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Drilling and tapping LiFePO4 battery terminal practicality? (programming.dev)
submitted 3 months ago by to c/askelectronics@discuss.tchncs.de
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I'm wondering how practical it would be to drill and tap terminals to add posts to batteries like this: https://batteryhookup.com/products/2x-sunwoda-lf314-314ah-lfp-prismatic-cells-grade-a-qualified-rohs-certified-ultra-long-life-10-000-cycles

The description says that you can only drill 5mm at most. Anybody do something like this before? I do have a shitty Harbor Freight drill press and couple hand tap wrenches.

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[–] 7 points 3 months ago

5mm is tiny

I'd sooner invest in the spot welding tools.

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    [–] 6 points 3 months ago

    It can be done, but I would suggest doing it outside to be safe. Set the depth stop on your drill press so you can't go too deep.

    You will need a normal tap to get started and a bottoming tap to finish threading the hole all the way to the bottom. 5mm is not a lot of thread to work with in soft aluminum. Those terminals are intended to have bus bars laser welded to them.

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    [–] 5 points 3 months ago (1 child)

    You can get handheld spot welders intended specifically for battery terminals for US$30-50. Spot welding is a lot less likely to damage the cell or risk puncturing it. Here's an example:

    https://ebay.us/m/adsJwa

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  • [–] [S] 3 points 3 months ago (1 child)

    I don't think those would work for these large batteries. I have one that I use for small cells though (i.e. 18650/21700).

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  • [–] 1 point 3 months ago (1 child)

    OK, I'm no expert but it says this at the end of that product listing:

    Secure this matched 2-pack of premium Sunwoda 314Ah cells—fresh stock from a respected brand, with flat studs for easy welding/integration.

    Are you saying they need a heavier gauge bus bar for the current, something too thick for a small spot welder? Would you MIG/TIG weld a battery contact?

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  • [–] [S] 4 points 3 months ago*

    Yeah, these are 0.5C cells, meaning they can safely discharge 157A (I would be using them for offgrid solar), so those little nickle strips would melt. I think TiG welding these would be extremely dangerous and produce too much heat (and I've never TiG welded before; just badly MiG welded a couple times). By "welding" in the description they mean commercial laser welders.

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