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NT_Pete 09-26-2013 06:03 AM

Magdyno, Solidstate Regulator and a 12 Volt Ni Battery
G'Day Gents, I am contemplating setting up a Solid State Regulator to Charge a 12 Volt Lithium Ion Battery on my 1936 L2/1 Tiger. I will only be running a tail lamp and very occasionally a head lamp. From what I can gather the L3HM-LO Dynamo that I am in the process of rebuilding will produce around 35watts, the Regulator that I have from Paul Goff will convert the 6 Volt to 12, but I am not sure if the output will be enough to charge the Li battery. Has anyone tried this and succeeded?:confused:

Triton Thrasher 09-26-2013 06:58 AM

Dynamos don't use rectifiers.

Snakeoil 09-26-2013 01:26 PM

Dynamo? Are you related to Edison?:D

That's a DC generator and there is no need to rectify DC current.

It may just be that you are not familiar with electrical terms.

What you need to step up a DC voltage to a higher DC voltage is a Boost converter. That is probably what Paul Goff has made for you.

The amperage of your 12 circuit will be reduced.

Power (watts) = Volts x Amps. And Power must be conserved (Conservation of Energy Law)

Your dynamo produces:
35 watts = 6 volts x 5.8 amps

Thru the boost converter
35 watts = 12 volts x 2.92 amps

So, you will never pump more than 2.92 amps into your battery assuming no losses in the system.

Now I'm straining what little electrical theory I still retain. But lets walk thru figuring out what you have here.

If you sum up the wattage requirements of your tail light and head light, and whatever the coils require, whatever remains will go to your battery. So....

Tailight - 5 watts
Coils - hmmm, let's assume 4 ohm coils in series. So about 1.5 amps x 12 volts = 18 watts. It might be less if in parallel

So that's 23 watts so far. Let's stop there. Leave the headlight off.

35watts - 23 watts = 9 watts.

So 9 watts is going to your battery.

9 watts = 12 volts x 0.75 amp

So you have 3/4 amp going to your battery.

That is a little higher than a trickle charger on "float" after the battery is fully charged, also called a maintenance charge. So, you are going to have to drive a long way to charge your battery.

Now let's flick on the headlight. I'll be kind and say it is a 30 watt bulb.

9 watts - 30 watts = -21 watts

You are requiring 21 watts more than your dynamo produces.

So, you are now running a total loss system with a 12 watt drain or 1 amp at 12 volts coming from your battery.

Will Dave or one of the other electrical gurus please check my work to make sure this is right or damn close anyway. I realize there are other losses in there due to connections and such, but this is probably best case scenario.


Triton Thrasher 09-26-2013 01:57 PM

Those crazy Triumph people called it a dynamo. They weren't as crazy as Snakeoil, who wants to put two ignition coils on a single cylinder bike with a magneto.

A 35W 6V dynamo will produce much more than 35W when regulated to 12V. That is a fact.

You could probably power a 35W headlight and a 5W tail lamp and charge the battery. However, the dynamo won't start charging until a higher rpm than when regulated to 6V, so you may find your battery going flat when using lights at low speed.

The other disadvantage of 12V is that the dynamo gets hotter when producing more power and it can break down. The higher your bulb wattage, the more likely is overheating. You will probably get off with a 35W head. An LED tail light is a worthwhile saving in current.

I know nothing about Li ion batteries. If they can't accept charge as fast as lead acid batteries, they're not what you want.

JohnA 09-26-2013 02:44 PM

Sorry, I have no idea about most of your question, but the only thing I can say is that you won't need arectifier with a dynamo. Rectifiers turn AC in to DC. Dynamos produce DC, hence no need for rectification.

I can say from experience (with a 1956 A10) that a dynamo system, when working properly, can be very reliable and can run fairly decent lights (not high-speed stuff, but that's probably not what you need on your old bike?)

Snakeoil 09-26-2013 03:01 PM

Sorry, saw Tiger and assumed it was a twin.

I did not think he was regulating the generator to 12 volts. I thought he was converting it since he is using a solid state device that he called a rectifier..

If the dynamo will produce more than 35 watts at 12v, then it must be able to produce more at 6v. I assumed that 35 watts was the max output of the device. So, whatever the max output is at 6v, becomes the max output at 12 volts and the same calcs apply.

I believe you when you say that you can run a 6v generator up to 12 volts. But at what cost to the windings? You said it can overheat. So my guess it is a bad idea. Plus it does not work at low rpm because the output is still too low.

But if you convert it? That is what I think he is asking about, the generator produces it's normal 6v output at whatever the max current limit is for some max power output. From there, my calcs still apply. If it works at all RPM, then I suspect it is more than just a regulator.

I found Goff's site and looked at his converter. It is listed as a regulator. It has current limit controller for the field current so the dynamo will not be overheated. I wonder if it just a regulator or a converter/regulator.


Triton Thrasher 09-26-2013 03:20 PM

It will be a regulator, I expect. Don't know if it's a good one. Some of the electronic DC regulators have daft feaures, like draining the battery at idle and requiring power from the battery to start charging.

The dynamo delivers (or tries to deliver) the same current at 12V as it does at 6V. Thus, in theory, power can be doubled. I have successfully powered a 60W 12V headlight with an E3H dynamo, which is rated at 40W at 6V.

Other people have had them burn out, it's only fair to say.

rambo 09-26-2013 04:24 PM

Much talk about Paul Goff making stuff.I think,by looking at his jumble stall,there are lots of Chinese built bits for sale.Not that they are bad.Does anyone know if Paul actually manufactures anything.Everything he has on the bench is also for sale by other vendors.Just saying.

Snakeoil 09-26-2013 07:18 PM

I sent an email to him asking if his gizmo was a converter/regulator or just a regulator and if so, if it required the dynamo to reach a certain speed before you got 12v going to you system.

I'll let you know what he says if he replies back.


NT_Pete 09-27-2013 04:27 AM

Thanks Snakeoil:)

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