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Old 03-09-2012, 09:23 PM   #1
MongoLikeBikes
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Default Triumph 6v Vs. 12v (Doug Wood Rant)

I was looking back at an email that Doug Wood sent me when I sent him a Lucas Mag and Dynamo. My generator for my '59 TR6 was rated for 6v. I am really only used to working with 12v and most modern components follow suit, so I asked if we could squeeze 12v out of the genny. What I got in return was "canned rant" about the considerations of 6v and 12v on old bikes. Basically he schooled me a little, and if I could help others learn by posting...all the better. The rant goes as follows:
-----

"There are several options for running a generator at 12 volts; all have their pros and cons. I'll try to outline them as best as I can.

Option 1: Run a 6 volt generator with a 12 volt regulator
Pros:
- No generator rebuild necessary if the generator presently works.
- Total output of the system slightly higher
- Regulator fits in original can
- Low cost
Cons:
- Stresses field coil (12V across a 6V coil)
- Lower reliability, theoretically (I have no supporting data)
- Charging voltage reached at higher RPM

Option 2: Use a 6 to 12 V conversion regulator
Pros:
- No generator rebuild necessary if the generator presently works.
- Total output of system higher
- High reliability
- Low cost
Cons:
- Charging voltage reached at higher RPM
- Regulator does not fit in original can
- Regulator need air flow for cooling

Option 3: Have generator built for 12 volts and use 12V regulator
Pros:
- High reliability
- Charging voltage reached at lower RPM
- Regulator fits in original regulator can
Cons:
- High system cost
- Total system output same as 6 volt
- Generator rebuild necessary

I recommend and sell PODtronics regulators. I normally have straight 12V regulators or 6-12V conversion regulators.

I am going to talk about 6 and 12 volt systems. We both know that the voltages really are neither 6 nor 12 volts but let's just stick with the nominals, it's much easier and the concepts are the same.

Now some additional detail:
- An E3L puts out about 60 Watts at 6V. So one would think that at 12V you could get 120W from it, right? No.

- E3L field coils are about 3 Ohms. With a 6V system they will draw about 2 amps and also implies that the coil will dissipate 12 Watts when the generator is called upon to charge the battery.

- So the total output of the armature is really 72 W, 60 available to external loads and 12 to the coil. Bear in mind that power (Watts) is voltage (volts) times current (amps). The current output is fixed by the wire size and solder connections at about 10 amperes (plus the two to the coil)

- If we regulate at 12V instead of 6 we now have the full 12V across the field coil. This means that we now have 4 amperes flowing through the field coil which causes a dissipation of 48 Watts. That's right, four time the power dissipation the coil was designed to handle.

- Also consider that two of those ten amps that were available to go to the load are now being diverted to the coil. That leaves 8 amps for the load or a net of 96 Watts. So you are getting about a 60% increase instead of a 100% increase. And that does not consider the potential effects of the additional heating from the field coil.

It is for these reasons that I tend to dissuade folks from just regulating E3Ls to 12V. But having said that I must say that I have read of it being done successfully. But I cannot guarantee a generator run under these conditions.

A full 12 V conversion (12V armature, 12V field coil) works well but the armature has smaller wire so is restricted in current capability. It is a 60W device.

The 6-12V conversion regulator will give good performance, keep the field coil
dissipation to 12W but requires a higher engine speed to reach charging equilibrium.

There you have it. Please let me know how I can help you.

Regards,
Doug Wood"


Dated March 7, 2011.
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Old 03-09-2012, 09:31 PM   #2
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Default Re: Triumph 6v Vs. 12v (Doug Wood Rant)

I found out more about modern components for old bikes from Bob Kizer, the PODtronics guy. He will also school you if you ask him dumb questions.
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Old 03-09-2012, 09:55 PM   #3
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Default Re: Triumph 6v Vs. 12v (Doug Wood Rant)

Great read, thanks for sharing. I will need the info
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Old 03-09-2012, 11:02 PM   #4
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Cool Re: Triumph 6v Vs. 12v (Doug Wood Rant)

That's excellent advice from Doug Wood. I have just recently been discussing this with a buddy as he is thinking about the possibility of 12 volts output from his E3L generator.
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Old 03-09-2012, 11:24 PM   #5
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Default Re: Triumph 6v Vs. 12v (Doug Wood Rant)

That's all bullshit. Everyone knows that electricity is magic, and is not to be fucked with.

Really though, thanks for the info.
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