To change from six volt to 12 volt you could buy one of those little gizmos sold on eBay that does it without a transformer. With this all your 12 volt circuitry goes to the 12 volt side and likewise 6 volt to 6 volt side. There would be no common return.

John Mason.

Location: Nottinghamshire

I would try asking the question to the cherished supplier of L E D lamps.

Location: Lincoln

@Squeak "My question is, it ok for the return path of a 12 circuit to arrive at a 6 volt battery?"
It is absolutely everyday practice in electrical circuits with different voltage rails for them to share a common rail..The chassis in the case of a car. So unless you can explain what problem you know of, the answer is:there is no problem.

@ John...Re the Gizmos on eBay..I haven't seen any straightforward 6volt to 12volt "boost" regulators on eBay. Could you post a link ? There are some adjustable ones but they are in case-less module form. The majority of these boost regulators are not classified as "isolated" output so they have a common connection inside linking the input and output ground circuit.
Only a device stating it was "isolated" would mean that the 12 volt side was electrically separate, but i can't see the need..

The situation is quite different for gizmos to go 12 > 6 volts however..Plenty of alumimiun cased options !

This looks like a suitable converter, Ive used this brand on my boat to run the led nav lights from a 18V drill battery and it gave no problems.
http://www.ebay.com/itm/NEW-Voltage-Booster-Power-DC-Converter-Regulator-5V-5-11V-Step-up-to-12V-4A-48W-/141935832186?hash=item210c08ec7a:g:LD4AAOSwu1VW77jC

A nice find Mark ! I'd bypassed the 5v ones having not noticed the wide input voltage range.
However..
Going down the boost converter route leaves the problem of switching side,stop, L & R flashers which are all separate circuits. Using 4 boost converters is impracticable (and expensive) so more electrical trickery is needed.
The simply solution is to use a relay for each circuit. Search eBay using "6v coil relay" for cheap sources..(like 10x for £5) Build the whole lot on the detachable Number plate board but note that a permanent 6 volt supply will be needed on the NP board.

For DC - DC converters with isolated outputs (i.e. the input and output side are not electrically connected), the 0V return path from the light board must be returned to 0V at the output side of the converter. It may be best to connect both input 0V and output 0V to the chassis (assuming negative earth) to remove the isolation.

For positive earth systems, an isolated output converter might help to reduce the complexity of connection, but the light board should be checked to ensure that it is not negative earth if it contains metalwork that would come into contact with the chassis.

Peter

In a race to the bottom you could try these:

http://www.ebay.com.au/itm/DC-DC-2-24V-to-2-28V-2A-SX1308-Adjustable-Power-Module-Step-Up-Boost-Converter-/252596426995?hash=item3acfeb98f3:g:w-IAAOSwpLNYBy8f

They have a wide input voltage which for spiky A7 voltage regulation would be good and at less than 1 pound ea. you would have one per circuit. Only 2A max should be OK for LEDs.

LED lights being plastic usually have pos and neg wires so no earthing problems with a floating output.

Location: Rokeby, Victoria, Australia

Have you seen this site?

http://www.dynamoregulatorconversions.com/led-light-boards-shop.php

I may have missed something but can't you just buy or make a lightboard using normal bayonet fitting bulb holders and fit 6v LED bulbs?

Location: Oxfordshire

Thanks for your many replies and emails, I will study carefully the options offered though not electrically knowledgable myself.
It had occurred to me to just use 6 volt LED bulbs or festoons but I imagined the brightness would be less than the multi LED arrays used in a typical modern 12v light.
The 12v lights available here for festoons are thinner in the body than the bulb fittings, and lend themselves to using 6v flashicators. I will ask Peter at CDRC what wattage equivalent his festoons are, AND purchase one of his 6 to 12 converters to experiment with. regard Russell

Location: oz

Squeak, am I correct in thinking that you are only fitting "flashers" at the rear of your Seven? I'm not sure about in the upside down world of Oz , but it would be illegal in the UK as they must be front and rear. Having said that I would recommend a 12 volt conversion using a two brush dynamo and electronic control regulator,that way you can upgrade all the electrics and gain reliability. Whatever route you take good luck.

Location: Piddle Valley

Thanks for that info Peter. I was unaware front was a requirement in UK, I will therefore incorporate front in the plan.
I intend to tour UK later this year in my recent purchase,a 27 Top Hat, and am trying to preassemble the components to fit when I arrive.
My cars here are all LED and 6volt (avatar excepted) See you at Beaulieu!
cheers Russell

Location: oz