Charge from 6hp Tohatsu

Discussion in 'OnBoard Electronics & Controls' started by 23feet, Jun 19, 2015.

  1. 23feet
    Joined: Dec 2014
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    23feet Junior Member

    Hi Bertku,

    That is sticking the voltmeter probes directly into the output wires from the outboard. Nothing is connected - no load or battery connection.

    thanks
    23feet
     
  2. BertKu
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    BertKu Senior Member

    Yes, what do you measure? With meter switched to DC reading 0 to greater than 18 Volt .
    Bert
     
  3. 23feet
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    23feet Junior Member

    Yes, that's right.
     
  4. BertKu
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    BertKu Senior Member

    If you have only 7 Volt on open circuit and it is indeed DC what your generator/alternator gives out. You have either only a 6 Volt device, or you have an internal short, which drops the Voltage to 1 Volt. Are you absolute sure, it is an DC generator and not an AC alternator, but regardless, I think you have an internal short in your generator/alternator. Sorry we can't help you.
    Bert
     
  5. CDK
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    CDK retired engineer

    No, it's not!

    According to the Tohatsu website there is an OPTIONAL 12V 5A alternator output on the MFS6 model, STANDARD only on the "Sail Pro" models.
    If you measure anything else than 14-16V at idle with no load attached, the charging circuit is not present. A digital multimeter has a very high impedance, it may pick up a signal from the ignition and show that as a voltage.

    The simplest way to test the charging output is to use a small 12V bulb (blinker or brake light from your car). If it lights up brightly the charging circuit is present, if nothing happens, the charging coil and/or rectifier are not installed or not properly connected.
     
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  6. BertKu
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    BertKu Senior Member

    Indeed, that is the way to solve problems. I also do that when I have an electrical problem on my trailer and cars. I forgot to ask him whether he was using a simple old fashioned multi-meter or whether he is measuring with a digital meter. I still like to know from him whether he has set his meter on AC 0 - ? volt or on DC 0 - ? volt. Bert
     
  7. 23feet
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    23feet Junior Member

    It is a 2014 Sail Pro model. So. you are saying that I can't check the output from the multimeter? It is a (cheap) digital multimeter, set to DC 0-20V.

     
  8. BertKu
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    BertKu Senior Member

    23feet, Just take CDK's advice and use a globe/lamp/bulb 12 Volt 10 watt from your car or buy it from the store. It is much easier and you have less chance that you come to the wrong conclusion. Digital multimeter has some irritating problems and sometimes I still use my old trusted old fashion meters. Bert
     
  9. 23feet
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    23feet Junior Member

    I tested it today with my test light. It glowed very weakly at idle and then went out as the revs increased.
     
  10. BertKu
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    BertKu Senior Member

    Hi 23Feet, I suspected already, you have an internal technical fault. Bert
     
  11. heikki
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    heikki Junior Member

    Been there and done that

    My Yamaha charging circuit on a 6 hp outboard is behaving the same way. Explanation is the charge regulator. Disconnect it and measure directly from AC from coils and you will notice it works. Measure with meter set to AC- voltage. The regulator needs a battery- like load that limits voltage around 14 V DC on the output. If voltage goes above acceptable charging voltage there are avalance-type diodes at AC-side of the regulator which short circuit AC side. As voltage goes to zero on every AC cycle this mentioned short circuit is opened. At least on Yamaha the regulator works that way. This behaviour led me to locate the regulator closer to battery and outside of the outboard.

    br: heikki
     
  12. CDK
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    CDK retired engineer

    That is important information!
    It seems both Yam and Tohatsu use a shunt regulator, the same principle as found in all solar controllers. So it is not just a rectifier, there also is a small active circuit that compares the output with a voltage reference. The circuit is powered from the battery, without one the AC coil is (almost) shorted.

    That means 23feet can connect the battery straightaway, no diodes or other circuitry!
     
  13. BertKu
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    BertKu Senior Member

    But that should he supposed to have done, open circuit without anything connected. (refer thread 14) A bulb/globe/lamp will then tell you whether there is sufficient voltage. Maybe he would burn his hand, because of unregulated voltage. The lamp/globe/bulb would be overheating. Hope he is able to get it right. Bert
     
    Last edited: Jun 27, 2015
  14. 23feet
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    23feet Junior Member

    OK, so let me see if I understand what you are saying. The outboard has a circuit that detects when a battery is present and will start delivering the DC voltage? So if I connect to the battery, will I be able to measure the charge voltage at the battery?

    Thanks for patience.

     

  15. CDK
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    CDK retired engineer

    That's another interpretation.
    The circuit that controls the charger output is powered by the battery, so no battery no output voltage. Connect a partly discharged battery and measure the voltage; it should be 11.5 to 12.5V.
    Then start the engine and measure again; the voltage should rise within a few minutes to 14.0-14.5V.
     
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