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  • Help with diagnosing battery bank problem

    Hello all,

    I have a very simple set-up so far:

    1x250W panel
    1x 20A Tracer charge controller with remote meter
    2x 110ah batteries connected in parallel.
    1x Waeco fridge

    I intend to connect more loads to the batteries but I can't understand why the State of Charge given by the remote meter drops to around 50% overnight...

    The meter reports the 24hr usage is around 20ah so how can this reduce the batteries in my bank to 50% SOC? I have tried connecting just one battery in the system and there seems to be little difference between the performance of this compared to the system with both batteries connected. Even with just one battery, how can such a small draw from the fridge account for such a drop in the SOC of my battery?

    Any advice greatly appreciated!

    David

  • #2
    Originally posted by davidcc View Post
    Hello all,

    I have a very simple set-up so far:

    1x250W panel
    1x 20A Tracer charge controller with remote meter
    2x 110ah batteries connected in parallel.
    1x Waeco fridge

    I intend to connect more loads to the batteries but I can't understand why the State of Charge given by the remote meter drops to around 50% overnight...

    The meter reports the 24hr usage is around 20ah so how can this reduce the batteries in my bank to 50% SOC? I have tried connecting just one battery in the system and there seems to be little difference between the performance of this compared to the system with both batteries connected. Even with just one battery, how can such a small draw from the fridge account for such a drop in the SOC of my battery?

    Any advice greatly appreciated!

    David
    Hello David and welcome to Solar Panel Talk!

    The first thing I would suspect is that the SOC meter is voltage based rather than integrating the discharge current and comparing it to an input battery capacity (which is what most sophisticated battery monitors do.)
    That means that that the 10AH drain during the night is actually dropping your 220AH battery bank to a voltage that would correspond to 50% SOC in a rested system.
    That in turn means that your battery capacity is currently far less than the 220AH you expect it to be.
    Check voltage and SC of all cells, and run a controlled charge and discharge test. You will almost certainly find that for some reason (sulphation from inadequate charging?) your batteries are now toast.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #3
      Simple SOC voltages on a working system are useless as you have discovered. Only works on a well rested battery for at least 4 hours. That means disconnected and left alone for several hours.

      Only accurate way to determine SOC is with a temperature corrected hydrometer. Otherwise you are just guessing.
      MSEE, PE

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      • #4
        Originally posted by Sunking View Post
        Only accurate way to determine SOC is with a temperature corrected hydrometer. Otherwise you are just guessing.
        Actually, one of these, properly calibrated, is the most accurate way to track SOC:



        I am curious as to what type of SOC meter is being used here. I am not familiar with the Tracer with remote meter as to whether or not it uses a shunt to measure current. Chances are there is nothing wrong other than the meter being bogus if it does not use a shunt.
        off-grid in Northern Wisconsin for 14 years

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