Dynamo v Alternator

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cococola
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Dynamo v Alternator

Post by cococola »

With many of the Minor upgrades that are out there I wonder how many Minors are still running with the standard Dynamo as oposed to the Alternator upgrade?
If still with the original dynamo set up do you find any issues with daily driving please?
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Chief
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Re: Dynamo v Alternator

Post by Chief »

I seem to recall that we were advised by a garage to switch to an alternator, and not knowing anything about cars and/or electronics I said okay and it got fitted. Haven't noticed any difference in the last 18 or so years of it being fitted between a dynamo or an alternator, and in truth I plan on reverting back to a dynamo when I can for authenticity :)
philthehill
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Re: Dynamo v Alternator

Post by philthehill »

There are dynamos with different outputs that look the same as the original Minor dynamo.
The later dynamos are better and have a better output.
The Lucas C42 dynamo has a power output of 50A.
https://www.ebay.co.uk/itm/154532091368 ... Swo7Zg8KIR
If you are not worried about originality I would go for an alternator every time.

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Re: Dynamo v Alternator

Post by KeithL »

We still run a standard dynamo and have no issues at all with it.

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Re: Dynamo v Alternator

Post by King Kenny »

My Traveller has had a dynamo since I bought her 43 years ago. Never been a problem. I have never seen the need to change. I recall an article in a car mag a long time ago talking about electrolytic corrosion on negative earth vehicles. If it 'aint broke....
1969 Traveller in Almond green. Owned since 1979.
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Re: Dynamo v Alternator

Post by oliver90owner »

The Lucas C42 dynamo has a power output of 50A.

Sorry, Phil, but I think you would find that only the C42 dynamos that have been converted to alternator innards will deliver 50A. The usual C42 output is 26A - and that is only at raised rpm, whereas an alternator will provide near full output at lower rpm.

One cannot believe all you see on the internet - particularly posted by ebay sellers! While most are honest, there are some who simply don’t know, but they are difficult to separate from those that do know and try to deceive unwary buyers.

If dynamos were so good, I’m surprised that they were superseded by alternators, for almost all installations. The only real reason to replace a dynamo, with like, is to retain originality, as far as I am concerned. They may be ‘adequate’ but not particularly good. New battery technology has also progressed in line with alternator installation. Smaller batteries with high CCA, but low tolerance for discharge to a low SOC are the order of the day.
myoldjalopy
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Re: Dynamo v Alternator

Post by myoldjalopy »

And there you have it - a dynamo is perfectly adequate for a standard Minor. Out of the four Minors I have had, three have had dynamos and I never had any problems, nor did I bother to change any of them because the charging system worked fine. You are more likely, however, to have problems with modern replacement voltage regulators if you are running a dynamo! :-?
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geoberni
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Re: Dynamo v Alternator

Post by geoberni »

There is absolutely no need to change from a Dynamo to an Alternator unless you need the extra current.
Having an alternator can actually leave you in a more stranded position, since a dynamo system will give indications that it is not at optimum performance, if you know what to look for.
Whereas an Alternator will usually suddenly fail without warning, when the integral control unit Diodes fail.
I believe Phil is mistaken in stating that the C42 provided a max of 50A, unless he has any latter published info; as my 1963 copy of 'Lucas Generator and Control Unit Tests' lists the maximum output of any Lucas Dynamo as 35A. :-?


I only know of Alternators disguised as Dynamos, such as the Dynator or the Dynalite which will provide 45/50Amp.
Dynamo testing.JPG
Dynamo testing.JPG (172.8 KiB) Viewed 12948 times


A dynamo system, correctly set up is no problem.
But if you're running halogen headlights, heated rear window sound system etc, an Alternator might be worthwhile.
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Re: Dynamo v Alternator

Post by liammonty »

Of the 7 Minors I’ve owned, 6 have had dynamos and the only issues I’ve encountered have been with faulty voltage regulators - all the modern Chinese copies. Charging is more than adequate, and as the standard system is reliable, I don’t really see the point in ‘upgrading’ to an alternator for little or no benefit. I take on board Oliver’s comment, but really, so many parts on modern cars are more advanced than on a Minor, where would you stop? Might as well just buy a new car :D
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Re: Dynamo v Alternator

Post by MCYorks »

geoberni wrote: Sat Jan 08, 2022 6:08 pm There is absolutely no need to change from a Dynamo to an Alternator unless you need the extra current.
Having an alternator can actually leave you in a more stranded position, since a dynamo system will give indications that it is not at optimum performance, if you know what to look for.
Whereas an Alternator will usually suddenly fail without warning, when the integral control unit Diodes fail.
I'll second that. I've had several alternators fail over the years and all, except one, didn't give any prior warning. It was usually the solid state regulator failing either short or open circuit, and one due to worn brushes after a very high mileage.

In my opinion the main advantages of an alternator are:
Generally smaller & much lighter than a dynamo, but with much higher output.
Provides a useful output at idle speed.
Good voltage regulation.
Current is inherently self limiting due to design.
Less maintenance (brushes last a very long time & no rear bush to oil)

While the main advantages of dynamo are:
Simple to work on and no polarity sensitive electronic components.
Normally it doesn't need power from the battery to start generating.
Originality (if you like that sort of thing :D )

I think the dynamo is adequate for a standard electrical system. Providing it's in good condition and you understand its limitations. e.g. no charge at idle speed and rather limited maximum output current. This usually only becomes a problem if you do a lot of night driving in slow traffic or overload the system with extra luxuries :wink: If you're stuck in traffic for more than a few minutes, with the headlamps, heater fan, radio and wipers all on, then the dynamo can't keep up and will struggle to fully recharge the battery once you start moving again.
cococola
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Re: Dynamo v Alternator

Post by cococola »

Great information and very informative many thanks :D
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Re: Dynamo v Alternator

Post by James k »

I kept the dynamo on my Traveller for years and it was fine most of the time but wasn't so great in the winter. I don't think it kicked out enough current to keep up with being driven to and from work in stop start traffic with the lights on every day and I had to bump start the car some mornings. I haven't had a problem since fitting an alternator.

I can only speak from my own experience, perhaps my dynamo was just in bad shape.

One thing I notice is that you get more fan belt squeal with an alternator and have to tighten it more regularly. Presumably because the alternator presents a bigger load so is more sensitive to low tension.
philthehill
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Re: Dynamo v Alternator

Post by philthehill »

Talcum powder or French chalk on the belt helps to reduce squeal.

Edward1949
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Re: Dynamo v Alternator

Post by Edward1949 »

I remember hearing that an advantage of the dynamo is that if you're stranded with a totally flat battery you can tow or roll downhill at sufficient speed for charging and the system will revive. An alternator requires a battery with some life in it in order to start charging. Can anyone confirm that this is correct?
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geoberni
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Re: Dynamo v Alternator

Post by geoberni »

Edward1949 wrote: Fri Jan 21, 2022 12:40 pm I remember hearing that an advantage of the dynamo is that if you're stranded with a totally flat battery you can tow or roll downhill at sufficient speed for charging and the system will revive. An alternator requires a battery with some life in it in order to start charging. Can anyone confirm that this is correct?
In theory, yes.
The Dynamo uses it's armature rotation in the magnetic field of the 'residual magnetism' in the Stator Windings to 'excite' it, and start it generating.
The Lucas Control Unit ensures the Dynamo is started with no load connected; the initial weak magnetic field induces a weak current in the rotor coils, which in turn creates an initial field current, increasing the field strength, thus increasing the induced current in the rotor, and so on until the machine "builds up" to full voltage.

That's why when you switch from Pos to Neg Earth you have to Flash the windings, to ensure the residual magnetism is of the correct polarity.

Generally speaking, the Alternator requires battery voltage to provide that excitation voltage.
I say 'generally' because it is possible to have an Alternator that excited only from the permanent magnets, but that doesn't usually apply to ones used in cars.
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Edward1949
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Re: Dynamo v Alternator

Post by Edward1949 »

Thanks for confirming. I can remember an incident decades ago when a friend's car with no battery was started in this way, he then drove many miles home by keeping the engine running at well above charging revs.
cococola
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Re: Dynamo v Alternator

Post by cococola »

Wow and the car can be driven in an emergency this way?
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Re: Dynamo v Alternator

Post by Edward1949 »

Yes. As can most motorbikes. Also many vintage cars with magneto ignition do not require a battery.
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svenedin
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Re: Dynamo v Alternator

Post by svenedin »

Edward1949 wrote: Fri Jan 21, 2022 3:08 pm Thanks for confirming. I can remember an incident decades ago when a friend's car with no battery was started in this way, he then drove many miles home by keeping the engine running at well above charging revs.
Just found this thread. Yes I can confirm that this can be done. When I was at school, my physics master (who had a Traveller) did not believe this could be done so I disconnected the battery and started my car with the starting handle. Of course one must be careful starting the car on the handle (I have done it many many times) as it is possible for the handle to kick back quite savagely and break the bone at the base of the thumb (scaphoid) if the handle is held incorrectly.
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Re: Dynamo v Alternator

Post by jagnut66 »

This debate has been going on forever and will no doubt continue to do so........
Horses for courses really.
Personally, because I like to use my classics on a regular basis (when they are behaving themselves :roll: :wink: ), I prefer an alternator.
Plus I have a radio / CD player, charge point for my phone, electric washers etc. I don't believe a dynamo would deliver an adequate charge in this situation.
I am sure that with a standard original set up the dynamo is fine, it really depends on what you want to do with your car and how often you want to use it.
A bit like cats and dogs, each to their own (though the problem is always down to the humans involved and not the animals :wink: ).
Best wishes,
Mike.
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