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Electrical Engineer, Woodworker, (long term) Turning a bus into an RV; interested in high- and low-tech off-grid technologies

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  • ensuring balanced parallel pairs is done from the beginning- it isn't industry standard to monitor every parallel cell. The thing is, every cell is going to be sliiiiightly different than the cells next to it coming off of the assembly line. If they're coming from the same batch from the same manufacturing run, they're going to be (nearly) indistinguishable, and identical-enough to not create problems with differences in capacitance.The issue that you're describing usually arrives when someone builds a pack with leftover/recycled laptop cells, or generic/poorly-manufactured/"bargain" cells. The tiny (or more) variances in capacitance from cell to cell, once added up, can become glaring. The pack's usable capacitance is then limited to the smallest parallel string's capacitance- …

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    ensuring balanced parallel pairs is done from the beginning- it isn't industry standard to monitor every parallel cell. The thing is, every cell is going to be sliiiiightly different than the cells next to it coming off of the assembly line. If they're coming from the same batch from the same manufacturing run, they're going to be (nearly) indistinguishable, and identical-enough to not create problems with differences in capacitance.The issue that you're describing usually arrives when someone builds a pack with leftover/recycled laptop cells, or generic/poorly-manufactured/"bargain" cells. The tiny (or more) variances in capacitance from cell to cell, once added up, can become glaring. The pack's usable capacitance is then limited to the smallest parallel string's capacitance- it can't be fixed with active electronics because the differences in capacitance are caused by manufacturing differences & chemical wear within the cell.Even if you're not stacking multiple cells in parallel, you should use the same manufacturer (and ideally the same batch) when stacking single cells in series. a cell with a large capacitance will still be limited by the capacitance of a smaller cell in series with it (Barkuti is right about multiple cells behaving like one larger cell)

    Important safety note for anyone planning on building this:Li-Ion cell terminals are only meant to be sonic welded- they should never be soldered. You can buy cells with solderable tabs already sonic welded to the cell terminals, but the terminals themselves should never be soldered directly to the wire; doing so can (and likely will) lead to cell-by-cell capacitance disparity (which can't be fixed by balancing because you now essentially have multiple cell capacitances), or worse- unscheduled rapid thermal disassembly (fiery explosion) - which can happen either during the solder process or while the pack is being charged/discharged during regular use.Please stay safe. A soldering iron should never touch a battery terminal, ever.

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  • Thanks! There is something to be said about simplicity, when it's available.

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  • rajones4 commented on ceciljohns's instructable Air Compressor Dryer

    This is pretty rad. From your description, it sounds like this system is set up as compressor --> tank --> dryer --> tools, which would still lead to a buildup on moisture in your air tank. Would it be possible to put this system in line between the compressor and its tank, thereby keeping the tank and tools dry(er)?I can also see it beneficial to have this system a distance away (several feet or more) from the compressor, with the pressure line at a downward slope-- the ambient temperature would help the hot air condense on its way to the filters, thereby removing more moisture from the air (downward slope to keep moisture from building up in the line)... That's how we do it in the transit bus industry, anyway.

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  • rajones4's instructable Smart-Enough Outdoor Cat House's weekly stats:
    • Smart-Enough Outdoor Cat House
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      1 comments