Portable Battery Bank Only Looks Like a Bomb

If one of the design goals of [wsw4jr]’s portable solar battery bank build was to make something that the local bomb squad would not hesitate to detonate with a water cannon if he leaves it unattended, then mission accomplished.

We kid, but really, the whole thing has a sort of “Spy vs. Spy” vibe that belies its simple purpose. A battery bank is just an array of batteries, some kind of charge controller, and an inverter. The batteries are charged by any means possible – in this case by a small array of solar panels. The mains output of the inverter is used to power whatever doodads you have.

[wsw4jr] didn’t mention of the inverter specs, but from the size of the batteries and the wiring – both of which he admits are not yet up to snuff in his prototype – it’s a safe guess that the intended loads are pretty small.  Tipping the scale at 60 pounds, the unit tends toward the luggable end of the portability scale. Still, this could be a great tool for working out in the field, or maybe even tailgating.

We’ve seen expedient battery banks and emergency power from cordless drill batteries before, but this build is quite a bit more sophisticated. We’ll be watching for updates on this one.

28 thoughts on “Portable Battery Bank Only Looks Like a Bomb

    1. “…conventional batteries…”
      Probably lead-acid, but I’m not 100% sure.

      i h8 imgur
      Seriously, it sucks on mobile devices; I can’t load the second half of images ATM.

    2. Imgur link, you know the drill.
      [https://i.imgur.com/kTf2M1n.webp]
      Unless it actually links correctly…
      https://i.imgur.com/kTf2M1n.webp
      “for now i have made a base and installed some batteries which are being held down by a strap. the base is screwed from the bottom up through the box and into the wood. these batteries are very small and are only temporary. eventually i would like to use lithium batteries with modules to charge them individually, but for now i have hooked these batteries in parallel.”

    1. They’re Lead-gel batteries by the looks of it. Lead-acid batteries can technically create some hydrogen when overcharged but the gel-type ones have this pretty well under control. They will just bloat, get very hot and/or leak smelly acidy liquids. Sometimes catch or cause fire but it’s very rare. I’ve never heard of one actually explode and I worked in tech support for a UPS manufacturer for a long time.

      Liquid lead acid batteries (such as car batteries) can generate hydrogen though, that’s why they’re always kept in the open air. If you have them indoors they can explode. I’ve seen liquid lead acid battery banks in telecoms buildings and they were very ridgid with hydrogen warning systems and no smoking signs everywhere.

      1. “LifePo4 and cut the weight in 1/2 while increasing capacity by 10X”

        Sorry, that’s BS. I did this on a pack designed to produce 300W AC for a half hour. I replaced four 8 Ah lead-acid cells with a single 15Ah LiFePO4 pack: This got me the SAME 30 amps x 30 minutes capacity, at 1/6th the weight, 1/3 the volume (and double the price). If I had chosen to use half the weight of LiFePO4s in place if the lead-acids, I would only get 3x the capacity, not “10X”.

        If you actually use lead-acids like they like to be used (at the 20 hour rate, not the 0.5 hour rate), then it looks even less favorable: closer to only 1.5X.

        My unit (battery, charger, case, inverter, 12V powerpole and 120V NEMA5 outlet bars) is a 5U rack-mount, massing an irritating 12.7 kg, despite the battery massing only 1.8 kg. It would mass 21.1 kg with the lead-acids, but now I have room for a second LiFePO4 battery.

        1. Well one problem with lead-gel batteries is that they don’t like to be used at all.. Use them 30-40 times and they’re dead. Especially if you discharge them beyond 20%.

          Of course there’s ones certified for ‘cyclic use’ but those are a lot more expensive.

          1. “akjsdflkj”, I apologize for offending your delicate sensibilities. But if I used the correct unit said it weighed 207 N, I expect you would feel even more alienated and indignant. Would you prefer I revert to that quaint “pound” unit and omit the “lbf” distinction? Because that would just be wrong.

    1. Not necessarily. Many “12V” fans are actually rated 7-15V nominal. Heck, back in the day, before overclocking was a market, we ran them strung between -5 and +12 to get the cfm up from pedestrian 20 to 30 or so of the average “computer” fan. Yeah equipment manufacturers could get 40 or so, but they were hard to get single unit.

  1. This unit DESPERATELY needs fuses, circuit breakers, fusible links… some sort of over current protection device. Especially with those front terminals. A cheap fused distribution block made for boats would do well,

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