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BSA M20 - 6v to 12v Conversion

Hello,

Just wanted the clarify the downside of converting a 6v motorcycle to 12v.

I have heard stories of motorcycles catching fire when this modification was not done properly.
What all should I ensure when I do this conversion?

1. Is it possible to use a rectifier instead of the MCR1 regulator? (Planning to Conceal this within the regulator box)
2. Should the ammeter be changed to 12V as well?
3. Is this conversion even necessary

Any thoughts on this will be highly appreciated

Tavery Peters

email (option): tavery.p@gmail.com

Re: BSA M20 - 6v to 12v Conversion

Changing from 6 volt to 12 volt isn't inherently risky. It has both benefits and disadvantages like most things...

I ran a 'civvy' M21 in this format for about 8 years as a commuter bike without any particular difficulties...Someone I know who has far more knowledge of Lucas dynamos than I have advised me a dynamo wound to produce 12 volts was not the best way to go...The 6 standard volt unit is capable of doing the job...However, using the 'long' 60 watt dynamo rather than the 'short'(earlier) WD unit would be the better choice purely because of the higher output...

The conversion to the dynamo can be done simply by changing the regulator for an electronic unit which can be wired to 'extract' 12 volts from the existing dynamo...As the saying goes though, 'you can't get something for nothing' and that certainly applies in this case...Having 12 volts available doesn't mean you can fit a 60 watt halogen headlamp bulb and drive round in perpetual daylight...The dynamo still has a limited output and will not achieve maximum output until higher in the rev range...

A practical set up would be to use a standard 12v/5 watt tail light (or perhaps an LCD version which uses virtually no power) and a headlamp bulb of moderate capacity...I found I got very good results with a 12v/35watt halogen bulb....

Use a decent size battery as well...Very small batteries just mean the dynamo is going through the feed/cut out cycle more frequently and that isn't really desirable...12 to 14 amp hours would be my recommendation...You will also need to fit a system fuse if you don't have one...

A Dyno Tec regulator can be used as either 6 or 12 volts just by joining two wires together, or not...If you have any doubts about installing one of those post here for advise as it's important that the correct system checks are carried out BEFORE connecting the regulator to a live circuit....I think I'm correct in saying that unit will fit inside a Lucas MCR1 regulator box..No doubt someone will comment if that's not the case...

The 60 watt dynamo can be identified easily by the fact it has two large countersunk screws through the body that hold the field coil in place...The 45 watt unit has only one screw...You'll need to change the regulator, bulbs, battery, horn and ammeter...Some people have said they retained the 6 volt horn but I have no experience of that set up...Ian

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

Re: BSA M20 - 6v to 12v Conversion

A 6 volt horn will work ok on 12 volt as it is not on long. The sound will go up about an octave.

Re: BSA M20 - 6v to 12v Conversion

That solves that one then...:relaxed: ....Ian

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

Re: BSA M20 - 6v to 12v Conversion

A couple of observations, now decent 6v halogen headlamp bulbs are available along with suitable led tail bulbs,a 6v system can be perfectly adequate. You won't be needing a rectifier as your dynamo will only make DC not AC wether you run it at 6 or 12v. The DVR2 electronic regulators available from Dynamo Regulators Ltd are very good.(I know Ron Pier is a fan ) There are also the AO Services ones available from Paul Goff which is what I have on my G3l. Both will do the job,but the AO one does not like badly discharged batteries.Apparently the Wassell ones are not very good quality...
Also your ammeter only measures current,it does not matter if it has 6 or 12v going through it. I prefer a fuse on the live side of the battery to protect the loom,some disagree - I prefer bikes not on fire.

Re: BSA M20 - 6v to 12v Conversion

['Also your ammeter only measures current,it does not matter if it has 6 or 12v going through it..']

Of course you are right Jon...and the '6 volt' ammeter has a sufficient range for the conversion....One thing (strangely) I did find with 12 volts was that my 12 volt reconditioned Altette horn didn't go wrong for the entire 8 years I ran the bike whereas EVERY 6 volt Altette I've had done (by the same person) failed to last a year....No idea why...Ian

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

Re: BSA M20 - 6v to 12v Conversion

My M20 I have owned for 12 years has a 12V system, not through my choice but the previous owner had a 60w dynamo installed/converted.
It has a DVR2 reg fitted in the original reg box and and happily runs 35W halogen headlamps. The battery is a Yuasa sealed pack which fits nicely in one of Ian's replica boxes.
I reckon a battery lasts about 4-5 years.
I built an Enfield CO from parts and put that 12volt only to save having lots of different spare bulbs and batteries. That works great, happy to ride them at night.

Re: BSA M20 - 6v to 12v Conversion

To avoid any dynamo or voltage regulator changes, I simply installed a 10A 6v to 12v digital converter (ebay) from the battery (after a 10A fuse) to run the 12v head lights, blinkers (repeaters), brake and tail lights. All you need are 12v bulbs - I used all LEDs. Also added a front brake light switch and blinkers, in order to be street legal in WA State in the US. The local constabulary is always looking to ticket someone to help fill the city coffers when the crime rate is low.

Dave W.

email (option): dwdiak4@gmail.com

Re: BSA M20 - 6v to 12v Conversion

All my BSA’s are converted to 12 v as I use them day and night all year round, all fitted with long 60w dynamos, Best results i’ve found are to use Dave Lindsley’s 6 to 12v electronic regulator conversion you have to swap the dynamo wires around and motor it up to make sure it’s running in the right direction all instructions included so pretty easy to do, I use a halogen headlight bulb and LED pilot and tail light bulbs 6v horn’s still work ok same with ammeter, only thing is if your pedantic you can’t hide the regulator inside the original case (make a loom extension and hide it under the tank) of course it would be a waste of time if your a rivet counter with a blackout 😎
Let there be more light, Tom Green.

email (option): rustytomm20@hotmail.com

Re: BSA M20 - 6v to 12v Conversion

['I simply installed a 10A 6v to 12v digital converter (ebay) from the battery (after a 10A fuse) ']...

Can you give some more details on this?...It sounds interesting....Ian

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

Re: BSA M20 - 6v to 12v Conversion

I just looked it up on ebay and found this (quite expensive) unfortunately the instructions are in German. Ron
https://www.ebay.co.uk/itm/SPANNUNGSWANDLER-6-auf-12-V-DC-10A-KONVERTER-6V-12V-m-E1-ECE-KFZ-OLDTIMER-2238-0/201525818864?hash=item2eebdff5f0:g:R84AAOSwpIdW7YBk

email (option): ronpier@talk21.com

Re: BSA M20 - 6v to 12v Conversion

If you not using the headlights to travel at night I would say it's pointless , most of us have the ww2 black out lampfitted , I don't use the bike when dark.

Stick with the 6v and put a modern regulator on it and replace the bulbs with LED ones, these are 50% brighter and use 50% less if not more in somecases , you can even get old glow leds now so it will keep it orginal looking, not the horrid modern white light .

email (option): chriscool@sky.com

Re: BSA M20 - 6v to 12v Conversion

I know that some people have expressed the opinion that whilst the amount of light is good from LED headlamp clusters the beam is poor...I haven't tried one myself that's just anecdotal information for discussion...

Personally I like to have a functioning headlamp...I rode back from Weymouth to S.Devon after attending the veterans parade one year (with a blackout) and it was a foggy day...I can't say I enjoyed the experience...At every junction I was unsure whether car drivers had spotted me and I thought if the Plod spotted me I'd get pulled for not having adequate lights in poor visibility which is an offence....

I got rid of the blackout after that...They're also about as much use as a chocolate teapot if your travelling to catch a night time ferry to France (or the same in reverse) which I've done more than once..There are plenty of other examples of the limitations.....The virtue of the system is dependent on what you use the bike for I guess...Ian

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

Re: BSA M20 - 6v to 12v Conversion

I realise that keeping the bike as original is important. If you have some where to store have another headlamp set up to change to for night riding. If you are on 12 volt use a Wipac Quadoptic unit fitted with a LED bulb of the sort Paul Goff sells. This is an H4 bulb which consumes 25 watt but gives about 70 watts output. This set up gives a good beam especially the dip. I have this set up on my bikes. The short time it would take to change over and the safer night riding that this would give will more then repay the effort.

Re: BSA M20 - 6v to 12v Conversion

Ian

Ebay. Here is one of many available:

https://www.ebay.com/itm/DIGITEN-DC-6V-5-11V-to-12V-10A-Step-up-Converter-Regulator-Waterproof-Boost/254543521061?epid=1477425765&hash=item3b43f9e525:g:lLgAAOSwq4VecP8D

Use the Ebay search function using "6v to 12v step up converter". You will find many options. Mine has worked fine for 3 years now. Easy to find many 6V and 12V LED bulbs online at:

superbrightleds.com

Just a note: I am not very concerned about originality regarding my M20. I'm sure there are many opinions on this out there. Functionality is more important to me. If it's not driveable and reliable, it's only 400 lbs. of scrap steel in my garage. I use mine all summer long here in WA state, in our short riding season, and I enjoy riding the M20 immensely.

Dave W.

email (option): dwdiak4@gmail.com

Re: BSA M20 - 6v to 12v Conversion

Thanks Dave...That is an interesting solution I hadn't previously considered....Ian

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

Re: BSA M20 - 6v to 12v Conversion

A friend has used a voltage converter which you can just “plug into” the 6 volt supply and use to selectively power a 12 volt appliance rather than convert the whole system. I think you need to make sure it is isolated from the rest of the loom but it is cheap as chips.
Obviously from china and takes a couple of weeks to arrive.
I bought a handful to play with but haven’t got around to it yet. They are standard little circuit boards.

Re: BSA M20 - 6v to 12v Conversion

eBay item number:392223569763

I found this one on ebay but I'm not up to speed with the function of this type of unit...How does it convert 6 volts into 12v/10amps/120watts?....Anyone conversant with the principles of the technology?....Ian

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

Re: BSA M20 - 6v to 12v Conversion

Ian

I'm not a circuit designer, but I'm sure it is a simple chip that steps up the voltage. I used the same kind of 3 connector chip in my '73 TR6 to supply 10v DC to the dash instruments. Can't fit much else into one of these small packages. When I spliced the converter into my m20's primitive circuitry, I used a common 6v and 12v ground. No issues. Of course, use separate +12v feed wires to the desired lights.

You can buy one and bench test it before installing it, just to make sure it suits your purposes.I

Dave W

email (option): Dwdiak4@gmail.com

Re: BSA M20 - 6v to 12v Conversion

I'm going to give one a try...Apart from lights it could be just the job for the electronic speedo I'm thinking of for one of my projects...Ian

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

Re: BSA M20 - 6v to 12v Conversion

Ian, if you want an electronic speedo have a Google of a Garmin Edge 200. Its a self contained GPS speedo designed for bicycles. I bought one to use on my rigid AJS trials bike after having allsorts of problems with the magnet in the wheel types,both wired and wireless.(The wireless one couldn't cope with the RF noise from the Mag...)
The good thing about it is that it easily detachable from the bike,I have mounts for it on 4 of my trials bikes,which make it cheap.You can hook it up to a computer and download each ride. This is really nice because you can see your route across country which is great on trials like the Arbuthnot and Moor to Sea in Devon.
Its also handy for checking the accuracy of speedo's on other bikes too.

Re: BSA M20 - 6v to 12v Conversion

Thanks Jon I'll check that out..Do you do the Lands End Trial?....I have spectated on that one at various times and sections...Usually at Fingle Bridge (very) early in the morning....Ian

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

Re: BSA M20 - 6v to 12v Conversion

Ian Wright
Thanks Jon I'll check that out..Do you do the Lands End Trial?....I have spectated on that one at various times and sections...Usually at Fingle Bridge (very) early in the morning....Ian
No, not the Lands End,although several friends do it.I don't think I could stay awake all night ! I did the Clee Hills trial in Shropshire, the South Devon Woo Hoo and the Golden Valley March Hare this year until the Cov19 stopped everything. The trials club I run with a friend has yet to run a trial this year,but we might be Ok in September.
Surprising how many trials riders also have WD bikes too.

Re: BSA M20 - 6v to 12v Conversion

Here is one of the converters I have. 6 volt in on the left and varaible up to >20V out on the right, voltage change dialed in using the little screw at the bottom left.

I can't remember what I paid but they are around 3 quid on ebay (search: DC 6A DC-DC Boost Converter 4.5V-32V to 5-42V Step-Up Adjustable)
Pete:relaxed:


voltage-converter

Voltage-12v

Voltage-20v

Voltage-8v

Re: BSA M20 - 6v to 12v Conversion

What is the amps output at 12 volts?...Ian

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

Re: BSA M20 - 6v to 12v Conversion

Just so you all know you don't get something for nothing with voltage converters, you can use a DC-DC boost converter to raise 6v from the bike up to 12v for whatever kit you wish to power but the input current will always be greater than the output.

Watts in (volts x amps) = Watts out (volts x amps)

So the 12v/10amp one that was mentioned earlier will require at least 20amps from the 6v side and actually a bit more as these devices aren't 100% efficient.

Cheers
Wookie

Re: BSA M20 - 6v to 12v Conversion

This was what my question was trying to get to...

The Lucas system is 10A at 6 volts with a 60watt dynamo...Are you saying a step up converter will produce 12v/5A if powered off the Lucas system and the wattage remains unaltered at 60watts?...Ian

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

Re: BSA M20 - 6v to 12v Conversion

Ian Wright
This was what my question was trying to get to...

The Lucas system is 10A at 6 volts with a 60watt dynamo...Are you saying a step up converter will produce 12v/5A if powered off the Lucas system and the wattage remains unaltered at 60watts?...Ian
Basically yes, the most you can get out is what you put in but these devises are never 100% efficient, 90% is a common figure.

If you have a 60 watt dynamo on your bike, then if you constantly draw more than 60 watts in total you will run down the battery.

So ideally you need to know how many watts the 6 volt stuff draws and then you'll know how much "spare" you have to potentially convert to 12 volts.

Things like your brake light you can ignore as you don't use it continuously but sidelights/headlights (if you will be using them) need to accounted for.

The ultimate thing to watch is whether your ammeter shows a charge or not,

All of the converters listed above are able to produce 12volt at 10amps (120watts), assuming 90% efficiency (which the German unit is) they will want 22amps at 6volt (132watts) to produce their maximum output which a 60watt dynamo simply can't supply. So assuming you have nothing using 6volts then the converter can have the full 60watts from the dynamo then using 90% efficiency it will make a make a maximum of 4.5amps at 12volts before you'll run down your battery.

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