I have a 500 and a 650 both with the Zener Diode and Solid State rectifier set ups. I rewire my own bikes-but by no means am I trained. I would not know if the Zener has failed. I keep seeing Power Boxes advertised which replaces both mentioned items. I have a two wire alternator with 10 amps on one bike which I am considering upgrading. Can one of you trained boffins explain how they work and where all the excess AC voltage goes to. I have electronic ignition with a dual coil which I fitted and works well. Some explanation of fitting and product recommendation would be useful please.
The rectifier just converts the AC voltage phase(s) from the alternator to DC. As revs and AC output increases so does the rectified DC voltage. If that was applied to the battery it would overcharge it and potentially boil it dry.
The zener is a diode designed to break down and conduct once the reverse voltage exceeds a certain threshold - for our bikes just above 6 or 12V depending on which system is fitted.
When this happens electricity flows (short circuits) through the zener to earth and the excess energy is converted to heat which is dissipated by the heatsink. That's the basic voltage regulation mechanism.
(Some of our older bikes without zeners use the headlight bulb and battery as a 'sink' for excess voltage and also use resistor wires but this was all a rather crude and unsatisfactory way of achieving what we need.)
The power boxes combine the rectifier/zener functions within a single unit using more modern electronics and typically work with 2 or 3 wire alternators. If your alternator is capable of producing sufficient AC to be rectified to produce 12V DC (at sensible RPM) then you also have the option of converting to 12V and if desired switching to -ve earth (I find this makes fitting LED lights easier as most are -ve earth). (Coils would also need to be changed or re-wired for the switch to 12).
I have fitted several different types of the controllers and all have seemed to work OK - here's a link to a page describing the operation of the units from BB....
http://www.boyerbransden.com/pdf/Power_Box_Leaflet.pdf
Cheers,
Bernie
Thanks Bernie, an answer at last. Very well explained, even I understand that. I am getting 13 volts across the battery on my 500 whilst running, which seems fine. The 650 however is showing 14.75 volts across the brand new gell battery whilst running, this is my reason for the thread. Will contact Boyer tomorrow and place an order, thanks again.
14.75 v is good. The Zener kicks in above 15.4 v so is working. If it stopped working, when you rev it above say 3500, without the lights on it would be showing a lot higher than 15.4v
Some cheaper powerboxes, like the one I had on my Thunderbolt actually slightly leak current from the battery when laid up, eventually draining it. As such, you need to isolate the battery or keep it on a maintenance charger all the time.
Zeners don't do that.
Thanks Editor, this is a quite a learning curve for me. I have borrowed another Zener from my mates restoration today and will just check the readings. What did we do without a Fluke Meter in the 1960's. A great Forum for us older boys. Regards ;D