On 18/11/2020 02:44:28, Nick Cat wrote:
On Thursday, 12 November 2020 at 00:55:46 UTC, Paul wrote:
Fredxx wrote:
On 11/11/2020 03:13:29, wrote:
On Tuesday, 10 November 2020 11:10:41 UTC, Fredxx wrote:
On 10/11/2020 03:04:36, tabbypurr wrote:
On Monday, 9 November 2020 10:16:51 UTC, Martin Brown wrote:
On 08/11/2020 13:59, Fredxx wrote:
On 08/11/2020 13:42:21, 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?.

An alkaline battery also has a nominal o/c voltage of 1.5V

A good fresh alkaline can be as high as 1.6v open circuit.

They start off above 1.5v. 1.5v is only nominal.

A well used one can go as high as 1.8v under odd circumstances. I had
a couple do that earlier this year. They were well used then
recharged, and gave a strangely high output. No idea why, none of the
others did.

Most articles suggest a brand new alkaline battery starts at 1.65V o/c
and goes down from there.

Do you have reference you can cite for a well used one with a o/c
voltage of 1.8V?

no, haven't looked.

I have and 1.65 is the highest I saw for a new battery. An old battery
will typically be 1V.

The only odd circumstance I can think of will be a duff meter.

I told you what the circumstances were. The meter's fine. But feel
free to get stupid again.

Perhaps it was user error then, or not recognising a malfunctioning meter?

If you have any non "stupid" reason for the erroneous measurement,
please do let us know.
Have we no electrochemists in the house ?

https://michaelbluejay.com/batteries/rechargeable.html

"NiZn's have the highest initial voltage of any rechargeable AA or
AAA battery. The nominal voltage is 1.65, and fresh out of the
charger the voltage is as high as 1.85V."

https://en.wikipedia.org/wiki/Nickel...93zinc_battery

(ˆ’) electrode: Zn + 4 OHˆ’ ‡Œ Zn(OH)42ˆ’ + 2eˆ’ (E0 = ˆ’1.2 V/SHE )

(+) electrode: 2 NiO(OH) + 2 H2O + 2 eˆ’ ‡Œ 2 Ni(OH)2 + 2 OHˆ’ (E0 = +0.50 V/SHE)

It's a redox reaction with two half-cell potentials, that give
the overall battery cell output voltage.

Was this battery mixed in with a lot of other batteries ?

Or did some other battery type leak, electrolyte got
between the inner cell metal jacket and the outer shell
steel covering ? The multimeter would need to be touching
the outer steel covering, instead of the tab on the
end, to (somehow) tap into the phantom voltage.

It makes more sense that it was a purpose-built NiZn cell.

Paul

it was a recharged alkaline

Please do give more details.

or ZnC.

So not a battery that any EE would refer to as alkaline.