Delco Alt/internal Voltage Regulator poor output

[joe_db]

Let us start with first principles:
There are only two ways to regulate an alternator - fixed set point and variable.
A fixed set point regulator increases field current when the voltage is less than the setpoint and decreases it when it is over the setpoint.

The second part of the equation is how storage batteries act. You can look up their data and find an acceptance curve. At a given state of charge and a given voltage, they only accept so many amps.

Thought experiment number 1. You have a huge alternator that can putout 1,000 amps at idle and has a fixed setpoint. You have a dead 100 AH wet cell. It will NOT be recharged in 6 minutes! What will happen is the battery charge will follow the acceptance curve, which might be somewhere between 1/4 and 1/2 C, so in this case someplace between 25 and 50 amps. As the battery charges the acceptance rate tapers off. Instead of being fully recharged in 2 to 4 hours, it might get half charged in two hours and take 4-6-8 more hours or even infinity hours to get all the way back to 100%*.
Here is the tricky part - the higher the voltage the faster it charges, but the higher the voltage the more likely the battery is to be damaged eventually if it just stays that high. Imagine filling a water balloon from a hose. If you set the valve to not have enough pressure to burst the balloon, it takes forever to fill it. If you turn it up full blast, the balloon will pop.
This is why so many sailors who bought big battery banks and big alternators back in the day found themselves with either slow charging and sulfated to death batteries or fast charging and boiled to death batteries.

More to follow.

* Easy way to think of this asymptote function - every X hours you fill up half the empty space in the battery. X hours is 50%, 2X hours is 75%, 3X hours is 87.5%, and so on. You never get to 100.

[joe_db]

Early attempts to solve this problem:
The first attempts were human controlled one way or another.
Some people made or bought regulators that could be adjusted manually. I had one of those for many years. You could turn it up for awhile and then when you judged the batteries near full you could turn it back down. This has obvious problems with human error, both in forgetting to turn the voltage up, forgetting to turn it down, and/or misjudging the state of the batteries.
The other manual method was called the "AutoMac" and looked like this:

What it did was for the duration of the timer (big twist knob) the regulator would be fully bypassed. There was no regulation at all - the alternator was what we call "full field", putting out as much as it possibly could. This actually could work well *if used and supervised* by someone who REALLY knew what they were doing. The potential downside was far worse and more dangerous than just leaving a regulator set to 14.8 instead of 13.8 volts, you could possibly see 15 - 18 - or even more volts and cause fires or battery explosions, not to mention really destroying the batteries and other gear

[joe_db]

This photo is similar to my regulator from 1994 to last year. It only had a single setpoint, but it was user adjustable. It was free, it came with a big alternator we ordered for a customer and he was not interested in a single voltage regulator and gave it back.
I generally had success with this, but three issues did crop up. The first odd one was until I stuck some ferrites on the leads, using a handheld radio near the engine would drive it to full output The second issue was if the connections got loose or corroded, it sensed less voltage than there was and drove the output too high. Some careful wiring work and dielectric grease solved that.
The third issue is one that I was never been able to fix: It burns out diodes. A stock alternator on an A4 with a 13.8 volt setpoint does not work very hard. Once you move away from stock alternator and the usual one car battery at a time setup, you are working your alternator much harder. Not only are you working it harder, you are doing it in a worst-case scenario. Best case is less field current and high RPMs, that runs cooler. Running more field current to get the same voltage and lower RPMs produces more heat, the cooling fan is going slower. My stock Motorola has lost diodes, the 10si I had lost diodes, and the shiny new Balmar lost diodes. Every few years is a visit to the alternator repair guy in Annapolis. The 10si didn't get repaired, it only cost $65 or so and the bearings were getting noisy too, it went right to the dumpster.