Hints and Tips - 6 Volt Systems

Maggie Shapland wrote:

> ... my 6v lights are so lousy...

David Cochrane Replied....

I have the same trouble with the Austin Seven Chummy, with the added irritation that the windscreen is vertical. This reflects the lights of following traffic, which makes the candlepower output of the Chummy's lights seem even less noticeable. I solved this latter problem by opening the top part of the screen a little and fitting a piece of pipe insulation over the top edge of the bottom half to seal the gap.

The illumination problem I have tackled by removing as much resistance from the electrical circuits as possible. Measures include:
- The use of the thickest wires practical, especially for the headlights and dynamo;
- Bonding the battery earth terminal to the engine with thick copper braid;
- Running thick earth return wires back from the headlights to a common earth point, which is attached by thick wire to the oil-pressure gauge pipe (which is of course attached to the engine);
- Switching the headlights via a relay, which not only eliminates the resistance inherent in a 75 year old switch panel, but also stops it overheating.

You might like to try measuring the voltage at the battery terminals and then across the headlight bulb (with the lights on) and seeing what the difference is. Don't forget that bulb power is proportional to the square of the voltage across it (eg a 24W bulb will produce 24W with 6V across it, but only 16.7W with 5V across it).

Hope that this sheds some light on the subject.



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