wrote:
On Sunday, 8 November 2020 13:42:26 UTC, Scott wrote:
My multimeter has a battery test facility that shows the battery as
good or bad (or on the margin). I understand a zinc carbon battery
has a voltage of 1.5 Volts and an alkaline battery has a voltage of
1.2 Volts? How does it know the difference between a very good
alkaline battery and a very bad zinc carbon battery?.

There are 2 requirements for a good battery: voltage & current. Terminal voltage often tells enough, but not always. The other test is to touch probes of a 1A meter to the battery for a fraction of a second, see how fast the needle flies up. Digital meters generally can't do this. Keep the probes on & you'll kill both meter & battery.


NT

https://learn.sparkfun.com/tutorials...nal-resistance

"We can only take a snapshot of the internal resistance
with this method. The internal resistance can vary with things
like battery age and temperature. In 10 minutes, the resistance
value might be different!

A common AA alkaline battery might have anywhere between
0.1 Ω and 0.9 Ω internal resistance."

https://data.energizer.com/PDFs/BatteryIR.pdf

"The typical effective resistances of fresh
Energizer alkaline cylindrical batteries (using a 5
mA stabilization drain followed by a 505 mA 100
millisecond pulse) will be approximately 150 to
300 milliohms, depending on size."

The Energizer method uses two load resistors, first
tests with the light load, then light+heavy load.

Paul