Solid State Voltage Regulators For 3 Brush Motorcycle Generators


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Antique motorcycles using three brush generators often have battery problems as well. Many of these problems are a direct result of the improper voltage and amperage output of the generator.   The three brush system does not limit, or control the generator voltage output.  The battery is essentially the voltage regulator.  The third brush does limit the current, or amperage output of the generator.  Due to the inherent difficulty of accurately setting the third brush correctly, the generator current output is often too high.  This results in an overcharging of the battery, so battery voltage increases and the acid begins to boil.  This leads to low liquid levels, leaks, damaged paint, overheated battery plates and eventual battery failure.

Here are some suggestions for optimizing battery performance:

1.      Installation of a good, accurate voltage regulator will significantly improve battery life, help prevent leakage of battery acid and also allow use of a gel type battery.

2.      Purchase a high quality lead acid, sealed lead acid, Gel, or AGM battery. Select the largest AH (amp-hour) rating that will fit in you battery enclosure.

3.      Maintain proper water and charge levels at all times. Purchase a good battery tender, or maintenance charger and attach it whenever the battery is sitting idle for any great length of time. 

4.       Periodically check battery terminals for tightness. Keep the battery terminals, enclosure and all battery surfaces clean and free of corrosion at all times. 

5.      Avoid conditions of prolonged discharge, especially in cold weather.

The Splitdorf generator is designed to work best with a 15 amp-hour lead acid battery. This is an odd size, no longer available. However a 12 amp-hour lead acid battery may still be available from some battery dealers as a special order. Look for # B49-6. These batteries fit well in the pre-1932 Indian, Henderson and Excelsior battery boxes, and are 6 3/8" tall by 3 1/2" by 3 1/4".

 Smaller batteries can be used; however, the voltage may run higher than 7.25 with no load on the system, which could potentially damage the battery.  Gel-Cell batteries can also be used with this regulator; however, with smaller batteries, the no-load voltage may run higher than desired which can damage the battery.

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