3 brush generator output

[1955fle]

Can anyone tell me what the optimum output for a 52 3 brush generator? Also what is the best way to measure it? Should I measure it at the battery terminals? I am most concerned with the output when the lights are on. Thanks for the help.

-Carl

[FlatHeadSix]

Carl,
output should be a little above 6 volts (6.5 to 7 is good) and a little below 3 amps (about 2 amps is best), lights on or off it should be about the same. You can measure either voltage or amperage, or both, at the battery connections. the voltage is easy, just connect across the terminals. Amps are best measured with an old analog meter, connect it in series to either terminal (remove the main connection and insert the meter connection BETWEEN the battery and the rest of the system), test your connection before starting the bike by turning something on like the ignition or lights, the meter should read NEGATIVE amps, if it swings the other way then reverse the connetions. Remember that most small meters have a limit of about 10 amps, any more load than that will fry the meter so be careful about measuring the load of any high amp stuff like a pair of spotlights and the headlight all at the same time.

mike

[beets]

When checking AMPS, make sure you keep the connections secure while the engine is running.
I once lost the connection( neg.) and the voltage must have spiked, because the low beam,taillight, and speedo lights burned out.

[1955fle]

Thanks for the response. I checked the voltage at the battery and had 6.7 volts with no lights. When I switched on the lights I had 7.8 volts. I guess I need to turn the third brush and lower the voltage.

-Carl

Carl,
output should be a little above 6 volts (6.5 to 7 is good) and a little below 3 amps (about 2 amps is best), lights on or off it should be about the same. You can measure either voltage or amperage, or both, at the battery connections. the voltage is easy, just connect across the terminals. Amps are best measured with an old analog meter, connect it in series to either terminal (remove the main connection and insert the meter connection BETWEEN the battery and the rest of the system), test your connection before starting the bike by turning something on like the ignition or lights, the meter should read NEGATIVE amps, if it swings the other way then reverse the connetions. Remember that most small meters have a limit of about 10 amps, any more load than that will fry the meter so be careful about measuring the load of any high amp stuff like a pair of spotlights and the headlight all at the same time.

mike

[FlatHeadSix]

Carl,
The voltage might be a little high but a lot of the 6 volt bulbs were actually rated for around 7 volts, so, if you are not blowing bulbs frequently you are probably OK as long as it isn't pushing too many amps. High amps is what boils the batteries dry on long runs, or cooks some of the modern low capacity batteries.

mike

[1955fle]

I am going to lower the voltage a little and also I will also check the amps. Thanks for the help.

Carl,
The voltage might be a little high but a lot of the 6 volt bulbs were actually rated for around 7 volts, so, if you are not blowing bulbs frequently you are probably OK as long as it isn't pushing too many amps. High amps is what boils the batteries dry on long runs, or cooks some of the modern low capacity batteries.

mike

[awander]

When checking AMPS, make sure you keep the connections secure while the engine is running.
I once lost the connection( neg.) and the voltage must have spiked, because the low beam,taillight, and speedo lights burned out.

Witha 3-brush generator, there IS no Voltage Regulator. The generator is adjusted(using the 3rd brush) for the proper amount of current into teh battery. If you disconnect the battery, the voltage will swing very high. I guess you could say that the Battery is the voltage regulator in a 3-brush system.

Carl:

the proper way to adjust the generator is to measure the current into the battery with the lights off, and adjust the brush for teh specified amount of current. Then when you switch the lights on, the second field coil is energized, making the generator put out more current, to cmpensate for the lights being on. If you do it the way you are planning to, and adjust for a lower voltage with the lights on, you will also want to check it with the lights off, to make sure it is still chartging the battery. You may have to settle for a slightly higher voltag ewith lights on, in order to avoid undercharging with teh lights off.

[Perry Ruiter]

I guess I need to turn the third brush and lower the voltage.

-Carl

The position of the third brush controls the amps not the volts. In a three brush system the battery is responsible for controlling voltage (and doesn't really do that great of a job of it which is why all the old bulbs are rated 6-8 volts). If you have a bad ground somewhere between the generator and the battery voltage will spike as the generator tries to match the battery (and is getting faulty feedback because of the impaired ground path). Now if you're running with a gel-cell from an alarm or something like that it just won't do the job with a three brush. You need a real honest to goodness wet lead acid battery. A gel-cell will be fine for running the grand kids around the block once a month but if you have a three brush and ride your bike more than that it's not suitable (different story with a two brush and a regulator, they're fine in that application).

With a 3-brush generator, there IS no Voltage Regulator. The generator is adjusted(using the 3rd brush) for the proper amount of current into the battery. If you disconnect the battery, the voltage will swing very high. I guess you could say that the Battery is the voltage regulator in a 3-brush system.

This is bang on and exactly how it works! ... Perry

[1955fle]

Thanks for all of the information. I do have a lead acid wet battery. I have adjusted the voltage with the lights off to 6.5 V at the battery. This has the lights on voltage of 7.2 V. I think this will work, but I will keep an eye on it until the brushes wear in.

-Carl