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Here's a story I heard from a coworker (means I wasn't there to gather extra info).

They had a table clock which had an old battery, either C or D. They took that out, and put an AA in. The battery started heating up and putting smoke off. When they replaced it with a new C, the clock worked correctly.

I can not understand how this could happen. I thought at first it might be of the battery internal resistance difference (I myself fried a circuit that used a 9V square battery once, by replacing it with 6AA). However, AA have more resistance than C. I also asked if the AA was maybe rechargeable, but it wasn't.

Any ideas how this could happen?

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  • \$\begingroup\$ It's amazing how people keep coming to the conclusion that "smoke was coming out of the electronic device /--/ but it works correctly now" without having performed any form of repairs. What burned up that didn't need repairs I wonder... \$\endgroup\$
    – Lundin
    Commented Dec 23, 2021 at 12:03
  • \$\begingroup\$ @Lundin He said that the battery smoked. \$\endgroup\$
    – ATCSVOL
    Commented Dec 23, 2021 at 12:53
  • \$\begingroup\$ @ATCSVOL Which means it shorted. Which means that something in the product shorted upon polarity reverse. There can be broken diodes, transistors, caps, how can you tell? \$\endgroup\$
    – Lundin
    Commented Dec 23, 2021 at 12:56
  • \$\begingroup\$ @Lundin see my answer. A battery short in the battery holder is a possibility. || I have seen products emit smoke and still function subsequently. Damage has probably occurred but not immediately fatal damage. \$\endgroup\$
    – ATCSVOL
    Commented Dec 23, 2021 at 13:00

2 Answers 2

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It might be he simply put the battery in reverse polarity : depending on the circuit, some components (mainly semiconductors) are conduct very well in reverse polarity, so you might get nearly a short circuit. That's enough to get smoke.

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Reverse polarity of the AA battery seems likely.

A possibility is that the battery holder which was made for a C cell shorted the slightly misaligned AA cell at one end. Some cells have positive and negative available in close proximity, making shorting possible.

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