I did a little more looking around at the regulators for the permanent magnet alternators we have in these small outboards. You can find a little on the net from forum discussion but possibly not of much use. However, always a good place to get good quality information on something that has been around as long as outboard alternators are US patents. A list of interesting US patents is:
7327123
6690145
6014324
4885493
4659978
4517483
4458195
4431959
4146838
(note – to look at any of these, simply google “patent #” for example, “patent 4431959”
What you will find are patents going way back (the last one on the list is from 1979) and there are many variations on circuit design for a regulator used in a permanent magnet alternator but in general, the rectifier has some sort of switched or controlled semiconductor device such as a SCR for either not switching in the coil output or only partially switching in the coil output. For example, a diode in a rectifier simply turns on when it is forward biased and all the energy from the coil is transferred to the output (battery). But with the switched SCR, the SCR would look like the diode when it’s switched on – but it may not be switched on for the complete duration of the current pulse from the coil. A control circuit looks at the output voltage (battery voltage) and controls the switching.
Also interesting is that patents for these regulator circuits as far back as 1984 have a method to accommodate the battery being discounted from the regulator while the alternator is running. I.e., the circuit has provisions so that it will not be damaged if the battery is disconnected. Patents back then were good for I believe 17 years so all this design is long since public – any manufacture can use this.
The type of load burning regulator we were just discussing (simply turns on a resistive load when some voltage is reached) turns out to be seriously outdated and probably hasn’t been used for “many decades”. I have seen plans for this type of device in several places on the internet from individuals but you probably would never find it on a commercial product.
Hard to still know for sure but at this point, I think based on this problem being around so long and from my own experience, that on my 2010 Nissan 9.8, I do not need to worry about it over-charging the batteries under any condition and also likely don’t need to worry about disconnecting the outboard from the battery while its running. This old problem probably is easy to solve and results in less hassle for the manufacture (less warranty issues) so almost for sure is in the design. This also means that I probably do not need the capacitors on the switch but I won’t be removing them either since I can’t be 100% sure and they don’t hurt anything.
The one thing I could not find in those patents is how to explain why I believe I was seeing 5 amps from my outboard at a fairly low rpm. Current should be proportional to rpm but I believe I saw near full rated current (spec is 6 amps) at a really low rpm. Some of those patents did talk about this a little with mechanical methods to change the permanent magnet flux by mechanical means but I doubt there is anything like that (too complex, expensive). It’s possible some sort of magnetic coil saturation is used but very little details about that also.
Anyhow, I’m liking the charging system in my 2010 Nissan 9.8 outboard more and more and also think that what Fourpoints did was likely a good mod for an older engine.
