Is it possible to run a 12 volt system on the original 6 volt dynamo? If so, how, and is there a need (I assume) to fiddle with the regulator?

I ran a 12 volt system on a standard 6 volt dynamo for about 8 years on my '47 M21...

I used an electronic regulator that was designed for the purpose (I think a few companies make those...)

Following the recommendations of a friend who ran a mag/dynamo overhaul business at the time (and also manufactured regulators), I fitted a 60 watt 'long dynamo'. His opinion was that the 'short' 45 watt dynamo was unsuitable for the set up...I've never tried it with the short dynamo so can't comment on that aspect...

Downside is that the dynamo does not balance the increased load until it is running faster than when set up for 6 volt output...

Also, though it is 12 volt you still have to balance the load against the output, so bulb sizes still have to be sensible...I ran a standard 21/5 watt rear light/brake light and a 35 watt halogen headlamp bulb..

With a good reflector this provided much improved lighting...I didn't experience any problems with the dynamo during the 8 years I ran it...I then sold the bike to a friend and it remains unaltered...Ian

email (option): ian@wright52.plus.com

It is possible to switch over to 12 volts but I wouldn't recommend it. A number of years ago I rewired a 1951 BSA A7 at the time it seemed a good idea to switch to 12 volts and most people agreed. I used a 12 volt battery with a Podtronics control unit. It worked ok for a few years but then the dynamo just stopped working. I spoke with an expert in the field who repairs old mags and dynamos he told me that opinions have changed about changing over because of a large number of dynamo failures I had to buy a rebuild kit for the dynamo which is an armature, field coil and other parts which was not cheap. Bryon

Although I tried this with some success (maybe I was just lucky) I basically agree with the comments in the last post...

The fact is, in principle, you can't have 'something for nothing' and there may well be implications in some cases when continuously demanding the maximum the dynamo is able to produce...

Currently I'm running 6 volt systems and with good connections, the correct wire, a good battery and a resilvered reflector the lights are quite acceptable...

Another improvement may also be achieved at the original voltage using LEDs instead of conventional bulbs...As yet I haven't gone down that route..

Replacing the rear lamp with an LED improves brightness but as a means of reducing the system load the benefit is marginal..The original is only rated at 5 watts after all and the 21 watt brake light only represents an intermittent load...

LED headlight arrays seem to offer the best gain in that regard I would have thought..

Does anyone know the power consumption of these arrays (watts) and is anyone able to comment on the quality of the light output/beam when running one?...Ian

email (option): ian@wright52.plus.com

I have been running a 12 volt system on my M33 and B33 for some years now. Admittedly with a 60 watt dynamo. They both have a 60/55 watt headlamp bulb with led stop and tail. I have to say that I have had no failures with the dynamos.

I suspect success or failure might be dependent to a degree on the condition of the dynamo and/or the quality of any rebuild it has had...Ian

email (option): ian@wright52.plus.com

I should have mentioned after the dynamo rebuild I went back to the 6 volt system to be on the safe side also I don't ride at night or very rarely. Bryon

I am not sure if I understand dynamos; meaning I don't understand them at all.

However, my thinking is as follows:

1) The dynamo pushes out a given voltage at a given speed (at idle it maybe a bit over 6-7 volts at normal road speeds it maybe say 13 or 14 volts),

2) The dynamo doesn't know what it is connected to i.e. it continues to do what it does if it is connected to a 12v regulator or a 6v regulator or if a 12 or 6v battery is used,

3) If you have to give the engine a good thrashing at the traffic lights to keep the lights on, then something will probably wear out prematurely.

I would be interested to learn more as I suspect my approach to electronics is total bo%$ocks.

regards

Pat

email (option): sacombsashtrees@hotmail.com

Hi Ian

My experience of LED headlights isn't fantastic.

I have a re-silvered reflector which has made a difference.

However, with the LEDs on the front you get a lot of bright light, but not much focus.

Everything at the side of the road seems a lot brighter.

I don't know what power they consume, but all I can say is that it is no way near normal filament bulbs.

Regards

Pat

email (option): sacombsashtrees@hotmail.com

I ran a Dave lindsley 12v system 32 years ago. It went kaput somewhere in Italy. It was the long dynamo. Probably not helped by running a 60watt halogen bulb.....

My 1962 Velocette with a 60 watt Lucas 6V dynamo has been running a 12V Boyer regulator for going on 20 years now and I have never had a single problem.

I wonder if where it's set on the motorcycle has a bearing on how long it lasts?

Hello,

As it was mentioned here, a dynamo is a machine which produces
An output voltage depended on it's RPM.
You can get more than 20V, usually out of a 6V dynamo, if turned fast enough,
So there is no problem converting 6V to 12V system.
All the difference is that the regulator allows higher "field" coil voltage,
Which in turn makes the armature "cut" through stronger magnetic field,
Which, in turn, produces higher output voltage.

All you need to do is replacing the regulator-
Electronic or not, but as Ian mentioned,
The down side would be charging in about 30% faster RPM,
So may be useless in town riding, from traffic light to the next one...
(There is an article on "Powerdynamo.biz" website, I believe its on the common Q&A section)
The benefit is ability to find any part you want,
Also, as the voltage is doubled, the current running in the system
Reduces to half for the same wattage so less "voltage drops"/loses at the system.

Regarding a LED head bulb- I have tried that:
When I used a 12V, 6 1/2" original LED "sleeve" - closed reflector,
The lighting was just wonderful !
I will try to find and post a photo, BUT, I failed MOT...
(Just because the tester was, let's say- "not smart")
When I put a LED bulb into the original system, the light was
Bright when looking at it, but it is not focused in any way,
And has no value for night ride.
At the end- I put a LED as a low light bulb and a regular H light bulb,
So when I want to conserve the battery, I use the L,
And when I want to see I use the H...

Noam.