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1 kWh Solar Generator Build Review

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  • 1 kWh Solar Generator Build Review

    Hi All - I'm getting started building a battery to set up a solar system to quite simply run a large box fan!
    There seems to be a million guides on how to build the battery itself, how to weld it, how to orient the batteries in a series, and what BMS to use and how to wire it. I can't be sure which one of these guides gives safe advice.
    I'm looking to create a ~1kWh, 48V battery from 18650 battery cells that can be charged by solar panels at 48V and power a 140W box fan.
    1. Is there a good guide to follow to SAFELY piece together the battery itself? What about wiring?
    2. Will the BMS selected function properly for the battery cells and my application?
    3. Does my diagram or parts list raise any red flags?

    Parts List:
    Thank you so much!
    1kw_solar generator_build_review.png

  • #2
    To me, I stay away from the 18650, especially 120 of them. Totaling only 20 ah. You could get 16 Lithium Phosphate 25 ah cells for around $25 each delivered.

    !000 watt inverter seems kind of big, mostly because it will be tempting to run too much off the system. Voltage is more than enough, but the battery capacity is around 1000 watt hours.

    The PWM controller, might not be the best choice for lithium batteries, but check absorption and float voltages. You are using a Lithium Ion pack, maybe ?LTO? with 18650s, which has different charging requirements than Lithium Iron Phosphate

    Check the panel voltages. With a PWM controller, this can be pick. Probably need both panels in parallel to stay within voltage specs.

    With the fan, you’re going to pull about 3.5 amps to spin the fan. Check the output of your LTO cells to make sure this can be sustained for hours, and what is the peak? The motor spinning up will take more energy than the 3.5 amps I mentioned. I don’t know what the surge will be. Perhaps you’ll need the 1kw inverter for that.

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    • #3
      Yes I would agree that you should stay away from the 18650 batteries. If just one out of that 120 pops off your going to have a major fire!
      The 25ah LifePO4 batteries are a much better option.

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      • #4
        I presume you will show the wire size and overcurrent protection for each wire in that diagram.

        Not sure how you plan to build that battery with 120 units.

        Also that 20Ah battery may be a little small to run that fan very long.

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        • #5
          Have you looked into a 12V automotive radiator fan ? DC, no inverter needed. Or if car fans are too large, motorcycle fan ?
          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

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          • #6
            There are 24VDC and 48VDC fans used in telco equipment, generally with a
            variable speed ability. I have a few running up to 300CFM. Bruce Roe

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