I volt-metered a cr2032 battery and the result was like -1v. No, I am not getting the polarity of the probes mixed up. My other batteries are fine. I also measured using a better true RMS DMM, and same result. Does this result make sense?
(edit) Another question: what if I insert into an appliance upside down, to reverse the polarity. Will I have a +1v battery?
Yes the voltage on a battery can invert.
https://electronics.stackexchange.com/questions/10654/negative-voltage-on-aa-battery#%3A~%3Atext=A+battery+can+have+a+negative+voltage%2Ctaking+positive+charge+from+the+negative+terminal
That’s rather interesting. Didn’t realise you can overdrain a battery so it flips the voltage direction.