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  • Multiple pre-assembled battery packs

    New to solar, this is more of a battery question here.
    I have dozens of Li-ion battery packs. Each pack has its own BMS integrated into it.

    10S3P 36Volt 7800mAh/280Wh

    I would love to connect them in parallel to achieve a higher current capability but Im not sure if I have to do that through the BMS or can I just use the main (+)(-) lead wires to achieve this? Also, each pack will have its own dedicated solar panel(s) to charge it.

    My goal is to make a complete system Where I can easily remove and replace packs and have the ability to monitor each individual pack. The BMS has built in Bluetooth capabilities so I can connect my phone to them and see each cells condition in any individual pack.

  • #2
    You can connect them in parallel through the main lead wires. I would consider fusing the positive lead. Do they have separate charging leads? Is their a reason you want to charge eack pack separately? It would be less expensive to have several large solar panels and one charge controller. The BMSs should take care of balancing within the packs and it should cutoff any pack that has reached the top.
    Last edited by Ampster; 04-23-2019, 04:40 PM.
    9 kW solar, 42kWh LFP storage. EV owner since 2012

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    • #3
      Awesome. That's great news!!!
      1.Yes, each pack has separate charging lead wires.
      2. No specific reaon for each pack to have its own charge controller. I Just havent planned out the best possible solution yet on charge controllers and solar panels. I'm building the system based on the battery systems that i currently have on hand. I havent been researching charge controllers because i wasnt sure parrallel connecting my sepertate packs with individual BMS's would work or be hindered by the BMS from an overload current being drawn.

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      • #4
        Next step is to decide on the best inverter for 36v. Modified Sine wave for now. But once I start connecting devices that require pure sine wave I'll add in one of those suckers.. For now im Just trying to power a window AC unit and some lights.

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        • #5
          Originally posted by Valence View Post
          Awesome. That's great news!!!
          1.Yes, each pack has separate charging lead wires.
          2. No specific reaon for each pack to have its own charge controller. I Just havent planned out the best possible solution yet on charge controllers and solar panels. I'm building the system based on the battery systems that i currently have on hand. I havent been researching charge controllers because i wasnt sure parrallel connecting my sepertate packs with individual BMS's would work or be hindered by the BMS from an overload current being drawn.
          I think one reason for the separate charging leads is then you can charge when under load and charging can be cutoff without affecting the loads. From what you have said that fits your application. You may be using the load when you are charging. I would still consider a single charge controller or maybe two but that is not my area of expertise. I would also fuse the charging leads but based on the wire size you could use a smaller fuse than on the load side. The fuses could be a simple disconnect that would allow you to check voltages if the bluetooth fails. As far as an overload current being drawn, the BMS may also cutoff when that occurs. Do you have specs on the BMSs?

          There is another thread where that poster had similar batteries. Do you have a good source? I could use some for some e-bikes I am working on. I also have a GEM that I am working on. I am intrigued with the bluetooth capability.
          Last edited by Ampster; 04-23-2019, 07:00 PM.
          9 kW solar, 42kWh LFP storage. EV owner since 2012

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          • #6
            Originally posted by Valence View Post
            Next step is to decide on the best inverter for 36v. Modified Sine wave for now. But once I start connecting devices that require pure sine wave I'll add in one of those suckers.. For now im Just trying to power a window AC unit and some lights.
            Modified sine is notably problematic with compressors. FYI. There are a few Chinese 36V large inverters out there.

            You can connect them all in parallel. I would recommend using a breaker for every single battery if you are planning on swapping them often; a single dropped live wire can really ruin your day unless you can depower it.

            I would not recommend using a panel for each battery if you have dozens. That's a nightmare. Connect them all to one bus and then use one large charge controller connected to one large array. You can monitor each separately but that will be expensive; instead I'd get a clamp on ammeter so you can spot check while charging or discharging.

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            • #7
              Originally posted by Ampster View Post

              I could use some for some e-bikes I am working on. I also have a GEM that I am working on. I am intrigued with the bluetooth capability.
              Whats the best way to reach you outside of this forum.

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              • #8
                Originally posted by Valence View Post

                Whats the best way to reach you outside of this forum.
                REMOVED at gmail dot com. Please acknowledge that you got this so I can remove even this vague link.
                Last edited by Ampster; 10-08-2019, 10:15 AM. Reason: Remove email
                9 kW solar, 42kWh LFP storage. EV owner since 2012

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                • #9
                  hmm you sure about big volt/amp cc price being less than several small ones??

                  actually keeping the voltage the same across the system is very important (suppose even current is too..)

                  so one charge controller with correct panel rating is also important for the system—not just the price...

                  still wondering if high amps in the battery bank is a charge controller concern?? i like the cheap ones...

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