Battery Terminal Corrosion: Endpoint

So the outdoor thermometer hanging over my desk became very, very faint, which suggested it was time for a new alkaline cell. The last time that happened, the insides were pretty bad, so I expected the worst, but, surprisingly, neither the cell nor the negative contact spring were corroded. So I popped in a new cell, buttoned it up, and … it didn’t work. At all. As in: blank display.

Taking the back off revealed the simple cause:

Outdoor thermometer - corroded battery lead
Outdoor thermometer – corroded battery lead

Evidently, the negative terminal wire had corroded completely through and popped off when I replaced the cell. There’s plenty of green-blue corrosion on the terminal inside the case, where it can’t be seen from outside; three years ago I cleaned up both the outside and inside, so this is new news.

The negative wire was discolored all the way from end to end and couldn’t be soldered. I think the corrosion products are just slightly hygroscopic and wick their way along the copper strands inside the insulation: the solder pad on the circuit board was also discolored.

I removed the terminal, neutralized the alkaline corrosion, ran it through an Evapo-Rust bath, scrubbed it clean, installed it, replaced both the positive and negative wires, resoldered everything, and it works perfectly again.

This can’t go on, can it?


10 thoughts on “Battery Terminal Corrosion: Endpoint

  1. NO, this cannot go on, you will eventually throw something AWAY, Right? lol

    JK, I don’t toss anything either…


    1. eventually throw something AWAY

      When we throw something out, it’s completely used up… maybe a couple of times!

    2. Is this a good time to consider alternative, exotic battery chemistry? Various sorts of lithium primary cells? Plain old carbon-zinc?

      1. IMO the battery chemistry will only affect corrosion if the cells leak. Cathodic Protection might help, but keeping moisture out is likely the best bet here. Seal an absorbent pack in there, maybe? Getting awfully involved, but such is the nature of
        “I LOVE
        The Smell of Molten Projects in the Morning” lol

        1. Seal an absorbent pack in there, maybe?

          Heck, I can’t even seal desiccant in the fireproof safe in the basement!

          As nearly as I can tell, though, alkalines corrode everything from the negative terminal on out after the potassium hydroxide eats its way through the sealant: damp corrosive goo begins wicking along the battery contact and wires. Maybe atmospheric humidity aids-and-abets the problem, but not by very much.

          Of course, if I replaced all the batteries every year, then I wouldn’t have these problems… [sigh]

      2. Plain old carbon-zinc?


        You can actually get a CR-V3 primary lithium cell shaped like two AA alkalines stacked side-to-side for five bucks, with roughly equal capacity under light loads. Brand-name alkalines run $1/pair and no-name CR123A cells hit $1/each, so I think CR-V3 cells have a long way to go before they become wildly popular…

        1. My line of thinking is sort of “carbon-zinc has a shelf life on the order of a decade, so if the draw is low enough then this should work OK. Just remember to change the batteries during presidential elections…” Of course, I could be totally off in space here. I’ve just had enough problems with alkalines over the years to start to wonder. Is it just me, or have they been getting worse?

        2. Eh… never mind. Decent shelf life, but basically dissolves itself as it discharges. Bad. Uggh. Will read application notes more carefully before replying in the future.

          1. dissolves itself as it discharges

            The only good thing about carbon-zinc cells: the carbon rods make a great homebrew arc lamp. I did that back in 5th grade, using a gallon of brine as a ballast resistor direct from line voltage. Why I’m alive with intact retinas remains a mystery…

  2. @Erik: Alkalines HAVE been getting worse, by a large margin. Some 2 or 3 years ago, they clearly downgraded the seals. The only way I know this, (and Duracell seems to have done it FIRST) is that I am in possession of a homemade “universal battery charger” of an open-source design, that I found online. It charge(d) alkalines ‘MARVELOUSLY’, up to original “package fresh” state, or slightly BETTER, all brands, across the board. Then, I saw certain commercially available Alkaline Chargers for maybe a year. Once that happened, Duracell was listed as “not compatible” with the commercial device. (on HSN/QVC) I also noticed that DuraCell was not working with my charger either, and all other brands followed suit within a year. :(
    It seems that they still charge quite easily, but the seals will degrade quite easily. I was once able to get a resting recharge over 2.0v+ (maybe 2.1?) but now, it seems the seals will blow even if I pushed it to 2.0v “under charge”, where before I would push well over 2.25-2.3 “under charge” with no problems. I even tried to go maybe 1.8 or 1.9, and the darn things would still leak. Seems the seals are quite junky now. Before, It took A LOT od charging to make it leak. Like pushing well over 2.5V on a good alkaline. I always was able to push 125% on any battery, over fully charged “resting voltage”.
    Now I cannot even get up to “resting Voltage” on ANY Alkaline brands. Not even close!
    They all leak, and many seem to leak in normal use. The moral of the story is, BUY RECHARGEABLES!!!

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