Boyer Powerbox for BSA, Triumph, Norton & Royal Enfield 12V Pre Circa 1978 Single Phase with alternator two, or three wire. This includes Single, Twins and Triples.
Consists of Rectifier, Capacitor, Zenor Diode so the originals will no longer be needed.
THE ADVANTAGES OF 12 VOLT CONVERSION
Most 6 volt permanent magnet alternator charging systems have no regulator to control the voltage output. Some use the
headlight switch to change over the charging coils when the lights are used. The load provided by the battery and bulbs
holds the voltage to approximately 7.5 volts, the value of a charged 6 volt battery. IF THE BATTERY BECOMES FAULTY OR
DISCONNECTED THE OUTPUT OF THE ALTERNATOR WILL RISE TO PEAK AT OVER 200 VOLTS, THE RECTIFIER AND/OR
ELECTRONIC IGNITION WILL BE DESTROYED. WE THEREFORE RECOMMEND THAT NO ELECTRONIC IGNITION BE FITTED
TO MACHINES WITH THIS TYPE OF 6 VOLT CHARGING SYSTEM.
Converting to 12 volts is going to provide more stable and reliable electrics, it will also improve lighting. Current through
the cables is halved and the output from the alternator will be up by at least 25% with no extra load to itself.
A typical alternator at 2000 rpm will charge approximately 8 amps into a 6 volt battery - 48 watts (volts x current). If the
battery is replaced with a 12 volt unit the current will drop to 6 amps giving 72 watts. In practice this is closer to 84 watts as
the battery voltage on charge is nearer 14 volts. At just under 15 volts the battery is fully charged. At this point, without a
regulator, the current is no longer stored by the battery and is lost as heat. The battery would eventually boil dry or explode.
This will not occur with a correctly fitted Boyer Bransden power box in place. In addition it is possible to start the machine
despite a discharged battery.
WHAT TO DO
The change to 12 volts is carried out by: fitting 12 volt bulbs, not forgetting instrument and warning lights, fitting 12 volt
battery with in line 15-25 amp fuse, fitting 12 volt ignition coils (6 volt coils can be used with some electronic systems or by
fitting a 1.5 ohm ballast resistor in series).
Remove the rectifier and disconnect the wires. The power box can be connected to these. The two yellow wires connect directly
to the alternator. Two of the original wires can be used and any connection to the headlight switch can be disconnected, some
machines have a resistor wire in the wiring harness, this can also be disconnected at one end and is no longer needed. The
third wire on the alternator is connected to one of the other two (see wiring diagram). The earth terminal on the rectifier is
normally the centre bolt, the wires on this can be bolted back to the chassis, along with the red wire if positive earth, or
black wire if negative earth from the power box. The opposite wire is then the main power feed to the ammeter or battery
and connects to the appropriate wire removed from the rectifier. The conversion is now complete.
For starting with a flat battery remove the fuse and kick, or bump start, rev up and while running fast replace the fuse.
The battery will then start to charge, if healthy.
The power box is a self regulating rectifier with an internal current and voltage storing capacitor. Connecting directly to the
alternator the output is approximately 15 volts with no current being drawn and 14.5 volts with some load. These values
are just right for charging a 12 volt battery or running the electrics direct. The unit has been designed using the latest
power technology semi-conductors to provide stable, direct current from standard permanent magnet alternators. Three
types are available: Single phase, Bi phase and Three phase. In each case a charging lamp control, or lighting delay circuit,
which prevents the lights being turned on until after the engine is started, is available.