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  • Getting the best out of my system

    I have my system up and running but I would like to have some input if I can improve on what I have. I have 8 -160 watt 12 volt panels. One 3000 watt 12v inverter and one 80 amp charge controller. I also have 1 extra 80 amp controller but not in system and 6 (6volt) T-105 batteries. I don't have that much load on the system at this time and still have about 12 volt charge in the batteries after shut down at night. Thanks for the help

  • #2
    Hello ufoexpert and welcome to Solar Panel Talk

    My first concern is you have too much panel wattage for a 12 volt battery system. At 12 volts an MPPT CC can usually handle only 1000watts or 80amps. So unless you have some of those 8 panels aimed in a different direction 1280watts may be pushing your CC a little.

    Next issue I see is having 3 sets of 2 x 6v batteries wired in parallel. Unless you have taken steps to improve the parallel wiring that usually shortens the life of the batteries.

    Finally that 3000 amp 12volt inverter can draw over 250amps so your wire needs to be pretty big to carry that load or the fusing sized to protect it. Also large inverters tend to be very inefficient and will slowly suck your battery dry.

    Otherwise I am sure someone else will come along and put their two cents in.
    Last edited by SunEagle; 03-08-2017, 12:48 PM.

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    • #3
      Originally posted by SunEagle View Post
      Hello ufoexpert and welcome to Solar Panel Talk

      My first concern is you have too much panel wattage for a 12 volt battery system. At 12 volts an MPPT CC can usually handle only 1000watts or 80amps. So unless you have some of those 8 panels aimed in a different direction 1280watts may be pushing your CC a little.

      Next issue I see is having 3 sets of 2 x 6v batteries wired in parallel. Unless you have taken steps to improve the parallel wiring that usually shortens the life of the batteries.

      Finally that 3000 amp 12volt inverter can draw over 250amps so your wire needs to be pretty big to carry that load or the fusing sized to protect it. Also large inverters tend to be very inefficient and will slowly suck your battery dry.

      Otherwise I am sure someone else will come along and put their two cents in.
      I appreciate the return from my question. I have mostly 8 gauge wiring though-out the system but I'm not sure what you mean by improve the wiring of the batteries? I have a lot of charge controllers, 2 -30 amp and 1-
      20 amp, could I double up on one of those? checked the specs on the inverter and its just a 12v input and 220 out.

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      • #4
        http://www.smartgauge.co.uk/batt_con.html

        WWW

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        • #5
          Thank you very much White Wolf, your help was just what I was looking for. It looks like I wired up the batteries pretty close to what they said was correct. Now I'll work on not over working the charge controllers. I live in Florida in a manufacture home and I'm very conservative on my usage of energy. All led lighting, etc. The purpose of doing this is to keep this retired old man busy and out of the wife way. Thanks again

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          • #6
            Thank you WWW for adding the link to the smartgauge. That website shows some better ways to wire batteries in parallel.

            As for using multiple or different charge controllers. That is a possibility to break up the panels into smaller groups so that each group is balanced with a charge controller but IMO now you run the risk of multiple chargers connected to a single battery system which may fight each other and not provide equal charging.

            Others may chime in and provide different view points or if the chargers can "talk" to each other then you might be able to have a system that works together.

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            • #7
              I was concern about using two controllers in the same system but maybe something I was over looking. I knew I was pushing the controller beyond its limit as I found out the hard way and smoked the first one.....so much for safe limits build in. I'll be doing some more research on this. Thanks SunEagle

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              • #8
                Originally posted by SunEagle View Post
                Hello ufoexpert and welcome to Solar Panel Talk

                My first concern is you have too much panel wattage for a 12 volt battery system. At 12 volts an MPPT CC can usually handle only 1000watts or 80amps. So unless you have some of those 8 panels aimed in a different direction 1280watts may be pushing your CC a little.

                Next issue I see is having 3 sets of 2 x 6v batteries wired in parallel. Unless you have taken steps to improve the parallel wiring that usually shortens the life of the batteries.

                Finally that 3000 amp 12volt inverter can draw over 250amps so your wire needs to be pretty big to carry that load or the fusing sized to protect it. Also large inverters tend to be very inefficient and will slowly suck your battery dry.

                Otherwise I am sure someone else will come along and put their two cents in.
                Would you expound on that? I have wired my bank to Method #3

                thanks.

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                • #9
                  OK you have a few issues, one serious issue.

                  1. You have more panel wattage than your controller can handle. An 80 amp controller has the following power input limit vs battery voltage.

                  1000 watts @ 12 volts
                  2000 watts @ 24 volts
                  4000 watts @ 48 volts

                  2. There is no reason to use parallel battery configuration especially on stationary systems in a home. You can get away with it but the consequences are you just cut your battery cycle life in half. That means you wil be replacing your battery frequently.

                  3. For a stationary home system, 12 volts was a poor choice and the most expensive and dangerous choice. Minimum is 24 volts up to 1500 watts, but best for any stationary over 1500 is 48 volts. Much safer and less expensive. Example with your panel wattage of 1260 watts on a 48 volt battery only requires a 30 amp Controller. A whole lot less expensive than your 80 amp model that already has to much panel wattage and no room to grow. 12 volt is pretty much limited to RV and mobile applications.

                  4. OK here is the bad news. A 12 volt 1000 watt Inverter is dangerous, a 3000 watt Inverter is just plain dangerous. You are talking 300 amps to drive 3000 watts @ 12 volts. All the 12 volt Inverters on the market I know of do not carry a UL Certification because the Battery Input Terminals are not designed to carry 300 amps, nor can they terminate a large enough wire to safely carry 300 amps. To make matters worse, it is almost impossible for a DIY to terminate a wire large enough because you do not have access to the tooling required or experience and training to do so. Now here is where it gets really dangerous. You said you used 8 AWG wire right? At 300 amps minimum requirement is 2/0 in free air. However being low voltage means to use 2/0 without significant voltage loss requires the distance to be no more than 1-foot. In reality you are looking at 4/0 AWG. Your 3000 watt Inverter cannot terminate a 2/0 or larger cable. The 8 AWG wire you are using is limited to 55 amps. Essentially you are configured to push the 8 AWG to 600% excess of maximum safety rating. At best if you run 300 amps you wil burn the insulation off your wire. Jus tone loose connection, and you are now vaporizing either copper, steel, or the lead on your battery term post. As a general rule of thumb your Inverter should be no larger than your panel wattage. With an 80 amp controller into a 12 volt battery, 1000 watts maximum.
                  MSEE, PE

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                  • #10
                    In fairness, as in my case, having a 3000w inverter doesn't mean he's actually using that wattage. There are variables (cost, size, options like a charger) that could make it a better option in a particular setup. I know that with the unit I bought, there is zero difference in its efficiency to a 1500w model.

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                    • #11
                      Originally posted by -TX- View Post
                      In fairness, as in my case, having a 3000w inverter doesn't mean he's actually using that wattage.
                      It does not matter what your intent is. It is just plain dangerous. Would you buy your kid a Corvette if he never intends to go faster than the speed limit?

                      MSEE, PE

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                      • #12
                        Effective analogy

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                        • #13
                          Originally posted by -TX- View Post

                          Would you expound on that? I have wired my bank to Method #3

                          thanks.
                          Method #3 is ok for 12 volt batteries. But you still run the risk of unequal charging/discharging due to different resistance values at each termination or wire lengths. If those were "bus bar connections you minimize the resistances of the wire lengths and only have to worry about the connection points. Still the internal resistance of each battery create different path for the charging currents.

                          As for the high wattage inverter. The best way to keep the amperage down to safe levels is to install fuses low enough to open before the wire insulation melts and causes a fire. But if you use low amp fuses to protect the wire you have to ask why do I need such a big wattage inverter?

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                          • #14
                            I redid the busbar as the board requested, and each length of 2awg to the 3 strings is of the same length. As far as my inverter, if I did it all over again I'd choose 36v input and 6s2p for my battery bank.

                            BB.jpg

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                            • #15
                              Put that bus bar on Cherry Isolators silly and save the woody for your wife. Note buss bars are made for two hole connectors. Single hole is asking for a failure and fire, If mobile like an RV, single hole is just begging for trouble and fire to come visit you. Where are the washers and locking hardware?

                              Last edited by Sunking; 03-09-2017, 01:22 PM.
                              MSEE, PE

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