On Saturday, 3 October 2020 14:56:00 UTC+1, John Rumm wrote:
On 03/10/2020 11:56, NY wrote:

My wife has always believed that if you touch both (and maybe just one)
terminal of a flat disc "button" battery (eg CR2032, CR1620 as used in a
watch, key fob, PC BIOS), you will cause the battery to discharge, so
you must take care when fitting a new battery not to "short the
terminals with your fingers".

I think this is one of those old wives tales that started with a grain
of truth, but then the actual detail got lost along the way, and now the
"fact" recalled is nothing to do with the actual issue[1]

I can imagine that sweat on the metal terminals *may* cause a bit of
oxidation over a long period of time, but I can't see how a body
resistance of many kilohms will cause the battery to go flat.

Indeed. Things like button cells can be used in applications where they
will last years, so making sure there is no contamination of the
surfaces makes sense. However you will not drain any noticeable energy
though your fingers while poking it into its socket.

Is there any truth in what she's always believed and what she advises me
to do?

[1] Bit like when people try to tell you that turning on a fluorescent
light will use 15 mins worth of electricity. The real deal is that
starting a lamp will use up some of the life on the heater coils, and
eventually could cause a lamp to fail to start - thus raising the
overall costs per hour..- but drawing 15 mins of energy in the couple of
seconds required to start it, is something the circuit breaker might
have a thing or two to say about!

I once did a calcualtion on that & concluded that the total costs of leaving a linear fluorescent light on were only beneficial for a matter of seconds, beyond that it was cheaper to switch off. A molehill had been made into a mountain somewhere.


NT