Single wire alternator and the R solenoid terminal

[ndutton]

Background
Several years back I replaced my stock 35A Motorola with a 100A Delco 10Si single wire alternator. It worked very well, the only annoyance was I had to bump the RPM up to around 1500 to wake her up (get it to self excite as designed), it would then work fine at all RPM's, even idle. In a short time I decided the fixed point charging voltage was too high for my taste so I had the alternator shop replace the internal regulator. On their own initiative they also added an external excite wire. When I reinstalled the alt I connected the new excite wire the conventional way, to the coil + post. It delivered output immediately upon start up without the need for the RPM bump but not without a consequence. The internal self excite circuit was backfeeding 12V to the external excite wire and therefore to the coil + post. Turning off the ignition after the initial test did nothing, the engine kept running so I disconnected the external wire and operation returned to normal. The excite wire has remained disconnected since.

A new strategy
I've recently been rethinking it and today tried a new strategy. I connected the external excite wire to the starter solenoid R terminal to give the alt a field jump without the need for the RPM bump and also the benefit of disconnection when the starter was disengaged. The idea was after a wake up jolt the internal self excite would take over.

Worked GREAT!

[joe_db]

The other way to do that is a diode - they are pretty common.
Good idea to to use the R solenoid

Background
Several years back I replaced my stock 35A Motorola with a 100A Delco 10Si single wire alternator. It worked very well, the only annoyance was I had to bump the RPM up to around 1500 to wake her up (get it to self excite as designed), it would then work fine at all RPM's, even idle. In a short time I decided the fixed point charging voltage was too high for my taste so I had the alternator shop replace the internal regulator. On their own initiative they also added an external excite wire. When I reinstalled the alt I connected the new excite wire the conventional way, to the coil + post. It delivered output immediately upon start up without the need for the RPM bump but not without a consequence. The internal self excite circuit was backfeeding 12V to the external excite wire and therefore to the coil + post. Turning off the ignition after the initial test did nothing, the engine kept running so I disconnected the external wire and operation returned to normal. The excite wire has remained disconnected since.

A new strategy
I've recently been rethinking it and today tried a new strategy. I connected the external excite wire to the starter solenoid R terminal to give the alt a field jump without the need for the RPM bump and also the benefit of disconnection when the starter was disengaged. The idea was after a wake up jolt the internal self excite would take over.

Worked GREAT!

[ndutton]

The other way to do that is a diode - they are pretty common.

Another suggestion a while back was to put a manual switch in the excite wire. Given a choice of the three (add a switch, add a diode or connect to the R terminal) I'd choose economy of parts every time.

I now need to revise my engine electrical drawing.

[joe_db]

I suspect modern electronic ignition has made the R terminal a rare thing now.

Another suggestion a while back was to put a manual switch in the excite wire. Given a choice of the three (add a switch, add a diode or connect to the R terminal) I'd choose economy of parts every time.

I now need to revise my engine electrical drawing.

[ndutton]

I suspect modern electronic ignition has made the R terminal a rare thing now.

Well, it's a standard feature on our late model starter solenoids and it's been put to various uses in the past. Originally intended to bypass a ballast resistor, it can still serve the same purpose if one chooses, OPSS bypass during starting is commonly done and now I've used it to my advantage. The R terminal was sitting there unused anyway, a vestige of simpler times.

[Al Schober]

My experience with single wire alternators is that the internal regulator should be removed and an external field wire installed. This facilitates use of an external regulator (ie: Balmar) intended for charging of deep cycle batteries.

[romantic comedy]

I have a Balmar 100 amp alternator for 20 years. It uses a smart regulator, ARS 3 from Balmar. I dont have much new fangled electronics and such, but I believe in the smart regulators.

[joe_db]

I did that myself - I got a 120 amp 10Si alternator and took it apart and converted it to external regulation. I like it that way, but obviously there is a market for people that would rather have just one wire than be able to adjust the output voltage. I did not bother with one wire since I was removing the stock regulator anyway.

My experience with single wire alternators is that the internal regulator should be removed and an external field wire installed. This facilitates use of an external regulator (ie: Balmar) intended for charging of deep cycle batteries.

[joe_db]

What is the max charge you get from that alternator?
Given the pulley ration on the A4, even my 120 amp alternator maxes out around 50-55 amps or so.

I have a Balmar 100 amp alternator for 20 years. It uses a smart regulator, ARS 3 from Balmar. I dont have much new fangled electronics and such, but I believe in the smart regulators.

[ndutton]

. . . . obviously there is a market for people that would rather have just one wire than be able to adjust the output voltage.

Manually adjustable regulators have created problems for a few members in the past. More accurately, the tweakers created their own problems, the adjustable regulator was the mechanism. This became apparent during the coil studies. Some system voltages were scary high affecting the V=IR balance.

As you said, they're not for everybody.

[joe_db]

I need the opposite - gel cells use LESS voltage than the typical on wire is set for I would have used my 10si with the internal regulator if it was set for 14.1, but 14.4/14.8 will kill the gels.
Speaking of regulators, one of my frustrations is the "true" smart regulator no longer exists. They guess at the battery charge state, sometimes pretty well, but they don't KNOW for sure. We used to sell a regulator that interfaced with an amp-hour meter. It had shunts in both the battery and alternator wiring. It could do the following:
Soft start to be easy on belts.
Independent limits on voltage and max alternator amps. This also could save belts from being ripped up or limit the load on a small engine.
Control the charge voltage by the state of charge of the battery instead of guessing from total load. If you left the dock with full batteries and ran an inverter that drew 100 amps, the regulator could see 100 amps going somewhere else besides the battery, which it knew was full anyway, and not kick into bulk charge mode because it thought the battery was low. It knew to kick back into float mod as the amp-hours missing from the battery counted back up to 0 even if there were other heavy loads.
Sadly it was troublesome to keep working correctly to the point I always installed a second basic regulator and a switch and the company quit developing it

[ndutton]

I need the opposite - gel cells use LESS voltage than the typical one wire is set for

As did I with conventional flooded batteries. My single wire came with a 14.7V output. I gave it a regulator transplant with one more civilized but still fixed point. Like Ron Popeil said about his Showtime Rotisserie, I prefer to set it and forget it.

[joe_db]

If I could have found a 14.1 volt 10si regulator I would have used it.
I did find this device that seems interesting:

http://store.alternatorparts.com/partnod7044.aspx

I didn't feel like spending the money because I had already done the conversion.

[ndutton]

Lewco advised me the lowest replacement internal regulator they could get for the 10Si was 14.0V. I agree though, once you solved it by other means what's the point in spending more?

As part of the transplant Lewco ran the alternator on their dynomometer. It delivered 55A @ 2000 RPM (they were impressed). At 1.75:1 pulley ratio that translates to a tic over 1100 engine RPM. If there is a next time I have the alternator in their shop I'll ask them to run it up to 3500 RPM (= 2100 engine RPM, typical for me) to see what she'll do.

[romantic comedy]

What is the max charge you get from that alternator?
Given the pulley ration on the A4, even my 120 amp alternator maxes out around 50-55 amps or so.

I have mine mounted on the front of the engine. The 3/8 belt is not enough for 100 amps. I know that Don has since offered a 1/2 inch pulley. I turn mine slower then I should. This really is by accident because I happened to have the pulley. I should spin it faster for better cooling. But I never did the extended cruising I had hoped to do.
I have a great shunt wired ammeter, and have seen up to 85-90 amps for a short time.

If I can find it, there should be a picture here....