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  • #16
    Originally posted by ButchDeal View Post

    Not that it helps too much but it is a 200Ah bank (paralleled 100Ah 48V).
    It is marginal but the wires are way too small
    THX Butch you made me go back and read over every reply carefully. Still leaves more question than answers. However if we run the numbers through the protein computer and consider the Air Conditioner points to another problem.

    A 3000 watt Inverter at 48 volts requires at most 80 amps assuming the Inverter efficiency is 80% at full power. So I have doubts a 3-feet 1-way run of 4 AWG is the real problem here. One clue we have is trying to run an air conditioner, and the OP did not specify anything about the AC like BTU's and SEER. Let's assume for a moment it is a 12,000 BTU, 10 SEER window shaker from the box store being low quality is a fair reasonable assumption. At full load will pull 1200 to 1400 watts on a 3 Kva Inverter or or roughly 30 to 40 amps off the batteries. On paper that should work just, but there is another issue or two in real life application.

    If I were to bet, I would say Power Factor is the problem and overloaded Inverter at start-up. A cheap window shaker LRA is likely 6 to 8 times more than FLA, however again I don't think that is a problem with the wiring. Me thinks the LRA combined with the Inverter poor Power Factor is the problem. Assume a reasonable LRA is 5X FLA or 6500 VA with a PF = 0.5. The Inverter can only handle 3000 VA @ 0.8 PF. What would happen is exactly what the OP describes. So my money is on the Inverter, not the wiring.

    Still comes down to the design. Not designed to do what is intended.

    OP if you insist on running Air Conditioners off solar/battery, you cannot use conventional AC units like window shakers running off AC power. Well you can if money, space and weight are of no concern. You have to use very efficient split systems designed to run from either 24 or 48 volt battery. They are 2 to 3 times more efficient and do not have the heavy start up loads and their power is variable so it can ramp power up and down as needed to meet conditions. Just one little catch, extremely expensive. Either way is very expensive, large, and HEAVY

    What you are discovering is you cannot have luxuries like Air Conditioning, Heat, or Cooking with solar. You have to do without those things, or use a fossil fuel source to be economical and physically possible. Even if the Inverter could work, with the batteries you have would only last a few hours per day, and at that rate would wear them out in a year being that deeply discharged and discharged fast. A heavy load like that changes your 200 AH batteries into more like 100 to 125 AH batteries. Mr Peukert dictates and enforces that law with no tolerance.

    Like I said before, it is doing exactly what is was designed to do.
    Last edited by Sunking; 03-03-2019, 01:27 PM.
    MSEE, PE


    • #17
      I will see what happens in the next few day


      • #18
        thank you all