a BSA would you expect it to work?

But now I am further confused, are you saying the power output from an alternator and regulator is irrelevent and only a ploy to sell you something you dont need?As if voltage were the only number to be concerned with?To my sensibilities the overall power ouput from yur rect/reg is ABSOLUTELY CRITICAL! The way I understand it , in an oversimplified Goldielocks and the 3 bears sorta scenario, too low aint right , too high aint right , just right is just right . low power output simply wont run the bike properly , too high output could overcharge battery (it is part of the load seen by the output)possibly blow fuses/melt wires ,burn out regulators,not pretty . The high output parts offered these days are a great upgrade if you ride with lights on all the time,higher powered lights , have added turn signals etc..that the bike was not originally designed to power ,the aging stock units , no matter how well regulated , aren't always up to the task, a weak rotor magnet can drop the power considerably .On the other hand , using a H.O. alt with a more or less original machine with lights off will lead to failure of the zener diode as it passes excess power as heat and they are not typically overengineered for their task .IMO a zener diode is not very well suited for this application. I can apreciate the simplicity of the circuit but it just may be too simple .

FWIW-BONZO

Last edited by BONZO; 06/01/11 1:18 am.
#376582 - 06/01/11 6:12 am Re: Alternator wiring [Re: BONZO R.I.P.]  
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Originally Posted By: BONZO
If you attempt to install an alternator designed for a Kenworth and try to regulate it with a zener diode from a BSA would you expect it to work?

Automotive alternators are a different critter. Our permanent-magnet rotor is replaced by an excited field. Regulation is achieved by varying the "excitement" (the field current.)
In some alternate universe I suppose one could build an alternator with a large enough permanent magnet to provide enough power for a semi and regulate it with many zener diodes in parallel. No single diode could handle the current.
Originally Posted By: BONZO

IMO a zener diode is not very well suited for this application. I can apreciate the simplicity of the circuit but it just may be too simple .

FWIW-BONZO

Even the more complex, "modern," regulators use a zener diode as a reference. The excess current is passed through other transistors.
In my experience the weak spot in the original charging system is the rectifier bridge, not the zener. Maybe I've been lucky, but I've replaced many a rectifier, never a zener.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
#376610 - 06/01/11 1:02 pm Re: Alternator wiring [Re: plonkerboy]  
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Hey bonzo, all nuances aside, it's pretty simple. As David sez, our permanent magnet alternators are much cruder than what you have in a car. They pretty much just put out a fixed amount of power for a given RPM. Since power=voltage * current, the voltage depends on how much current is drawn. If your alternator puts out 80 watts and your headlamp draws 4 amps and it's the only load, your voltage will be 20 volts ( 80 watts/4 volts). To keep the voltage from getting too high and frying your battery or making bulbs pop, your voltage regulating device, be it a zener or transistorized voltage control just draws enough current to lower the voltage to the appropriate level. So you see, the alternator really has very little to do with the system voltage. Hope that helps.


A smattering:
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#376625 - 06/01/11 3:38 pm Re: Alternator wiring [Re: plonkerboy]  
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Quote:
They pretty much just put out a fixed amount of power for a given RPM.


And this is where all the technical stuff and logic comes to a stop!

These discussions about alternators bring forth everything, but the fact that if you don't drive the bike at an rpm that produces more electrons than you are using the battery is going to sulphate and die. It will die just as fast in a running bike as it would left unattended over the winter.

EVEN IF the alternator/regulator PASSES all of the normal tests the battery will sulphate and die if you are not riding in such a manner as to replace the electrons you are using.

The typical Lucas system "balances," that is replaces as many electrons back into the battery as the amount taken out to run light the bulbs and run the ignition at around 2,500 to 3,000 rpm. Take more out by adding an accessory or higher wattage bulbs for a given size alternator and you will have to turn the engine faster than 2,500 or 3,000. With some quartz bulbs you might have to turn a stock single phase alternator 5,000 rpm or more all the time to prevent the battery from sulphating.

This is something one should consider when replacing the original 19 tooth counter shaft sprocket for a 21 or 22 teeth replacement. Change the gearing and update the alternator to a higher output three phase so it will again balance at 2500 to 3,000 rpm.

Run the motorcycle below the "balance" point and the battery will be in a constant state of discharge. A battery that is in a state of constant discharge will sulphate in short order. It doesn't matter if the battery is in winter storage or it is mounted in a bike that is being used. A battery left in a constant state of under charge, no matter how the under charge is caused, will sulfate rendering it useless ESPECIALLY IF YOU HAVE AN ELECTRONIC IGNITION.


#376654 - 06/01/11 7:17 pm Re: Alternator wiring [Re: John Healy]  
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John Healy sez:

"EVEN IF the alternator/regulator PASSES all of the normal tests the battery will sulphate and die if you are not riding in such a manner as to replace the electrons you are using."

To put this in simple American.....TWIST THE D@MN THROTTLE!

laughing



Life is too short to drink cheap, bad beer.
#376659 - 06/01/11 7:39 pm Re: Alternator wiring [Re: BONZO R.I.P.]  
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Hi Bonzo,

Hmmm ... I'm not sure I can explain everything within the confines of the post/thread/forum format - there are complete books out there on this subject! smile However, I'll give it a shot ...

As a very, very basic principle, if you wave a magnet near a piece of metal, you will induce some the electrons that make up the piece of metal's atoms to jump from one atom to another. This is Electromotive force, aka e.m.f., aka Volts.

As David points out, there are different types of alternator. The ones that Lucas made for BSA (and Triumph) are 'permanent magnet'; i.e. (in this case) the rotor is the magnet I mentioned in the first paragraph and, to all intents and purposes, the magnetism is permanent.

All magnets have North and South poles. Wave the North pole near the aforementioned piece of metal, the electrons jump in one direction; wave the South pole near the aforementioned piece of metal, the electrons jump the other way.

So, if your magnet is cylindrical, if your "pieces of metal" are coils of thin wire arranged around the cylindrical magnet and you spin the magnet, as each pole of the magnet passes a given coil, the magnet induces the electrons in the wire to flow first one way and then the other. Aka Alternating Current. bigt And, depending on the strength of the magnet, how far away it is from the coils and how fast the magnet's spinning all add up to how many electrons (aka Volts) you're moving about.

Notice I haven't made any mention of 6 Volts or 12 Volts. While the relationship isn't linear, the faster you spin certainly a permanent magnet, the higher the (AC) Volts generated - as others have said, they've seen 20V and 50V unregulated from standard Lucas alternators.

So it's a rectifier that turns the AC Volts produced by an alternator into DC Volts, and a regulator that stops the high AC Volts (e.g. the aforementioned 20V or 50V) generated by spinning the rotor at high rpm damaging the users that need around 6V or 12V. You're familiar with the objects we all refer to as "a rectifier" but the most common "regulator" on Brit. bikes is the Zener diode.

Digressing slightly, I know of a light aircraft engine that used one of the Lucas alternators we're familiar with. The engine spun at a constant rpm - something like 5,000rpm (driving a variable-pitch propellor for control). At those revs., the plain, unregulated alternator output was 16V so, to keep things simple, the aircraft's electrics were all 16V.

Originally Posted By: BONZO
Until I read your followup stating that an alternator that doesnt put out6 or 12 V is crap.

That should be read following your, "if you dont have voltage/current being generated (within set parameters)" [my brackets]. As long as you want to keep things simple/cheap (on a mid-1960's BSA motorcycle, say wink ), you can only regulate the AC Volts down to DC Volts; an alternator that's only producing an unregulated 6V or 12V AC, except at very low rpm, is crap.

As I say, there are no '6V' or '12V' alternators; the useable Volts on any vehicle are down to the regulator.

Originally Posted By: BONZO
now I am further confused, are you saying the power output from an alternator and regulator is irrelevent and only a ploy to sell you something you dont need?

I didn't mean to confuse you, but I did say it's another story ... wink

Lucas rated all its alternators at 'x' Amps @ 5,000rpm (the italicised bit becomes clear further on) and gave a roughly-equivalent Watts figure; e.g.:-

. the RM21 single-phase alternator that was pretty much o.e. standard '68-on is rated at 10.5A (@ 5,000rpm) and 120W;

. its high-power single-phase partner, the RM23, is rated at 14.5A (@ 5,000rpm) and 180W;

. the high-power version of the 3-phase RM24 is also rated at 14.5A and 180W;

. etc., etc.

As Alex mentioned, the formula that links Watts and Amps with Volts is Watts = Amps x Volts (scientifically-written as P=IE). So, using the figures in the previous paragraph, you get 11.43V on the RM21 and 12.41V on the RM23 and RM24; there might be reason why Lucas didn't use exactly 12V but the figures are near enough not to matter.

Turn to pattern alternators like the Wassell or the Sparx and their adverts. blart much bigger Amps or Watts figures. However, these are copies - they have to be to fit in place of a Lucas - cheap and Far Eastern-made; you'll search the adverts. in vain for details of the remarkable advances that have been incorporated to get the much bigger Amps or Watts figures.

That's because Wassell and Sparx have simply manipulated the figures. frown

Wassell claim 16A from their copy of the RM23 (remember, Lucas 14.5A @ 5,000rpm). What Wassell fail to mention is that you have to spin it at about 8,000rpm to get 16A. If you look at the Lucas RM23 rpm vs. Amps plot, it'll also produce about 16A @ 8,000rpm ... whistle

Sparx claim something like 210W from their copy of the RM24 high-power 3-phase (remember, Lucas 14.5A, 12.41V and 180W). What Sparx fail to mention is that they use the maximum Volts their regulator goes up to - about 14.5V - multiplied by the 14.5A - to get 210W. If you put a meter across a battery supplied by a Lucas RM24 high-power and regulated by anything else - Zeners, Tympanium, Podtronics, yadda, yadda, the meter'll probably still go up to 14.5V ... whistle

Note I'm not suggesting there's anything intrinsically wrong with either product. Just, if you buy one, don't think you're getting something magic.

Originally Posted By: BONZO
too low aint right , too high aint right , just right is just right . low power output simply wont run the bike properly , too high output could overcharge battery

Depends what unit you're talking about.

Volts "just right is just right" is correct; low Amps "simply wont run the bike properly" is correct. "Too high" Amps "could overcharge battery" is wrong, even on a 6V system today; if a battery is being overcharged, either the regulator is faulty or the owner has selected too low a maximum.

Originally Posted By: BONZO
using a H.O. alt with a more or less original machine with lights off will lead to failure of the zener diode

Comes under "the owner has selected too low a maximum". Nothing electric/electronic has an infinite capacity. The normal standard Zener has a capacity of about 12.5A/150W @ 12V. If the bike's alternator has a higher maximum, you either use two Zeners in parallel or you swap to a Trispark/Tympanium/Podtronics/B-B Powerbox/etc.; only thing with twin Zeners is they must be a 'matched pair' for switching voltage; such things are available. My T160's have had high-power RM24 alternators with twin 'matched' Zeners for nearly thirty years without any problems.

Originally Posted By: BONZO
The high output parts offered these days are a great upgrade if you ride with lights on all the time,higher powered lights , have added turn signals etc..

Only partially correct. If the bike has a high-power alternator and you're, say, riding at high speed (revs.) without lights on, any excess electricity generated but not required should be simply turned into heat by the regulator and it then blows away in the slipstream. And before you extrapolate that into 'waste' of some sort, a single horsepower is about 760 Watts, so even the entire output of a high-power 3-phase Lucas or pattern alternator is some piffling fraction.

Originally Posted By: BONZO
the aging stock units , no matter how well regulated , aren't always up to the task,

They are; as John points out, it depends what total consumption you're trying to 'balance' by generation. As I've said, a standard RM21 generates 10.5A @ 5,000rpm; it's up to the rider/owner whether he fits a 100W main beam bulb and revs. an old Brit. 4-stroke like a modern Jap 4-stroke ... wink If not, he needs a more-powerful alternator.

Originally Posted By: BONZO
a weak rotor magnet

... is the simple failure of a component after decades of use ... it's a 'shit happens' of running any old vehicle.

Originally Posted By: BONZO
IMO a zener diode is not very well suited for this application.

Zeners might not be the best but, given the system and the bikes were built to a price originally, it's a simple and robust system with low replacement-part costs. Yes, there's better - yer pays yer money and yer makes yer choice.

Phew! For further light reading on the subject, can I suggest something like, "Motorcycle Electrical Techbook" by Tony Tranter? Then I can stop spending hours in front of a screen ... wink

Hth.

Regards,

#376703 - 06/02/11 1:15 am Re: Alternator wiring [Re: plonkerboy]  
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BONZO R.I.P. Offline
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Michigan, USA
Stuart, that's pretty much exactly what I expected to read, I probably have known dozens of people who think just like you .Did you even glance at Mr. Healeys post ?It's really refreshing to read a tech response from a guy with the tech knowledge,practical experience and the tact to explain something in a way that makes sense to most of us .KUDOS Mr.H.....

Alex , You surprised me ?There are a lot of factors engineered into even such a crude device as this .everything from the number/strength/location/orientation of the magnet poles on the rotor to the number of poles/location /wire size/turns ratio and lamination thickness on the stator.Even things like the insulation and bonding agents/epoxy on the stator have to function in their environment. this wasn't a random occurence ,not something they picked up at the tractor supply and made it work, there were several stages of development,there are still improvements to be made.Hardly irrelevent , maybe not as exciting as the rectification/regulation to the self gratifying number monkey,but it has to be "right"to perform properly.

FWIW-BONZO


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