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I have here a silver-oxide button-cell SR626-size watch battery. It's still in the package. There's no well-known brand name printed on it. My dad bought the battery from the store 12 years ago, based on the attached receipt. I haven't voltmetered the battery yet.

The top of the battery says "+". It looks like it's in fairly good condition.

The bottom of the battery is lightly covered with a whitish or very pale greenish substance.

I've tried various Google searches, including [ silver-oxide battery shelf life ], and haven't found answers to my questions:

  • What could the mystery substance be?

  • Is the battery likely to be still good?

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Although close to on topic, consumer electronics support is off topic. – Kortuk♦ Mar 15 '12 at 23:19
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In the interests of safety - your battery has leaked. Be careful not to touch the white stuff it is likely corrosive. en.wikipedia.org/wiki/Alkaline_battery#Leaks – spearson Mar 15 '12 at 23:22
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Batteries contain "electrolytes" which are usually liquids or pastes. Some use solids which the electrolyte isembedded or soaked in. Electrolytes are usually corrosive - usually alkaline. Silver Oxide batteries usually use sodium or potassium hydroxide. What you are seeing are corrosion products from the reaction of the electrolyte with the various parts of the cell. SO batteries have a shelf life of about 5 years and also typically start leaking after that time - so your battery will be rather dead, alas. – Russell McMahon Mar 16 '12 at 1:16
Silver Oxide batteries used to contain about 1 part in 500 of mercury to help reduce corrosion. Not a lot but one more compound to beware of. Manufacturers started excluding Mercury from 2004 on so your battery will contain it. | FWIW much (not all) of the above information is contained in the Wikipedia page linked to above – Russell McMahon Mar 16 '12 at 1:16
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Question started because someone was curious about a consumer device (watch), but it's really about electrochemistry, not specific to any type of watch or model of battery. On-topic, in my opinion. – zebonaut Mar 16 '12 at 7:09
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closed as off topic by Kortuk♦ Mar 15 '12 at 23:19

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