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Language: en

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I’m off to the Arctic for three weeks.

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And while I’m gone, some guest presenters
are going to be taking over this channel.

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We start with Sally le Page,

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a biologist from Oxford University,

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who is going to be talking about the world’s
longest lasting battery.

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Be nice, be kind, I’ll see you in three
weeks.

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Take it away, Sally!

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I’m in the Clarendon lab in Oxford,

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where physicists keep a battery with the longest
battery life the world has ever seen.

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It powers the Oxford Electric Bell,

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and it’s been running almost continuously
for over 176 years.

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It was bought by the Reverend Robert Walker,

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who was a reader in experimental philosophy
at Oxford.

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That’s what they used to call physicists
in those days,

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and should hopefully give you an idea of quite
how long ago we’re talking.

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He brought it back in 1840.

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So let’s just take a second to put that
in some context.

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If we skip back another 60 years, the year
is 1780.

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Mad King George is still on the British throne,

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the US declared independence just four years
earlier,

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and Napoleon is still a schoolboy.

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Over in Italy, a physicist, Luigi Galvani,

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was dissecting a frog’s leg with metal tools,

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but when he touched the nerve, he saw the
frog’s muscles twitch

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and he thought that this was “animal electricity”.

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Another Italian physicist, Alessandro Volta,
heard of this experiment,

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and realised that the frog’s leg was just
a fancy electrolyte

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that allowed current to flow between the copper
and iron tools that Galvani was using.

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And Volta went on to invent the first ever
battery in 1800,

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called the voltaic pile, made by piling up
discs of copper and zinc

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— well, here I’ve got aluminium foil —

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and sandwiching them with discs of cardboard
that was soaked in brine.

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And by piling up cells like this,

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you can see that you produce a battery, and
it still works!

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And then in 1825, the London instrument makers
Watkin and Hill made this:

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the Oxford Electric Bell and the dry pile
battery that powers it.

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And although it was just 25 years after Volta
invented the first ever battery,

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this battery here went on to outlive every
single other battery the world has ever produced

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and has won the Guinness World Record for
the world’s most durable battery.

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How does such an old battery last so long?

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Well, it’s a dry pile battery, so it’s
got a paste inside

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with the minimum amount of water needed for
the electrolyte to work.

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And all that water is kept in with this solid
sulfur coating.

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But beyond that, we don’t really know what’s
inside it.

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Looking at diagrams of other batteries from
around the time,

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it’s probably got about 2000 of these discs
made from zinc and manganese dioxide all stacked up.

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But to find out what it’s exactly made of,

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we’d have to cut it open and end its 176-year
run.

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In this time, the bells have run around 10
billion times, give or take,

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although this is an active physics laboratory,

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so thankfully for all the physicists around
here

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it’s now inaduble and it’s behind two
panes of glass.

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Each time the bell rings, the clapper takes
a tiny one nanoamp of current,

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but the voltage between the bells is a whopping
2 kilovolts.

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That’s nearly 10 times the voltage of UK
mains electricity.

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How long can it keep on running for?

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Well, no one really knows.

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The people round here reckon that the bell
will break from wear and tear

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long before the battery runs out of power.

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In 1841, just one year after Oxford bought
the bell,

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the instrument makers themselves wrote in
a letter,

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“The residual electrical power sufficient
to keep up the ringing of the bells

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“seldom lasts more than three or four years.

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“It’s a pretty apparatus, but alas,

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“very transient in its working powers.”

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How wrong could they be?

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That was Sally le Page, she has some great
videos on her channel,

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check it out — links are on screen or in
the description now.

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Thank you also to the University of Oxford’s
physics department for letting us film the bell.

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Next time: we have someone with some teeth
dissolving in soda.