BOYER BRANSDEN DYNAMO REGULATORS
THESE ARE THE BEST REGULATORS WE KNOW.
Turn the output of your Lucas DC dynamo into a usable 6 or 12Volt current.
Make sure you have a good battery and a properly working dynamo and you should be allright. No quibble guarantee. (But I can't remember having a duff one. If there was a problem it was always a loose connection or a bad battery)