High Charging Voltage

Discussion in 'Mechanic and Repair' started by hdtvluvr, Nov 1, 2009.

  1. hdtvluvr

    hdtvluvr LawnSite Senior Member
    Posts: 466

    I have an old JD 111 mower that I re-powered with a 12 HP B&S engine about 2 years ago. When I installed the engine I replaced the stator to a higher output one since the mower has an electric PTO.

    At 3300 rpm it puts out 17.6 volts with the PTO off. With the PTO on I get 15.3 volts. I use this mower mostly for pulling a garden cart. Therefore, most of the time it is outputting 17.6 volts. The mower has a diode to convert AC to DC. This too was replaced when I installed the new engine.

    I know this high voltage is bad on batteries. What can I do about it? Should I get a regulator?

    Using my meter set to 30 and AC, it read 0.15 volts with PTO off.
     
  2. unkownfl

    unkownfl LawnSite Gold Member
    Posts: 3,838

    check with a different meter. .15 should be 15 volts when converted.
     
  3. hdtvluvr

    hdtvluvr LawnSite Senior Member
    Posts: 466

    The 0.15 volts was AC across the battery terminals. From what I understand, I shouldn't get an AC reading - but 0.15 is extremely small and may be an invalid reading.

    I'm not sure what " .15 should be 15 volts when converted" means.
     
  4. unkownfl

    unkownfl LawnSite Gold Member
    Posts: 3,838

    Sorry I thought you had a old meter where you select the max voltage. First take it to your outlet in your house and make sure it is correct it is not uncommon for them not to be. Once you have checked tell me what size diode you have and Ill need you to take some readings and give me the results.
     
  5. hdtvluvr

    hdtvluvr LawnSite Senior Member
    Posts: 466

    My meter is a digital Radio Shack model. One does have to select a max voltage (3, 30, 300, etc.) by turning a knob. It has another knob to select ohms, AC, DC, etc. Using the meter on house current, I get 120V with the setting on 300.

    But given I selected 30 as the max voltage, .15 is well below 30.

    I can't tell you the size of the diode. It is John Deere part # AM38783. It is inside heatshrink tubing and appears to be approx. 3/8 inches long by 1/8 inch wide. I know this isn't the "size" you are looking for but it is all I know.

    Since I am getting a DC reading on the battery side of the diode, isn't the diode OK?
     
  6. unkownfl

    unkownfl LawnSite Gold Member
    Posts: 3,838

    Yes the diode sounds to be fine, but you said you changed the stator so that would mean a different diode could be needed. They have different sizes.
     
  7. hdtvluvr

    hdtvluvr LawnSite Senior Member
    Posts: 466

    I purchased the diode and stator at the same time. I hope they sold me the correct one.

    The wire on the original diode had been "repaired" a few times. I'm not sure why it needed repairing since I got the 111 used from my father in law.
     
  8. hdtvluvr

    hdtvluvr LawnSite Senior Member
    Posts: 466

    Since the diode is wired between the stator and battery circuit, doesn't it just allow flow of electricity 1 way and make the current DC? In order to regulate voltage wouldn't it have to be connected to ground somehow in order to dump the excess voltage?
     
  9. unkownfl

    unkownfl LawnSite Gold Member
    Posts: 3,838

    However diodes can have more complicated behavior than this simple on-off action, due to their complex non-linear electrical characteristics, which varies with the construction of their P-N junction. These are exploited in special purpose diodes that perform many different functions. Diodes are used to regulate voltage (Zener diodes), electronically tune radio and TV receivers (varactor diodes), generate radio frequency oscillations (tunnel diodes), and produce light (light emitting diodes).
     
  10. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    How many wires are coming off this stator ?

    What color are these wires ?

    What color is the plug connector on the end of these wires ?

    Lastly, What's the engine model and type numbers ?
     

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