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 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.

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

'Short' is a binary term for something that in this case is far from binary.

typical resistance between fingers will be in he several hundred kilohm
range. Not enough to upset a low voltage battery.

Two wet fingers across my multimeter got me about 180k
Note that 30mA is RCD trip current for safety, so that implies a human
body might be somewhere on the 50mA at 240v = 4.8K region worst case
with two hands wrapped around conductors...

I managed to pickup a live lamp-holder I was working on the other month
and got a nice 'trembler' Didn't trip the RCD...



--
"First, find out who are the people you can not criticise. They are your
oppressors."
- George Orwell