help wanted from any electronic experts, 12v system

[7iain7]

Hi everyone,

My father passed away in 2015 and inherited his 1952 Gold flash.
 He was an electronics engineer and he had converted the bike to a 12V system himself.
One day, he told me that I would need to install a  resistor (looks to be 18 ohm 5 watt?) across two of the wires to prevent the battery from going flat??? (at least that's what i think he said) I have had the bike in my garage for a while now, and I have only just started to take an interest in it. I was wondering if anyone could make sense of the crude diagram he drew, he was quite ill at the time.
https://imgur.com/a/jUU8P6I
Many thanks in advance.

mod edit: descriptive title \ added picture as attachment (use of image hosting sites not allowed)

[fido]

The easiest way to convert to 12 volts is simply to replace the original Lucas 6 volt regulator with a car type 12 volt one, as fitted to a 1960s car. There are also electronic versions of that and perhaps your bike has a home made electronic regulator? If it still has the magneto you don't need a battery for starting the engine. If the concern is just to stop the battery going flat at times when the bike is likely to be left for a few weeks I would suggest you remove the in line fuse (if fitted) to the battery. If there is no fuse holder you need to wire one in.

[Bsareg]

That looks like a resistor to supply the field coil with current  before the electronic regulator kicks in. There'll be insufficient current to allow the dynamo to overcharge the battery and there's probable a diode to prevent the dynamo discharging the battery when stopped. You could sell dad's design to AO regulators (if he'd listen).

[Rex]

AO regulators (the VReg2 thing) are crap, but  I doubt he'd listen anyway!
Never really gone along with the idea of 6V-12V, just stick a 12V reg on, as the nominally 6V dynamo has to spin a lot faster to give 12v.
On my A7 I bought a 12V armature, a 12V field coil and a DVR2 regulator, and now it gives a a good reliable and constant 12V.

[Bsareg]

I think it depends where a person rides. If most of your riding is out of town, the 6v conversion is and works fine. If you're in an urban area then the full 12v kit is the way to go. The disadvantages of the full kit is cost and a more fragile armature due to the wires being thinner.

[RDfella]

I have electric start on the A10 together with 200A 12v battery. Dynamo is std 6v with 12v DVR2. Most of my riding is in those damned 30mph zones, but battery is recharged within a mile or two of starting off. Admittedly I no longer ride at night, but in reality 12v requires no more output than 6v - it's the wattage that's the limiting factor and 12v is half the amperage of 6v for the same wattage requirement.