Hey DD, I see your rationale, but that would mean the AC is only getting half-wave rectification then fed to the battery; this will result in a severe drop in available DC Volts in an already-inferior charging system. Ideally we want to send full-wave rectified DC, thus the battery gets charged efficiently.
First of all, please ignore my previous posting where I was thinking the AC on the light switch was being diverted onto the headlight cct. I was totally wrong there, and you put me right. Excuses: a) I don't have a running bike or a lighting switch to hand to experiment with and b) the dog ate my homework...(arf!).
I do have, however, both CA & CB wiring diagrams, in fact a complete workshop manual on CD (if anyone wants PDFs of specific pages, just ask and I'll email them).
Now, looking at the CB77 WD, the alt has 3 sets of coils which, under normal 'day' running (ie: no lights), are series-connected, thus producing ACV across the Yellow & Brown wires to the rec. This voltage will be, to some degree, RPM dependent. But, with AC power generation, once the voltage 'peaks out', then the variation is more frequency-related than it is voltage-related. We're not concerned with frequency here, as we're bridge-rectifying from ACV to DCV. I use the term 'peaking out' as the coil - or winding - is only capable of producing a maximum voltage which is directly proportional to the number of turns involved within the winding, the flux (strength, measured in tesla[Φ]) of the rotor's magnetism and the air-gap between the rotor and stator. The winding is a coil of lacquer-coated copper wire, the gauge of which determines how much current it can produce; the number of turns - coils - around the stator's ferrous core determines the maximum voltage available. Reducing the air-gap between the rotor (magnet) and stator (ferrite core/winding assembly) results in an increase in produced voltage, as does increasing the tesla of said magnet. Bored yet?
A modern automotive alt employs an electromagnetic rotor which is excited by applying vehicle battery voltage across it (from the ignition circuit) via a carbon brush / slip-ring assembly; this means that the output of the alt can be regulated by controlling said voltage by either pulsation or attenuation. This is known as regulation.
Without major re-engineering, we are stuck with the alt that we have.
That's got the theory out of the way. Anyone caught glazing-over or yawning will get detention!
So, let's take a CB77 alt/dyn/gen (just to please everyone): 3 stator windings electrically connected in series, day mode (see pic), permanent magnet rotor, pre-determined air-gap, pre-determined tesla; shove this produced ACV into an old selenium-diode rectifier and you have a DCV attenuation of around 6V, which is why it's a 'good idea' to replace the selenium rec with a silicon-diode type. Rationale: selenium diodes have a forward volt-drop of about 1.5V whereas silicon diodes drop by 0.7V; you gain, in theory, 2.8V (as there ar 4 diodes in a bridge rec). If you really want to supercharge, seek out a Schottky-diode rec; these devices nominally drop by a mere 0.2V each, but that may result in overcharging or 'boiling' of the battery, so therefore I can't recommend it without further experimentation. A modern flooded (wet) 12V battery requires a nominal 13.8VDC to charge efficiently, a gel or AGM (Absorbed Glass Mat) 14.1V but 13V to 14V for most flooded batts is usually acceptable.
I'm ad-libbing now, but I do remember overcoming a faulty alternator - until I found the dry solder joint on one of the alt coils - on my CB77 by switching on the lights: when the lighting switch is operated it bridges out two of the three coils (it links the Pink & Yellow), thus increasing the current available to support the lighting whilst still (hopefully) trickle-charging the battery. This design, coupled to the old, heat-producing selenium rec, was Honda's idea of charge regulation; simple but appallingly inefficient. In the nearly-fifty-years or so since the system was first thought up, battery technology has moved forwards a bit and, as a result, such stringent charge-attenuation is no longer the issue.
To close, what we're ideally looking for is 13-14VDC with 2 to 4 Amps of charge, 'day' mode. If someone would take the time to provide me with some voltage readings from their bikes' alternators I could work on the theory and post improvement suggestions. What I need to know is:
ACV across the Yellow & Brown wires at the rectifier (headlight switch 'off')
ACV across the Yellow & Brown wires at the rectifier (headlight switch 'on')
ACV across the Yellow & Pink wires at the headlight switch (switch 'off')
ACV across the Pink at the switch and the Brown at the rec (switch 'off')
all at around 2000 to 4000 RPM
That would be a start.
Regards to all posters,
Steve
Let's test a rectifier (celenium diode [pack])
Just to add to my last post (some are, by now, wishing....), your theory is correct, I think, DD. You could experiment with 3 sets of 2-diode rectification, sort of as shown in the automotive alt pic, but I'm not sure if 'our' alt will produce sufficient volts-per-winding. I'd suggest the silicon rectifier route unless you have plenty of time to spend with meters, cables & diodes. Maybe a spare stator so that you can tear apart the pre-made links within and rewire to suit. It could mean losing the will to live if it all goes horribly wrong!
When I'm up & running I shall try as you suggest, but let's get some AC measurements first. It'd be great if you could help. Rgds Good and bad news. The Good: rewired and installed Radioshack rectifier and now with lights on and over 2000 RPM voltage is at 13.25 !! The bad news: by the time I got done servicing the bike and installing the rectifier, I did not get you the volt readings.
that's great! i just dug up a radio shack bridge rectifier i had kicking around. i would love to use it on my ca77. is it laid out like the schematics on this post? on mine it has a beveled corner, which is the positive post. does that mean the opposite post (diagonally) is negative, and the other two are for the brown, and yellow wires? i'm really loving this forum. i hope i'm not butting in here. thanks The wiring diagram was on the back of the package. I am at work right now, but when I get home I will let you know. Mine did have a beveled edge and one of the spades were in a differn't direction. And no your not butting in, that is what this website is for............. Yes that is how it is wired. I also installed a heat sink (Radio Shack catalog #276-1363) to help dissipate the heat. It does get very hot so I am not sure how it will hold up.
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