generator charging adjustment

[oldspert]

My amp meter shows a continuous +7 or 8 amps charge. I thought as my battery charged it might go down, but it stays at that rate. How do I adjust the cutout to lower the charge rate? I do not want to fry my battery.

[ndnchf]

My short video shows how to adjust it.

https://youtu.be/PL94VX3GIq8?si=vvCRKPfgXzAmP9f6

[Marshall V. Daut]

Until the third brush is moved, the charging rate will remain the same. Alternators will reduce charging when it is sensed that the battery is sufficiently charged. An aftermarket EVR installed in a generator will regulate the charging rate, but not a bone stock generator.
An easy way to remember which way to move the brush holder: If you want the charging rate to go UP, move the third brush DOWN (in the direction of rotation). If you want the rate to go DOWN, move the brush holder UP. Look at the third brush's tip and you'll see why moving the holder changes the charging rate. When the brush is higher up, only the thin edge of the brush contacts the armature's commutator plates. As the holder is moved down, the wider part of the brush contacts the commutator, so more electricity passes through the brush material = higher charging rate.
Marshall

[oldspert]

Originally Posted by ndnchf

My short video shows how to adjust it.

https://youtu.be/PL94VX3GIq8?si=vvCRKPfgXzAmP9f6

Thanks, that explains a lot. Is the third brush is only held in place by friction?

[ndnchf]

Originally Posted by oldspert

Thanks, that explains a lot. Is the third brush is only held in place by friction?

Yes - its just friction tight.

[rotorwrench]

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The 3rd brush is the only way a person can adjust output. The battery is all that holds the voltage within a normal range since there is no voltage regulator. It's important to maintain the battery and its connections in good condition. 6-amps is OK if the vehicle is driven mostly in daylight hours. It would need more if a lot of night time driving is expected. A person doesn't want to overcharge the battery.

[nkaminar]

To know your battery health, measure its voltage. When charging it should be about 7 or 7.2 volts for a 6 volt battery. Twice that for a 12 volt battery. You can add a voltmeter to your instrument panel if you want to.

Here is the real way the third brush works. As the speed of the generator increases the location of the peak voltage on the commutator moves. As the speed increases this location moves away from the third brush thus reducing the current which would otherwise increase dramatically with the generator speed. Changing the position of the third brush moves it away or closer to the peak voltage point on the commutator. The third brush makes the same amount of contact to the commutator regardless of its position.

The location of the peak voltage on the commutator changes with speed because of impedance in the windings in the armature.

[Marshall V. Daut]

"The third brush makes the same amount of contact to the commutator regardless of its position."

True. But my understanding was that when the third brush holder is moved down, the spring tension forces the brush firmer against the commutator, which increases the charging rate. If that is incorrect, I stand corrected. Maybe some old timer told me the wrong thing back in the 1960's and I believed it all these years. 'Sure helped me keep straight in my mind which way to move the brush, though. Thanks for the correction.
Marshall

[Charlie Stephens]

Just turn on your lights and the charge rate will go down. Long term fix is move the 3rd brush.

Charlie Stephens

[Kurt in NJ]

The charging rate has to match your use on the car, 8 amps may be what you need for your use, I have a 14 amp rate, has be that way for the last 30 years, 50% of my driving is at night, and idle speed parades, if i drive a lot in daytime I will turn on the headlights for part of the drive.
I do not use a battery tender/ charger, just charging by driving, last battery lasted 16 years, got 6 years on this one so far (optimas) , with a regular battery you can use a hydrometer to monitor battery charging, , the procedure for adjusting is in the owners instruction book

[Badpuppy]

Originally Posted by Charlie Stephens

Just turn on your lights and the charge rate will go down.

With incandescent bulbs. LED's, not so much.

[katy]

Originally Posted by Marshall V. Daut

[I]"The third brush makes the same amount of contact to the commutator regardless of its position."

Ditto

[Keith True]

The third brush rotates around the commutator like a pencil does in a compass.It stays in the exact same plane throughout it's whole travel.If only one edge of the brush touches then it sounds like a used brush put in backwards.You can wrap some sandpaper around the commutator and turn it to bed the brush in for 100% contact.It will take a few tries to get everything to stay in place while you do it,but after you fumble around a bit you can do it.

[ndnchf]

Not to beat a dead horse, but this shows the adjustable brush, contact with the commutator remains the same in any position. This is a 1935 V8 generator I'm rebuilding, but the 3 brush layout is very similar to model A.

Steve

[MrTheRich]

To add a little explanation why the adjustment does what it does. The middle brush picks up electricity that electrifies the outside still standing coils, creating an electromagnet, that generates even more electricity inside the rotating coils.

By adjusting that pickup to the middle, you lower the voltage of the still standing coils, making them weaker magnets, lowering the overall output of the generator.

If you turn it to the right it will pick up more electricity, increasing the voltage on the outside coils, making a stronger electromagnet, which gives a higher overall output.

Some of you might notice that this is kind of a circular pattern. And indeed, it would be a runaway effect, were you to short the wires. But because there is a 6v battery, like an empty bucket filling up. The electricity from the generator will pour into the battery instead, making it hang a little higher than 6v (most likely 7v).

If your battery is full, the generator will keep pouring in more, making your battery heat up, and having the voltage in the system go higher and higher, and it might eventually break your light bulbs. So if your battery is often on the full side, make sure to lessen the generator output, to save your electrical system.