On Tue, 24 Aug 2010 10:53:14 +0100, john hamilton wrote:

I'm replacing a small button battery (CR 2032) with two AAA batteries,
I'm intending to leave the old discharged button battery in its place
and solder the leads from the AAA batteries directly on to the button
battery.

Yes, they can go bang when soldering if you apply too much heat for too
long. Applying power to one probably isn't a good idea, either (you'd
basically be trying to recharge an no-rechargeable cell - I doubt it'd
outright explode or catch fire, but it might leak, and ever the vapours
from batteries can make a real mess of PCB traces).

Personally I'd desolder it - preferably cutting it from the PCB first and
then desoldering the legs that remain. What the device is would dictate
whether I'd fit a direct replacement, or a socket, or trailing wires to a
socket, or trailing wires to a holder to take AAAs etc.

cheers

Jules