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  • Potentially an incredible energy storage opportunity for me? Free Lion's

    Close thread. I'm going to do more research before asking any more questions.
    Last edited by aaronllewellyn; 09-12-2016, 12:16 PM.

  • #2
    Old Lithium cells are dangerous, especially ones that have deteriorated as much as you indicated. Personally I would not risk having many around. Old cells are prone to thermal runaway, and once it starts you cannot stop it or put the fire out. All you can do is get back and let it burn itself out. Fire department wil not even try, just keep it contained to your house. So if you are OK with that, have at it.

    What kind of Lithium Cells are you talking about? If they have any Cobalt or Manganese I would not touch them. Perhaps if they are LiFeP04 or Titanate but in small quantities. Another huge issue is how are you going to integrate them into a Solar System designed to operate at voltages of 12. 24, or 48 volts? You would have to tear them apart to get down to individual cells and reconfigure. Otherwise you would have to design and build the equipment to work with Queer non-standard operating voltages the batteries are configured for.

    Lots of challenges and risk.
    Last edited by Sunking; 09-09-2016, 05:39 PM.
    MSEE, PE

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    • #3
      Originally posted by aaronllewellyn
      , would it be possible to wire three 40v modules in series and reach 120v DC? that seems like a far more standardized voltage.
      120V DC wouldn't be standard.
      12, 24, 48 - those are standard (or at least common) DC voltages.
      IIRC at 60V or higher there are more requirements for properly handling/wiring DC.

      Even large datacenters with huge amounts of batteries stick with 48V for what they do.



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      • #4
        Originally posted by foo1bar View Post
        120V DC wouldn't be standard.
        12, 24, 48 - those are standard (or at least common) DC voltages.
        IIRC at 60V or higher there are more requirements for properly handling/wiring DC.

        Even large datacenters with huge amounts of batteries stick with 48V for what they do.



        I was thinking 120v AC (possibly being able to use an inverter to convert 120 DC to AC) would be essentially wall power. I'm just trying to brainstorm. I understand the dangers of HV I bus up and de bus these batteries to and from 640 volts regularly. You're very right, I have first hand experience dealing with handling HV, as far as safety goes. right now I'm just trying to come up with a way to potentially use these modules as storage at the cost of free, if only as an experiment.
        Last edited by aaronllewellyn; 09-09-2016, 06:28 PM.

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        • #5
          Originally posted by foo1bar View Post
          Even large datacenters with huge amounts of batteries stick with 48V for what they do.
          No that is not entirely accurate. Telecom is -48 volt, and some of the equipment you find in a Data Center operates directly from - 48 volt battery plants. However that is prety much for Transport, not processing. In a Data Center most of the processing equipment runs on 240/208/120 volts AC power supplied by a UPS. A Large Data Center can have up to a 2 Mw UPS and battery voltages on those can be as high as 590 volts the maximum voltage NEC will allow without significantly stricter requirements over 600 volts.

          One very common Voltage you see for small UPS and Industrial Inverter is 144 volts. There are tons of 144 volt Inverters on the Telecom and Electric Utility Salvage markets. Any electrical sub-station you see will likely have a 144 volt battery bank and a 2 to 5 Kwh Inverter used to power SCADA and Protective Relay Switching Control Circuits.

          From a code perspective there are 2 lines drawn in the sand. One at 50 volts and another at 600 volts. When you cross those lines, rules change significantly.
          Last edited by Sunking; 09-09-2016, 06:25 PM.
          MSEE, PE

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          • #6
            Originally posted by aaronllewellyn View Post


            I was thinking 120v AC (possibly being able to use an inverter to convert 120 DC to AC) would be essentially wall power. I'm just trying to brainstorm. I understand the dangers of HV I bus up and de bus these batteries to and from 640 volts regularly.
            Voltage the Inverter operates at if designed properly depends on the Invert's Wattage. Higher wattage requires higher voltages to keep current manageable, cost effective, and safe.

            12 volts up to 1000 watts.
            24 volts up to 2000 watts
            48 volts up to 4000 watts.

            What does this all have in common? Answer is 100 amps or less.

            Note pushing those limits does not mean a good practice. At 4000 watts I would prefer 330 volts. But you consumers and DIY's cannot do anything over 48 volts.
            Last edited by Sunking; 09-09-2016, 06:34 PM.
            MSEE, PE

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            • #7
              And some data centers have experimented with running their power distribution at high (300-400V) DC voltages instead of running AC to the racks. The touted efficiency increases do not seem to have materialized yet though.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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              • #8
                Originally posted by Sunking View Post

                Voltage the Inverter operates at if designed properly depends on the Invert's Wattage. Higher wattage requires higher voltages to keep current manageable, cost effective, and safe.

                12 volts up to 1000 watts.
                24 volts up to 2000 watts
                48 volts up to 4000 watts.

                What does this all have in common? Answer is 100 amps or less.

                Note pushing those limits does not mean a good practice. At 4000 watts I would prefer 330 volts. But you consumers and DIY's cannot do anything over 48 volts.

                thanks for the good info. I'm surprised there's not an easier way to convert 40 volts to 24 volts.
                Last edited by aaronllewellyn; 09-09-2016, 06:42 PM.

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                • #9
                  Originally posted by Sunking View Post
                  From a code perspective there are 2 lines drawn in the sand. One at 50 volts and another at 600 volts. When you cross those lines, rules change significantly.
                  I think for DC they upped it to 60V. That's nice for us, since the -48V plants are floated above 50V.

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                  • #10
                    Originally posted by sdold View Post
                    I think for DC they upped it to 60V. That's nice for us, since the -48V plants are floated above 50V.
                    From a code perspective Nominal Battery Voltage is used, not charging voltages. That means 48 is less than 50 in the NEC eyes.

                    Point is the same be it 50 or 60 volts. Once you cross 50/60 volts the rules get a lot more strict like no exposed conductors, connector, or any live voltage exposed. If you notice commercial providers like Bosch and what was suppose to be Tesla battery systems wee operating well above 100 volts enclosed in cabinets. The consumer cannot access the batteries or equipment.
                    Last edited by Sunking; 09-09-2016, 07:46 PM.
                    MSEE, PE

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                    • #11
                      Originally posted by inetdog View Post
                      And some data centers have experimented with running their power distribution at high (300-400V) DC voltages instead of running AC to the racks. The touted efficiency increases do not seem to have materialized yet though.
                      Pretty sure that is the equipment manufactures problem as they are the ones who have to convert down to whatever voltage their equipment actually operates at.

                      It can be done, but there would have to be s standard voltage as no manufacture is going to go to the expense of various voltage profiles. It would have to be like 48 volts where every peice of equipment uses 48 volts. 48 volt sis a low voltage standard any communications manufactures must comply with or will be left out of the market. Telecom is huge market to miss. Right now - 48 volt DC and 208/240/120 VAC are the Standards.

                      UPS on the other hand is a bit all over the place depending on IInverter Power. However the output is the same everywhere of 208/240/120
                      MSEE, PE

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                      • #12
                        Originally posted by Sunking View Post
                        Pretty sure that is the equipment manufactures problem as they are the ones who have to convert down to whatever voltage their equipment actually operates at.

                        It can be done, but there would have to be s standard voltage as no manufacture is going to go to the expense of various voltage profiles. It would have to be like 48 volts where every peice of equipment uses 48 volts. 48 volt sis a low voltage standard any communications manufactures must comply with or will be left out of the market. Telecom is huge market to miss. Right now - 48 volt DC and 208/240/120 VAC are the Standards.

                        UPS on the other hand is a bit all over the place depending on IInverter Power. However the output is the same everywhere of 208/240/120
                        My company has been trying to get some of the UPS manufacturers to get rid of the PDU's that supply 120 volt power to computer hardware and go to with either 240volt or 208volt to help eliminate the zero sequence harmonics that can build up on the neutrals. It would be help with improving power quality.

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                        • #13
                          Originally posted by Sunking View Post
                          Pretty sure that is the equipment manufactures problem as they are the ones who have to convert down to whatever voltage their equipment actually operates at.

                          It can be done, but [B]there would have to be s standard voltage as no manufacture is going to go to the expense of various voltage profiles[/B]. It would have to be like 48 volts where every peice of equipment uses 48 volts. 48 volt sis a low voltage standard any communications manufactures must comply with or will be left out of the market. Telecom is huge market to miss. Right now - 48 volt DC and 208/240/120 VAC are the Standards.

                          UPS on the other hand is a bit all over the place depending on IInverter Power. However the output is [B]the same everywhere of 208/240/120[/B]
                          There is a good paper on the subject published by APC. It is a bit dated (2008) but still generally valid.
                          They suggest a standard DC distribution voltage of 380V which corresponds to the output voltage of a DC UPS which runs off standard (outside the US and Japan) three phase AC voltage of 400Y/230. (Not quite the same way we would label it, but close.) That 380V DC is based on the starting DC available from a six pulse rectifier from that AC source.

                          Note that the paper suggests that the oddball countries with 120/240, 208Y/120, or 480Y/277 would just have to put transformers on the AC inputs of their UPS.

                          The US may be the heart of data technology, but I believe that most of the large data centers for global companies are being located in countries with different service voltages.
                          Last edited by inetdog; 09-09-2016, 08:25 PM.
                          SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                          • #14
                            Originally posted by inetdog View Post

                            There is a good paper on the subject published by APC. It is a bit dated (2008) but still generally valid.
                            They suggest a standard DC distribution voltage of 380V which corresponds to the output voltage of a DC UPS which runs off standard (outside the US and Japan) three phase AC voltage of 400Y/230. (Not quite the same way we would label it, but close.) That 380V DC is based on the starting DC available from a six pulse rectifier from that AC source.
                            I am familar with and have read the document years ago.

                            As for large scale UPS in the USA typically use battery voltages of 500 to 590 volts to stay under 600 volts. The Inverters are 3-phase 480 volt Delta. The magic happens in the equipment rooms. In the equipment rooms are strategically placed PDU's (Power Distribution Units). The PDU's contain a Transformer, AC Distribution Branch Circuits with Breakers, some power line conditioning and monitorig/alarm/control circuits. Th ePDU's are supplied with 480 volt delta, and trnasformed most commonly to D 208 / Y 120 volts to supply equipment racks in need of AC power.


                            MSEE, PE

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                            • #15
                              Anyway back to the OP question. I am not saying it cannot be done because it can be done. Questions are:

                              1. Are you willing to take the risk?
                              2. Do you have the skill sets and resources to do it?

                              Based on your comments and answers I think you are wiling to take the risk, but likely lack the skills and resources to pull it off. On paper it is simple. However in practice even if you have the skill sets and resources is difficult to implement.
                              Last edited by Sunking; 09-09-2016, 10:24 PM.
                              MSEE, PE

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