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Good LVD + relay combination for 12V 100 ah 3C pack?

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  • Good LVD + relay combination for 12V 100 ah 3C pack?

    I've got a GBS 100ah LifePO4 pack I've been sitting on for a couple of months. I finally have time to go through the bottom balancing procedure, so I've made my list of things to do in order, and now I'm starting to think about operating the pack on a regular basis. Which means I'll need to get my LVD operational sometime soon.

    I bought this: http://www.amazon.com/LVD-Low-Voltag.../dp/B01B52H98C which comes with this wiring diagram: http://jumpycalm.com/file/LVD.pdf
    That LVD has a disconnect voltage of 11.6V on a 15 second delay, which is a bit low for sub-C operation, but I think it'll be fine.

    The C rating for this pack is 3C, so, while I'll probably never draw anywhere close to 3C from the pack, I guess I should buy a 12V 300 amp relay?

    I see this 12V 150 amp golf cart solenoid: http://www.amazon.com/CONTINUOUS-SOL.../dp/B008R1T5IM
    Looks like it draws 6 watts when it's on. Seems like a fairly large power draw. Is there a more efficient way to do this?

    Thanks.
    Last edited by Mike90250; 04-11-2016, 07:51 PM. Reason: added Tags (Moderator)

  • #2
    How about a solid state relay ? (SSR, not a SCR) https://en.wikipedia.org/wiki/Solid-state_relay
    takes some looking to find good DC ones., digi-key has them, and a good search engine
    http://www.digikey.com/product-searc...=0&pageSize=25
    don't forget they often need some heat sinking
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • #3
      Originally posted by Mike90250 View Post
      How about a solid state relay ? (SSR, not a SCR) https://en.wikipedia.org/wiki/Solid-state_relay
      takes some looking to find good DC ones., digi-key has them, and a good search engine
      http://www.digikey.com/product-searc...=0&pageSize=25
      don't forget they often need some heat sinking
      I can't find any SSRs over 100A. This one might work if 100A is all I want: http://www.digikey.com/product-detai...685-ND/2060413
      It's expensive: $142
      Also, I can't tell from that page how much power it draws.

      I was thinking something more along the lines of a magnetic latching contactor.
      Last edited by createthis; 04-10-2016, 09:50 PM.

      Comment


      • #4
        Maybe I'm thinking about this the wrong way. Most inverters have a remote switch option. Maybe a simple low current circuit like this, designed to turn off the inverter at my voltage set point is the answer: https://youtu.be/0q8uq5ntjvI

        I doubt I'll ever need an LVD for DC loads. They're just typically lower current. But if I do, I have an APO3 sitting around from a previous project that I could use inline.

        Comment


        • #5
          Yow ! 100A on a 12V system ?
          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            Originally posted by Mike90250 View Post
            Yow ! 100A on a 12V system ?

            Yeah. I was looking at inverters last night. A 2000W inverter will require less than six feet of 3/0 wire between the battery and inverter. A 2800W inverter will require less than six feet of 4/0 wire.

            Kinda cool though. You can run air conditioners off of that.

            Comment


            • #7
              Originally posted by createthis View Post


              Yeah. I was looking at inverters last night. A 2000W inverter will require less than six feet of 3/0 wire between the battery and inverter. A 2800W inverter will require less than six feet of 4/0 wire.

              Kinda cool though. You can run air conditioners off of that.
              But the amount of amps you will be drawing on that 4/0 cable may eventually break it down. I hope you have taken precautions to protect the wire with the correct fusing and insulated all of the terminal points.

              Comment


              • #8
                Originally posted by SunEagle View Post

                But the amount of amps you will be drawing on that 4/0 cable may eventually break it down. I hope you have taken precautions to protect the wire with the correct fusing and insulated all of the terminal points.

                Why does everyone here assume I've already built what I'm talking about? I like to research things before I build anything. This is all just talk right. It's also a toy system for my own experimentation. I am going to buy some 4/0 cable today though.

                Comment


                • #9
                  Originally posted by createthis View Post


                  Why does everyone here assume I've already built what I'm talking about? I like to research things before I build anything. This is all just talk right. It's also a toy system for my own experimentation. I am going to buy some 4/0 cable today though.
                  I guess with the 40 years of electrical experience behind me I tend to worry about people getting hurt (I have seen it many times) therefore I try to raise the red flag to warn people about the hazards of electrical circuits.

                  When you purchase that 4/0 cable make sure you get a certified lug compression system or you could end up with less than desired krimps on the terminal lugs which will increase the resistance and heat generated.

                  Comment


                  • #10
                    Originally posted by SunEagle View Post
                    When you purchase that 4/0 cable make sure you get a certified lug compression system or you could end up with less than desired krimps on the terminal lugs which will increase the resistance and heat generated.
                    I was planning to use this crimper: http://www.amazon.com/Hydraulic-Batt.../dp/B00GXQ2E5E
                    My second choice would probably be this: http://www.amazon.com/Greenlee-K09-2.../dp/B000LDGRV2

                    Which tool do you recommend?

                    I'll be keeping an eye on it either way, looking for heat, melting, etc. I won't trust it. But honestly, I probably won't use it at high amperages often. I mostly just plan to prove I can. But who knows. I might find a use case for high amps and use it that way all the time, in which case I'll be sure to watch it like a hawk. Sounds like a good excuse to buy a thermal camera.

                    I bought some 4/0 THHN today. It was fairly inexpensive, but after thinking about it for a minute, it's not going to work in this application. This is a portable system, so I need flexible cable. 4/0 THHN is super stiff. I can barely bend it with my bare hands.

                    I'm going to check the local welding supply tomorrow. Looks like 4/0 welding wire is what I want. Here's my benchmark for price. It ain't cheap: http://www.amazon.com/Crimp-Supply-U.../dp/B0161NYP1Y

                    Comment


                    • #11
                      1) the hydraulic crimper is the better, the Greenlee will be VERY difficult to use with 4/O cable
                      2) welding cable has extra fine strands and requires non-standard Lugs for crimping. Lugs need to be tin plated, not bare copper
                      3) will this ever be inspected or used in an insured structure ? If NO, then you have some room to play with.
                      4) the lugs may not stamp a cert # onto the barrel, = failed inspection
                      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                      solar: http://tinyurl.com/LMR-Solar
                      gen: http://tinyurl.com/LMR-Lister

                      Comment


                      • #12
                        Originally posted by Mike90250 View Post
                        1) the hydraulic crimper is the better, the Greenlee will be VERY difficult to use with 4/O cable
                        2) welding cable has extra fine strands and requires non-standard Lugs for crimping. Lugs need to be tin plated, not bare copper
                        3) will this ever be inspected or used in an insured structure ? If NO, then you have some room to play with.
                        4) the lugs may not stamp a cert # onto the barrel, = failed inspection

                        Which crimper would put a cert # on the barrel? I can't imagine this ever being inspected as it's a portable personal unit, but I like to know what will or won't pass an inspection anyway.

                        Welding wire lugs must be tin plated according to whom? Is that a personal experience statement or a code statement, and if code, which code? Some California code?
                        Also, are you saying the non-standard lugs are non-standard because they are tin plated, or are you saying they are non-standard AND they should be tin plated?

                        I've read tinned lugs slow corrosion, so that's fine. Apparently once the corrosion starts the cable must be cut to remove bad sections. Tinned welding wire is a thing too, so that might be something I look for. Will these work? http://www.amazon.com/TINNED-BATTERY.../dp/B008D54R0S

                        Comment


                        • #13
                          $400+ UL certified Crimpers put a code on the lug, so inspectors know it's a good crimp. When a crimp is done properly, it cold welds the strands to the lug and the metal internally stays corrosion free, in dry indoor conditions. Bare copper starts corroding the instant it comes out of the forming machine, tin plating stops most of that, and allows for a superior attachment.
                          When you are pushing 200A through a cable, even small amounts of resistance become dangerous and damage the cable insulation from the generated heat. That's one reason soldering is not a recommended method, the joint heats, solder melts, and wires fall off the lug.
                          Welding wire insulation is not rated for installs, you need machine tool wire (MTW)
                          http://www.quickcable.com/products.php?pageId=854 "can be used as battery cable, motor lead, and power hook-up cable"
                          I've also heard (maybe an electrician can back me up) that locomotive cable is also rated for battery use
                          DLO RHH/RHW Cable http://www.quickcable.com/products.php?pageId=855

                          Lugs
                          http://www.quickcable.com/products.php?pageId=78 "MagnaLugs feature a wider footprint and thicker walls than conventional lugs and are listed by UL/CUL when applied with Quick HexCrimp™ tools."

                          And these look interesting, compression lugs, like a flare pipe fitting http://www.quickcable.com/products.php?pageId=329 4/O is really big stuff !

                          A little more on codes and MTW / DLO cables ( look for RHH/RHW cert)
                          http://forums.mikeholt.com/showthread.php?t=98209 Scroll down to post #6 about the fine strands and required lugs for them.

                          What happens when it goes bad ?
                          see page 3 - https://www.altestore.com/store/medi...es_Article.pdf
                          Last edited by Mike90250; 04-11-2016, 07:59 PM. Reason: more stuff
                          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                          solar: http://tinyurl.com/LMR-Solar
                          gen: http://tinyurl.com/LMR-Lister

                          Comment


                          • #14
                            It's funny. I read the MTW spec and it looks inferior to welding cable. One thing both wires lack is UV resistance. This is a portable unit, so it will be outside most of the time. I guess I'll need to put the wire inside garden hose or something to keep it from rotting.

                            Comment


                            • #15
                              Originally posted by createthis View Post
                              It's funny. I read the MTW spec and it looks inferior to welding cable. One thing both wires lack is UV resistance. This is a portable unit, so it will be outside most of the time. I guess I'll need to put the wire inside garden hose or something to keep it from rotting.
                              Either electrical conduit or the flexible water tight conduit, not garden hose. Only a couple wire types are rated for UV, wires are supposed to be protected.

                              This is going to be Portable ?
                              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                              solar: http://tinyurl.com/LMR-Solar
                              gen: http://tinyurl.com/LMR-Lister

                              Comment

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