Thread: Polarity Reversal on a Battery

Today I took out my trusty calculator to crunch some numbers but it does not turn on. Strange, I say to myself, it was working just fine a few days ago and the low battery indicator was not on. So I take out the batteries (4 regular AAA's) and check their voltage with a multimeter. Three are fine at around 1.35 V but one of them registers at -1V!

How is that possible? My understanding of how batteries work is limited but I had no idea that the polarity of a simple alkaline battery could reverse. Mind you this battery used to work fine just a few days ago.

Hello,

I'm sorry if this is a really dumb question, but are you 100% sure that you connected your voltmeter to the battery correctly (POS to POS, COM to COM, parallel). Negative volt reading is usually caused by connecting the meter wrong. That could also explain the voltage loss.

Best regards,
Shan

Yeah, I'm sure. The other batteries registered correct positive voltage.

Most likely your battery simply became high resistance, higher than the normal load, thus whun 'powered on' the other batteries simply reverse charged it. It also happens where you have dissimilar batteries ie 3 new and one old or three by one manufacturer and one by another, when the weakest becomes 'flat' and if the appliance is left on it can be reverse charged.

Always use a 'set' ie all new all the same type and manufacturer.