National Luna battery box trouble shooting





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  1. #1
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    Default National Luna battery box trouble shooting

    On my recent shakedown trip i tested my entire setup. Had a fail on the 3rd and last night with incorrect voltage readings.

    I have my fridge and canopy lights setup with 2x120AH batteries in Parallel using the National Luna Battery box. The problem i have is that the position of where the box is fitted i cannot easily read the battery monitor. So i got one of the portable monitors from Outdoor warehouse. But they do not sell the connector fittings to attach it to the box. I never had time to hunt around so i thought why not just attach it directly to the battery

    2 and a half days later this thing is still reading 100%. (Without charging). So i make the mission to read the National luna box directly and take a series of pictures with my phone. It shows the light flickering between 12.3/12.4v mark under load.

    I go out for a drive for an hour to see how much it will charge. It then was sitting more comfortably at 12.4/.5v

    Not even 30 minutes later as i put the first chop on the braai the dam low voltage alarm goes off! Have to turn the whole system off until the drive home when i can recharge.

    Checking back on my photos now as i took quite a few to make sure i got a goo picture. One of them shows it sitting just above the low voltage mark which i missed. What is the reason for these phantom readings? Why would the secondary monitor not pick up the correct voltage at all?

  2. #2
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    Default Re: National Luna battery box trouble shooting

    Are the batteries identical?
    Are you charging both batteries with one Luna unit?

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    Default Re: National Luna battery box trouble shooting

    Identical units.

    I checked them with a voltmeter and they are reading the same voltage as well. Yes one National Luna Battery box.

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    Default Re: National Luna battery box trouble shooting

    I am trying to wrap my head around this. 2 x 120ah batteries in parallel.

    Is one inside the NL battery box ?

    Is the other connected via the terminals ? How is that one housed. ?
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    Default Re: National Luna battery box trouble shooting

    what vehicle?
    Possibly smart alternator issue

  6. #6
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    Default Re: National Luna battery box trouble shooting

    I have the second battery in another box. Just cut holes in the lid to run the cables.

    Its not an alternator issue, i wasn't even charging the batteries as i was trying to see how far i could push it. So the issue is that the built in battery monitor was showing a reading too high and the second battery monitor was not working at all. It was constantly sitting at 100%.

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    Default Re: National Luna battery box trouble shooting

    The battery monitor ? is it attached directly to the terminals on one battery ?

    Please try and attach 1 positive to 1 terminal on battery A and 1 negative on battery B and post what it reads please.
    Lusted for a Landy but the Pajero was sexier and bigger in the right departments, just like my Missus.

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    Default Re: National Luna battery box trouble shooting

    Quote Originally Posted by Stranger View Post
    The battery monitor ? is it attached directly to the terminals on one battery ?

    Please try and attach 1 positive to 1 terminal on battery A and 1 negative on battery B and post what it reads please.
    I will do. It was 10pm night before install situation so i just made a plan on the moment when i installed the second monitor. I wasn't 100% sure it would work just running the monitor off the one battery but my thinking was that surely if its reading the voltage of one of the batteries in the same string it would be the same as reading off both.

  9. #9
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    Default Re: National Luna battery box trouble shooting

    I can understand that the internal monitor on the NL box could get a bit confused if there are 2 in parallel, but the separate monitor should read both batteries as one big one if you connect as I asked. If you get a reading that looks correct, you then disconnect the two and take separate readings. This will eliminate or confirm if one battery is on it's way out and is dragging the other one down to equalise.

    You can check your readings and compare with a multi meter
    Lusted for a Landy but the Pajero was sexier and bigger in the right departments, just like my Missus.

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    Default Re: National Luna battery box trouble shooting

    The important thing to remember here is what Stranger said above, if you connect the batteries as he described you now have one big battery. Therefore measuring the Volts on either battery will show you the Volts of both Batteries as one...

    You will have to disconnect the 2 from each other and then measure them separately to see the voltage of each one alone.

  11. #11
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    Default Re: National Luna battery box trouble shooting

    Quote Originally Posted by Haas View Post
    The important thing to remember here is what Stranger said above, if you connect the batteries as he described you now have one big battery. Therefore measuring the Volts on either battery will show you the Volts of both Batteries as one...

    You will have to disconnect the 2 from each other and then measure them separately to see the voltage of each one alone.
    Ok i am with you now....

    Ill do some trouble shooting tonight when i get home. We had a long 6/7 hour run home (With the fridge running) on Tuesday and they have been sitting unused since. So i will disconnect them and test both voltages and see what i get. Should also tell me if they were charged up properly. Im pretty sure they were charged properly, as i had the fridge running at -8 from Thursday evening until Saturday morning when we left. It then ran until Monday evening uncharged.

    I was also very stupid not thinking this through.I think 2 and a half days of running the fridge with no charge is pushing it :-)

  12. #12
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    Default Re: National Luna battery box trouble shooting

    Quote Originally Posted by Stranger View Post
    The battery monitor ? is it attached directly to the terminals on one battery ?

    Please try and attach 1 positive to 1 terminal on battery A and 1 negative on battery B and post what it reads please.
    HomeBrewer, to add to what Stranger is saying, it is also good practice to pull power from battery A's + (pos) and battery B's - (neg) or vice versa, not both poles on one battery.

    You should also charge them like this. But you must first fully charge them individually, then connect them, then use them and now you can charge them together.
    Last edited by DC Polokwane; 2019/06/20 at 12:00 PM.
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    Default Re: National Luna battery box trouble shooting

    Quote Originally Posted by DC Polokwane View Post
    HomeBrewer, to add to what Stranger is saying, it is also good practice to pull power from battery A's + (pos) and battery B's - (neg) or vice versa, not both poles on one battery.

    You should also charge them like this. But you must first fully charge them individually, then connect them, then use them and now you can charge them together.
    Yip that is how they are setup.

    I bought them to use them as battery backup for home so i have run them in and charged them a few times together. It's probably a good exercise to maybe do that a few more times.

    It's only the battery monitor that i ran off of one battery, as it was a bit of an afterthought

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  15. #14
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    Default Re: National Luna battery box trouble shooting

    Ok did testing. Together the string is testing at 12.79v

    Individually 12.82 and 12.79/8v

    So looks like its charging fine. Its purely down to fauly voltage readings.

    Ive now connected the monitor to the positive of the one batter and negative of the other. Will see how that works

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  17. #15
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    Default Re: National Luna battery box trouble shooting

    I think that you have it right now. On my NL box I have the monitor and I also have a separate meter. They always differ slightly.
    Lusted for a Landy but the Pajero was sexier and bigger in the right departments, just like my Missus.

    2004 Gen 3. 3.8i petrol V6 (PAJTU)
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