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  1. #61
    Join Date
    Feb 2009
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    Hi all,
    to recover this post, I have check in my boat today step by step the installation and it is ok. But an extra 3A is added to charge current when I push the light in BM1.
    Anyone with the same sympthom.
    Regards

  2. #62
    VicS is offline Registered User
    Location : Home: Kent. Boat: Chichester
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    Jul 2002
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    I think people have run out of ideas.

    Maybe it is a faulty unit.

    Perhaps it is time to contact Nasa for advice.

  3. #63
    pieter2 is offline Registered User
    Location : the Netherlands
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    Aug 2010
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    Hi All,

    Perhaps will someone copy this thread and mail it to Nasa? I could do it myself ofcourse, but I feel not to much competent to explain the problem and the answer (as English is not my native language).

  4. #64
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    Feb 2009
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    I have just sent the thread to NASA Marine Instruments.
    I ask NASA to write the answers or news here directly or to send my by mail. If I receive something I will copu here asap.
    Good look. regards

  5. #65
    Join Date
    Jan 2011
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    77

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    Hi,
    I might have found the cause of the problem.
    The negative of the two batteries have to be connected to the engine mass seperately to avoid them influencing each other the shunt is connected next to the domestic battery. Otherwise a slight difference in rest voltage ( caused by different resistance in the negative connections) will give a strong charge or discharge depending on which negative is highest.N.b.
    Have a look at the picture. Its how its connected in my boat for 5 or 6 years and working great.
    n.b. Only the domestic battery is measured.
    Ad
    http://commondatastorage.googleapis....l/47038702.jpg
    There is one other possible fault that sometimes is overlooked.
    With only one battery the alternator B+ is connected to the starter so the charging goes through the starter cable.
    With two batteries and a diodesplitter or similar this connection MUST be removed and a seperate charge lead has to be connected from the alternator to the input of the splitter.
    Otherwise the + of both batteries will stay connected what makes the splitter obselete.
    This can be seen e.g. on
    http://www.vetusweb.com/manuals/file...03%2001-03.pdf
    Especially when a second battery is installed later this fault is often made.
    Ad
    Last edited by YELLOW BOAT; 24-01-11 at 15:26.

  6. #66
    pieter2 is offline Registered User
    Location : the Netherlands
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    Aug 2010
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    Thanks lula.
    Update from me: I have checked and double checked and changed everything according to the advice given in this thread. I checked and measured the black and white wires. Everything as it should be.
    There still remains about 2A difference between backlight off (higher dicharge)and on (lower discharge). The values as given with the backlight on seems the right values, so there is no possibility to use the offset and get an avarage value.
    Furthermore I noticed that the BM-1 measures a voltage of the battery during discharging (lamps on) and shows quite a big drop in voltage and capacity. These values are the same as measured directly on the battery with a multimeter, but shouldn't the bm-1 show the 'real' capacity as shown when the battery is at rest?

  7. #67
    VicS is offline Registered User
    Location : Home: Kent. Boat: Chichester
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    It will be interesting to see what Nasa have to say.


    As far as I can see, having given this some more thought, the only thing that will give a false, or increased charge reading when the back light is turned on is a poor connection between the white and black wires and the shunt.

    A poor connection there will also give a reduced reading for the battery volts when the back light is turned on but poor connections on the positive (red) connection or the fuse would also do that.

    The voltage between the black and white wires reported earlier in the thread indicates a poor connection between the white and black wires within the crimp .... If the connection was good there would not, could not, be a voltage between the two!

    Personally I would either solder the black and white wires into the crimp or cut off the crimp and simply solder the two together and then make doubly, trebly certain that there was a 100% good connection with the shunt.
    I would check for any voltage between the battery connection and the black and white wires when the back light is on... there should be none!

  8. #68
    pieter2 is offline Registered User
    Location : the Netherlands
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    Aug 2010
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    Just to be sure:
    Next weekend I will remove the crimp and solder black and white together on the shunt side.
    Thanks for all the help!

  9. #69
    VicS is offline Registered User
    Location : Home: Kent. Boat: Chichester
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    Quote Originally Posted by pieter2 View Post
    Just to be sure:
    Next weekend I will remove the crimp and solder black and white together on the shunt side.
    Thanks for all the help!
    It's what I would do. Others do not approve of soldering connections on boat installations.

  10. #70
    Join Date
    Feb 2009
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    Quote Originally Posted by lula6894 View Post
    I have just sent the thread to NASA Marine Instruments.
    I ask NASA to write the answers or news here directly or to send my by mail. If I receive something I will copu here asap.
    Good look. regards
    NASA answer follows

    Dear Sir,

    After reading the thread it appears you have been given some good advice: The backlight draws about 10mA. This current is supplied through the red wire and returned back to the battery through the black wire. If the black wire is not properly connected then the return will pass through the white wire which is one of the shunt sense wires. It only takes 50mV accross the sense wires for the display to read 100A. So even a few mA throughthe sense wire will cause a problem.Check all the connections. Make sure the terminal screws are tight and on the wire rather than the plastic sleeve. The offset is caused by stray voltages generated in the sense wire(white and yellow wires) terminals and should never be more than 0.1 to 0.2 Amp. It can, of course be ballanced out but if it's as high as 2amp then there is something wrong and ballancing it out should not be attempted. If you can't sort the issue recommend you reyurn the unit to us for test.
    Regards,

    NASA Marine
    Boulton Road
    Stevenage
    Herts
    SG1 4QG

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