How and why do batteries leak?

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Ashley Rose

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How and why do batteries leak?
« on: 01/08/2008 12:17:43 »
Ashley Rose  asked the Naked Scientists:

Hey guys, I love your show!

I have a question about batteries.

I was looking around the house for some AA batteries to put into my camera and found some in my dad's torch.  I guess it hadn't been used in a long time because when I opened the torch, the batteries, still intact, were covered in goo.  I think it might be the acid from inside the batteries, but what's really going on here?  How is the acid escaping?

Thanks, Ashley, Vancouver, Canada

What do you think?


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How and why do batteries leak?
« Reply #1 on: 02/08/2008 18:10:40 »
Most standard disposable batteries consist of a metal pot that forms one electrode this contains the liquid or jelly electrolyte and a central conducting rod as the other electrode. Discharging the battery dissolves the metal pot and eventually allows the electrolyte to leak out.  Old fashioned batteries used to leak very badly because they only had a cardboard jacket and they could start leaking well before they were fully discharged.  Nowadays all batteries are "leak proof" and have a metal case around the cardboard jacket and this considerably reduces the risk of leaking and batteries will not leak until they have been discharged well beyond any useful level but if you leave discharged batteries inside a unit or accidentally discharge them totally by leaving something switched on they will leak electrolyte.
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