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

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  • #16
    Originally posted by Mike90250 View Post

    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 ?

    I'll take a look at flexible water tight conduit. That might work if it's flexible enough.

    Yup, it's going to be portable. As in, on wheels in small pelican style cases.

    BTW, Machine Tool Wire (MTW) is a real pain to find. Nobody carries it locally, and all the online shops want you to contact them for a quote. I really hate products like that. It's so 1999.

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    • #17
      Originally posted by createthis View Post


      I'll take a look at flexible water tight conduit. That might work if it's flexible enough.

      Yup, it's going to be portable. As in, on wheels in small pelican style cases.

      BTW, Machine Tool Wire (MTW) is a real pain to find. Nobody carries it locally, and all the online shops want you to contact them for a quote. I really hate products like that. It's so 1999.
      That DLO RHH/RHW cable has a UL sun resistant listing although UV may still make the insulation a little brittle after a while in direct sunlight.

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      • #18
        Originally posted by SunEagle View Post

        That DLO RHH/RHW cable has a UL sun resistant listing although UV may still make the insulation a little brittle after a while in direct sunlight.
        I saw that. Not sure what resistant means in this case. Is that like where they say it's water resistant, but if you splash water on it it breaks? ha.

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        • #19
          I bought 25' of this in red and black: http://www.wireandcabletogo.com/Copp...09-Strand.html

          It arrived today. Looks like it's tinned copper, which is nice.

          I also bought some of these to go with it: http://www.amazon.com/TINNED-BATTERY.../dp/B008D54R0S
          They also arrived today. They look a little short to me, but I reckon it'll do when crimped down.

          Also bought some 1" dia adhesive backed heat shrink (hasn't arrived yet) and some 4/0 SB350 anderson connectors. Man those things are beasts.

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          • #20
            Originally posted by createthis View Post
            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 [B]bottom balancing [/B]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..
            Hold the bus a minute. If you Bottom Balance, you eliminate the need for a LVD. Does not mean you cannot use one, it just means you do not need one. Top Balancing requires a LVD triggered on any cell that dips below 2.5 volts.

            Having said that. if you intend to use an Inverter, even cheap ones have LVD built into the. Buy a good one and you can program what voltage you want to set the LVD voltage you want to disconnect at. The critical voltage on 4S Bottom Balance is 10 volts. However you want to disconnect at 12 volts or roughly 10 to 15%.

            The beauty of Bottom Balance is it does not take any special equipment like a BMS or LVD to operate and protect the batteries.


            MSEE, PE

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            • #21
              I'm going to be using a xantrex 2000w inverter. The low voltage cut off is set at 10.5v and not programmable. I'm betting that's too low at max load.

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              • #22
                Which inverters have the programmable low voltage shutoff, BTW? Outback and Magnasine? Those might be an option if I permanently mounted them in one location and maybe attached them to the rest of the generator with a 4/0 anderson connector when I want to use them. I doubt those 4/0 anderson connectors are NEC approved though, which I'm guessing they would have to be if they were permanently mounted. I just think those inverters are probably a little large for a portable solution, unless permanently mounted to an RV. These will be in pelican style cases for portability.

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                • #23
                  Originally posted by createthis View Post
                  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?
                  That's right. That C rating of C3 is only for short bursts. C1 is the realistic maximum, and C/5 or less is better for max life.

                  High-current done safely doesn't come cheap, in both parts and the tools to make it safe as you've seen.

                  You may want to look into marine LVD's, like the Blue Sea Systems m-LVD product or similar.

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                  • #24
                    I just realized my Victron BMV-700 SOC meter has programmable relay contacts on the back. Looks like it'll drive 15mA @ 12v, which isn't a lot. However, it looks like I can use it in conjunction with either a 500A battery isolator relay, via a smaller relay, or else with this Victron BP-220: https://www.victronenergy.com/blog/2...says-and-more/

                    220A is a little lower than my 250A class-t fuse, but it'll probably be fine. They mention the VE Bus BMS in that article. I wonder why they don't mention using the relay outputs from the BMV-700?

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