Dynamo Regulator FAQ

12V Upgrade?

There are two basic ways of doing this, neither are fool proof. So your answer is to understand the options.

6V Dynamo with a 12V regulator; this is the first and cheapest option. The first problem occurs in that the speed of the dynamo is often not fast enough at tick-over / town speeds to get a good charge to the battery. So provided you are aware of this, keep a good battery backup, i.e. start a run with a well charged battery, make sure the AMP-Hrs are adequate (more anon). Do not expect to sit in town traffic for long periods with headlight on (especially with up-rated lights). Do not expect a 'town' bike with such a conversion to cope well with coil ignition (electronic or points). On a more positive note you could expect to safely use 50% more power from your dynamo as long as you keep is 'spinning' with this type of conversion.

12V Dynamo with a 12V regulator; In this case the dynamo gets rewound with greater turns in the field and armature. In most cases this results in the dynamo system starting to charge the battery at about the same dynamo / engine revs as it did when a 6V system. All would appear an answer to a 'maidens prayer'. But a problem can occur as the dynamo is a willing animal, and when rewound it can give more power than it was intended to, especially if you ask more from it (a modest increase in power out does seem to be acceptable, but not as much as with using a "6V dynamo for 12V" as above). There is no regulator yet seen on a British motorcycle with power limiting build in to it although the V-Reg2b addresses this situation indirectly with its thermal overload protection. Bear all this in mind when you make your decisions. One fact to remember at all times, any motorcycle battery used on such a system using Lucas E3 or similar dynamo on a Classic motorcycle over 250cc must be fitted with a battery of at least 5 Amp-hrs capacity, smaller batteries will tend to overcharge.

Polarity?

What factors affects the polarity I use?

There is no strict rule nor technical reason, except that the electronic regulator IS polarity conscious, therefore once you have chosen a specific polarity regulator you are committed.

Some points to bear in mind if you are undecided:

• What polarity do you expect? (Just about all BSA came out of the factory with positive earth.)
• Also think about the next owner of the bike-hence keeping it original might be a good idea.
• What colour is your earth wire? Red is Positive earth. Black is Negative earth. This might sound obvious but there is a lot of 'casual' wiring out there which eventually leads to confusion/damage.
• What polarity do you expect on your bikes? ie If you have many bikes keeping them all the same can save further confusion/damage. ('till you sell it!)