Bullet – the electrics

I was amazed when I tried out the electrics.  I was taken back in time to my first Scooter, a Lambretta LD. 

Why? Because there were basically no lights at all at a tick over! (I always seem to see electrical problems – see my motorhome posts. Maybe it’s because I used to be an electronic engineer.)

The electrics are powered by single phase alternator with three coils.  One coil’s output is rectified and used to charge the battery and power a few lights. The other two are connected in parallel and power the main light with AC.

My original plan was to parallel all the coils, rectify them and power everything from DC as on most modern bikes.

But then, looking at various forums, lots of folk were very complimentary about the AC lighting – mine was rubbish so I decided to investigate.
To cut a long story short, I found a coil was short circuited to chassis via a star anti shake washer on a stator fixing.  I replaced the nuts without washers using Loctite.

The lights were transformed, still not much a tick over but at slow to normal riding speeds they are very good. I quite like it now.  I can’t drain the battery through the headlight

To aid visibility (i.e. make me more visible to other motorists) I have made a few changes:-

  1. I Added a yellow filter to the headlight bulb.  Yellow lights are not common in the UK so motorists are more likely to take a second glance.
  2. I fitted a couple of high intensity but low powered LED lights to the crash bars as daylight driving lights.  They are actually quite bright and could be used in an emergency if the headlight bulb fails.
  3. I replaced the bulbs in the angel eye lights with high intensity leds.  They now seem at least 10 times as bright.
  4. I fitted strips of LEDs behind the red plastic reflector on my Givi box and they come on with the stop light.
  5. I replaced the pilot light bulb in the headlamp with a LED bulb – it’s now much brighter too.
  6. I replaced the indicator bulbs with LED bulbs – about the same brightness but easier on the power. I had to replace the indicator flasher relay for a one designed for LED bulbs to suit.
  7. I replaced the indicator tell tale bulb in the speedo with a  very bright LED.  Now I can easily tell when the indicators are on – even in bright sunlight.  I had to re-arrange the wiring and incorporate a couple of diodes as the original circuit has current flowing both ways through the bulb.
  8. I have fitted a new battery.  I rarely use the electric start as the bike usually starts first kick, but if I stall in traffic I do hit that button.
    I worried about the battery though – although only a year old it was a 9AH jobby. I know that a wimpy battery can cause kickback which is detrimental to the sprag clutch. So hI have fitted a Motobat 16.5AH AGM battery in it’s place.  It is bright yellow, and as it can be seen was, frankly, an eyesore. Corrected by the application of black Duck Tape
  9. I added an alarm to the bike.  It works off vibration or movement.  It is connected to the battery but if someone cuts the battery leads it continues to work off a PP3 battery. It is activated and deactivated by a remote fob – similar to that used for remote locking on cars.
  10. I have fitted heated grips.  These take around 3.5A when on full and I was a bit worried about drain in the battery. As described at the top of this page, the DC side only gets 1/3 of the alternators output. Two coils can power the headlight at medium engine speed – that is 60 Watts. At higher speeds the AC regulator kicks in so the alternator is probably (an educated guess with no information) capable of 80 Watts.  Which implies that the single coil for the DC side is good for about 40 watts.To run the grips at full power with the ignition and lights I’d need a tad over 40 watts.
    Sure enough when the grips are on on 100% the ammeter shows no charge, but at least it’s not a discharge.  On 75%, the grips simply switch off an on, and the ammeter moves between charge and zero much like it did with the indicators before I fitted LEDs.
    Gosh they are so cosy.  After a half hours riding at 10C with very thin non-motorcycle gloves ny hands were still warm.  

Update:- October 2019
I have moved the heated grips onto the BMW.  But I thought I’d investigate the bullet electrics further. 
 As I mentioned above the heated grips take about 3.5Amps.  (50W)
When running the coil takes around 4Amps but only for about 25% of the time so that is 1 amp.  (14W)
The rear light is 5W.
The led driving lights are 6W
The pilot light and angel eyes probably total about 0.3A between them or 4W .
The remaining filament lights in the ammeter and speedo probably amount to another 6W
That totals out at around 85W or 6Amps. 
Now the RE handbooks specifies  8.5A at 14V or 120W.  I could not really tell how much was going into the battery but it looked to me like the ammeter was at about zero. So this was all the alternator could provide.
But the speeds I was doing were only around 50mph or around 3200rpm.  I suspect the alternator is rated at a faster speed.
So where does that leave the AC??
It is specified as 5.2A, or 73 W, but if it is down by the same ratio that is only 50W
yet the headlight is 60W/55!
I suspect the specs are not correct.
Simplest way for proper control is to rectify the AC add a big capacitor and use a conventional Rec/reg. Maybe a diy FET rec reg?? There will be losses,
The only prblem is that I found that the amber lead to the headlight was connected to chassis somewhere.  But where?  It only connects the alternator, the AC regulator and the headlight, and the autostart cut off.- it could be in the harness too.
Tested – it is connected in the regulator and somewhere else too.

Still to do

  1. I want to investigate the AC regulator.
    It intrigues me. 
    A quick test shows that at does nothing at all with the voltage in one direction, but it collapses to zero when the voltage reaches 12V in the other direction.  So when the peak-peak voltage reaches 12V it will start operating on half wave rectification.  This cannot operate over a wide range but it suggests that the headlamp bulb, the power of the alternator, and the regulator all work together to produce a regulated voltage at about 14V rms but with a very strange looking waveform.  I have an oscilloscope so I’ll check it out.

    I checked it out.
     I don’t have an ac source handy for that voltage but I used an old transformer which gave 40V p-p. I fed it through a bulb (to avoid short circuiting it) and monitored the voltage across the regulator.  At -17.5 V after the trough it crashed to zero.  Putting this into a spreadsheet to calculate the RMS of this waveform, showed it to be 13.35V.  The positive ride was not affected.
    So there is something else in there rather than a simple zener and SCR. The waveform is very steady clipping at the same point every cycle so it is not a heating effect. It is really very clever.

  2. I’ll fit an ignition amp.  I’ll still use the points but take the strain off them.  Velleman make such a device but its an old, and in my opinion unreliable, design (at least on a vehicle where the engine is stationary – as when checking the timing?)
    Done -see here
  3. I’d like to find a decent LED stop tail bulb. I may have to make one.
  4.  At some stage I may tidy up the wiring.  The Indian wiring harness is very complicated for what is quite a simple circuit.