Topic: Alternator improvements-and warnings...

[HondaMan]

1. Rectifiers.
There are some modern rectifier diodes, specifically called "Schottky diodes", that can improve the power output from the older SOHC4 alternators. These diodes have a lower forward voltage drop, which becomes less waste heat, and in turn becomes more battery stoage power. These nice units are pricey: I have seen them selling for up to $60    on some websites, and they are a good way to recover some lost power from your aging OEM unit.

HondaMan, I'd like to try this upgrade; can you recommend some specific diodes to look for? I'm interested in your thoughts on silicon carbide Schottky diodes and their possible application, as well. Any new thoughts/changes/improvements in the last four years since you originally posted this?

Thanks for all of the help you've provided me and others over the years. Can't say enough how valuable it's been.

Ron

It's been a while since I looked around (or designed that Schottky bridge!), but I think they are still 'out there' on the Internet. I stopped making mine when I found one already available, so I suppose it's still there? I think it was on a chopper parts site, and would fit the 500/550 or 750 system. My next personal move will be to make one for my new toy, the CB350F I got last year for fun and experiments. Those are so seriously power-limited that I hope to come up with several enhancements, in the hope of running a halogen headlight in the 45/50w range.

[Bodi]

I have an older Oregon Electric regulator - mine does not have the adjustable voltage feature I see on their website now. presumably the basic operation is unchanged. The one I have works like the original Honda one, varying the field coil current to control the alternator output.

[HondaMan]

1. Rectifiers.
There are some modern rectifier diodes, specifically called "Schottky diodes", that can improve the power output from the older SOHC4 alternators. These diodes have a lower forward voltage drop, which becomes less waste heat, and in turn becomes more battery stoage power. These nice units are pricey: I have seen them selling for up to $60    on some websites, and they are a good way to recover some lost power from your aging OEM unit.

HondaMan, I'd like to try this upgrade; can you recommend some specific diodes to look for? I'm interested in your thoughts on silicon carbide Schottky diodes and their possible application, as well. Any new thoughts/changes/improvements in the last four years since you originally posted this?

Thanks for all of the help you've provided me and others over the years. Can't say enough how valuable it's been.

Ron

The Schottky diode has long been an efficiency-improving device in these sorts of systems, developed during the Apollo Program to reach the moon. They have a forward voltage drop of just 0.3v, where normal silicon diodes are about 0.7v. Germanium is better at 0.25v, but almost impossible to find since about 1980.

You can buy Schottky bridge rectifiers from places like Digi-Key or Mouser Electronics, to build one yourself. In the Tips & Tricks there used to be an article on building your own silicon bridge: just sub in appropriate Schottky bridges and you're there. Get at least 50 PIV rating at 25 amps, and mount it to a metal (aluminum is best) plate about 3"x4" (or larger in area), and it will work fine.

[thrutheframe]

  Great info here.  Thanks Hondaman.

[Coronet]

Hey Hondaman, what type regulator does the guy from Oregon motorcycle parts sell? (assuming you've seen/heard of them)
thanx.....

  I e-mailed and asked him and he said his were solid state series regulators not shunt style regulators.

[HondaMan]

Hey Hondaman, what type regulator does the guy from Oregon motorcycle parts sell? (assuming you've seen/heard of them)
thanx.....

  I e-mailed and asked him and he said his were solid state series regulators not shunt style regulators.

That would at least keep them from burning up the windings. The shunt-type I've seen are made for alternators with a different kind of insulation from the SOHC4 types, one that withstands the heat of shunt regulators better. I suspect then, that this Oregon design is likely a full-on field coil (or near it) with a series impedance device that "holds back the water" so to speak, monitoring the progress as battery voltage. Not a bad arrangement, provided the regulator device (usually a thyristor or transistor) can withstand the heat of a full-short now and then. Some of these types contain a cutoff circuit, so if the load gets too high (like a short) it just folds itself back to a safe level to survive. That would make it pretty goof-proof, and reliable.