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CT_WANDERER's avatar
CT_WANDERER
Explorer
Aug 02, 2015

Battery Line Voltage

Looking at my Morningstar TM45 today. I have for now, 3X 120Watt panels. Going thru the remote panel readings and paying attention to it. At the time, it is in PWM , I see battery voltage of 14.54, then if I go to where it gives me the battery sensor voltage I have a reading of 14.45 volts. The lost difference I assume is line resistance. My question, would you consider this .09 volt a high lost? I am happy with my solar system. Still have two more panels to added once I find the money. Just wondering. Thanks Gary

9 Replies

  • CT_WANDERER's avatar
    CT_WANDERER
    Explorer
    Aug 02, 2015
    smkettner wrote:
    What is the programmed absorption voltage set point?

    Exactly where are the measured points? Battery terminals and controller output terminals?

    You have the battery sense wires connected? Are you reading voltage on these? what end?

    All these reading are off the remote TS45 panel. I assume the battery voltage of 14.54 volts is at the controller output. And the 14.45 is at the batteries post thru the remote sensor line to the controller. My Trimetic panel shows 14.5 volts, but it does not read that extra digit.
    I am running the #4 program on the solar charge controller. I believe the absorption set point is 14.4. If I understand the instructions. Gary
  • CT_WANDERER's avatar
    CT_WANDERER
    Explorer
    Aug 02, 2015
    MrWizard wrote:
    quit worrying.. your doing great
    0.09v drop.. nothing to bother me
    i wish mine was that low
    i got a LOT of wire in my system and more drop than that
    but my solar and batteries keep chugging along


    As I said I am happy with the system, I felt like the drop was not bad. Just one of the number things I was looking at. Thanks all for your input. Gary
  • red31's avatar
    red31
    Explorer
    Aug 02, 2015
    .09v is a bunch if the amps are very low, 20A not a bunch!
  • MrWizard's avatar
    MrWizard
    Moderator
    Aug 02, 2015
    quit worrying.. your doing great
    0.09v drop.. nothing to bother me
    i wish mine was that low
    i got a LOT of wire in my system and more drop than that
    but my solar and batteries keep chugging along
  • time2roll's avatar
    time2roll
    Nomad
    Aug 02, 2015
    What is the programmed absorption voltage set point?

    Exactly where are the measured points? Battery terminals and controller output terminals?

    You have the battery sense wires connected? Are you reading voltage on these? what end?
  • red31's avatar
    red31
    Explorer
    Aug 02, 2015
    <1%

    What's the current?

    Measure before abs set point (bulk) AND current is high.
  • Matt_Colie's avatar
    Matt_Colie
    Explorer II
    Aug 02, 2015
    Gary,

    A lot depends on what instrument you are using to read that voltage.
    If you are not reading both with the same instrument, there can be calibration differences.
    If you are reading both with the same instrument, but that instrument is not true RMS then the PWM may mess up the reading.

    Matt
  • donn0128's avatar
    donn0128
    Explorer II
    Aug 02, 2015
    I think your being paranoid over nothing. Battery voltage is around 14.5VDC. That's good enough for most of us.

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