0
\$\begingroup\$

I have some AA and AAA batteries that are sitting on my desk - I decided to test them before throwing them out. Some are Duracell "Duralock" brand, the others are Kendal "Super Heavy Duty - Pile Saline".

I recently bought a Fluke 115 multimeter, so I decided to use that to measure the voltage between the positive and negative poles of the battery.

I set the multimeter to DC V mode; when I attach the probes to the battery (red on the positive terminal, black on the negative terminal) the display reads 1.329 V for about 5-10 seconds, then the number suddenly drops to 0 V over about 2 seconds, then it stays there.

This happens consistently with the other batteries on my desk (the initial voltages are all around 1.3-ish Volts) except one, which stays at 1.329 V and never drops.

What is happening?

\$\endgroup\$
8
  • \$\begingroup\$ The cell is almost out of reactants. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Nov 26, 2016 at 22:40
  • \$\begingroup\$ The ones that go to 0 are dead. throw them out. The ones that stay above 1.0V are still OK to use (in some products - try them and see). Technically, you need a load resistor, like 27 ohms, to test the health of the AA or AAA. \$\endgroup\$
    – Rich S
    Nov 26, 2016 at 22:44
  • \$\begingroup\$ @RichS But why do they start at 1.3V and then drop? Why aren't they 0V from the beginning? \$\endgroup\$
    – Dai
    Nov 26, 2016 at 22:46
  • \$\begingroup\$ They are probably just very old, and were not used. From age, their internal resistance increased, because of internal chemical reaction. Do they have date codes? \$\endgroup\$
    – Rich S
    Nov 26, 2016 at 22:48
  • 2
    \$\begingroup\$ Make sure that your probes were not connected to the mA socket. \$\endgroup\$
    – Andy aka
    Nov 27, 2016 at 10:33

1 Answer 1

Reset to default
1
\$\begingroup\$

I am answering to counter some of the misinformation in the comment section. I don't have a good explanation for what is happening, and I have never seen something like that before. Normally, the voltage holds steady when the Voltmeter is connected. I suspect there is some problem with the probe or the voltmeter (although fluke is a very good brand) or the test setup. Maybe you are making intermittent contact because you are not pushing hard enough.

But for an alkaline battery, if the open circuit voltage is at 1.3V, the battery has little or no life left in it. If you discharge an alkaline battery under load until it reaches 1V or 0.9V, then remove the load, it can easily rebound to 1.3V. But as soon as you put the load back on it, it will go right back down to 1V or 0.9V. Personally, if I see anything under 1.4, I toss the cell. If it is close to 1.4, I consider it about half way used up. Fresh cells are between 1.5 and 1.6, usually.

\$\endgroup\$
2
  • 1
    \$\begingroup\$ You toss the cell at 1.4V??? Dude Alkaline cells are good down to 1.2V. What you are suggesting is very wasteful. \$\endgroup\$
    – crowie
    Nov 27, 2016 at 8:44
  • 1
    \$\begingroup\$ @crowie, they are over half discharged. And this is only if I find them in a pile of unknown batteries. The normal flow is for the batteries to be new and fresh, then go into a device until the device says they are dead, then they are discarded according to local regulations. But if you pay for the postage I will be happy to send any 1.2-1.4 V cells I find to you. \$\endgroup\$
    – user57037
    Nov 27, 2016 at 9:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.