Still more electrical diagnostics

Is five years about par for the course for the lifespan of a generator? Two years for a regulator?

And does anybody have the time to explain exactly how a generator/regulator/battery works? I have the diagram for my tractor.

What follows is copied from two pages earlier:

OK, So about five years ago, I had my generator rebuilt, then about three years ago, I had the regulator replaced. Ever since then, it's run and charged just fine. Now over the last month or so, it just won't charge. I thought it might be the ammeter, since it shows it not charging, but when I tried starting it just now, it deflected to the left, so THAT must be working. I suppose the battery's kaput, since I've had to trickle charge it just to get it started for the last couple of months. It won't even hold a charge after trickle charging it for an hour or two, starting it, and then stopping it five minutes later and trying to start it back up immediately. But is the battery the actual problem, or is it an indicator of another electrical problem? If the battery is bad, won't the ammmeter still deflect to the right when it's running?
Should I just replace the battery, or is there some test I can do to see how the rest of the electrical system is working? I have a multimeter, but I'm no electrical engineer.
By the way, it's a 2135 Industrial (Gas)

and then,Briar Creek Stables wrote:

Sometimes a battery will get a short in the one of the cells and it will not allow a charge. I have had this happen before on a John Deere tractor. The meter would show no charge whatsoever and the batter would barely hold any charge even trickle charging it.
The acid could be weak if it's an older battery, but most of the time the lead cells corode and short out the cell with age.

If you disconect your battery and trickle charge it over night it should read just above 12 volts on a meter (12.1 - 12.5).

To check the charging system of your tractor you could hook a volt meter to the battery and start the tractor. The volt meter should read 13 to 14.5 volts max. If the meter is 12 volts and falling as the tractor runs, you have a charging problem.

6 Volt systems should read 7 to 8 volts while the engine is running and the battery should be around 6.3 volts just setting fully charged.

The battery's voltage rises while its charged, to a maximum voltage of 2.35 volts per cell, 7.1 volts for a 6 volt, 14.2 volts for a 12 volt system. An ideal charger holds 14.2 volts (or 7.1) and the battery takes whatever current it needs to charge up to that voltage.

A voltage regulator has two or three parts. One part, the cut out, disconnects the generator from the battery when the reverse current (current into the generator discharging the battery) exceeds a few amps.

The second part always present in the regulator is a voltage regulator function itself. It senses the generator output voltage and adjusts it by adjusting the field current. In an electromechanical regulator it does that by vibrating changing the duty cycle of the voltage applied to the field coils. The very inductive field coils average that on-off switching.

The third unit in some regulators is the current limit or current regulator. It samples the charging current and if its more than the generator can sustain without frying, the current regulator reduces the field current (and so the output voltage) to protect the generator armature. from overload.

The generator on my '68 MF-135 is the original as far as I know, its run 20 years for me. The regulator was replaced a few years before I got the tractor and after I adjusted it, it has been fine ever since. The last couple years I've been working it harder using it for an electric sprayer where the spray pump draws 12 amps and with recirculation, filling, and mixing it runs continuously for 6 hours at a time. The generator keeps up.

An ammeter makes for easier charging system troubleshooting. It shows the battery energy transfers, positive for charging, and it confirms the proper charging voltage by the charge current tapering to zero. When the engine isn't running, it shows loads on the battery. Its very much more sensitive than a voltmeter.

Checking a battery voltage with a voltmeter alone, you won't see a great deal of voltage change immediately after starting unless the battery is being charged at a fairly high current, but you will see the battery voltage rise slowly as the battery charges. The change is small from 12 volts up to 14.2 volts probably with a good charging system in at least a half hour.

When the ammeter shows no charge when the engine is running, but (after external charging) started the tractor, the battery is less suspect than the generator, regulator, and wiring. Generator brushes do wear out. Grounds and wiring connections corrode. Belts and pulleys wear so a generator will produce enough voltage to not discharge, but won't charge either. Such a slipping alternator belt cost me a car when it got hit while helping someone with that problem.

Gerald J.