Hello,
Why battery tester's readings fluctuate? I bought it over a decade ago. Since it didn't fall down, could contacts degrade? https://streamable.com/rk3yp2
Tested lithium AAA battery and it seems okay but when attempted testing rechargeable AA readings started going back and forth.
A rechargeable AA that starts at 0.95V is already basically empty. There’s practically no energy left in it, so any load just drags down the voltage. The fluctuation is likely due to the variable contact of the battery contacts. I bet if you squeezed on the contacts to give it a better connection, you’d get a more stable reading.
I also expect that with a new battery, the voltage would remain much more stable.
Is black probe good with red probe from another set?
I managed to measure and here is what I found:
With multi-meter: voltage fluctuates between 1.22 - 1.23
With battery tester: voltage fluctuates between 1.14 - 1.15
My assumption is that multi-meter does not put load on battery while battery tester does.
Yes, you can mix and match probes, but why? I can tell from the picture that those are very cheap probes. Do yourself a favor and get something a bit nicer.
You are exactly right about the load: that’s what makes a battery tester a battery tester and not just a voltmeter. A battery tester applies a load so that you don’t get tricked by a no-load high voltage in a nearly dead battery, while a multimeter is designed to apply as little load as possible (so as to not affect the circuit under test).